river pollution assignment

• History & Society
• Science & Tech
• Biographies
• Animals & Nature
• Geography & Travel
• Arts & Culture
• Games & Quizzes
• On This Day
• One Good Fact
• New Articles
• Lifestyles & Social Issues
• Philosophy & Religion
• Politics, Law & Government
• World History
• Health & Medicine
• Browse Biographies
• Birds, Reptiles & Other Vertebrates
• Bugs, Mollusks & Other Invertebrates
• Environment
• Fossils & Geologic Time
• Entertainment & Pop Culture
• Sports & Recreation
• Visual Arts
• Demystified
• Image Galleries
• Infographics
• Top Questions
• Britannica Kids
• Saving Earth
• Space Next 50
• Student Center
• Introduction & Top Questions

Domestic sewage

Solid waste, toxic waste, thermal pollution, petroleum (oil) pollution, effects of water pollution on groundwater and oceans, water quality standards.

How does water pollution affect aquatic wildlife?

Is red tide caused by water pollution.

water pollution

Our editors will review what you’ve submitted and determine whether to revise the article.

• National Geographic - What Is Water Pollution?
• Frontiers - Effects of Water Pollution on Human Health and Disease Heterogeneity: A Review
• Harvard T.H. Chan School of Public Health - Water Pollution
• Environmental Pollution Centers - What Is Water Pollution?
• National Resources Defense Council - Water Pollution: Everything You Need to Know
• Chemistry LibreTexts - Water Pollution
• water pollution - Student Encyclopedia (Ages 11 and up)
• Table Of Contents

What is water pollution?

Water pollution is the release of substances into bodies of water that makes water unsafe for human use and disrupts aquatic ecosystems. Water pollution can be caused by a plethora of different contaminants, including toxic waste , petroleum , and disease-causing microorganisms .

What human activities cause water pollution?

Human activities that generate domestic sewage and toxic waste cause water pollution by contaminating water with disease-causing microorganisms and poisonous substances. Oil spills are another source of water pollution that have devastating impacts on surrounding ecosystems.

Sewage can promote algae growth, which can eventually result in eutrophic “dead zones” where aquatic life cannot survive because of a lack of oxygen. Microplastics are often found in marine wildlife and can become concentrated in humans who consume seafood because of biomagnification . Oil spills, such as the Deepwater Horizon oil spill in 2010, strand and kill many different marine species.

While some studies point to human activity as a catalyst for red tide, scientists are unsure about its cause. Red tide is a common term for harmful algal blooms that often poison or kill wildlife and humans who consume contaminated seafood. Red tides can severely impact ecosystems and local economies.

Recent News

water pollution , the release of substances into subsurface groundwater or into lakes , streams, rivers , estuaries , and oceans to the point that the substances interfere with beneficial use of the water or with the natural functioning of ecosystems . In addition to the release of substances, such as chemicals , trash, or microorganisms, water pollution may include the release of energy , in the form of radioactivity or heat , into bodies of water.

Types and sources of water pollutants

Water bodies can be polluted by a wide variety of substances, including pathogenic microorganisms, putrescible organic waste, fertilizers and plant nutrients , toxic chemicals, sediments, heat , petroleum (oil), and radioactive substances . Several types of water pollutants are considered below. (For a discussion of the handling of sewage and other forms of waste produced by human activities, see waste disposal and solid-waste management .)

Water pollutants come from either point sources or dispersed sources. A point source is a pipe or channel, such as those used for discharge from an industrial facility or a city sewerage system . A dispersed (or nonpoint) source is a very broad unconfined area from which a variety of pollutants enter the water body, such as the runoff from an agricultural area. Point sources of water pollution are easier to control than dispersed sources, because the contaminated water has been collected and conveyed to one single point where it can be treated. Pollution from dispersed sources is difficult to control, and, despite much progress in the building of modern sewage-treatment plants, dispersed sources continue to cause a large fraction of water pollution problems.

Domestic sewage is the primary source of pathogens ( disease -causing microorganisms) and putrescible organic substances. Because pathogens are excreted in feces , all sewage from cities and towns is likely to contain pathogens of some type, potentially presenting a direct threat to public health . Putrescible organic matter presents a different sort of threat to water quality. As organics are decomposed naturally in the sewage by bacteria and other microorganisms, the dissolved oxygen content of the water is depleted. This endangers the quality of lakes and streams, where high levels of oxygen are required for fish and other aquatic organisms to survive. In addition, domestic sewage commonly contains active pharmaceutical ingredients, which can harm aquatic organisms and may facilitate antibiotic resistance . Sewage-treatment processes reduce the levels of pathogens and organics in wastewater, but they do not eliminate them completely ( see also wastewater treatment ).

Domestic sewage is also a major source of plant nutrients , mainly nitrates and phosphates . Excess nitrates and phosphates in water promote the growth of algae , sometimes causing unusually dense and rapid growths known as algal blooms . When the algae die, oxygen dissolved in the water declines because microorganisms use oxygen to digest algae during the process of decomposition ( see also biochemical oxygen demand ). Anaerobic organisms (organisms that do not require oxygen to live) then metabolize the organic wastes, releasing gases such as methane and hydrogen sulfide , which are harmful to the aerobic (oxygen-requiring) forms of life. The process by which a lake changes from a clean, clear condition—with a relatively low concentration of dissolved nutrients and a balanced aquatic community —to a nutrient-rich, algae-filled state and thence to an oxygen-deficient, waste-filled condition is called eutrophication . Eutrophication is a naturally occurring, slow, and inevitable process. However, when it is accelerated by human activity and water pollution (a phenomenon called cultural eutrophication ), it can lead to the premature aging and death of a body of water.

The improper disposal of solid waste is a major source of water pollution. Solid waste includes garbage, rubbish, electronic waste , trash, and construction and demolition waste, all of which are generated by individual, residential, commercial, institutional, and industrial activities. The problem is especially acute in developing countries that may lack infrastructure to properly dispose of solid waste or that may have inadequate resources or regulation to limit improper disposal. In some places solid waste is intentionally dumped into bodies of water. Land pollution can also become water pollution if the trash or other debris is carried by animals, wind, or rainfall to bodies of water. Significant amounts of solid waste pollution in inland bodies of water can also eventually make their way to the ocean. Solid waste pollution is unsightly and damaging to the health of aquatic ecosystems and can harm wildlife directly. Many solid wastes, such as plastics and electronic waste, break down and leach harmful chemicals into the water, making them a source of toxic or hazardous waste.

Of growing concern for aquatic environments is plastic pollution . Since the ocean is downstream from nearly every terrestrial location, it is the receiving body for much of the plastic waste generated on land. Several million tons of debris end up in the world’s oceans every year, and much of it is improperly discarded plastic litter. Plastic pollution can be broken down by waves and ultraviolet radiation into smaller pieces known as microplastics , which are less than 5 mm (0.2 inch) in length and are not biodegradable. Primary microplastics, such as microbeads in personal care products and plastic fibers in synthetic textiles (e.g., nylon ), also enter the environment directly, through any of various channels—for example, from wastewater treatment systems , from household laundry, or from unintentional spills during manufacturing or transport. Alarmingly, a number of studies of both freshwater and marine locations have found microplastics in every aquatic organism tested. These tiny plastics are suspected of working their way up the marine food chains , from zooplankton and small fish to large marine predators, and have been found in seafood. Microplastics have also been detected in drinking water. Their health effects are unknown.

Waste is considered toxic if it is poisonous , radioactive , explosive , carcinogenic (causing cancer ), mutagenic (causing damage to chromosomes ), teratogenic (causing birth defects), or bioaccumulative (that is, increasing in concentration at the higher ends of food chains). Sources of toxic chemicals include improperly disposed wastewater from industrial plants and chemical process facilities ( lead , mercury , chromium ) as well as surface runoff containing pesticides used on agricultural areas and suburban lawns ( chlordane , dieldrin , heptachlor). (For a more-detailed treatment of toxic chemicals, see poison and toxic waste .)

Sediment (e.g., silt ) resulting from soil erosion or construction activity can be carried into water bodies by surface runoff . Suspended sediment interferes with the penetration of sunlight and upsets the ecological balance of a body of water. Also, it can disrupt the reproductive cycles of fish and other forms of life , and when it settles out of suspension it can smother bottom-dwelling organisms.

Heat is considered to be a water pollutant because it decreases the capacity of water to hold dissolved oxygen in solution, and it increases the rate of metabolism of fish. Valuable species of game fish (e.g., trout ) cannot survive in water with very low levels of dissolved oxygen . A major source of heat is the practice of discharging cooling water from power plants into rivers; the discharged water may be as much as 15 °C (27 °F) warmer than the naturally occurring water. The rise in water temperatures because of global warming can also be considered a form of thermal pollution.

Petroleum ( oil ) pollution occurs when oil from roads and parking lots is carried in surface runoff into water bodies. Accidental oil spills are also a source of oil pollution—as in the devastating spills from the tanker Exxon Valdez (which released more than 260,000 barrels in Alaska’s Prince William Sound in 1989) and from the Deepwater Horizon oil rig (which released more than 4 million barrels of oil into the Gulf of Mexico in 2010). Oil slicks eventually move toward shore, harming aquatic life and damaging recreation areas.

Groundwater —water contained in underground geologic formations called aquifers —is a source of drinking water for many people. For example, about half the people in the United States depend on groundwater for their domestic water supply . Although groundwater may appear crystal clear (due to the natural filtration that occurs as it flows slowly through layers of soil ), it may still be polluted by dissolved chemicals and by bacteria and viruses . Sources of chemical contaminants include poorly designed or poorly maintained subsurface sewage-disposal systems (e.g., septic tanks ), industrial wastes disposed of in improperly lined or unlined landfills or lagoons , leachates from unlined municipal refuse landfills, mining and petroleum production, and leaking underground storage tanks below gasoline service stations. In coastal areas, increasing withdrawal of groundwater (due to urbanization and industrialization) can cause saltwater intrusion: as the water table drops, seawater is drawn into wells.

Although estuaries and oceans contain vast volumes of water, their natural capacity to absorb pollutants is limited. Contamination from sewage outfall pipes, from dumping of sludge or other wastes, and from oil spills can harm marine life, especially microscopic phytoplankton that serve as food for larger aquatic organisms. Sometimes, unsightly and dangerous waste materials can be washed back to shore, littering beaches with hazardous debris. In oceans alone, annual pollution from all types of plastics was estimated to be between 4.8 million and 12.7 million tonnes (between 5.3 million and 14 million tons) in the early 21st century, and floating plastic waste had accumulated in Earth’s five subtropical gyres, which cover 40 percent of the world’s oceans.

Another ocean pollution problem is the seasonal formation of “ dead zones” (i.e., hypoxic areas, where dissolved oxygen levels drop so low that most higher forms of aquatic life vanish) in certain coastal areas. The cause is nutrient enrichment from dispersed agricultural runoff and concomitant algal blooms. Dead zones occur worldwide; one of the largest of these (sometimes as large as 22,730 square km [8,776 square miles]) forms annually in the Gulf of Mexico , beginning at the Mississippi River delta.

Although pure water is rarely found in nature (because of the strong tendency of water to dissolve other substances), the characterization of water quality (i.e., clean or polluted) is a function of the intended use of the water. For example, water that is clean enough for swimming and fishing may not be clean enough for drinking and cooking. Water quality standards (limits on the amount of impurities allowed in water intended for a particular use) provide a legal framework for the prevention of water pollution of all types.

There are several types of water quality standards. Stream standards are those that classify streams, rivers , and lakes on the basis of their maximum beneficial use; they set allowable levels of specific substances or qualities (e.g., dissolved oxygen , turbidity, pH) allowed in those bodies of water, based on their given classification. Effluent (water outflow) standards set specific limits on the levels of contaminants (e.g., biochemical oxygen demand , suspended solids, nitrogen ) allowed in the final discharges from wastewater-treatment plants. Drinking-water standards include limits on the levels of specific contaminants allowed in potable water delivered to homes for domestic use. In the United States , the Clean Water Act and its amendments regulate water quality and set minimum standards for waste discharges for each industry as well as regulations for specific problems such as toxic chemicals and oil spills . In the European Union , water quality is governed by the Water Framework Directive, the Drinking Water Directive, and other laws . ( See also wastewater treatment .)

Water Pollution: Everything You Need to Know

Our rivers, reservoirs, lakes, and seas are drowning in chemicals, waste, plastic, and other pollutants. Here’s why—and what you can do to help.

• Share this page block

What is water pollution?

What are the causes of water pollution, categories of water pollution, what are the effects of water pollution, what can you do to prevent water pollution.

Water pollution occurs when harmful substances—often chemicals or microorganisms—contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and rendering it toxic to humans or the environment.

This widespread problem of water pollution is jeopardizing our health. Unsafe water kills more people each year than war and all other forms of violence combined. Meanwhile, our drinkable water sources are finite: Less than 1 percent of the earth’s freshwater is actually accessible to us. Without action, the challenges will only increase by 2050, when global demand for freshwater is expected to be one-third greater than it is now.

Water is uniquely vulnerable to pollution. Known as a “universal solvent,” water is able to dissolve more substances than any other liquid on earth. It’s the reason we have Kool-Aid and brilliant blue waterfalls. It’s also why water is so easily polluted. Toxic substances from farms, towns, and factories readily dissolve into and mix with it, causing water pollution.

Here are some of the major sources of water pollution worldwide:

Agricultural

Toxic green algae in Copco Reservoir, northern California

Aurora Photos/Alamy

Not only is the agricultural sector the biggest consumer of global freshwater resources, with farming and livestock production using about 70 percent of the earth’s surface water supplies , but it’s also a serious water polluter. Around the world, agriculture is the leading cause of water degradation. In the United States, agricultural pollution is the top source of contamination in rivers and streams, the second-biggest source in wetlands, and the third main source in lakes. It’s also a major contributor of contamination to estuaries and groundwater. Every time it rains, fertilizers, pesticides, and animal waste from farms and livestock operations wash nutrients and pathogens—such bacteria and viruses—into our waterways. Nutrient pollution , caused by excess nitrogen and phosphorus in water or air, is the number-one threat to water quality worldwide and can cause algal blooms , a toxic soup of blue-green algae that can be harmful to people and wildlife.

Sewage and wastewater

Used water is wastewater. It comes from our sinks, showers, and toilets (think sewage) and from commercial, industrial, and agricultural activities (think metals, solvents, and toxic sludge). The term also includes stormwater runoff , which occurs when rainfall carries road salts, oil, grease, chemicals, and debris from impermeable surfaces into our waterways

More than 80 percent of the world’s wastewater flows back into the environment without being treated or reused, according to the United Nations; in some least-developed countries, the figure tops 95 percent. In the United States, wastewater treatment facilities process about 34 billion gallons of wastewater per day . These facilities reduce the amount of pollutants such as pathogens, phosphorus, and nitrogen in sewage, as well as heavy metals and toxic chemicals in industrial waste, before discharging the treated waters back into waterways. That’s when all goes well. But according to EPA estimates, our nation’s aging and easily overwhelmed sewage treatment systems also release more than 850 billion gallons of untreated wastewater each year.

Oil pollution

Big spills may dominate headlines, but consumers account for the vast majority of oil pollution in our seas, including oil and gasoline that drips from millions of cars and trucks every day. Moreover, nearly half of the estimated 1 million tons of oil that makes its way into marine environments each year comes not from tanker spills but from land-based sources such as factories, farms, and cities. At sea, tanker spills account for about 10 percent of the oil in waters around the world, while regular operations of the shipping industry—through both legal and illegal discharges—contribute about one-third. Oil is also naturally released from under the ocean floor through fractures known as seeps.

Radioactive substances

Radioactive waste is any pollution that emits radiation beyond what is naturally released by the environment. It’s generated by uranium mining, nuclear power plants, and the production and testing of military weapons, as well as by universities and hospitals that use radioactive materials for research and medicine. Radioactive waste can persist in the environment for thousands of years, making disposal a major challenge. Consider the decommissioned Hanford nuclear weapons production site in Washington, where the cleanup of 56 million gallons of radioactive waste is expected to cost more than $100 billion and last through 2060. Accidentally released or improperly disposed of contaminants threaten groundwater, surface water, and marine resources.

To address pollution and protect water we need to understand where the pollution is coming from (point source or nonpoint source) and the type of water body its impacting (groundwater, surface water, or ocean water).

Where is the pollution coming from?

Point source pollution.

When contamination originates from a single source, it’s called point source pollution. Examples include wastewater (also called effluent) discharged legally or illegally by a manufacturer, oil refinery, or wastewater treatment facility, as well as contamination from leaking septic systems, chemical and oil spills, and illegal dumping. The EPA regulates point source pollution by establishing limits on what can be discharged by a facility directly into a body of water. While point source pollution originates from a specific place, it can affect miles of waterways and ocean.

Nonpoint source

Nonpoint source pollution is contamination derived from diffuse sources. These may include agricultural or stormwater runoff or debris blown into waterways from land. Nonpoint source pollution is the leading cause of water pollution in U.S. waters, but it’s difficult to regulate, since there’s no single, identifiable culprit.

Transboundary

It goes without saying that water pollution can’t be contained by a line on a map. Transboundary pollution is the result of contaminated water from one country spilling into the waters of another. Contamination can result from a disaster—like an oil spill—or the slow, downriver creep of industrial, agricultural, or municipal discharge.

What type of water is being impacted?

Groundwater pollution.

When rain falls and seeps deep into the earth, filling the cracks, crevices, and porous spaces of an aquifer (basically an underground storehouse of water), it becomes groundwater—one of our least visible but most important natural resources. Nearly 40 percent of Americans rely on groundwater, pumped to the earth’s surface, for drinking water. For some folks in rural areas, it’s their only freshwater source. Groundwater gets polluted when contaminants—from pesticides and fertilizers to waste leached from landfills and septic systems—make their way into an aquifer, rendering it unsafe for human use. Ridding groundwater of contaminants can be difficult to impossible, as well as costly. Once polluted, an aquifer may be unusable for decades, or even thousands of years. Groundwater can also spread contamination far from the original polluting source as it seeps into streams, lakes, and oceans.

Surface water pollution

Covering about 70 percent of the earth, surface water is what fills our oceans, lakes, rivers, and all those other blue bits on the world map. Surface water from freshwater sources (that is, from sources other than the ocean) accounts for more than 60 percent of the water delivered to American homes. But a significant pool of that water is in peril. According to the most recent surveys on national water quality from the U.S. Environmental Protection Agency, nearly half of our rivers and streams and more than one-third of our lakes are polluted and unfit for swimming, fishing, and drinking. Nutrient pollution, which includes nitrates and phosphates, is the leading type of contamination in these freshwater sources. While plants and animals need these nutrients to grow, they have become a major pollutant due to farm waste and fertilizer runoff. Municipal and industrial waste discharges contribute their fair share of toxins as well. There’s also all the random junk that industry and individuals dump directly into waterways.

Ocean water pollution

Eighty percent of ocean pollution (also called marine pollution) originates on land—whether along the coast or far inland. Contaminants such as chemicals, nutrients, and heavy metals are carried from farms, factories, and cities by streams and rivers into our bays and estuaries; from there they travel out to sea. Meanwhile, marine debris— particularly plastic —is blown in by the wind or washed in via storm drains and sewers. Our seas are also sometimes spoiled by oil spills and leaks—big and small—and are consistently soaking up carbon pollution from the air. The ocean absorbs as much as a quarter of man-made carbon emissions .

On human health

To put it bluntly: Water pollution kills. In fact, it caused 1.8 million deaths in 2015, according to a study published in The Lancet . Contaminated water can also make you ill. Every year, unsafe water sickens about 1 billion people. And low-income communities are disproportionately at risk because their homes are often closest to the most polluting industries.

Waterborne pathogens, in the form of disease-causing bacteria and viruses from human and animal waste, are a major cause of illness from contaminated drinking water . Diseases spread by unsafe water include cholera, giardia, and typhoid. Even in wealthy nations, accidental or illegal releases from sewage treatment facilities, as well as runoff from farms and urban areas, contribute harmful pathogens to waterways. Thousands of people across the United States are sickened every year by Legionnaires’ disease (a severe form of pneumonia contracted from water sources like cooling towers and piped water), with cases cropping up from California’s Disneyland to Manhattan’s Upper East Side.

A woman using bottled water to wash her three-week-old son at their home in Flint, Michigan

Todd McInturf/The Detroit News/AP

Meanwhile, the plight of residents in Flint, Michigan —where cost-cutting measures and aging water infrastructure created a lead contamination crisis—offers a stark look at how dangerous chemical and other industrial pollutants in our water can be. The problem goes far beyond Flint and involves much more than lead, as a wide range of chemical pollutants—from heavy metals such as arsenic and mercury to pesticides and nitrate fertilizers —are getting into our water supplies. Once they’re ingested, these toxins can cause a host of health issues, from cancer to hormone disruption to altered brain function. Children and pregnant women are particularly at risk.

Even swimming can pose a risk. Every year, 3.5 million Americans contract health issues such as skin rashes, pinkeye, respiratory infections, and hepatitis from sewage-laden coastal waters, according to EPA estimates.

On the environment

In order to thrive, healthy ecosystems rely on a complex web of animals, plants, bacteria, and fungi—all of which interact, directly or indirectly, with each other. Harm to any of these organisms can create a chain effect, imperiling entire aquatic environments.

When water pollution causes an algal bloom in a lake or marine environment, the proliferation of newly introduced nutrients stimulates plant and algae growth, which in turn reduces oxygen levels in the water. This dearth of oxygen, known as eutrophication , suffocates plants and animals and can create “dead zones,” where waters are essentially devoid of life. In certain cases, these harmful algal blooms can also produce neurotoxins that affect wildlife, from whales to sea turtles.

Chemicals and heavy metals from industrial and municipal wastewater contaminate waterways as well. These contaminants are toxic to aquatic life—most often reducing an organism’s life span and ability to reproduce—and make their way up the food chain as predator eats prey. That’s how tuna and other big fish accumulate high quantities of toxins, such as mercury.

Marine ecosystems are also threatened by marine debris , which can strangle, suffocate, and starve animals. Much of this solid debris, such as plastic bags and soda cans, gets swept into sewers and storm drains and eventually out to sea, turning our oceans into trash soup and sometimes consolidating to form floating garbage patches. Discarded fishing gear and other types of debris are responsible for harming more than 200 different species of marine life.

Meanwhile, ocean acidification is making it tougher for shellfish and coral to survive. Though they absorb about a quarter of the carbon pollution created each year by burning fossil fuels, oceans are becoming more acidic. This process makes it harder for shellfish and other species to build shells and may impact the nervous systems of sharks, clownfish, and other marine life.

With your actions

We’re all accountable to some degree for today’s water pollution problem. Fortunately, there are some simple ways you can prevent water contamination or at least limit your contribution to it:

• Learn about the unique qualities of water where you live . Where does your water come from? Is the wastewater from your home treated? Where does stormwater flow to? Is your area in a drought? Start building a picture of the situation so you can discover where your actions will have the most impact—and see if your neighbors would be interested in joining in!
• Reduce your plastic consumption and reuse or recycle plastic when you can.
• Properly dispose of chemical cleaners, oils, and nonbiodegradable items to keep them from going down the drain.
• Maintain your car so it doesn’t leak oil, antifreeze, or coolant.
• If you have a yard, consider landscaping that reduces runoff and avoid applying pesticides and herbicides .
• Don’t flush your old medications! Dispose of them in the trash to prevent them from entering local waterways.
• Be mindful of anything you pour into storm sewers, since that waste often won’t be treated before being released into local waterways. If you notice a storm sewer blocked by litter, clean it up to keep that trash out of the water. (You’ll also help prevent troublesome street floods in a heavy storm.)
• If you have a pup, be sure to pick up its poop .

With your voice

One of the most effective ways to stand up for our waters is to speak out in support of the Clean Water Act, which has helped hold polluters accountable for five decades—despite attempts by destructive industries to gut its authority. But we also need regulations that keep pace with modern-day challenges, including microplastics, PFAS , pharmaceuticals, and other contaminants our wastewater treatment plants weren’t built to handle, not to mention polluted water that’s dumped untreated.

Tell the federal government, the U.S. Army Corps of Engineers, and your local elected officials that you support water protections and investments in infrastructure, like wastewater treatment, lead-pipe removal programs, and stormwater-abating green infrastructure. Also, learn how you and those around you can get involved in the policymaking process . Our public waterways serve every one of us. We should all have a say in how they’re protected.

This story was originally published on May 14, 2018, and has been updated with new information and links.

This NRDC.org story is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the story was originally published by NRDC.org and link to the original; the story cannot be edited (beyond simple things such as grammar); you can’t resell the story in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select stories individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our stories.

Related Stories

The Global Plastics Treaty: It’s Time to Clean Up Our Mess

​​The Smart Seafood and Sustainable Fish Buying Guide

How to Become a Community Scientist

When you sign up, you’ll become a member of NRDC’s Activist Network. We will keep you informed with the latest alerts and progress reports.

• Random article
• Teaching guide
• Privacy & cookies

Water pollution: an introduction

by Chris Woodford . Last updated: October 1, 2023.

O ver two thirds of Earth's surface is covered by water ; less than a third is taken up by land. As Earth's population continues to grow, people are putting ever-increasing pressure on the planet's water resources. In a sense, our oceans, rivers , and other inland waters are being "squeezed" by human activities—not so they take up less room, but so their quality is reduced. Poorer water quality means water pollution .

We know that pollution is a human problem because it is a relatively recent development in the planet's history: before the 19th century Industrial Revolution, people lived more in harmony with their immediate environment. As industrialization has spread around the globe, so the problem of pollution has spread with it. When Earth's population was much smaller, no one believed pollution would ever present a serious problem. It was once popularly believed that the oceans were far too big to pollute. Today, with around 7 billion people on the planet, it has become apparent that there are limits. Pollution is one of the signs that humans have exceeded those limits.

Photo: Stormwater pollution entering a river from a drain. Photo by Peter C Van Metre courtesy of US Geological Survey .

What is water pollution?

Water pollution can be defined in many ways. Usually, it means one or more substances have built up in water to such an extent that they cause problems for animals or people. Oceans, lakes, rivers, and other inland waters can naturally clean up a certain amount of pollution by dispersing it harmlessly. If you poured a cup of black ink into a river, the ink would quickly disappear into the river's much larger volume of clean water. The ink would still be there in the river, but in such a low concentration that you would not be able to see it. At such low levels, the chemicals in the ink probably would not present any real problem. However, if you poured gallons of ink into a river every few seconds through a pipe, the river would quickly turn black. The chemicals in the ink could very quickly have an effect on the quality of the water. This, in turn, could affect the health of all the plants, animals, and humans whose lives depend on the river.

Photo: Pollution means adding substances to the environment that don't belong there—like the air pollution from this smokestack. Pollution is not always as obvious as this, however.

Thus, water pollution is all about quantities : how much of a polluting substance is released and how big a volume of water it is released into. A small quantity of a toxic chemical may have little impact if it is spilled into the ocean from a ship. But the same amount of the same chemical can have a much bigger impact pumped into a lake or river, where there is less clean water to disperse it.

"The introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to marine activities, including fishing, impairment of quality for use of sea water and reduction of amenities." [1]

What are the main types of water pollution?

When we think of Earth's water resources, we think of huge oceans, lakes, and rivers. Water resources like these are called surface waters . The most obvious type of water pollution affects surface waters. For example, a spill from an oil tanker creates an oil slick that can affect a vast area of the ocean.

Photo: Detergent pollution entering a river—an example of surface water pollution. Photo courtesy of US Fish & Wildlife Service Photo Library.

Not all of Earth's water sits on its surface, however. A great deal of water is held in underground rock structures known as aquifers, which we cannot see and seldom think about. Water stored underground in aquifers is known as groundwater . Aquifers feed our rivers and supply much of our drinking water. They too can become polluted, for example, when weed killers used in people's gardens drain into the ground. Groundwater pollution is much less obvious than surface-water pollution, but is no less of a problem. In 1996, a study in Iowa in the United States found that over half the state's groundwater wells were contaminated with weed killers. You might think things would have improved since then, but, two decades on, all that's really changed is the name of the chemicals we're using. Today, numerous scientific studies are still finding weed killers in groundwater in worrying quantities: a 2012 study discovered glyphosate in 41 percent of 140 groundwater samples from Catalonia, Spain; scientific opinion differs on whether this is safe or not. [2]

Surface waters and groundwater are the two types of water resources that pollution affects. There are also two different ways in which pollution can occur. If pollution comes from a single location, such as a discharge pipe attached to a factory, it is known as point-source pollution . Other examples of point source pollution include an oil spill from a tanker, a discharge from a smoke stack (factory chimney), or someone pouring oil from their car down a drain. A great deal of water pollution happens not from one single source but from many different scattered sources. This is called nonpoint-source pollution .

When point-source pollution enters the environment, the place most affected is usually the area immediately around the source. For example, when a tanker accident occurs, the oil slick is concentrated around the tanker itself and, in the right ocean conditions, the pollution disperses the further away from the tanker you go. This is less likely to happen with nonpoint source pollution which, by definition, enters the environment from many different places at once.

Sometimes pollution that enters the environment in one place has an effect hundreds or even thousands of miles away. This is known as transboundary pollution . One example is the way radioactive waste travels through the oceans from nuclear reprocessing plants in England and France to nearby countries such as Ireland and Norway.

How do we know when water is polluted?

Some forms of water pollution are very obvious: everyone has seen TV news footage of oil slicks filmed from helicopters flying overhead. Water pollution is usually less obvious and much harder to detect than this. But how can we measure water pollution when we cannot see it? How do we even know it's there?

There are two main ways of measuring the quality of water. One is to take samples of the water and measure the concentrations of different chemicals that it contains. If the chemicals are dangerous or the concentrations are too great, we can regard the water as polluted. Measurements like this are known as chemical indicators of water quality. Another way to measure water quality involves examining the fish, insects, and other invertebrates that the water will support. If many different types of creatures can live in a river, the quality is likely to be very good; if the river supports no fish life at all, the quality is obviously much poorer. Measurements like this are called biological indicators of water quality.

What are the causes of water pollution?

Most water pollution doesn't begin in the water itself. Take the oceans: around 80 percent of ocean pollution enters our seas from the land. [16] Virtually any human activity can have an effect on the quality of our water environment. When farmers fertilize the fields, the chemicals they use are gradually washed by rain into the groundwater or surface waters nearby. Sometimes the causes of water pollution are quite surprising. Chemicals released by smokestacks (chimneys) can enter the atmosphere and then fall back to earth as rain, entering seas, rivers, and lakes and causing water pollution. That's called atmospheric deposition . Water pollution has many different causes and this is one of the reasons why it is such a difficult problem to solve.

With billions of people on the planet, disposing of sewage waste is a major problem. According to 2017 figures from the World Health Organization, some 2 billion people (about a quarter of the world's population) don't have access to safe drinking water or the most basic sanitation, 3.4 billion (60 people of the population) lack "safely managed" sanitation (unshared, with waste properly treated). Although there have been great improvements in securing access to clean water, relatively little, genuine progress has been made on improving global sanitation in the last decade. [20] Sewage disposal affects people's immediate environments and leads to water-related illnesses such as diarrhea that kills 525,000 children under five each year. [3] (Back in 2002, the World Health Organization estimated that water-related diseases could kill as many as 135 million people by 2020; in 2019, the WHO was still estimating the annual death toll from poor water and sanitation at over 800,000 people a year.) In developed countries, most people have flush toilets that take sewage waste quickly and hygienically away from their homes.

Yet the problem of sewage disposal does not end there. When you flush the toilet, the waste has to go somewhere and, even after it leaves the sewage treatment works, there is still waste to dispose of. Sometimes sewage waste is pumped untreated into the sea. Until the early 1990s, around 5 million tons of sewage was dumped by barge from New York City each year. [4] According to 2002 figures from the UK government's Department for the Environment, Food, and Rural Affairs (DEFRA), the sewers of Britain collect around 11 billion liters of waste water every day; there are still 31,000 sewage overflow pipes through which, in certain circumstances, such as heavy storms, raw sewage is pumped untreated into the sea. [5] The New River that crosses the border from Mexico into California once carried with it 20–25 million gallons (76–95 million liters) of raw sewage each day; a new waste water plant on the US-Mexico border, completed in 2007, substantially solved that problem. [6] Unfortunately, even in some of the richest nations, the practice of dumping sewage into the sea continues. In early 2012, it was reported that the tiny island of Guernsey (between Britain and France) has decided to continue dumping 16,000 tons of raw sewage into the sea each day.

In theory, sewage is a completely natural substance that should be broken down harmlessly in the environment: 90 percent of sewage is water. [7] In practice, sewage contains all kinds of other chemicals, from the pharmaceutical drugs people take to the paper , plastic , and other wastes they flush down their toilets. When people are sick with viruses, the sewage they produce carries those viruses into the environment. It is possible to catch illnesses such as hepatitis, typhoid, and cholera from river and sea water.

Photo: Nutrients make crops grow, but cause pollution when they seep into rivers and other watercourses. Photo courtesy of US Department of Agriculture (Flickr) .

Suitably treated and used in moderate quantities, sewage can be a fertilizer: it returns important nutrients to the environment, such as nitrogen and phosphorus, which plants and animals need for growth. The trouble is, sewage is often released in much greater quantities than the natural environment can cope with. Chemical fertilizers used by farmers also add nutrients to the soil, which drain into rivers and seas and add to the fertilizing effect of the sewage. Together, sewage and fertilizers can cause a massive increase in the growth of algae or plankton that overwhelms huge areas of oceans, lakes, or rivers. This is known as a harmful algal bloom (also known as an HAB or red tide, because it can turn the water red). It is harmful because it removes oxygen from the water that kills other forms of life, leading to what is known as a dead zone . The Gulf of Mexico has one of the world's most spectacular dead zones. Each summer, according to studies by the NOAA , it typically grows to an area of around 5500–6500 square miles (14,000–16,800 square kilometers), which is about the same size as the state of Connecticut. [21]

Waste water

A few statistics illustrate the scale of the problem that waste water (chemicals washed down drains and discharged from factories) can cause. Around half of all ocean pollution is caused by sewage and waste water. Each year, the world generates perhaps 5–10 billion tons of industrial waste, much of which is pumped untreated into rivers, oceans, and other waterways. [8] In the United States alone, around 400,000 factories take clean water from rivers, and many pump polluted waters back in their place. However, there have been major improvements in waste water treatment recently. Since 1970, in the United States, the Environmental Protection Agency (EPA) has invested about $70 billion in improving water treatment plants that, as of 2021, serve around 90 percent of the US population (compared to just 69 percent in 1972). However, another $271 billion is still needed to update and upgrade the system. [15]

Factories are point sources of water pollution, but quite a lot of water is polluted by ordinary people from nonpoint sources; this is how ordinary water becomes waste water in the first place. Virtually everyone pours chemicals of one sort or another down their drains or toilets. Even detergents used in washing machines and dishwashers eventually end up in our rivers and oceans. So do the pesticides we use on our gardens. A lot of toxic pollution also enters waste water from highway runoff . Highways are typically covered with a cocktail of toxic chemicals—everything from spilled fuel and brake fluids to bits of worn tires (themselves made from chemical additives) and exhaust emissions. When it rains, these chemicals wash into drains and rivers. It is not unusual for heavy summer rainstorms to wash toxic chemicals into rivers in such concentrations that they kill large numbers of fish overnight. It has been estimated that, in one year, the highway runoff from a single large city leaks as much oil into our water environment as a typical tanker spill. Some highway runoff runs away into drains; others can pollute groundwater or accumulate in the land next to a road, making it increasingly toxic as the years go by.

Chemical waste

Detergents are relatively mild substances. At the opposite end of the spectrum are highly toxic chemicals such as polychlorinated biphenyls (PCBs) . They were once widely used to manufacture electronic circuit boards , but their harmful effects have now been recognized and their use is highly restricted in many countries. Nevertheless, an estimated half million tons of PCBs were discharged into the environment during the 20th century. [9] In a classic example of transboundary pollution, traces of PCBs have even been found in birds and fish in the Arctic. They were carried there through the oceans, thousands of miles from where they originally entered the environment. Although PCBs are widely banned, their effects will be felt for many decades because they last a long time in the environment without breaking down.

Another kind of toxic pollution comes from heavy metals , such as lead, cadmium, and mercury. Lead was once commonly used in gasoline (petrol), though its use is now restricted in some countries. Mercury and cadmium are still used in batteries (though some brands now use other metals instead). Until recently, a highly toxic chemical called tributyltin (TBT) was used in paints to protect boats from the ravaging effects of the oceans. Ironically, however, TBT was gradually recognized as a pollutant: boats painted with it were doing as much damage to the oceans as the oceans were doing to the boats.

The best known example of heavy metal pollution in the oceans took place in 1938 when a Japanese factory discharged a significant amount of mercury metal into Minamata Bay, contaminating the fish stocks there. It took a decade for the problem to come to light. By that time, many local people had eaten the fish and around 2000 were poisoned. Hundreds of people were left dead or disabled. [10]

Radioactive waste

People view radioactive waste with great alarm—and for good reason. At high enough concentrations it can kill; in lower concentrations it can cause cancers and other illnesses. The biggest sources of radioactive pollution in Europe are two factories that reprocess waste fuel from nuclear power plants : Sellafield on the north-west coast of Britain and Cap La Hague on the north coast of France. Both discharge radioactive waste water into the sea, which ocean currents then carry around the world. Countries such as Norway, which lie downstream from Britain, receive significant doses of radioactive pollution from Sellafield. [19] The Norwegian government has repeatedly complained that Sellafield has increased radiation levels along its coast by 6–10 times. Both the Irish and Norwegian governments continue to press for the plant's closure. [11]

Oil pollution

Photo: Oil-tanker spills are the most spectacular forms of pollution and the ones that catch public attention, but only a fraction of all water pollution happens this way. Photo by Lamar Gore courtesy of US Fish & Wildlife Service Photo Library and US National Archive .

When we think of ocean pollution, huge black oil slicks often spring to mind, yet these spectacular accidents represent only a tiny fraction of all the pollution entering our oceans. Even considering oil by itself, tanker spills are not as significant as they might seem: only 12 percent of the oil that enters the oceans comes from tanker accidents; over 70 percent of oil pollution at sea comes from routine shipping and from the oil people pour down drains on land. [12] However, what makes tanker spills so destructive is the sheer quantity of oil they release at once — in other words, the concentration of oil they produce in one very localized part of the marine environment. The biggest oil spill in recent years (and the biggest ever spill in US waters) occurred when the tanker Exxon Valdez broke up in Prince William Sound in Alaska in 1989. Around 12 million gallons (44 million liters) of oil were released into the pristine wilderness—enough to fill your living room 800 times over! Estimates of the marine animals killed in the spill vary from approximately 1000 sea otters and 34,000 birds to as many as 2800 sea otters and 250,000 sea birds. Several billion salmon and herring eggs are also believed to have been destroyed. [13]

If you've ever taken part in a community beach clean, you'll know that plastic is far and away the most common substance that washes up with the waves. There are three reasons for this: plastic is one of the most common materials, used for making virtually every kind of manufactured object from clothing to automobile parts; plastic is light and floats easily so it can travel enormous distances across the oceans; most plastics are not biodegradable (they do not break down naturally in the environment), which means that things like plastic bottle tops can survive in the marine environment for a long time. (A plastic bottle can survive an estimated 450 years in the ocean and plastic fishing line can last up to 600 years.)

While plastics are not toxic in quite the same way as poisonous chemicals, they nevertheless present a major hazard to seabirds, fish, and other marine creatures. For example, plastic fishing lines and other debris can strangle or choke fish. (This is sometimes called ghost fishing .) About half of all the world's seabird species are known to have eaten plastic residues. In one study of 450 shearwaters in the North Pacific, over 80 percent of the birds were found to contain plastic residues in their stomachs. In the early 1990s, marine scientist Tim Benton collected debris from a 2km (1.5 mile) length of beach in the remote Pitcairn islands in the South Pacific. His study recorded approximately a thousand pieces of garbage including 268 pieces of plastic, 71 plastic bottles, and two dolls heads. [14]

Alien species

Most people's idea of water pollution involves things like sewage, toxic metals, or oil slicks, but pollution can be biological as well as chemical. In some parts of the world, alien species are a major problem. Alien species (sometimes known as invasive species ) are animals or plants from one region that have been introduced into a different ecosystem where they do not belong. Outside their normal environment, they have no natural predators, so they rapidly run wild, crowding out the usual animals or plants that thrive there. Common examples of alien species include zebra mussels in the Great Lakes of the USA, which were carried there from Europe by ballast water (waste water flushed from ships ). The Mediterranean Sea has been invaded by a kind of alien algae called Caulerpa taxifolia . In the Black Sea, an alien jellyfish called Mnemiopsis leidyi reduced fish stocks by 90 percent after arriving in ballast water. In San Francisco Bay, Asian clams called Potamocorbula amurensis, also introduced by ballast water, have dramatically altered the ecosystem. In 1999, Cornell University's David Pimentel estimated that alien invaders like this cost the US economy $123 billion a year; in 2014, the European Commission put the cost to Europe at €12 billion a year and "growing all the time. [18]

Other forms of pollution

These are the most common forms of pollution—but by no means the only ones. Heat or thermal pollution from factories and power plants also causes problems in rivers. By raising the temperature, it reduces the amount of oxygen dissolved in the water, thus also reducing the level of aquatic life that the river can support. Another type of pollution involves the disruption of sediments (fine-grained powders) that flow from rivers into the sea. Dams built for hydroelectric power or water reservoirs can reduce the sediment flow. This reduces the formation of beaches, increases coastal erosion (the natural destruction of cliffs by the sea), and reduces the flow of nutrients from rivers into seas (potentially reducing coastal fish stocks). Increased sediments can also present a problem. During construction work, soil, rock, and other fine powders sometimes enters nearby rivers in large quantities, causing it to become turbid (muddy or silted). The extra sediment can block the gills of fish, effectively suffocating them. Construction firms often now take precautions to prevent this kind of pollution from happening.

What are the effects of water pollution?

Some people believe pollution is an inescapable result of human activity: they argue that if we want to have factories, cities, ships, cars, oil, and coastal resorts, some degree of pollution is almost certain to result. In other words, pollution is a necessary evil that people must put up with if they want to make progress. Fortunately, not everyone agrees with this view. One reason people have woken up to the problem of pollution is that it brings costs of its own that undermine any economic benefits that come about by polluting.

Take oil spills, for example. They can happen if tankers are too poorly built to survive accidents at sea. But the economic benefit of compromising on tanker quality brings an economic cost when an oil spill occurs. The oil can wash up on nearby beaches, devastate the ecosystem, and severely affect tourism. The main problem is that the people who bear the cost of the spill (typically a small coastal community) are not the people who caused the problem in the first place (the people who operate the tanker). Yet, arguably, everyone who puts gasoline (petrol) into their car—or uses almost any kind of petroleum-fueled transport—contributes to the problem in some way. So oil spills are a problem for everyone, not just people who live by the coast and tanker operates.

Sewage is another good example of how pollution can affect us all. Sewage discharged into coastal waters can wash up on beaches and cause a health hazard. People who bathe or surf in the water can fall ill if they swallow polluted water—yet sewage can have other harmful effects too: it can poison shellfish (such as cockles and mussels) that grow near the shore. People who eat poisoned shellfish risk suffering from an acute—and sometimes fatal—illness called paralytic shellfish poisoning. Shellfish is no longer caught along many shores because it is simply too polluted with sewage or toxic chemical wastes that have discharged from the land nearby.

Pollution matters because it harms the environment on which people depend. The environment is not something distant and separate from our lives. It's not a pretty shoreline hundreds of miles from our homes or a wilderness landscape that we see only on TV. The environment is everything that surrounds us that gives us life and health. Destroying the environment ultimately reduces the quality of our own lives—and that, most selfishly, is why pollution should matter to all of us.

How can we stop water pollution?

There is no easy way to solve water pollution; if there were, it wouldn't be so much of a problem. Broadly speaking, there are three different things that can help to tackle the problem—education, laws, and economics—and they work together as a team.

Making people aware of the problem is the first step to solving it. In the early 1990s, when surfers in Britain grew tired of catching illnesses from water polluted with sewage, they formed a group called Surfers Against Sewage to force governments and water companies to clean up their act. People who've grown tired of walking the world's polluted beaches often band together to organize community beach-cleaning sessions. Anglers who no longer catch so many fish have campaigned for tougher penalties against factories that pour pollution into our rivers. Greater public awareness can make a positive difference.

One of the biggest problems with water pollution is its transboundary nature. Many rivers cross countries, while seas span whole continents. Pollution discharged by factories in one country with poor environmental standards can cause problems in neighboring nations, even when they have tougher laws and higher standards. Environmental laws can make it tougher for people to pollute, but to be really effective they have to operate across national and international borders. This is why we have international laws governing the oceans, such as the 1982 UN Convention on the Law of the Sea (signed by over 120 nations), the 1972 London (Dumping) Convention , the 1978 MARPOL International Convention for the Prevention of Pollution from Ships , and the 1998 OSPAR Convention for the Protection of the Marine Environment of the North East Atlantic . The European Union has water-protection laws (known as directives) that apply to all of its member states. They include the 1976 Bathing Water Directive (updated 2006), which seeks to ensure the quality of the waters that people use for recreation. Most countries also have their own water pollution laws. In the United States, for example, there is the 1972 Clean Water Act and the 1974 Safe Drinking Water Act .

Most environmental experts agree that the best way to tackle pollution is through something called the polluter pays principle . This means that whoever causes pollution should have to pay to clean it up, one way or another. Polluter pays can operate in all kinds of ways. It could mean that tanker owners should have to take out insurance that covers the cost of oil spill cleanups, for example. It could also mean that shoppers should have to pay for their plastic grocery bags, as is now common in Ireland, to encourage recycling and minimize waste. Or it could mean that factories that use rivers must have their water inlet pipes downstream of their effluent outflow pipes, so if they cause pollution they themselves are the first people to suffer. Ultimately, the polluter pays principle is designed to deter people from polluting by making it less expensive for them to behave in an environmentally responsible way.

Our clean future

Life is ultimately about choices—and so is pollution. We can live with sewage-strewn beaches, dead rivers, and fish that are too poisonous to eat. Or we can work together to keep the environment clean so the plants, animals, and people who depend on it remain healthy. We can take individual action to help reduce water pollution, for example, by using environmentally friendly detergents , not pouring oil down drains, reducing pesticides, and so on. We can take community action too, by helping out on beach cleans or litter picks to keep our rivers and seas that little bit cleaner. And we can take action as countries and continents to pass laws that will make pollution harder and the world less polluted. Working together, we can make pollution less of a problem—and the world a better place.

If you liked this article...

Don't want to read our articles try listening instead, find out more, on this site.

• Air pollution (introduction)
• Climate change and global warming
• Environmentalism (introduction)
• Land pollution
• Organic food and farming

For older readers

For younger readers.

• Earth Matters by Lynn Dicks et al. Dorling Kindersley, 2008: A more general guide to problems Earth faces, with each major biome explored separately. In case you're interested, I contributed the polar regions chapter. The book is mostly a simple read and probably suitable for 7–10 (and maybe 9–12).

Selected news articles

Water pollution videos, notes and references.

Text copyright © Chris Woodford 2006, 2022. All rights reserved. Full copyright notice and terms of use .

This article was originally written for the UK Rivers Network and first published on their website in April 2006. It is revised and updated every year.

Rate this page

Tell your friends, cite this page, more to explore on our website....

• Get the book
• Send feedback

River Water Pollution and Solutions

By Emma Cheriegate, Staff Researcher & Writer at Save the Water™ | November 27, 2021

Water’s nickname is the “ universal solvent ” due to its capacity to dissolve more material than any other liquid on our planet. This ability makes water easily polluted, which poses a significant risk to our ecosystems and our drinking water. In the United States alone, almost half of our rivers and streams are not safe enough for swimming, fishing, or drinking . But you can learn about river pollution and help with solutions. 

We get most of our water from rivers . As worldwide populations increase, so does pollution. Primary water pollution sources are farming, industrial factories, and towns/cities.

From the Nile in Africa to the Amazon in South America, rivers worldwide face these same pollution issues. So how is each community responding, and what can we learn from one another? To understand this, we must first look at the similarities and differences in causes of river water pollution.

What Causes River Pollution?

Riverine pollution refers to the pollution of river water from human activity.  Rivers naturally transport organic and inorganic pollutants. Some examples of river pollution causes include:

• Nutrients (such as phosphorus and nitrate)
• Chemicals (such as heavy metals)
• Groundwater pollutants (from pesticide use in agriculture)
• Oil spills or wastewater seeping into the ground

Each region experiences one or more of these forms of pollution. In Brazil , the main contributors to Amazon River pollution are mining, deforestation, and dam construction. The United States’ Ohio River receives high levels of nitrate concentration from steel factories. The world’s longest river, the Nile River, stretches 4,132 miles , and its basin affects 11 different countries, including Ethiopia. The Nile’s largest threats are contamination from human waste and new dam construction in Ethiopia. 

Increased water pollution starts geopolitical conflicts . Rivers often pass through multiple boundary lines that separate counties, states, and countries. These regions often have contrasting laws and regulations on water pollution, which makes a collective solution difficult. This difficulty can also allow one group to contribute more pollution to water that flows down into another group’s region. 

Furthermore, a state or country such as Ethiopia might decide to construct a dam , preventing water from reaching another area such as Egypt. This causes resource disparity, as some regions will naturally receive more water than others. In sum, many communities suffer both environmental and economic consequences of water pollution.

Diverse Solutions to River Pollution

Many people are trying to stop river pollution. People dump trash and plastic into the Nile River . To counteract this, activist groups conduct clean-ups and training to raise awareness and decrease plastic use. Also, the activists galvanize corporations to construct boats to clean up. The United Nations supports one of these initiatives. 

People are also pushing back to protect the Amazon River. Similar to the people dependent on the Nile, groups advocate for sustainable management and accountability for the Amazon River. In 2018, the World Wide Fund for Nature published a comprehensive report to tackle the pollution caused by mining . The publication makes recommendations to governments, buyers, and gold and mercury retailers for better, safer practices.

In contrast, the United States emphasizes legislation. These environmental regulations aim to control and limit the amount of toxic river pollution. In addition to regulatory action, some researchers suggest wetland restoration to reduce excess nutrients such as nitrate and phosphorus. 

How You Can Help Reduce River Pollution

Solving river pollution can feel overwhelming. Thankfully, you can help :

• Dispose of hazardous materials safely by contacting your county’s waste management department in the United States, as they usually accept some hazardous waste.
• Don’t pour cleaners, paints, or grease down your drain.
• Stop using fertilizers and pesticides. These chemicals pollute rivers.
• Attend clean-ups. Organizations often plan clean-up events, so find one near you!
• Donate to Save the Water TM .
• Don’t flush pills down the drain.

You May Also Like

Contamination From Nuclear Power Plant Threatens Major South Florida Aquifer

Water Quality and Your Wallet: Economic Impacts of Water Contamination

• Privacy Overview
• Strictly Necessary Cookies

This website uses cookies so that we can provide you with the best user experience possible. Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful.

You can read our Privacy Policy

Strictly Necessary Cookie should be enabled at all times so that we can save your preferences for cookie settings.

If you disable this cookie, we will not be able to save your preferences. This means that every time you visit this website you will need to enable or disable cookies again.

National Rivers and Streams Assessment:

The third collaborative survey.

This report summarizes the National Rivers and Streams Assessment’s key findings. EPA and its state and tribal partners conducted the survey in 2018-19.

Photo: A fast-flowing alpine river. EPA .

Draft copy for peer review.

Introduction

Clean and healthy rivers and streams enhance the quality of our lives. They supply our drinking water, irrigate our crops, provide highways for shipping, and offer us recreation. They support aquatic life and provide shelter, food, and habitat for birds and wildlife. Rivers and streams shape America’s landscape. They are the land’s vast, interconnected circulatory system, carrying water from the mountains to the sea.

The National Rivers and Streams Assessment (NRSA) is an EPA, state, and tribal partnership to assess the condition of rivers and streams across the U.S. (see report acknowledgments for a list of partners). The National Rivers and Streams Assessment: The Third Collaborative Survey presents the results of the 2018-19 survey of perennial rivers and streams in the conterminous United States. The first survey took place in 2008-09, with the second in 2013-14. A pilot study of streams (the Wadeable Streams Assessment ) was conducted between 2000 and 2004.

During spring and summer of 2018 and 2019, 61 field crews sampled 1,851 sites, using standardized sampling procedures to collect data on biological, chemical, physical, and human health indicators. The measured values were compared to benchmarks developed specifically for NRSA, to EPA recommended water quality criteria, or to EPA fish tissue screening levels to assess river and stream condition.

The NRSA is designed to answer the following questions about rivers and streams across the United States:

• What percentage of rivers and streams support healthy ecological communities and recreation?
• What are the most common problems?
• Are conditions improving or getting worse?
• Are investments in water quality focused appropriately?

The NRSA is one of four statistical surveys that make up the National Aquatic Resource Surveys (NARS) program, the first program to assess the condition of all waters nationally over time. The NRSA can help stakeholders plan for the protection and restoration of rivers and streams across the United States. For more information, see the NARS history web page .

In addition to examining the health of rivers and streams on a national scale, the NRSA is designed to provide statistically valid results on the condition of broad regions and other subpopulations.

This report focuses on results at the national scale, comparing the 2018-19 condition of perennial rivers and streams to that from the earlier NRSA studies. Regional highlights are also provided.

The report also summarizes results for an additional study of rivers conducted during NRSA 2018-19 for the fish tissue contaminants mercury, polychlorinated biphenyls (PCBs), and per- and polyfluoroalkyl substances (PFAS) (with a focus on perfluorooctane sulfonate (PFOS)). (See Fish Tissue Contamination in Rivers below.) Detailed results are available on EPA’s fish tissue study page.

Penns Creek, Centre County, Pennsylvania. EPA .

Results from the NRSA can help us better understand the condition of rivers and streams in the United States, some of the stressors affecting them, and how stressors relate to local conditions. While this report analyzes associations between biological indicators and stressors, it does not establish a cause-and-effect relationship between them. This report describes changes in condition from 2008-09 to 2018-19; data from future assessments will help determine whether these changes represent a trend or are the result of natural variability.

KEY FINDINGS ON 2018-19 CONDITION

Following standard practices (described in the Assessment Benchmarks, Criteria, and Screening Levels section), EPA analysts classified results for most indicators as good, fair, or poor. For a few indicators, the results instead show whether chemicals were detected or whether values exceeded a benchmark, criterion, or screening level.

Many of the measures included in the NRSA are natural components of river and stream ecosystems. For example, some level of nutrients like phosphorus is necessary to support stream communities such as fish, and algal toxins like microcystins occur naturally. At elevated levels, however, these substances can cause harm to biological communities or human health.

Healthy habitat occurred in over half of our river and stream miles.

• Physical habitat indicator scores revealed that 68% of river and stream miles were rated good for in-stream fish habitat, 57% scored good for streambed sediment levels, and 56% of river and stream miles had good ratings for riparian vegetation (vegetation on or adjacent to the river or stream banks).
• However, 64% of river and stream miles had moderate or high levels of riparian disturbance.

Less than one-third of our river and stream miles (28%) had healthy biological communities, based on an analysis of benthic macroinvertebrate communities.

• Biological condition was based on the abundance and diversity of benthic macroinvertebrates (bottom-dwelling invertebrates such as dragonfly and stonefly larvae, snails, worms, and beetles).
• Close to half of river and stream miles (47%) were in poor condition.

Just over one-third (35%) of river and stream miles had healthy fish communities.

• Fish community health was based on fish abundance and diversity.
• Sixteen percent of river and stream miles were not assessed for fish. The remainder (49%) were in fair or poor condition.

Nutrients (phosphorus and nitrogen) were the most widespread stressors.

• Forty-two percent of the nation’s river and stream miles were in poor condition, with elevated levels of phosphorus, and 44% were in poor condition for nitrogen.
• Poor biological condition was more likely when rivers and streams were in poor condition for nutrients.

Reducing nutrient pollution could improve biological condition.

• NRSA analyses indicated that approximately 20% of the river and stream miles in poor biological condition could be improved if nutrient condition changed from poor to fair or good. The level of improvement was estimated to be similar regardless of nutrient and biological indicator analyzed.

Field crew members measuring physical stream characteristics. EPA.

Bacteria exceeded EPA’s recreational benchmark in 20% of river and stream miles.

• Enterococci, bacteria that indicate fecal contamination, were above EPA’s benchmark in 20% of river and stream miles.
• Swimming and recreating in water contaminated with pathogens could make people ill.

Algal toxins were present, but at very low levels, with minimal recreational human health concerns.

• Microcystins and cylindrospermopsin were detected in 9% and 10% of river and stream miles, respectively, but did not exceed EPA recommended criteria in any samples.

Contaminants were present in all fish tissue, but risk varied by contaminant and fish consumption levels. In samples composed of fillet tissue from multiple fish, concentrations exceeded screening levels as follows (as a percentage of the 41,099 river miles comprising the sampled population):

• Mercury: 26%.
• Total PCBs: 45% for general fish consumers, 74% for high-frequency fish consumers.

Additionally, PFOS was detected in 91% of the 290 fish fillet composite samples analyzed for NRSA 2018-19. EPA is not currently comparing PFOS concentrations in fish to screening levels because the toxicity assessment used to calculate screening levels is draft. When the assessment is final, EPA intends to update the PFOS information provided in this report to include screening level exceedances.

Field crew member entering observations into a tablet. University of Houston-Clear Lake.

KEY FINDINGS ON CHANGES FROM 2013-14 TO 2018-19

For the benthic macroinvertebrate community indicator, little changed between surveys nationally.

For fish community, there were statistically significant changes in condition.

• River and stream miles in good condition increased from 25% to 35%.

Significant changes occurred for some physical habitat measures.

• The percentage of river and stream miles in good condition increased for riparian disturbance by 9 percentage points between 2013-14 and 2018-19.
• The percentage of river and stream miles in good condition also increased for streambed sediments by 6 percentage points.
• For in-stream fish habitat, the percentage in poor condition decreased by 4 percentage points.

Two human health indicators showed improvement.

• There was a significant decrease (13 percentage points) in river and stream miles exceeding EPA’s benchmark for enterococci in recreational waters.
• There was also a significant decrease (6.7 percentage points) in river miles containing fish with detectable levels of PFOS.

For most water chemistry parameters (except phosphorus), there was little change between surveys at the national level.

• Phosphorus showed a significant increase in river and stream miles in good condition (16 percentage points) and a significant decrease in river and stream miles in poor condition (18 percentage points).

NRSA DASHBOARD

EPA has developed an interactive dashboard to accompany this report. It contains full regional results and allows comparisons between different subpopulations of rivers and streams (e.g., EPA regions and river basins).

Users can also get to the dashboard by following the link at the bottom of each graph in this report. Those links will bring users to a customized page with regional data for each indicator. Users can then navigate to other dashboard views using the "Condition Estimate" dropdown and other dashboard controls.

HOW CAN I FIND OUT MORE?

Read the other sections of this report for more detail on the results for each indicator, including data from 2008-09. Explore the interactive dashboard to compare national and regional conditions. See the NRSA 2018-19 Technical Support Document (U.S. EPA 2023) for technical details on the survey design and data analyses that underpin the findings in this report. Additional information on the NRSA and the previous reports is available on EPA’s NRSA home page . Readers may want to visit the main NARS website periodically to view additional products using the science and data from the assessments, such as published scientific research and results for other surveys in the NARS program.

Eastern dobsonfly ( Corydalus cornutus ), a type of benthic macroinvertebrate. connor_elliot. iNaturalist , CC BY-NC 4.0 . Cropped.

This section provides a brief background on the survey methodology. For details on survey design, field methods, and quality assurance plans, see EPA’s NARS manuals page . For additional details on the NRSA survey design, see EPA’s design documents page .

CHOOSING INDICATORS

EPA used 16 indicators to assess the biological, chemical, and physical condition of rivers and streams, as well as characteristics that pose risks to human health. Although there are others that could be used to describe river and stream condition, EPA has determined that these indicators align with the survey goals described earlier and are representative at a national scale. The NRSA also included collection of some data, such as periphyton (microscopic organisms such as algae and bacteria), for research purposes. Results for research indicators are not included in this report but will be posted on the NRSA website as they become available. For this report, EPA grouped indicators into four categories.

The survey included two biological indicators: Benthic macroinvertebrate community | Fish community

There were four chemical indicators: Nutrients (total nitrogen and total phosphorus) | Acidification | Salinity

EPA measured four physical indicators: In-stream fish habitat | Riparian disturbance | Riparian vegetation cover | Streambed sediments

Lastly, the survey tracked six human health indicators: Algal toxins (microcystins and cylindrospermopsin) | Enterococci bacteria | Fish tissue contaminants ( mercury in plugs ; mercury, PCBs, and PFAS in fillet composite samples)

SELECTING RIVERS AND STREAMS

EPA used a statistical sampling approach to select river and stream sites for this assessment, to ensure that survey results were unbiased. For more information on statistical surveys, see What Are Probability Surveys? and Selecting a Sampling Design . The target population for the NRSA was the set of rivers and streams in the conterminous U.S. meeting the definition in the box below.

How Were Rivers and Streams Defined for This Survey?

The target population of the survey includes all perennial streams and rivers, from the smallest headwater streams to the largest rivers, including those that are tidally influenced but still freshwater.

Tidally influenced rivers and streams with salinity of 0.5 parts per thousand or more are considered estuaries and are addressed in the National Coastal Condition Assessment. Very slow-moving segments of rivers created by dams, with a residence time greater than seven days, were excluded from the NRSA because they are more like lakes. These systems are included in the National Lakes Assessment.

The 1,851 river and stream sites were identified using a stratified random sampling design. This approach is also used in other environmental, social science, and health fields to determine the status of populations, whether ecological, human, or other. Using this method, rivers and streams are categorized into groups (for instance, by size or location), and every river and stream in the target population has a known probability of being selected for sampling. The NRSA 2018-19 design was stratified by state, stream order (stream size), and broad ecoregions to ensure adequate geographic distribution of sites.

The statistical design of the survey allows EPA to extrapolate the results from the 1,851 river and stream sites sampled to the approximately 1,543,290 river and stream miles meeting the definition in the box above. For example, if the condition is described as poor for 10% of river and stream miles nationally, this means that the number of miles estimated to be degraded for that indicator is 154,329.

To produce the results for each indicator, EPA assigned each randomly selected site a weight based upon the total number of miles that the site represented. This enabled EPA to estimate the proportion of all miles in each condition category (e.g., good, fair, or poor). See the appendix and technical support document for details.

When designing the survey, EPA considered the number of river and stream sites that should be sampled. The greater the number of sites sampled, the more confidence in the results. The 1,851 sites sampled in NRSA 2018-19 allow EPA to determine the percentage of miles in each condition category within a margin of error of ±5%, with 95% confidence at the national scale. See Exhibit 1 for a map of the 2018-19 sampling sites and their distribution across ecoregions.

Map of NRSA 2018-19 Sampling Sites in Each Ecoregion

FIELD SAMPLING

Field crew members electrofishing to collect fish for fish community and fish tissue analyses. EPA.

To ensure consistency in collection procedures and to assure the quality of resulting data, field crews participated in training, used standardized field methods, and followed strict quality control protocols (visit NRSA manuals for details, including diagrams of sampling locations at each site).

Field protocols used in NRSA were designed to collect data relevant to biological condition and key stressors. A three- or four-person field crew spent a full day sampling each site under normal flow conditions. Crews measured out and marked the stretch of river or stream to be sampled and 11 transects to guide data collection (see EPA’s Rivers and Streams Field Methods for more on sampling). At each site, crews collected water and fish tissue samples for chemical analysis, collected macroinvertebrate samples, and identified fish species found at the site. Crews also recorded visual observations, including data on the characteristics of each stream and the riparian area.

ASSESSMENT BENCHMARKS, CRITERIA, AND SCREENING LEVELS

NRSA analysts reviewed the raw data for each indicator independently and assigned the values in each dataset to categories (for example, "above criterion" or "at or below criterion"; good, fair, or poor). To assign the appropriate condition category, EPA used two broad types of assessment benchmarks for NRSA 2018-19.

The first type consisted of fixed benchmarks applied nationally based on values in the peer-reviewed scientific literature, EPA published values, or EPA-derived screening levels. For example, EPA’s recommended water quality criteria were used nationally to classify rivers and streams as above or below a criterion or benchmark for microcystins, cylindrospermopsin, enterococci, and mercury. Similarly, EPA fish tissue screening levels, developed using information on human health risk and fish consumption rates, were applied for PCBs.

The second type consisted of NRSA-specific ecoregional benchmarks based on the distribution of indicator values from a set of river and stream reference sites . EPA chose this regional benchmark approach because river and stream characteristics in different ecoregions vary due to climate, geology, and ecology, as well as human disturbance. Numerous scientific studies described in the technical support document, as well as peer reviews of other NRSA and NARS documents, support the use of regional benchmarks to evaluate the condition of rivers and streams and other types of waters.

The technical support document provides indicator-specific details about benchmarks, criteria, and screening levels, and it describes reference site selection (U.S. EPA 2023).

The steps below describe EPA’s process for setting regional benchmarks and determining condition. Exhibits 2-5 provide an example of how the total nitrogen benchmark was derived for the Coastal Plains ecoregion. The process for other indicators and ecoregions was similar, resulting in regionally relevant benchmarks for each of the other ecoregions assessed. EPA developed these benchmarks during earlier NRSA surveys. For NRSA 2018-19, EPA reviewed the new data to see if recalculation would improve the statistical robustness of the benchmarks but ultimately determined that revisions to the benchmarks were unnecessary.

1. Screen River and Stream Sites to Identify Reference Sites. First, EPA analysts evaluated information from the randomly selected rivers and streams and a smaller set of hand-picked sites thought to have low levels of human disturbance. EPA scientists evaluated these sites by considering reference screening factors such as chloride and sulfate concentrations and land use data. Rivers and streams that passed screening were considered less disturbed than others and were used in establishing the reference distribution. Exhibit 2 shows a map of reference sites in the Coastal Plains ecoregion.

Reference Sites in the Coastal Plains Ecoregion

In the exhibit below, each dot indicates the observed nitrogen level (in parts per million, or ppm) at one of the reference sites. Many of the dots overlap because they have similar values.

Nitrogen Values at Coastal Plains Reference Sites

2. Calculate Condition Benchmarks Using Reference Data. EPA then used the 75th and 95th percentiles of the reference site distribution for nitrogen to set the benchmarks for the condition categories (see the exhibit below).

Nitrogen Condition Benchmarks in the Coastal Plains Ecoregion

3. Assign Condition Categories to River and Stream Sites. Using those regional benchmarks, EPA assigned the nitrogen condition (good/fair/poor) to each of the sites that were randomly sampled as part of NRSA 2018-19. As an example, the exhibit below shows the nitrogen value for each river or stream sampled in the Coastal Plains ecoregion and the condition category in which it (and the site) falls.

Nitrogen Values at Coastal Plains Sites Randomly Sampled as Part of the NRSA

The NRSA assessment benchmarks have no legal effect and are not equivalent to individual state water quality standards. NRSA condition categories also may not correspond to the categories states and tribes use when they assess water quality relative to their specific water quality standards under the Clean Water Act. For example, a rating of poor condition under NRSA does not necessarily mean a site is "impaired" as defined by state and tribal water quality standards assessment protocols. For additional information on state-specific and local water quality data and assessments, visit EPA’s How’s My Waterway application. To learn more about water quality standards, visit the EPA’s Water Quality Standards Academy .

National Results for Biological, Chemical, and Physical Indicators

This chapter presents information on each of the biological, chemical, and physical NRSA indicators. Each indicator section contains three parts: a brief explanation of why the indicator matters, results from the 2018-19 survey, and changes in condition. To download raw data from the survey, visit EPA’s NARS data page . Note that the results reported here for 2008-09 and 2013-14 will differ from those reported in the previous reports due to statistical adjustments that allowed EPA to present results for the full target population (see the appendix). All comparisons between earlier NRSA reports and NRSA 2018-19 should be made using the new information presented in the 2018-19 report and dashboard.

The graphs below show the estimated proportion of river and stream miles in each condition class, as well as the proportion of miles not assessed (for instance, if fish were not caught). Each estimate is accompanied by a 95% confidence interval (shown by the thin line at the end of each bar) that conveys the level of certainty in the estimate. The technical support document (U.S. EPA 2023) explains the underlying assumptions and analysis.

The graphs present national data, but each graph contains a customized link to ecoregional data in the dashboard. Additional ecoregional highlights are included in the text for many indicators. Visit EPA’s NARS ecoregions page for maps and characteristics of each ecoregion.

BIOLOGICAL INDICATORS

The biology of a water body (the biological condition) can be characterized by the presence, number, and diversity of macroinvertebrates, fish, and other organisms. Together, they provide information about the health and productivity of the ecosystem. EPA chose both benthic macroinvertebrates and fish as indicators because they are sensitive to human-caused disturbances and can have different sensitivities to the same stressor. Assessing multiple communities provides a more complete assessment of biological condition.

Benthic Macroinvertebrate Community

Insect larvae such as this net-spinning caddisfly spend most of their lives on river and stream bottoms, emerging only as they become adults. Emilio Concari. iNaturalist , CC BY-NC 4.0 .

Benthic macroinvertebrates include aquatic insect larvae and nymphs, small aquatic mollusks, crustaceans such as crayfish, aquatic worms, and leeches. They live among the rocks, sediments, and vegetation at the river or stream floor. These organisms were selected as indicators of biological condition because they spend most or all of their lives in water and their community structure responds to human disturbance. Given their broad geographic distribution, abundance, and food web connections, they serve as good indicators of the biological quality of rivers and streams.

The benthic macroinvertebrate indicator uses an index that relies on ecological traits and classification of organisms into related groups (taxa) such as families or genera. The index combines six different aspects of macroinvertebrate community structure into one score: taxonomic composition , taxonomic diversity , feeding groups , habits/ habitats , taxonomic richness , and pollution tolerance . The measures chosen for each of these aspects vary between ecoregions and are described in the technical support document.

Less than a third, 28%, of U.S. river and stream miles were rated good for benthic macroinvertebrates. The assessment also showed that 25% of river and stream miles were in fair condition and 47% were in poor condition. By ecoregion, good condition ranged from 9% in the Coastal Plains to 61% in the Western Mountains.

No statistically significant changes occurred nationally between 2013-14 and 2018-19. However, a number of statistically significant changes in condition were observed for several survey subpopulations. In the Northern Plains, good condition declined significantly, by 13 percentage points, while in the Western Mountains it increased by 12 percentage points.

Fish Community

Field crew members count and identify fish (such as this sunfish) caught at the site. Most are then released. EPA .

Evaluation of fish diversity and abundance is an important component of water monitoring. Fish are sensitive indicators of physical and chemical habitat degradation, environmental contamination, migration barriers, and overall ecosystem productivity. They need plants, insects, and benthic macroinvertebrates to eat; in-stream and streambank cover for shelter; high-quality streambed substrate conditions for spawning; and overhanging vegetation to shade and cool the water.

To evaluate fish community condition, EPA biologists developed a fish community index using an approach similar to that used to develop the benthic macroinvertebrate index. The index is based on a variety of metrics, including taxonomic richness, taxonomic composition, pollution tolerance, habitat and feeding groups, spawning habits, the number and percentage of taxa that are migratory, and the percentage of taxa that are native. The measures chosen for each of these aspects vary between ecoregions and are described in the technical support document.

As shown below, 35% of U.S. river and stream miles were rated good for the fish community indicator. The assessment also showed that 19% of river and stream miles were in fair condition and 29% were in poor condition. Poor condition ranged from a low of 17% in the Upper Midwest to 50% in the Coastal Plains.

Statistically significant changes occurred nationally in good, fair, and poor condition. Good condition increased by 10.6 percentage points, while poor condition decreased by 10 points. Statistically significant changes in condition were also observed for survey subpopulations.

CHEMICAL INDICATORS

Four chemical indicators were assessed as part of NRSA: nutrients (total phosphorus, total nitrogen), salinity, and acidification. These four indicators were selected because of national or regional interest in the extent to which they might be affecting the quality of the biological communities in rivers and streams. EPA compared sample results either to regional benchmarks developed from a set of reference sites in each ecoregion (for nutrients) or to nationally consistent literature-based benchmarks (for acidification and salinity).

For this assessment, EPA evaluated total phosphorus and total nitrogen, both of which are critical nutrients required for all aquatic life. In appropriate quantities, these nutrients power the primary algal production necessary to support river and stream food webs. Phosphorus and nitrogen are linked; they jointly influence both the concentrations of algae in rivers and streams and the clarity of water. In many rivers and streams, phosphorus is considered the limiting nutrient, meaning that the available quantity of this nutrient controls the pace at which algae are produced. This also means that modest increases in available phosphorus can cause rapid increases in algal growth. The naturally occurring levels of these indicators vary regionally, as does their relationship with turbidity and algal growth. For phosphorus and nitrogen, rivers and streams were assessed relative to NRSA-specific regional benchmarks.

Nutrient levels in parts of the Colorado River have caused extensive algal growth, making the river appear green. Navajo Bridge, Arizona. Mobilus in Mobili. Flickr , CC BY-SA 2.0 .

Common sources of excess nutrients include sewage treatment plant discharge, septic systems, fertilizer used on lawns and farms, and animal waste. For more information, see EPA’s nitrogen and phosphorus indicator pages.

More river and stream miles were in poor condition for nitrogen (44%) than in good condition (32%). Good condition ranged from 7% of river and stream miles in the Temperate Plains to 67% in the Western Mountains.

For more details, download the data for this chart, or visit the NLA dashboards for ecoregional data on nitrogen (total).

Phosphorus condition was similar to nitrogen condition, with 42% of river and stream miles rated poor and 36% rated good.

For more details, download the data for this chart, or visit the NLA dashboards for ecoregional data on phosphorus (total).

No statistically significant change was noted for nitrogen nationally between 2013-14 and 2018-19. There were several subpopulations with significant changes in stream condition for total nitrogen. For example, between 2013-14 and 2018-19, results from the Temperate Plains ecoregion indicated a decline in good condition of 11 percentage points.

Nationally, between 2013-14 and 2018-19, the percentage of river and stream miles in good condition for total phosphorus increased significantly, by 16 percentage points, while the percentage of river and stream miles in poor condition decreased significantly, by 17.7 percentage points. As with total nitrogen, statistically significant changes in condition were observed for several survey subpopulations. Of note, seven of the nine ecoregions showed statistically significant improvements in good condition. Future NRSAs will help EPA determine whether such changes are a sustained trend or natural fluctuation.

Acidification

Stream impacted by acid mine drainage from a mid-Atlantic abandoned coal mine. EPA .

Acid rain and acid mine drainage can change the pH of rivers and streams, impacting fish and other aquatic life. High acidity can, for instance, hinder shell formation in mollusks and crustaceans. EPA uses acid-neutralizing capacity (ANC) to indicate sensitivity to changes in pH for the NRSA. ANC is determined by the soil and underlying geology of the surrounding watershed. Rivers and streams with high levels of dissolved bicarbonate ions (e.g., in limestone watersheds) are able to neutralize acid deposition and buffer the effects of acid rain. Conversely, watersheds that are rich in granites and sandstones contain fewer acid-neutralizing ions and have low ANC; these systems have a predisposition to acidification.

Most aquatic organisms function best when pH is 6.5 to 8.5. Sufficient ANC in surface waters will buffer acid rain and prevent pH levels from straying outside this range. In naturally acidic systems, the ANC may be quite low, but the presence of natural organic compounds in the form of dissolved organic carbon (DOC) can mitigate the effects of pH fluctuations.

To classify rivers and streams for acidification, EPA considered ANC measurements along with DOC concentrations. Condition categories used in all ecoregions are defined below:

• Good: Non-acidic sites and naturally acidic sites. Naturally acidic sites include "blackwater" rivers high in tannic acid derived from decaying organic matter. They have low ANC and high DOC.
• Fair: Sites with episodic acidification, which can occur during high-flow events.
• Poor: This category includes sites affected by acid rain and acid mine drainage. These sites have low ANC and low DOC.

Most river and stream miles, 99%, were not acidic based on this indicator. Most of the acidification detected was due to acid mine drainage in the Southern Appalachians ecoregion. Episodic acidification occurred in the Northern Plains and Northern Appalachians.

Nationally, there was no significant change in river and stream condition based on acidification between 2013-14 and 2018-19.

The Upper Missouri River Breaks National Monument in Montana. Bob Wick . Flickr , CC BY-NC 2.0 .

Salts can be toxic to freshwater plants and animals, and they can make water unsafe for drinking and agriculture. Excess salinity can occur in areas where evaporation is high and water is repeatedly reused for irrigation or water withdrawals; where road de-icing compounds are applied; and where mining, oil drilling, and industrial wastewater are discharged. Conductivity, a measure of water’s ability to pass an electrical current, was used as a measure of salinity for NRSA.

Most river and stream miles, 85%, were in good condition. The assessment also found that 11% of river and stream miles were in fair condition and 4% were in poor condition. The Northern Plains ecoregion had the fewest river and stream miles in good condition at 49%.

Nationally, there was no significant change in stream condition based on salinity between 2013-14 and 2018-19. However, significant changes occurred in some survey subpopulations.

PHYSICAL INDICATORS

The condition of shoreline habitat provides important information relevant to stream biological health. Human activities such as construction, urbanization, agriculture, and removal of vegetation buffers can degrade rivers and streams. NRSA used four indicators of physical habitat condition: in-stream fish habitat, riparian disturbance, riparian vegetation, and excess streambed sediments. Three of these were compared to regionally relevant reference benchmarks, while riparian disturbance was scored using the same method and benchmarks nationally.

In-stream Fish Habitat

Multicolored and speckled rocks help these juvenile Atlantic salmon hide from predators. E. Peter Steenstra, U.S. Fish and Wildlife Service. Flickr .

Healthy fish and macroinvertebrate communities are typically found in rivers and streams that have complex and varied forms of habitat, such as rocks and boulders, undercut banks, overhanging vegetation, brush, and tree roots and logs within the stream banks. NRSA used a habitat complexity measure that reflects the amount of such in-stream fish habitat and concealment features within the water body and its banks.

More than two-thirds of river and stream miles (68%) were rated good for in-stream habitat, while 22% were rated fair and 10% were rated poor. For ecoregions, good condition ranged from 46% in the Northern Appalachians to 85% in the Temperate Plains.

Nationally, the only significant change to in-stream habitat was a decrease (4 percentage points) in the percentage of river and stream miles in poor condition between 2013-14 and 2018-19. Additionally, several significant changes occurred within survey subpopulations. NRSA results indicated statistically significant changes in good condition for three ecoregions: the proportion of miles in good condition increased by 14 percentage points in the Coastal Plains and by 11 percentage points in the Temperate Plains, while the proportion in good condition decreased by 14 percentage points in the Upper Midwest.

Riparian Disturbance

Railroads are one sign of riparian disturbance that field crews check for. Brent Moore. "Vertical lift railroad bridge - Decatur, Alabama." Flickr , CC BY-NC 2.0 .

The riparian disturbance indicator reflects the extent and intensity of direct human alteration of the shore itself. These disturbances can range from minor changes, such as the removal of a few trees to develop a picnic area, to major alterations, such as the construction of a large residential complex. Shoreland development can contribute to excess sedimentation, alteration or loss of native plant communities, loss of vegetation structure and complexity, and modifications to river and stream bottom materials. These impacts, in turn, can negatively affect fish, wildlife, and other aquatic communities.

Riparian disturbance was widespread. Nationally, only 36% of riparian areas were rated good (had low levels of human disturbance), 42% were rated fair (moderate levels of disturbance), and 22% were in poor condition (high levels of human disturbance). In the ecoregions, the percentage of river and stream miles in good condition ranged from 5% in the Northern Plains to 55% in the Western Mountains.

For riparian disturbance, there was a significant increase (9 percentage points) in the percentage of river and stream miles rated good, and a significant decrease (5 percentage points) in the percentage of river and stream miles in poor condition between 2013-14 and 2018-19. Additionally, there were several significant changes within survey subpopulations. For example, the proportion of river and stream miles in poor condition in the Southern Plains and Xeric ecoregions increased by 15 and 16 percentage points, respectively, while declining 14 percentage points in the Coastal Plains.

Riparian Vegetation Cover

The banks of this Appalachian stream have healthy understory, midstory, and overstory vegetation. Natalie Auer.

Evaluation of riparian or shoreland vegetation cover is based on observations of three layers of vegetation: understory grasses and forbs , midstory woody and nonwoody shrubs, and overstory trees. Healthy, multilayered vegetation covering this corridor can buffer the effects of human disturbance. Cover can slow runoff; filter nutrients and sediments; reduce streambank erosion; shade water, reducing algae growth; and supply leaf litter, branches, and logs that serve as food and habitat. Generally, riparian habitats are in better condition when vegetation cover is high in all layers; however, not all three layers occur in all areas of the country. For example, Northern Plains rivers and streams typically have less natural overstory tree cover. Such natural differences have been factored into the calculation of the riparian vegetation cover indicator score.

Just over half of rivers and streams (56%) had good levels of riparian vegetation cover; 17% were in fair condition and 27% were in poor condition for riparian cover.

No statistically significant changes occurred between 2013-14 and 2018-19 at the national level, and only one subpopulation showed significant changes. The percentage of river and stream miles in poor condition increased by 11 percentage points in the Northern Appalachians.

Streambed Sediments

Vegetated buffer zones between farmland and streams can help prevent excess sediment loading. Minnesota Pollution Control Agency . All rights reserved .

The size mix of particles that make up riverbeds and streambeds is important for maintaining stable and healthy river and stream systems. Human activities that disturb land can interfere with river and stream sediment balance by increasing the amount of fine sediment entering river and stream channels. Human activities can also lead to increases in the magnitude or frequency of flooding. For example, the presence of paved surfaces in a watershed prevents rainwater from soaking into the ground and can increase the volume and velocity of water entering streams and the frequency of high-magnitude floods. In turn, frequent floods can lead to incised and eroded banks, widened channels, scouring of streambeds, washing away of aquatic microhabitats (e.g., woody debris and other organic material), and deposition of fine and less stable sediments (e.g., silt or clay). Excess fine sediments can fill in the spaces between cobbles and rocks where many benthic macroinvertebrates live and breed.

NRSA found that streambed sediments were in good condition in 57% of river and stream miles, were in fair condition in 23% of miles, and in poor condition in 20%.

For streambed sediments, the percentage of river and stream miles in good condition increased significantly (6 percentage points) between 2013-14 and 2018-19. Additionally, significant changes occurred in several survey subpopulations. Results indicated that the Southern Appalachians ecoregion experienced an increase in good condition of 11 percentage points, and the Xeric ecoregion experienced a decrease of 16 percentage points.

Associations Between Stressors and Biological Condition

Sampling equipment. Sarah Lehmann, EPA.

Restoring water quality requires not only an understanding of current condition and change over time, but also of stressors associated with degraded biological condition and the potential for improved conditions when stressors are reduced. This knowledge can help decision makers prioritize stressors for reduction.

To address these questions at the national and regional level, EPA performed three calculations for each stressor, focusing on the benthic macroinvertebrate indicator (presented here) and the fish community indicator (presented in the dashboard ) as the indicator of biological condition. Stressors in this case were those measured using the chemical and physical indicators. Note that EPA did not examine associations for human health indicators.

• First, EPA determined the extent of river and stream miles in poor condition for stressors (the relative extent).
• EPA then evaluated the extent to which poor biological condition was more likely when a stressor or indicator was rated poor (the relative risk).
• Lastly, EPA assessed the potential improvement that could be achieved by reducing or eliminating the stressor (the attributable risk).

Highlights of the national results on relative extent, relative risk, and attributable risk for the benthic indicator are described below. Visit the NRSA dashboards to explore risk results for selected survey subpopulations. For more detailed information on these analyses, visit EPA’s NARS risk web page .

The NRSA indicators with the highest national relative extent were nitrogen, phosphorus, and riparian vegetation cover with 44%, 42%, and 27% of river and stream miles in poor condition, respectively. These were the most widespread stressors.

For benthic macroinvertebrates, acidification was the stressor with the highest relative risk estimate nationally (2.1). That is, rivers and streams with acidification in poor condition were 2.1 times more likely to rate poor for benthic macroinvertebrates than waters that weren’t poor for acidification. Phosphorus and nitrogen showed relative risks of 1.7 and 1.5, respectively, indicating rivers and streams rated poor for nutrients were more likely to rate poor for biological condition.

Combining the relative extent and relative risk values for each indicator into a single value provides us with attributable risk. Attributable risk analysis estimates a percentage of river and stream miles for which biological condition could improve (that is, change to either good or fair condition) if the stressor were reduced from poor to fair or good.

Calculating attributable risk involves assumptions, including: 1) that a causal relationship between stressors and biological condition exists; 2) that a river or stream’s poor biological condition would be reversed if the stressor were improved to fair or good levels; and 3) that the stressor’s impact on a river or stream’s biological condition is independent of other stressors. Despite these limitations, attributable risk can provide general guidance as to which stressors might be higher priorities for management nationally or regionally.

Attributable risk analysis shows that reducing nutrients could result in the greatest benefit to biological condition at the national scale, as shown in Exhibit 26. This exhibit shows attributable risk (including point estimates and 95% confidence intervals) for each stressor whose risk is greater than zero. If poor condition were improved to fair or good for nutrients, the percentage of river and stream miles with poor benthic macroinvertebrate condition could be reduced by approximately 20%.

Attributable Risk from Exposure to Stressors Nationally (2018-19)

To see graphs for relative extent, relative risk, and attributable risk together, visit the risk estimate section of the NRSA dashboard.

National Results for Human Health Indicators

In addition to physical, chemical, and biological indicators of the quality of the nation’s rivers and streams, NRSA included data collection for six human health indicators: two algal toxins (microcystins and cylindrospermopsin), the fecal contamination indicator enterococci, and three contaminants in fish tissue (mercury, PCBs, and PFAS).

For algal toxins and enterococci, the results were compared to EPA recommended water quality criteria or benchmarks designed to protect human health against recreational exposure such as swimming or boating. For mercury, the results were compared to EPA’s recommended fish tissue-based water quality criterion for methylmercury. For PCBs, EPA derived fish tissue screening levels (described in more detail in the appendix ) and compared the fish tissue results to these screening levels. Of the PFAS compounds, PFOS was the most frequently detected, and the PFOS concentrations were not compared against fish tissue screening levels because the EPA PFOS toxicity assessment is not yet final.

The results described below provide national- and some regional-scale estimates for these indicators. For information on state-specific and local water quality data and assessments, visit EPA’s How’s My Waterway application . People should check with state, tribal, or local agencies for advisories for swimming, boating, or fishing in specific rivers and streams.

ALGAL TOXINS

Microcystins can cause harm to recreational water users such as kayakers or anglers. Sassafras River, Maryland. Eric Vance, EPA .

Cyanobacteria (sometimes called blue-green algae) are one-celled photosynthetic organisms that normally occur at low levels. Under eutrophic conditions, generally characterized by high nutrients, cyanobacteria can multiply rapidly. Not all cyanobacterial blooms are toxic, but some may release toxins, such as microcystins and cylindrospermopsin. Recreational exposure is typically a result of inhalation, skin contact, or accidental ingestion. Health effects of exposure include skin rashes, eye irritation, respiratory symptoms, gastroenteritis, and in severe cases, liver or kidney failure and death. See EPA’s algal toxins page for more information. Pets are also susceptible to health effects from exposure to algal toxins.

EPA has set recreational freshwater criteria and swimming advisory recommendations for microcystins and cylindrospermopsin: 8 parts per billion (ppb) and 15 ppb, respectively (U.S. EPA 2019). Note that some types of algae release other toxins not monitored as part of the NRSA. The NRSA assesses risk of exposure to microcystins and cylindrospermopsin at national and regional levels. For information about risks at specific locations, recreational water users should check with state, tribal, or local governments.

Microcystins were detected in 9% of river and stream miles but did not exceed EPA’s criterion recommendation of 8 ppb.

For more details, download the data for this chart, or visit the NLA dashboards for ecoregional data on microcystins risk.

Cylindrospermopsin was detected in 10% of river and stream miles and did not exceed EPA’s criterion recommendation of 15 ppb.

For more details, download the data for this chart, or visit the NLA dashboards for ecoregional data on cylindrospermopsin risk.

Microcystin detection decreased significantly, by 29 percentage points, between 2013-14 and 2018-19. No significant change in miles exceeding the recommended criterion occurred between 2013-14 and 2018-19. Note that microcystins were first sampled in 2013-14. Cylindrospermopsin data were not collected in earlier surveys, so no change data are available.

ENTEROCOCCI BACTERIA

Pet waste can wash into storm drains and contaminate waterways with enterococci and other microbes. Dan Keck . Flickr .

Enterococci are bacteria that live in the intestinal tracts of warm-blooded animals, including humans. While not considered harmful to humans, their presence in water indicates that disease-causing microbes may be present. Enterococci are therefore used as indicators of possible fecal contamination from sources such as wastewater treatment plant discharges, leaking septic systems, storm water runoff, pet waste, and farm runoff. For NRSA, water samples were analyzed using a method that measures enterococci DNA (qPCR, or quantitative polymerase chain reaction). Results were compared to an EPA benchmark (1,280 calibrator cell equivalents per 100 milliliters) included in EPA’s recommended recreational criteria document for protecting human health in ambient waters designated for swimming (U.S. EPA 2012).

Enterococci exceeded EPA’s benchmark in 20% of river and stream miles.

Enterococci showed a significant decrease (13 percentage points) in river and stream miles above EPA’s benchmark. Note that enterococci data were first collected in 2013-14.

MERCURY IN FISH TISSUE PLUGS

Contaminants in Fish Tissue

EPA used two sampling approaches to examine levels of contaminants in fish tissue:

• Collection and analysis of mercury in fish tissue plugs.
• Collection of whole fish composite samples and preparation of fillet composite samples for analysis of mercury, PCBs, and PFAS.

This section describes mercury in fish tissue plugs. The other approach is described in more detail in Fish Tissue Contamination in Rivers below.

NRSA field crew member placing a plug of fish tissue into a vial. EPA .

For this study, fish tissue samples were analyzed for mercury . Crews collected small tissue plugs from fillet tissue in target fish species of a minimum size suitable for human consumption. Fish species included bluegill, catfish, northern pike, and smallmouth bass among others; the minimum size was 190 millimeters (7.5 inches). Crews attempted to collect fish tissue plugs at all river and stream sites. The NRSA assessed total mercury levels against EPA’s recommended fish tissue-based methylmercury water quality criterion of 300 ppb (U.S. EPA 2001).

The results for mercury in fish tissue plugs apply to the full NRSA target population of rivers and streams, and, as with most of the other indicators, the portion of the river and stream miles that was not assessed is included in the results. Note that mercury results for fish fillet composite samples described in the next section apply to the sampled population of river miles, and these results should not be directly compared to fish plug mercury results.

Mercury was detected in all fish tissue plug samples. Fish in 5% of river and stream miles (approximately 82,000 miles) had concentrations above the 300 ppb mercury criterion, while 21% did not. It is important to note that 74% of river and stream miles were not assessed primarily due to the absence of fish that met the minimum size requirement. Regionally, high levels of mercury in fish tissue were more common in the Coastal Plains and Southern Plains, where 12% of river and stream miles exceeded the mercury criterion. See the next section for additional information on contaminants in fish tissue.

For mercury in fish tissue plugs, there was no significant difference in river and stream miles with plug concentrations above 300 ppb nationally between 2013-14 and 2018-19. Note that EPA began measuring mercury in fish tissue plugs in 2013-14.

FISH TISSUE CONTAMINATION IN RIVERS

Consuming fish can be an important part of a balanced diet. Fish are low in saturated fat and provide certain essential omega-3 fatty acids that the human body cannot make. Fish can be an important source of protein, especially for communities with high-frequency fish consumers such as subsistence fishers, some recreational fishers, or some fishers in underserved communities. However, contaminants that enter the environment can accumulate in fish. At high enough levels, these accumulated contaminants may contribute to human health impacts such as cancer or neurological problems in people who eat fish. People should consult local fish consumption advisories to determine whether the fish species and quantities of fish they have caught are safe to eat.

As part of NRSA 2018-19, EPA conducted a study of contamination in fish from rivers to determine whether eating river fish poses risks to human health. See the technical support document (U.S. EPA 2023) for more information on this study, including the rationale for focusing on rivers. The sampling approach for this study involved collecting a whole fish composite sample at each site, from rivers defined as Strahler fifth order or greater. Field crews collected fish species that are commonly caught and consumed by recreational and subsistence fishers.

At the laboratory, the whole fish samples were scaled and filleted , and the fillets were ground. EPA analyzed these fillet composite samples for total mercury, total PCBs (based on the full 209 congener analysis), and 33 PFAS (a list of PFAS is provided in the technical support document ). Fillet tissue concentration results were reported on a wet-weight basis.

Note that contaminant results for the fillet composite samples are reported for the sampled population of river miles only; therefore, mercury composite fillet results should not be compared directly to results for the mercury fish tissue plug indicator.

For PCBs, EPA developed screening levels for two types of consumers:

• One for general fish consumers , which is based on a fish consumption rate of one 8-ounce meal of locally caught river fish per week.
• One for high-frequency fish consumers , which is based on a fish consumption rate of four to five 8-ounce meals of locally caught river fish per week.

These PCB screening levels differ from those used in the 2013-14 report. See the appendix or the technical support document for details on screening level derivation.

For fish tissue contaminant analysis, field crew members attempt to catch fish on a list of targeted species, such as this brook trout. Julia Woods . iNaturalist , CC BY-NC 4.0 . Cropped.

About 80% of all fish consumption advisories in the United States involve mercury. Most mercury in water comes from air deposition related to coal combustion and waste incineration. Mercury particles, mostly from these sources, fall to land and are washed into rivers and streams. People are exposed to methylmercury (the most toxic form of mercury) primarily by eating fish and shellfish. Fetal or early childhood exposures to mercury transmitted from pregnant and nursing mothers can lead to impaired neurological development, affecting cognitive and fine motor skills. Exposure to unsafe levels of methylmercury can also affect adult health, leading to cardiovascular disease, loss of coordination, muscle weakness, and impaired speech and hearing. EPA applies the conservative assumption that all mercury in fish is methylmercury and therefore measures total mercury in fillet tissue to be most protective of human health.

As with fish plugs, the mercury levels in fillet composite samples were compared to EPA’s recommended fish tissue-based water quality criterion for methylmercury of 300 ppb to identify potential human health risks from consumption of locally caught river fish.

What was the condition in 2018-19?

Mercury was detected in 100% of the 290 fish fillet composite samples analyzed for NRSA 2018-19.

Mercury concentrations in the fish fillet samples exceeded the EPA recommended criterion of 300 ppb in 26% of the sampled population of 41,099 river miles. See Exhibit 35.

Percentage of River Miles with Fillet Mercury Concentrations Above 300 ppb

Did the condition change?

Comparisons of fillet composite results for mercury between NRSA 2013-14 and NRSA 2018-19 did not reveal statistically significant differences.

Polychlorinated Biphenyls (PCBs)

PCBs accumulate in the tissues of aquatic organisms and are known to cause cancer in animals. Based on those findings and additional evidence from human studies, EPA classifies PCBs as a probable human carcinogen. Other potential human health effects that could result from higher dietary exposure to PCBs include liver disease and reproductive impacts, along with neurological effects in infants and young children. PCBs have been banned for over four decades, but they persist in the environment.

In previous reports, EPA included total PCB results for both cancer and noncancer health effects, based on risk to general fish consumers. However, cancer health effects can occur at lower PCB levels than noncancer health effects, so applying a lower screening level to reduce the risk of cancer health effects also reduces risks of noncancer health effects from dietary exposure to PCBs. EPA’s previously reported results also did not apply to high-frequency fish consumers such as subsistence fishers, some recreational fishers, or some fishers in underserved communities. For this report, EPA used fish tissue screening levels for total PCBs to characterize cancer human health risks for general and high-frequency fish consumers:

• For general fish consumers , EPA applied a 12 ppb cancer screening level for total PCBs in fish tissue.
• For high-frequency fish consumers , EPA applied a 2.8 ppb cancer screening level for total PCBs in fish tissue.

PCBs were detected in 100% of the 290 fish fillet composite samples analyzed for NRSA 2018-19.

Total PCB concentrations exceeded the cancer screening level of 12 ppb for general fish consumers in 45% of the sampled population of 41,099 river miles. See Exhibit 36.

Percentage of River Miles with Fillet Total PCB Concentrations Above 12 ppb

Total PCB concentrations in the fish fillet composite samples exceeded the cancer screening level of 2.8 ppb for high-frequency fish consumers in 74% of the sampled population of 41,099 river miles. See Exhibit 37.

Percentage of River Miles with Fillet Total PCB Concentrations Above 2.8 ppb

Comparisons of fillet composite sample results for total PCBs between NRSA 2013-14 and NRSA 2018-19 did not reveal statistically significant differences in exceedances of the cancer screening levels applied to general fish consumers or to high-frequency fish consumers.

Per- and Polyfluoroalkyl Substances (PFAS)

PFAS are a group of synthetic chemicals used in the manufacture of many products, including non-stick cookware, food packaging, waterproof clothing, and stain-resistant carpeting. PFAS are toxic and persistent in the environment. Most people in the United States have been exposed to PFAS and have PFAS in their blood , especially perfluorooctane sulfonic acid and perfluorooctanoic acid (PFOA). Certain PFAS levels have been linked to immune, cardiovascular, hepatic (liver), and developmental health effects such as decreased fertility or low birth weight, as well as an increased risk of certain cancers. PFOS (perfluorooctane sulfonate) is a form of perfluorooctane sulfonic acid and is the most frequently detected PFAS in freshwater fish tissue.

Results for the full set of 33 PFAS included in the fish fillet tissue analyses for NRSA 2018-19 are presented in the technical support document; only PFOS results are described in this section because of the prevalence of PFOS in freshwater fish tissue. This report does not contain screening levels for PFOS because EPA has not finalized the PFOS toxicity assessment. When that is final, EPA intends to update the PFOS information in this report.

PFOS was detected in 91% of the 290 fish fillet composite samples analyzed for NRSA 2018-19, corresponding to PFOS being detected in 92% of the sampled population of 41,099 river miles. When PFOS concentrations were above the method detection limit of 0.35 ppb, they were recorded as detected. For further details, see the technical support document.

Comparisons of fillet composite sample results for PFOS between NRSA 2013-14 and NRSA 2018-19 showed a statistically significant decrease (6.7 percentage points) in the sampled population of river miles containing fish with detectable levels of PFOS in fillet tissue.

Field collection of a water sample. Sarah Lehmann, EPA .

The NRSA provides findings that water resource managers can use to inform resource management priorities and strategies. Nationally, 28% of river and stream miles were in good biological condition, while almost half were in poor condition. The most widespread stressors were excess nitrogen, phosphorus, and riparian vegetation cover, with poor conditions in 44%, 42%, and 27% of river and stream miles, respectively. The NRSA found that the percentage of river and stream miles in poor biological condition could be reduced by 20% if excess nutrient levels could be reduced from poor to good or fair.

While the survey results provide national and regional estimates of condition, they do not address all information needs at all scales. For example, the survey does not measure all stressors and cannot be used to infer local condition. In-depth monitoring and analysis of individual waters and watersheds are required to support specific restoration and protection efforts.

EPA and its state and tribal partners are continually refining the NRSA and will apply lessons learned to determine if changes need to be made to the design, indicators, field methods, laboratory methods, and analysis procedures for the future. Sampling for the fourth NRSA will take place in the summers of 2023 and 2024.

NRSA 2018-19 would not have been possible without the involvement of state and tribal scientists and resource managers. EPA will continue to help these partners translate the expertise gained through these national surveys to their own state-scale surveys. Additionally, EPA will work to encourage use of the data to evaluate the success of efforts to protect and restore water quality.

Other National Aquatic Resource Surveys

In addition to the NRSA, the NARS program also includes the following surveys:

• The National Coastal Condition Assessment (2005, 2010, 2015, and 2020).
• The National Lakes Assessment (2007, 2012, 2017, and 2022).
• The National Wetland Condition Assessment (2011, 2016, and 2021).

Other reports from NARS are available on the NARS home page . EPA will post additional reports and data as they become available.

About This Report

This version of the report was published in December 2023. Results presented in the report and interactive dashboard were last updated 06/07/2023.

Any corrections or updates will be described in this section.

A suggested citation for the report is: U.S. Environmental Protection Agency. 2023. National Rivers and Streams Assessment: The Third Collaborative Survey. EPA 841-R-22-004. U.S. Environmental Protection Agency, Office of Water and Office of Research and Development. https://riverstreamassessment.epa.gov/webreport

U.S. Environmental Protection Agency (U.S. EPA). 2001. Water quality criterion for the protection of human health: methylmercury. EPA-823-R-01-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC. https://www.epa.gov/sites/default/files/2020-01/documents/methylmercury-criterion-2001.pdf

U.S. EPA. 2012. Recreational water quality criteria . EPA 820-F-12-058. U.S. Environmental Protection Agency, Office of Water, Washington, DC. https://www.epa.gov/sites/default/files/2015-10/documents/rwqc2012.pdf

U.S. EPA. 2019. Recommended human health recreational ambient water quality criteria or swimming advisories for microcystins and cylindrospermopsin . EPA 822-R-19-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC. https://www.epa.gov/sites/production/files/2019-05/documents/hh-rec-criteria-habs-document-2019.pdf

• Subject List
• Take a Tour
• For Authors
• Subscriber Services
• Publications
• African American Studies
• African Studies
• American Literature
• Anthropology
• Architecture Planning and Preservation
• Art History
• Atlantic History
• Biblical Studies
• British and Irish Literature
• Childhood Studies
• Chinese Studies
• Cinema and Media Studies
• Communication
• Criminology

Environmental Science

• Evolutionary Biology
• International Law
• International Relations
• Islamic Studies
• Jewish Studies
• Latin American Studies
• Latino Studies
• Linguistics
• Literary and Critical Theory
• Medieval Studies
• Military History
• Political Science
• Public Health
• Renaissance and Reformation
• Social Work
• Urban Studies
• Victorian Literature
• Browse All Subjects

How to Subscribe

• Free Trials

In This Article Expand or collapse the "in this article" section River Pollution

Introduction, general overviews.

• Heavy Metals
• Polynuclear Aromatic Hydrocarbons (PAHs)
• Polychlorinated Biphenyls (PCBs)
• Persistent Organic Pollutants (POPs)
• Contaminant Source
• Role of Flow Regime
• Role of River Geometry
• Role of Biota
• Role of Chemistry
• Temporal and Spatial Scales
• Remediation
• Clark Fork River, Montana, USA
• Chang Jiang (Yangtze River), China
• Cuyahoga River, Ohio, USA
• Danube River, Europe
• Gold Mining, South America
• Hudson River, New York, USA
• Illinois River, Illinois, USA
• Mississippi River, United States
• Murray-Darling River, Australia
• Nile River, Africa
• Ob River, Russia

Related Articles Expand or collapse the "related articles" section about

About related articles close popup.

Lorem Ipsum Sit Dolor Amet

Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Aliquam ligula odio, euismod ut aliquam et, vestibulum nec risus. Nulla viverra, arcu et iaculis consequat, justo diam ornare tellus, semper ultrices tellus nunc eu tellus.

• Acid Deposition
• Arsenic Contamination in South and Southeast Asia
• Case Studies in Groundwater Contaminant Fate and Transport
• Case Studies in Industrial Contamination
• Contaminant Dispersal in the Environment
• Ecohydrology
• Economics of Fisheries
• Endocrine Disruptors
• Environmental Engineering
• Environmental Forensics
• Global Phosphorus Dynamics
• Hazardous Waste
• Human Impact on Historical Fluvial Sediment Dynamics in Europe
• Human Manipulation of the Global Nitrogen Cycle
• Hydraulic Fracturing
• India and the Environment
• Large Wood in Rivers
• Legacy Effects
• Rachel Carson
• Restoration of Physical Integrity of Rivers
• Riparian Zone
• Sediment Budgets and Sediment Delivery Ratios in River Systems
• Sediment Regime and River Morphodynamics
• Soil Salinization
• Use of GIS in Environmental Science
• Water Availability
• Water Quality in Freshwater Bodies
• Water Quality Metrics
• Water Resources and Climate Change
• Water Security

Other Subject Areas

Forthcoming articles expand or collapse the "forthcoming articles" section.

• Community Forest Management
• Environmental History of the Middle East and North Africa
• Histories of U.S. Environmentalism
• Find more forthcoming articles...
• Export Citations
• Share This Facebook LinkedIn Twitter

River Pollution by Ellen Wohl LAST REVIEWED: 29 September 2014 LAST MODIFIED: 29 September 2014 DOI: 10.1093/obo/9780199363445-0003

People who are not researchers are most likely to intersect environmental science in the context of protecting or restoring a place or species about which they are concerned, or in the context of pollution—trying to understand the sources and effects of contaminants, or trying to prevent or remediate environmental contamination. The works in this entry address pollutants affecting river ecosystems, including the people who live within or use resources from those ecosystems. Pollution is commonly subdivided based on the primary medium affected by contamination, creating categories such as air pollution, soil pollution, freshwater pollution, groundwater pollution, or marine pollution. In reality, of course, all of these media are intimately connected. Atmospheric deposition of contaminants pollutes soil and water bodies. Contaminated groundwater seeps into rivers, and contaminated rivers recharge groundwater aquifers. Fluxes of water, sediment, solutes, and even organisms carrying contaminants within their tissues create vectors to disperse pollutants. This is one of the great challenges to understanding and mitigating pollution: the contaminant is seldom an inert substance that stays in one place. Another great challenge is that there are many different types of contaminants, including human and animal wastes such as sewage or intestinal bacteria, excess nutrients, heavy metals, petroleum products, radioactive isotopes, and an enormous array of synthetic chemicals such as pesticides and personal care products. Each type of contaminant can disperse through environmental media, combining with other chemical compounds to form metabolites that may have different levels of toxicity for organisms or different dispersal mechanisms than the original contaminant. Yet another challenge in understanding and managing pollutants is that a substance that is harmful to one type of organism may not cause harm to another type of organism, but detailed knowledge of how individual pollutants affect the spectrum of living organisms is almost never available. Consequently, the environmental standards set by government agencies for maximum permissible levels of contaminants are based on very limited knowledge and are likely to be inadequate. Most of the standards are also based on acute effects that show up very quickly. Contaminant levels below permissible standards can cause chronic effects—subtle but pervasive changes that eventually degrade the health of individual organisms and populations. Some chronic effects result from bioaccumulation, as an organism accumulates contaminants within its tissues over the course of its life, and biomagnification, as organisms pass on their accumulated doses to predators or scavengers.

The works cited in this section provide broad overviews of topics, including the diverse types of contaminants that can be present in river environments, as well as the physical and chemical properties and environmental toxicity of these contaminants; methods of sampling contaminants in water, sediment, and biota; regulatory standards for contaminants and how these standards are established and enforced; and methods of mitigating or remediating river pollution. Edzwald 2011 focuses on these issues in the context of drinking-water quality, whereas Haslam 1994 focuses more on the effects of pollutants on river plants and animals. Steingraber 1998 provides a highly readable account of the sources of environmental contamination, including rivers, and the effects on human health. Wohl 2004 examines diverse sources of river pollution across the continental United States in the context of historical developments in technology that result in pollution. Gallo and Ferrari 2008 includes treatments of these issues in several countries, facilitating comparisons between countries and regions. Both Smol 2008 and Heim and Schwarzbauer 2013 provide a good introduction to using river sediments to understand the contemporary distribution and historical dissemination of pollutants. Jain 2009 exemplifies book-length treatments of pollution in individual rivers, in this case the Yamuna River of India.

Edzwald, J. K., ed. 2011. Water quality and treatment: A handbook on drinking water . 6th ed. New York: McGraw-Hill.

This book provides an overview of diverse sources and types of water pollution, and of drinking water standards and regulations, but primarily focuses on treatments to improve water quality. Individual chapters cover both theory and practice with respect to specific water treatments.

Gallo, M. N., and M. H. Ferrari, eds. 2008. River pollution research progress . New York: Nova Science.

This edited volume includes twelve chapters summarizing diverse aspects of the state of the science as of 2009. These include case studies from Russia, the United States, Greece, Brazil, and Zimbabwe, as well as overviews of processes, modeling, human perceptions, and different types of river pollution.

Haslam, S. M. 1994. River pollution: An ecological perspective . Chichester, UK: Wiley.

This book provides an overview of different types of river pollution and how pollution affects river biota. The writing is readily accessible to nonspecialists, but includes extensive referencing for research uses. Although now more than twenty years old, this text is a good introduction to the topic of river pollution.

Heim, S., and J. Schwarzbauer. 2013. Pollution history revealed by sedimentary records: A review. Environmental Chemistry Letters 11:255–270.

DOI: 10.1007/s10311-013-0409-3

A useful and thorough review of how sediments can be used to evaluate distribution and concentration of persistent pollutants within rivers through time and across space. The paper describes different types of contaminants, including heavy metals, PCBs, PAHs, pesticides, and pharmaceuticals; contamination sources and pathways; and numerous case studies.

Jain, A. K. 2009. River pollution: Regeneration and cleaning . New Delhi: A. P. H. Publishing Corporation.

This book is a comprehensive case study of a single large river in India, the Yamuna, and of the large cities, including Delhi, that pollute the river. Following an introduction to the river’s ecology, geomorphology, and flow regime, the book focuses on pollutants and remediation of pollution in the river.

Smol, J. P. 2008. Pollution of lakes and rivers: A paleoenvironmental perspective . 2d ed. Malden, MA: Blackwell.

This book covers diverse types of pollutants from the perspective of sedimentary records of changing types and concentrations of pollutants through time. Because river channels, floodplains, alluvial fans, and deltas preserve thousands of years of river sediments, these depositional environments provide a unique perspective on river pollution over long time spans. First published in 2002 (London: Arnold).

Steingraber, S. 1998. Living downstream: A scientist’s personal investigation of cancer and the environment . New York: Vintage.

Written for nonspecialist readers, this highly readable book provides an overview and in-depth introduction to river pollution and other forms of environmental contamination, and reviews a wide array of studies documenting the resulting impairment of human and animal health.

Wohl, E. 2004. Disconnected rivers: Linking rivers to landscapes . New Haven, CT: Yale Univ. Press.

DOI: 10.12987/yale/9780300103328.001.0001

This book examines human effects on rivers throughout the continental United States, and includes an extensive discussion of diverse types, sources, and effects of river pollution. The book discusses specific examples of river pollution from the Great Lakes region and provides an overview of riverine water quality throughout the country.

back to top

Users without a subscription are not able to see the full content on this page. Please subscribe or login .

Oxford Bibliographies Online is available by subscription and perpetual access to institutions. For more information or to contact an Oxford Sales Representative click here .

• About Environmental Science »
• Meet the Editorial Board »
• Agricultural Land Abandonment
• Agrochemical Pollutants
• Agroforestry Systems
• Agroforestry: The North American Perspective
• Anthropocene
• Applied Fluvial Ecohydraulic
• Arctic Environments
• Arid Environments
• Beavers as Agents of Landscape Change
• Berry, Wendell
• Burroughs, John
• Bush Encroachment
• Carbon Dynamics
• Carbon Pricing and Emissions Trading
• Carson, Rachel
• Citizen Science
• Climate Change and Conflict in Northern Africa
• Common Pool Resources
• Coral Reefs and Coral Bleaching
• Deforestation in Brazilian Amazonia
• Desert Dust in the Atmosphere
• Determinism, Environmental
• Digital Earth
• Disturbance
• Ecological Integrity
• Economic Valuation Methods for Non-market Goods or Service...
• Economics, Environmental
• Economics of International Environmental Agreements
• Economics of Water Management
• Effects of Land Use
• Endocrinology, Environmental
• Engineering, Environmental
• Environmental Assessment
• Environmental Flows
• Environmental Health
• Environmental Law
• Environmental Sociology
• Ethics, Animal
• Ethics, Environmental
• European Union and Environmental Policy, The
• Extreme Weather and Climate
• Fair Water Distribution: From Theory to Application
• Feedback Dynamics
• Fisheries, Economics of
• Forensics, Environmental
• Forest Transition
• Geodiversity and Geoconservation
• Geology, Environmental
• Groundwater
• Henry David Thoreau
• Historical Changes in European Rivers
• Historical Land Uses and Their Changes in the European Alp...
• Historical Range of Variability
• History, Environmental
• Human Impact on Historical Fluvial Sediment Dynamics in Eu...
• Humid Tropical Environments
• Industrial Contamination, Case Studies in
• Institutions
• Integrated Assessment Models (IAMs) for Climate Change
• International Land Grabbing
• Karst Caves
• Key Figures: North American Environmental Scientist Activi...
• Lakes: A Guide to the Scientific Literature
• Land Use, Land Cover and Land Management Change
• Landscape Architecture and Environmental Planning
• Lidar in Environmental Science, Use of
• Management, Australia's Environment
• Marine Mining
• Marine Protected Areas
• Mediterranean Environments
• Mountain Environments
• Multiple Stable States and Regime Shifts
• Murray-Darling Basin Plan: Case Study in Market-Based Appr...
• Natural Fluvial Ecohydraulics
• Nitrogen Cycle, Human Manipulation of the Global
• Non-Renewable Resource Depletion and Use
• Olmsted, Frederick Law
• Payments for Environmental Services
• Periglacial Environments
• Physics, Environmental
• Psychology, Environmental
• Remote Sensing
• River Pollution
• Rivers and Their Cultural Values: Assessing Cultural Water...
• Rivers, Effects of Dams on
• Rivers, Restoration of Physical Integrity of
• Sea Level Rise
• Secondary Forests in Tropical Environments
• Security, Energy
• Security, Environmental
• Security, Water
• Sediment Budgets and Sediment Delivery Ratios in River Sys...
• Semiarid Environments
• Soils as an Environmental System
• Spatial Statistics
• Stream Mitigation Banking
• Sustainable Finance
• Sustainable Forestry, Economics of
• Technological and Hybrid Disasters
• The Key Role of Energy in Economic Growth
• Thresholds and Tipping Points
• Treaties, Environmental
• Tropical Southeast Asia
• Water, Virtual
• White, Gilbert Fowler
• Wildfire as a Catalyst
• Zone, Critical
• Privacy Policy
• Cookie Policy
• Legal Notice
• Accessibility

Powered by:

• [195.158.225.230]
• 195.158.225.230

Ecoengineered Approaches for the Remediation of Polluted River Ecosystems

• First Online: 11 November 2021

Cite this chapter

• Shabnam Shaikh 8 ,
• Kunal R. Jain 9 ,
• Datta Madamwar 9 &
• Chirayu Desai   ORCID: orcid.org/0000-0001-8211-3575 8  

Part of the book series: Environmental Chemistry for a Sustainable World ((ECSW,volume 70))

1012 Accesses

Rivers are the vital support system providing sustainable development and agricultural production to our highly industrialized world. However, extreme anthropogenic inputs have disturbed the natural ecological balance, structures and functions of riverine matrices. The origins, fate and various health hazards of the riverine contaminants are outlined in this chapter. To mitigate the river pollution and restoring its healthy status, effective restoration strategies are required to be adopted, this chapter reviews the application of eco-engineered systems for remediation of the polluted rivers. Different laboratory scale and on-site treatment technologies for river bioremediation are reviewed in this chapter for instance, constructed wetlands, floating islands, bioracks, ecotanks, biofilters, microbial nano-bubble systems, periphyton based bioremediation systems, as well as hybrid integrated treatment systems. The application of combined bioremediation technologies and engineering approaches are discussed for removal of various river pollutants. Suggestions have been made on future research for developing pragmatic approaches in the remediation of polluted riverine ecosystems.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Subscribe and save.

• Get 10 units per month
• Download Article/Chapter or eBook
• 1 Unit = 1 Article or 1 Chapter
• Cancel anytime
• Available as PDF
• Read on any device
• Instant download
• Own it forever
• Available as EPUB and PDF
• Compact, lightweight edition
• Dispatched in 3 to 5 business days
• Free shipping worldwide - see info
• Durable hardcover edition

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Similar content being viewed by others

Bioremediation of Aquatic Environment

Reversing the damage: ecological restoration of polluted water bodies affected by pollutants due to anthropogenic activities

An Overview of Natural Water Contamination and Sustainable Attenuation Techniques: Challenges and Opportunities

Archana G, Dhodapkar R, Kumar A (2016) Offline solid-phase extraction for preconcentration of pharmaceuticals and personal care products in environmental water and their simultaneous determination using the reversed phase high-performance liquid chromatography method. Environ Monit Assess 188(9):512. https://doi.org/10.1007/s10661-016-5510-1

Article   CAS   Google Scholar  

Azim ME (2009) Photosynthetic periphyton and surfaces. In: Likens GE (ed) Encyclopedia of inland waters. Academic, Oxford, pp 184–191. https://doi.org/10.1016/B978-012370626-3.00144-7

Chapter   Google Scholar  

Balakrishna K, Rath A, Praveen Kumar Reddy Y et al (2017) A review of the occurrence of pharmaceuticals and personal care products in Indian water bodies. Ecotoxicol Environ Saf 137:113–120. https://doi.org/10.1016/j.ecoenv.2016.11.014

Article   CAS   PubMed   Google Scholar  

Bohn BA, Kershner JL (2002) Establishing aquatic restoration priorities using a watershed approach. J Environ Manag 64(4):355–363. https://doi.org/10.1006/jema.2001.0496

Bona F, Cecconi G, Maffiotti A (2000) An integrated approach to assess the benthic quality after sediment capping in Venice lagoon. Aquat Ecosyst Health Manag 3(3):379–386. https://doi.org/10.1080/14634980008657035

Article   Google Scholar  

Brix H (1997) Do macrophytes play a role in constructed treatment wetlands? Water Sci Techchnol 35(5):11–17. https://doi.org/10.1016/S0273-1223(97)00047-4

Bu F, Xu X (2013) Planted floating bed performance in treatment of eutrophic river water. Environ Monit Assess 185(11):9651–9662. https://doi.org/10.1007/s10661-013-3280-6

Cao W, Zhang H, Wang Y et al (2012) Bioremediation of polluted surface water by using biofilms on filamentous bamboo. Ecol Eng 42:146–149. https://doi.org/10.1016/j.ecoleng.2012.02.018

Cao W, Wang Y, Sun L et al (2016) Removal of nitrogenous compounds from polluted river water by floating constructed wetlands using rice straw and ceramsite as substrates under low temperature conditions. Ecol Eng 88:77–78. https://doi.org/10.1016/j.ecoleng.2015.12.019

Central Pollution Control Board (2018a) Restoration of polluted river stretches, concept and plan, Delhi, January 2018. https://cpcb.nic.in/wqm/Restoration-of-Polluted-River-Stretches-Concept-Plan.pdf

Central Pollution Control Board (2018b) River stretches for restoration of water quality, state wise and priority wise, Delhi, September 2018. https://www.cpcb.nic.in/wqm/PollutedStretches-2018.pdf

Cestti R, Srivastava J, Jung S (2003) Agriculture nonpoint source pollution control: good management practices-the Chesapeake Bay Experience. In: Report of Environmentally & Socially Development Unit Europe and Central Asia. The World Bank, Washington, DC, pp 1–55. https://doi.org/10.1596/0-8213-5523-6

Chang J, Mei J, Jia W et al (2019) Treatment of heavily polluted river water by tidal-operated biofilters with organic/inorganic media: evaluation of performance and bacterial community. Bioresour Technol 279:34–42. https://doi.org/10.1016/j.biortech.2019.01.060

Chaudhary M, Walker TR (2019) River Ganga pollution: causes and failed management plans (correspondence on Dwivedi et al. 2018. Ganga water pollution: A potential health threat to inhabitants of Ganga basin. Environ Int 117: 327–338). Environ Int 126:202–206. https://doi.org/10.1016/j.envint.2018.05.015

Chaudhary M, Mishra S, Kumar A (2017) Estimation of water pollution and probability of health risk due to imbalanced nutrients in River Ganga, India. Intl J River Basin Manag 15(1):53–60. https://doi.org/10.1080/15715124.2016.1205078

Dong H, Qiang Z, Li T et al (2012) Effect of artificial aeration on the performance of vertical-flow constructed wetland treating heavily polluted river water. J Environ Sci 24(4):596–601. https://doi.org/10.1016/S1001-0742(11)60804-8

Du L, Trinh X, Chen Q et al (2018) Enhancement of microbial nitrogen removal pathway by vegetation in integrated vertical-flow constructed wetlands (IVCWs) for treating reclaimed water. Bioresour Technol 249:644–651. https://doi.org/10.1016/j.biortech.2017.10.074

Dudgeon D, Arthington AH, Gessner MO et al (2006) Freshwater biodiversity: importance, threats, status and conservation challenges. Biol Rev 81(2):163–182. https://doi.org/10.1017/S1464793105006950

Article   PubMed   Google Scholar  

Dwivedi S, Mishra S, Tripathi RD (2018) Ganga water pollution: a potential health threat to inhabitants of Ganga basin. Environ Int 117:327–338. https://doi.org/10.1016/j.envint.2018.05.015

Dzakpasu M, Wang X, Zheng Y et al (2015) Characteristics of nitrogen and phosphorus removal by a surface-flow constructed wetland for polluted river water treatment. Water Sci Technol 71(6):904–912. https://doi.org/10.2166/wst.2015.049

Fang T, Bao S, Sima X et al (2016) Study on the application of integrated eco-engineering in purifying eutrophic river waters. Ecol Eng 94:320–328. https://doi.org/10.1016/j.ecoleng.2016.06.003

Faulwetter JL, Gagnon V, Sundberg C et al (2009) Microbial processes influencing performance of treatment wetlands: a review. Ecol Eng 35(6):987–1004. https://doi.org/10.1016/j.ecoleng.2008.12.030

Gao YN, Li WG, Zhang DY et al (2010) Bio-enhanced activated carbon filter with immobilized microorganisms for removing organic pollutants in the Songhua River. Water Sci Technol 62(12):2819–2828. https://doi.org/10.2166/wst.2010.666

Gao H, Xie Y, Hashim S et al (2018) Application of microbial technology used in bioremediation of urban polluted river: a case study of Chengnan River, China. Water 10(5):643. https://doi.org/10.3390/w10050643

Guo W, Li Z, Cheng S et al (2014) Performance of a pilot-scale constructed wetland for storm water runoff and domestic sewage treatment on the banks of a polluted urban river. Water Sci Technol 69(7):1410–1418. https://doi.org/10.2166/wst.2014.027

Hamner S, Broadaway SC, Mishra VB et al (2007) Isolation of potentially pathogenic Escherichia coli O157: H7 from the Ganges River. Appl Environ Microbiol 73(7):2369–2372. https://doi.org/10.1128/AEM.00141-07

Article   CAS   PubMed   PubMed Central   Google Scholar  

Hester ET, Doyle MW (2011) Human impacts to river temperature and their effects on biological processes: a quantitative synthesis. J Am Water Resour Assoc 47:571–587. https://doi.org/10.1111/j.1752-1688.2011.00525.x

Holl KD, Crone EE, Schultz CB (2003) Landscape restoration: moving from generalities to methodologies. Bio Sci 53(5):491–502. https://doi.org/10.1641/0006-3568(2003)053[0491:LRMFGT]2.0.CO;2

Hubbard RK, Gascho GJ, Newton GL (2004) Use of floating vegetation to remove nutrients from swine lagoon wastewater. ASABE 47(6):1963. https://doi.org/10.13031/2013.17809

Jing Z, Li YY, Cao S et al (2012) Performance of double-layer biofilter packed with coal fly ash ceramic granules in treating highly polluted river water. Bioresour Technol 120:212–217. https://doi.org/10.1016/j.biortech.2012.06.069

Jones JL, Jenkins RO, Haris PI (2018) Extending the geographic reach of the water hyacinth plant in removal of heavy metals from a temperate Northern Hemisphere river. Sci Rep 8(1):11071. https://doi.org/10.1038/s41598-018-29387-6

Kadlec RH, Wallace SD (2009) Treatment wetlands, 2nd edn. CRC Press/Taylor & Francis Group, Boca Raton. https://doi.org/10.1201/9781420012514

Book   Google Scholar  

Kafilzadeh F (2015) Assessment of organochlorine pesticide residues in water, sediments and fish from Lake Tashk, Iran. Achiev Life Sci 9(2):107–111. https://doi.org/10.1016/j.als.2015.12.003

Kanan MW, Nocera DG (2008) In situ formation of an oxygen-evolving catalyst in neutral water containing phosphate and Co2+. Science 321(5892):1072–1075. https://doi.org/10.1126/science.1162018

Kangas P, Mulbry W (2014) Nutrient removal from agricultural drainage water using algal turf scrubbers and solar power. Bioresour Technol 152:484–489. https://doi.org/10.1016/j.biortech.2013.11.027

Kato Y, Takemon Y, Hori M (2009) Invertebrate assemblages in relation to habitat types on a floating mat in Mizorogaike Pond, Kyoto, Japan. Limnology 10(3):167. https://doi.org/10.1007/s10201-009-0274-8

Khatri N, Tyagi S (2015) Influences of natural and anthropogenic factors on surface and groundwater quality in rural and urban areas. Front Life Sci 8(1):23–39. https://doi.org/10.1080/21553769.2014.933716

Kleindienst S, Joye SB (2019) Global aerobic degradation of hydrocarbons in aquatic systems. In: Rojo F (ed) Aerobic utilization of hydrocarbons, oils, and lipids. Handbook of hydrocarbon and lipid microbiology. Springer, Cham, pp 797–814. https://doi.org/10.1007/978-3-319-50418-6

Lake Phillip S, Palmer MA, Biro P et al (2000) Global change and the biodiversity of freshwater ecosystems: impacts on linkages between above-sediment and sediment biota: all forms of anthropogenic disturbance-changes in land use, biogeochemical processes, or biotic addition or loss-not only damage the biota of freshwater sediments but also disrupt the linkages between above-sediment and sediment-dwelling biota. Biosci J 50(12):1099–1107. https://doi.org/10.1641/0006-3568(2000)050[1099:GCATBO]2.0.CO;2

Langergraber G, Giraldi D, Mena J et al (2009) Recent developments in numerical modelling of subsurface flow constructed wetlands. Sci Total Environ 407(13):3931–3943. https://doi.org/10.1016/j.scitotenv.2008.07.057

Li XN, Song HL, Li W et al (2010) An integrated ecological floating-bed employing plant, freshwater clam and biofilm carrier for purification of eutrophic water. Ecol Eng 36(4):382–390. https://doi.org/10.1016/j.ecoleng.2009.11.004

Li Y, Zhu G, Ng WJ, Tan SK (2014) A review on removing pharmaceutical contaminants from wastewater by constructed wetlands: design, performance and mechanism. Sci Total Environ 468:908–932. https://doi.org/10.1016/j.scitotenv.2013.09.018

Liu M, Wu S, Chen L et al (2014) How substrate influences nitrogen transformations in tidal flow constructed wetlands treating high ammonium wastewater? Ecol Eng 73:478–486. https://doi.org/10.1016/j.ecoleng.2014.09.111

Liu J, Wang F, Liu W et al (2016) Nutrient removal by up-scaling a hybrid floating treatment bed (HFTB) using plant and periphyton: from laboratory tank to polluted river. Bioresour Technol 207:142–149. https://doi.org/10.1016/j.biortech.2016.02.011

Liu G, He T, Liu Y et al (2019) Study on the purification effect of aeration-enhanced horizontal subsurface-flow constructed wetland on polluted urban river water. Environ Sci Pollut R 26:12867. https://doi.org/10.1007/s11356-019-04832-9

Loupasaki E, Diamadopoulos E (2013) Attached growth systems for wastewater treatment in small and rural communities: a review. J Chem Technol Biotechnol 88(2):190–204. https://doi.org/10.1002/jctb.3967

Lu HL, Ku CR, Chang YH (2015) Water quality improvement with artificial floating islands. Ecol Eng 74:371–375. https://doi.org/10.1016/j.ecoleng.2014.11.013

Malmqvist B, Rundle S (2002) Threats to the running water ecosystems of the world. Environ Conserv 29(2):134–153. https://doi.org/10.1017/S0376892902000097

Maurya PK, Malik DS, Yadav KK et al (2019) Bioaccumulation and potential sources of heavy metal contamination in fish species in River Ganga basin: possible human health risks evaluation. Toxicol Rep 6:472–481. https://doi.org/10.1016/j.toxrep.2019.05.012

Ministry of Water Resources, River Development and Ganga Rejuvenation Central Water Commission (2018) Status of trace and toxic metals in Indian rivers. http://www.indiaenvironmentportal.org.in/files/file/status_trace_toxic_materials_indian_rivers.pdf

Mitra S, Corsolini S, Pozo K et al (2019) Characterization, source identification and risk associated with polyaromatic and chlorinated organic contaminants (PAHs, PCBs, PCBzs and OCPs) in the surface sediments of Hooghly estuary, India. Chemosphere 221:154–165. https://doi.org/10.1016/j.chemosphere.2018.12.173

Mutiyar PK, Mittal AK (2014) Occurrences and fate of selected human antibiotics in influents and effluents of sewage treatment plant and effluent-receiving river Yamuna in Delhi (India). Environ Monit Assess 186(1):541–557. https://doi.org/10.1007/s10661-013-3398-6

Pan G, Zhang MM, Chen H et al (2006) Removal of cyanobacterial blooms in Taihu Lake using local soils. I Equilibrium and kinetic screening on the flocculation of Microcystis aeruginosa using commercially available clays and minerals. Environ Pollut 141(2):195–200. https://doi.org/10.1016/j.envpol.2005.08.041

Pan B, Yuan J, Zhang X et al (2016) A review of ecological restoration techniques in fluvial rivers. Int J Sediment Res 31(2):110–119. https://doi.org/10.1016/j.ijsrc.2016.03.001

Paul D (2017) Research on heavy metal pollution of river Ganga: a review. Ann Agrar Sci 15(2):278–286. https://doi.org/10.1016/j.aasci.2017.04.001

Philip JM, Aravind UK, Aravindakumar CT (2018) Emerging contaminants in Indian environmental matrices – a review. Chemosphere 190:307–326. https://doi.org/10.1016/j.chemosphere.2017.09.120

Porta A, Young JK, Molton PM (1993) In situ bioremediation in Europe. In: Abstracts of 2nd international symposium on in situ and onsite bioreclamation, San Diego, California, 5–8 April 1993. Website: https://www.osti.gov/servlets/purl/10175248

Priyadarshani N (2009) Ganga river pollution in India-a brief report. In: American Chronicle, 8 September 2009. Website: http://www.americanchronicle.com/articles/view/109078

Pure Earth and Green Cross, Blacksmith Institute (2016) World’s worst pollution problems, the toxics beneath our feet, Switzerland. https://www.worstpolluted.org/docs/WorldsWorst2016.pdf

Qiu L, Zhang S, Wang G (2010) Performances and nitrification properties of biological aerated filters with zeolite, ceramic particle and carbonate media. Bioresour Technol 101(19):7245–7251. https://doi.org/10.1016/j.biortech.2010.04.034

Rai UN, Tripathi RD, Singh NK, Upadhyay AK et al (2013) Constructed wetland as an ecotechnological tool for pollution treatment for conservation of Ganga river. Bioresour Technol 148:535–541. https://doi.org/10.1016/j.biortech.2013.09.005

Rai UN, Upadhyay AK, Singh NK et al (2015) Seasonal applicability of horizontal sub-surface flow constructed wetland for trace elements and nutrient removal from urban wastes to conserve Ganga River water quality at Haridwar, India. Ecol Eng 81:115–122. https://doi.org/10.1016/j.ecoleng.2015.04.039

Rajeshkumar S, Li X (2018) Bioaccumulation of heavy metals in fish species from the Meiliang Bay, Taihu Lake, China. Toxicol Rep 5:288–295. https://doi.org/10.1016/j.toxrep.2018.01.007

Rathour R, Patel D, Shaikh S et al (2019a) Eco-electrogenic treatment of dyestuff wastewater using constructed wetland-microbial fuel cell system with an evaluation of electrode-enriched microbial community structures. Bioresour Technol 285:121349. https://doi.org/10.1016/j.biortech.2019.121349

Rathour R, Kalola V, Johnson J et al (2019b) Treatment of various types of wastewaters using microbial fuel cell systems. In: Microbial electrochemical technology. Elsevier, pp 665–692. https://doi.org/10.1016/B978-0-444-64052-9.00027-3

Rehman K, Imran A, Amin I et al (2019) Enhancement of oil field-produced wastewater remediation by bacterially-augmented floating treatment wetlands. Chemosphere 217:576–583. https://doi.org/10.1016/j.chemosphere.2018.11.041

Revenga CI, Campbell R, Abell P et al (2005) Prospects for monitoring freshwater ecosystems towards the 2010 targets. Philos Trans R Soc B 360(1454):397–413. https://doi.org/10.1098/rstb.2004.1595

Ribot M, Martí E, von Schiller D et al (2012) Nitrogen processing and the role of epilithic biofilms downstream of a wastewater treatment plant. Freshw Sci 31(4):1057–1069. https://doi.org/10.1899/11-161.1

Shahid MJ, Arslan M, Ali S et al (2018) Floating wetlands: a sustainable tool for wastewater treatment. Clean-Soil Air Water 46(10):1800120. https://doi.org/10.1002/clen.201800120

Shangguan H, Liu J, Zhu Y et al (2015) Start-up of a spiral periphyton bioreactor (SPR) for removal of COD and the characteristics of the associated microbial community. Bioresour Technol 193:456–462. https://doi.org/10.1016/j.biortech.2015.06.151

Shanmugam G, Sampath S, Selvaraj KK et al (2014) Non-steroidal anti-inflammatory drugs in Indian rivers. Environ Sci Pollut R 21(2):921–931. https://doi.org/10.1007/s11356-013-1957-6

Sharma BM, Bečanová J, Scheringer M et al (2019) Health and ecological risk assessment of emerging contaminants (pharmaceuticals, personal care products, and artificial sweeteners) in surface and groundwater (drinking water) in the Ganges River Basin, India. Sci Total Environ 646:1459–1467. https://doi.org/10.1016/j.scitotenv.2018.07.235

Sheng Y, Qu Y, Ding C et al (2013) A combined application of different engineering and biological techniques to remediate a heavily polluted river. Ecol Eng 57:1–7. https://doi.org/10.1016/j.ecoleng.2013.04.004

Siddiqui E, Verma K, Pandey U et al (2019) Metal contamination in seven tributaries of the Ganga River and assessment of human health risk from fish consumption. Arch Environ Contam Toxicol 77(2):263–278. https://doi.org/10.1007/s00244-019-00638-5

Soldo D, Behra R (2000) Long-term effects of copper on the structure of freshwater periphyton communities and their tolerance to copper, zinc, nickel and silver. Aquat Toxicol 47(3–4):181–189. https://doi.org/10.1016/S0166-445X(99)00020-X

Sun S, Sheng Y, Zhao G et al (2017) Feasibility assessment: application of ecological floating beds for polluted tidal river remediation. Environ Monit Assess 189(12):609. https://doi.org/10.1007/s10661-017-6339-y

Sun Y, Wang S, Niu J (2018) Microbial community evolution of black and stinking rivers during in situ remediation through micro-nano bubble and submerged resin floating bed technology. Bioresour Technol 258:187–194. https://doi.org/10.1016/j.biortech.2018.03.008

Umphres GD IV, Roelke DL, Netherland MD (2012) A chemical approach for the mitigation of Prymnesium parvum blooms. Toxicon 60(7):1235–1244. https://doi.org/10.1016/j.toxicon.2012.08.006

United Nations Children’s Fund (2009) UNICEF water, sanitation and hygiene annual report 2009 UNICEF WASH Section, Programme Division. UNICEF, New York. https://www.unicef.org/wash/files/UNICEF_WASH_2008_Annual_Report_Final_27_05_2009.pdf

Google Scholar  

United Nations World Water Development (2003) Water for people water for life world water, Assessment Programme. Website: http://www.unesco.org/new/en/naturalsciences/environment/water/wwap/wwdr/wwdr1

Verones F, Hanafiah MM, Pfister S et al (2010) Characterization factors for thermal pollution in freshwater aquatic environments. Environ Sci Technol 44:9364–9369. https://doi.org/10.1021/es102260c

Viéet JC, Hilton-Taylor C, Stuart SN (2009) Wildlife in a changing world: an analysis of the 2008 IUCN Red List of threatened species. IUCN. https://portals.iucn.org/library/sites/library/files/documents/RL-2009-001.pdf

Wang J, Zhang L, Lu S et al (2012) Contaminant removal from low-concentration polluted river water by the bio-rack wetlands. J Environ Sci 24(6):1006–1013. https://doi.org/10.1016/S1001-0742(11)60952-2

Wang Y, Wu H, Gao L et al (2019) Spatial distribution and physical controls of the spring algal blooming off the Changjiang River Estuary. Estuar Coast 42(4):1066–1083. https://doi.org/10.1007/s12237-019-00545-x

Webb AA, Erskine WD (2003) A practical scientific approach to riparian vegetation rehabilitation in Australia. J Environ Manag 68(4):329–341. https://doi.org/10.1016/S0301-4797(03)00071-9

Whitehead C, Brown JA (1989) Endocrine responses of brown trout, Salmo trutta L., to acid, aluminium and lime dosing in a Welsh hill stream. J Fish Biol 35(1):59–71. https://doi.org/10.1111/j.1095-8649.1989.tb03393.x

Wohl E, Angermeier PL, Bledsoe B et al (2005) Opinions-W10301-river restoration. Water Resour Res 41(10). https://doi.org/10.1029/2005WR003985

World Health Organisation (2011) Guidelines for drinking-water quality. WHO Chronicle 38(4):104–108. https://apps.who.int/iris/bitstream/handle/10665/44584/9789241548151_eng.pdf;jsessionid=B3795CB30C01A35D6C916D5F5F132BOB

World Health Organisation (2019) Drinking-water, Key facts. 14, June, 2019. Website: https://www.who.int/news-room/fact-sheets/detail/drinking-water

Wu Y, He J, Yang L (2010) Evaluating adsorption and biodegradation mechanisms during the removal of microcystin-RR by periphyton. Environ Sci Technol 44(16):6319–6324. https://doi.org/10.1021/es903761y

Wu Y, Xia L, Yu Z et al (2014) In situ bioremediation of surface waters by periphytons. Bioresour Technol 151:367–372. https://doi.org/10.1016/j.biortech.2013.10.088

Wu H, Zhang J, Ngo HH et al (2015) A review on the sustainability of constructed wetlands for wastewater treatment: design and operation. Bioresour Technol 175:594–601. https://doi.org/10.1016/j.biortech.2014.10.068

Wu Y, Lin H, Yin W (2019) Water quality and microbial community changes in an urban river after micro-nano bubble technology in situ treatment. Water 11(1):66. https://doi.org/10.3390/w11010066

Xiao J, Wang H, Chu S et al (2013) Dynamic remediation test of polluted river water by Eco-tank system. Environ Technol 34(4):553–558. https://doi.org/10.1080/09593330.2012.704405

Xiao J, Chu S, Tian G et al (2016) An Eco-tank system containing microbes and different aquatic plant species for the bioremediation of N, N-dimethylformamide polluted river waters. J Hazard Mater 320:564–570. https://doi.org/10.1016/j.jhazmat.2016.07.037

Xu XY, Feng LJ, Zhu L et al (2012) Biofilm formation and microbial community analysis of the simulated river bioreactor for contaminated source water remediation. Environ Sci Pollut Res 19(5):1584–1593. https://doi.org/10.1007/s11356-011-0649-3

Yang Z, Cui B, Liu J (2005) Estimation methods of eco-environmental water requirements: case study. Sci China Ser D 48(8):1280. https://doi.org/10.1360/02yd0495

Yang Y, Zhao Y, Liu R et al (2018) Global development of various emerged substrates utilized in constructed wetlands. Bioresour Technol 261:441–452. https://doi.org/10.1016/j.biortech.2018.03.085

Zhang CB, Liu WL, Pan XC et al (2014) Comparison of effects of plant and biofilm bacterial community parameters on removal performances of pollutants in floating island systems. Ecol Eng 73:58–63. https://doi.org/10.1016/j.ecoleng.2014.09.023

Zhang L, Zhao J, Cui N (2016) Enhancing the water purification efficiency of a floating treatment wetland using a biofilm carrier. Environ Sci Pollut R 23(8):7437–7443. https://doi.org/10.1007/s11356-015-5873-9

Zheng Y, Wang X, Xiong J et al (2014) Hybrid constructed wetlands for highly polluted river water treatment and comparison of surface-and subsurface-flow cells. J Environ Sci 26(4):749–756. https://doi.org/10.1016/S1001-0742(13)60482-9

Zhong J, Fan C, Zhang L et al (2010) Significance of dredging on sediment denitrification in Meiliang Bay, China: a year long simulation study. Environ Sci Pollut Res 22(1):68–75. https://doi.org/10.1016/S1001-0742(09)60076-0

Download references

Acknowledgement

Authors are thankful to Charotar University of Science and Technology (CHARUSAT), Changa – 388 421, Gujarat, India for providing CHARUSAT Ph.D. Scholars’ Fellowship to Ms. Shabnam Shaikh.

Author information

Authors and affiliations.

Department of Biological Sciences, P. D. Patel Institute of Applied Sciences, Charotar University of Science and Technology (CHARUSAT), Changa, Gujarat, India

Shabnam Shaikh & Chirayu Desai

Environmental Genomics and Proteomics Lab, Post Graduate Department of Biosciences, UGC Center of Advanced Study, Sardar Patel University, Anand, Gujarat, India

Kunal R. Jain & Datta Madamwar

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to Chirayu Desai .

Editor information

Editors and affiliations.

Department of Applied Chemistry, Zakir Husain College of Engineering and Technology,, Aligarh Muslim University, Aligarh, India

Department of Chemistry, Faculty of Science, Aligarh Muslim University, Aligarh, India

Mohd Imran Ahamed

Aix Marseille University, CNRS, IRD, INRA, Coll France, CEREGE, Aix en Provence, France

Eric Lichtfouse

Department of Chemistry, College of Science, Taif University, Taif, Saudi Arabia

Tariq Altalhi

Rights and permissions

Reprints and permissions

Copyright information

© 2021 The Author(s), under exclusive license to Springer Nature Switzerland AG

About this chapter

Shaikh, S., Jain, K.R., Madamwar, D., Desai, C. (2021). Ecoengineered Approaches for the Remediation of Polluted River Ecosystems. In: Inamuddin, Ahamed, M.I., Lichtfouse, E., Altalhi, T. (eds) Remediation of Heavy Metals. Environmental Chemistry for a Sustainable World, vol 70. Springer, Cham. https://doi.org/10.1007/978-3-030-80334-6_10

Download citation

DOI : https://doi.org/10.1007/978-3-030-80334-6_10

Published : 11 November 2021

Publisher Name : Springer, Cham

Print ISBN : 978-3-030-80333-9

Online ISBN : 978-3-030-80334-6

eBook Packages : Biomedical and Life Sciences Biomedical and Life Sciences (R0)

Share this chapter

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Publish with us

Policies and ethics

• Find a journal
• Track your research

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 18 March 2024

Impact on urban river water quality and pollution control of water environmental management projects based on SMS-Mike21 coupled simulation

• Huaibin Wei 1 ,
• Yiding Rao 2 ,
• Jing Liu 3 , 4 ,
• Yao Wang 2 &
• Yongxiao Cao 2  

Scientific Reports volume  14 , Article number:  6492 ( 2024 ) Cite this article

1240 Accesses

Metrics details

• Environmental sciences

To explore the impact of expanding Nanyang Sewage Purification Center (NSPC) on the main sewage discharge area of Bai River, we constructed a 2D hydrodynamic-water quality model based on surface water modeling system (SMS) and Mike21. Simulating three sewage discharge conditions in wet, normal, and dry season, we evaluated three indicators (COD, NH 3 -N, and BOD 5 ) by the single-factor pollution index and provided recommendations for water environment management. The results showed that, maximum absolute error of water level was 0.08 m, percentage bias coefficient of COD, NH 3 -N and BOD 5 were 19.3%, 16.2% and 23.1%, indicating the SMS and Mike21 coupling model was applicable; water quality of the assessment section were upgraded from the original class IV, V, V (Condition 1) to class IV, III, II (Condition 2) and class IV, III, III (Condition 3) in the wet, normal and dry season, indicating that NSPC's expansion had improved the water quality of the assessment section; as the primary pollutant, BOD 5 concentration in the downstream was lower than the upstream, which was due to the dilution effect of river. Therefore, on the basis of expanding NSPC, we recommend to remediation of BOD 5 by physical, chemical, and biological methods. This study broadens new ideas for the application of Mike21, and provide a reference for the prevention and improvement of river water pollution in urban areas.

Similar content being viewed by others

Water quality assessment of east Tiaoxi River, China, based on a comprehensive water quality index model and Monte-Carlo simulation

A novel assessment considering spatial and temporal variations of water quality to identify pollution sources in urban rivers

Potential Impacts of Climate and Land Use Change on the Water Quality of Ganga River around the Industrialized Kanpur Region

Introduction.

As a population and industrial agglomeration area, population expansion and industrial development had increased the amount of sewage into urban rivers, which had hindered the development of cities 1 , 2 . When studying the changes of the rivers’ water environment, the hydrodynamic-water quality model is often used to simulate the water environment, and then figure out the water environment problems and put forward targeted measures, which has strong practical significance and guiding significance for water environment governance 3 , 4 , 5 , 6 .

Hydrodynamics and water quality are the two characteristics of water environment. Using real measured data, so as to investigate the influence of hydraulic conditions on water quality, and then construct a coupling model of hydrodynamic-water quality to predict water environment, it is a key direction of international water environment research 7 , 8 , 9 . The hydrodynamic-water quality model can not only quantitatively describe the water environment system and the complex processes that occur within it, but also intuitively display the scope and degree of pollution impact on the layer of geographic information system, so as to provide decision-making basis for the early warning and prevention of water pollution accidents 10 , 11 . During the years of practice, the hydrodynamic-water quality model has developed zero-dimensional model, 1D model, 2D model, 3D model and different dimensional model coupling 9 , 10 , 11 , 12 . Different kinds of model have different simulation priorities and applicability. The zero-dimensional model does not contain an input–output model of hydrodynamic information, only assumes the water body is well mixed. The 1D model can simplify the complex river network, and is suitable for the situation with little change in the horizontal and vertical directions, which is advantageous of high computational efficiency 13 . The computational result of the 2D model is more detailed, which can accurately simulate local flow patterns and pollutant migration, and is suitable for wider rivers and lakes 14 . The 3D model comprehensively considers the hydrodynamics and water quality changes of the three dimensions, and the calculation results are more accurate and comprehensive, but the calculation is a huge quantity 15 . The different dimensional model coupling is often constructed according to the characteristics of the study object and study purpose, then the model’s applicability is stronger. For example, the MIKE-11 model and the MIKE-21 model were coupled to simulate the flood inundation of the Ahoi River 16 . In this paper, the river’s channel is wide, the 2D hydrodynamic-water quality coupling model is applicable. While Mike21 has a multi-functional module and powerful pre-and post-processing functions, which can better reflect the influence of river bottom fluctuations on water level, flow regime and water quality, and is widely used in hydrodynamic-water quality simulation of rivers, lakes and reservoirs 17 , 18 , 19 . At the same time, considering that the mesh generated by SMS has more advantages in the computational speed and the convergence speed of the solution, we use SMS and Mike21 to establish a 2D hydrodynamic-water quality model, which is conducive to improve the model’s accuracy 20 . In addition, in the past studies on the hydrodynamic-water quality models, few scholars considered the water quality in different hydrology periods 21 , 22 , when setting the sewage discharge scenario, we comprehensively consider the upstream water volume and quality of the studied river in different hydrology periods, which can make the model closer to the actual situation and provide a scientific theoretical basis to refine the water pollution control of the river.

According to the water quality evaluation from 2017 to 2021 by the water environment quality monitoring network of Henan Province, it showed that the water quality indicators COD, NH 3 -N and BOD 5 of the main sewage discharge area of the Bai River (Nanyang section) continuously exceed the target water quality category of the assessment section. In this paper, we took the main sewage discharge area as the study area, it includes all the sewage discharge outlets in the Bai River (Nanyang section), and its downstream section is designated as a water quality control section by the water administrative authority. So we used SMS and Mike21 to establish a 2D hydrodynamic-water quality coupling model for it, and selected COD, NH 3 -N, and BOD 5 as water quality indicators, and designed nine sewage discharge scenarios from the perspectives of hydrology periods and sewage discharge into the river, the hydrology periods was divided into wet, normal and dry season, and the sewage discharge into the river is divided into Condition 1 (C1), Condition 2 (C2) and Condition 3 (C3) depending on the difference of the sewage discharge volume of each sewage discharge outlet before and after the expansion of NSPC. Based on the simulation results, we determined whether the water quality category of the assessment section meets the class III by the single factor pollution index of COD, NH 3 -N, and BOD 5 , and analyzed the spatial distribution of river water environmental pollution factors, then discussed the impact of the expansion of NSPC on the water environment of the Bai River, and proposed suggestions for the prevention and control of water environment pollution, so as to provide the scientific basis for the formulation of water environment treatment policies in the Bai River.

Materials and methods

The urban area of Nanyang City is located in the south of Henan Province (112°17′-112°50′ E, 32°37′–33°17′ N). Recently, with the rapid development of industrialization and urbanization, the volume of domestic and industrial wastewater drained into the urban river of Nanyang City had increased. Md Anawar et al., summarized the common measures of improving the rivers’ water environment are categorized into physical (mechanical aeration processes, water transfer or diversion and dilution, mechanical algae removal), chemical (flocculation, precipitation, oxidation, algaecides), biological (microbial bioremediation, biofilms, membrane bioreactor technology, plant purification treatment), ecological (ecological floating beds, artificial floating islands, constructed wetlands), engineering (building hydraulic structures, dredging river sediment) techniques, and hybrid techniques 23 . The sewage treatment works is a kind of water environmental management projects, with the function of decomposing and transforming the pollutants in sewage, which can reduce the discharge of water environmental pollutants, and effectively improve the urban water environment 24 , 25 . In order to prevent the deterioration of water quality and to promote the development of a safe water environment in the Bai River, NSPC planned to expand. NSPC is located on the north bank of the main sewage discharge area of the Bai River, with a current design scale of 200,000 m 3 /d, consisting of the first phase (100,000 m 3 /d, which was completed and put into operation in 2006) and the second phase (100,000 m 3 /d, which was completed and put into operation in 2016). With the development of urbanization and industrialization in the urban area of Nanyang City, the sewage treatment scale of NSPC cannot cover the current amount of sewage to be treated, and the municipal government plans to carry out a third phase project (200,000 m 3 /d) expansion. After the completion of the expansion, the scale of NSPC will reach 400,000 m 3 /d.

Examining the primary sewage discharge region of the Bai River (Nanyang section) as a case study, we assessed the repercussions of NSPC expansion on water quality. The Bai River, a key waterway coursing through Nanyang City’s urban expanse, is part of the primary arteries within the Han water system of the Yangtze River basin. NSPC features two sewage discharge outlets, S1 and S2, situated on the north bank of the Bai River. S1 releases untreated sewage, while S2 releases treated sewage. Additionally, on the south bank, Nanyang Tianguan Water Treatment Plant (NTWTP) has a sewage discharge outlet, S3, releasing treated sewage. Analyzing the combined impact of these three sewage discharge outlets provides a more precise understanding of their influence on the Bai River's water environment. These outlets are strategically positioned within the central area of the main sewage discharge region, as depicted in Fig.  1 , which is beneficial for more comprehensive simulation of pollution discharge conditions. Figure  1 is created using ArcMap10.2, URL, www.arcgis.com . Furthermore, Fig.  1 illustrated hydrological data monitoring points, namely P1, P2, and P3. P1 served as the water level monitoring point for the fourth hydrological monitoring station, P2 as the water quality monitoring point for the Dingfengdian Section, P3 as the water quality monitoring point for the Shangfanying section. Therefore, we selected the main sewage discharge area of the Bai River (Nanyang section) as the modelling area: the upstream boundary is the Nanyang fourth rubber dam section, and the downstream boundary is the Shangfanying section, with a total length of 5 km. In this paper, the Shangfanying section is the assessment section designated by the water administrative authority, which is used to judge whether the water quality of the main sewage discharge area meets the standard or not. When the water quality category of the assessment section reaches the standard of surface water class III, it means that the water environment of the main sewage discharge area meets the standard.

The location of the study area.

Model principle

Mike21 is a powerful 2D simulation tool for hydrodynamic-water quality of rivers, lakes, reservoirs, bays, etc. In this study, most of the main sewage discharge area of the Bai River have lateral spans of more than 200 m. Pollutant transport is characterized by obvious lateral diffusion, which cannot be uniformly mixed over a short distance. The hydrodynamic module calculates the resulting flow of forcing and boundary conditions, and the transport module computes the material transport outcome by considering the flow conditions determined in the hydrodynamic calculations. Therefore, the specific simulation process uses the Hydrodynamic Module (Mike21 HD) and the Transport Module (AD) of the Mike21 model, which is widely used to simulate water quality changes in 2D free-surface flow in wide-channel rivers.

Hydrodynamic model

The Hydrodynamic model (HD) adheres to the principles of three-dimensional incompressibility, Reynolds-valued homogeneous Navier–Stokes equations, and complies with the assumptions of Boussinesq and hydrostatic pressure. The Mike21 HD includes both the continuity and momentum equations 26 , 27 . The basic set of equations for the HD is:

where t is the time; η is the water level; d is the static water depth; h  =  η  +  d is the total water depth; the velocity components in the x , y direction of u and v , respectively; f is the Coriolis parameter; S is the source emissions; S xx , Sxy , S yx , and S yy are the components of the radiant stress tensor, respectively. τ sx and τ sv are surface wind stresses, and τ bx and τ bv are bottom stresses. T xx , T xy , and T yy are lateral stresses; u s , v s are the flow velocity of the source and sink terms; the letter with a dash is the mean of that physical quantity.

Water quality model

We used the Transport Module (AD) to calculate the water quality model. Transport Module is a mathematical description of the pattern of change of pollutants in the water environment and the interrelationships between their influencing factors, which is both one of the contents of scientific research on the water environment and an important tool for water environment research 28 . In this paper, the Transport Module of the Mike21 was selected as the water quality module, and the transport and diffusion equations of pollutants are given in the following equation 29 :

where D x and D y are the turbulent diffusion coefficients in the x and y directions, respectively. C is the composite concentration (constant); F(C) is the biochemical reflection term.

The percentage bias coefficient

The Percentage Bias Coefficient (PBIAS) is frequently employed to assess the accuracy of water quality simulation outcomes from the model. This coefficient characterizes the extent of disparity between the measured and simulated values 30 . The formula for PBIAS is as follows 31 :

where M v represents the measured value, C v stands for the simulated value, and n denotes the number of measured data points. Typically, in water quality simulation outcomes, PBIAS ≤ 25% signifies excellent results, 25% < PBIAS ≤ 40% indicates good results, while values beyond these ranges suggest fair results.

Water quality evaluation

The single factor pollution index is often used as a method of evaluating individual pollution factors, and the measured value of the index is compared with the standard limit of the index in the Environmental Quality Standard for Surface Water (GB 3838-2002) , and the category of the worst index is used as the final water quality category. Should the indicator surpass the standard value associated with its respective functional category, it indicates that the water body fails to meet the pertinent water quality standards 32 . The method is simple and can help determine main pollutants and the relationship between the water quality status and assessment standards 33 , 34 . The calculation of the single factor index method can be expressed as 35 :

where SI is the single-factor pollution index of the pollutants; C i is actual concentration of pollutants i; S i is the evaluation standard value of pollutant i; and (SI i )max is the maximum classification for the pollutant parameters (the most polluted parameter).

Model construction and verification

Model construction, mesh processing.

Since the grid generated by the SMS grid generator is more advantageous in terms of computational speed and convergence rate of the solution, this paper utilized the SMS for mapping the grid topography of the Bai River 36 . By utilizing the measured data, we can acquire the geographical coordinates of points along the Bai River, in the SMS to draw the land and water boundary lines and smooth processing, and then use the unstructured triangular mesh to generate the triangular mesh delineation map, and screen the grid, adjusted the minimum angle of less than 30° of the mesh to reach the standard manually 37 , the production of the mesh delineation map is shown in Fig.  2 . The maximum cell side length of the grid in the grid topographic map is set to 50 m, the maximum cell area is set to 500 m 2 , and there are 5623 triangular adaptive grids. Finally, the topographic interpolation of the gridding map was carried out to generate the calculation grid, and the corresponding elevation data of the river came from the measured data of Nanyang Hydrology and Water Resources Survey Bureau.

Grid division of the study area.

Model boundary conditions

When setting the Mike21 model boundary conditions, it is generally accepted that the upstream boundary with inflow data and water level data as the downstream boundary condition could yield a more convergent and stable model 38 . The upstream boundary condition for model validation was the 2019 day-by-day inflow data at the Fourth Rubber Dam section of the Bai River, and the downstream boundary condition was the 2019 day-by-day outflow monitoring water level at the Shangfanying section of the Bai River.

Model parameter setting

In order to fit the natural geographical characteristics of the study river, so as to simulate the water environment condition, we chose CFL, Eddy viscosity, Manning number as the main parameters of the hydrodynamic model, and Diffusion coefficient, pollution factors degradation rate as the main parameters of the water quality model 39 . According to the water quality monitoring results of the assessment section of the Bai River in 2017 to 2021, COD, NH 3 -N, and BOD 5 were selected as the water quality indicators for model. After calibrated by the measured data of the Bai River in 2018, the value of the model parameters were shown in the Table 1 .

Model validation

Hydrodynamic model validation.

Day-by-day measured water level data of P1 from 1 January to 5 December 2019 were selected for hydrodynamic module validation, and the water level validation results are shown in Fig.  3 . The simulated water level values and their change trends closely aligned with the measured data in the model. The maximum absolute error between simulated and measured water levels is 0.08 m, with a maximum relative error of 0.073%. These findings indicate the reasonableness of the simulation results 26 .

The validation results of the water level.

Water quality model validation

The validation of the water quality module centered on P2 as the validation point. Measured concentrations of COD, NH 3 -N, and BOD 5 were selected for each month from January to December 2019 to compare with the corresponding simulated concentrations, and the water quality validation results were shown in Fig.  4 . The PBIAS of COD, NH 3 -N and BOD 5 in the simulation results of the water quality module are 19.3%, 16.2% and 23.1% respectively, which are all less than 25%, indicating that the simulation results were excellent, and it can be used for this study.

The validation results of the water quality. ( a ) COD, ( b ) NH 3 -N, ( c ) BOD 5 .

Results and discussion

Scenario setting.

Based on the actual situation of the construction of NSPC, the project were divided into three working conditions, from the operation stage of the first and second phases of NSPC in 2019 to the operation of the third phase of NSPC, and used the SMS-Mike21 coupling model to explore the impact of the three working conditions on the water environment under different hydrology periods. It should be added that we selected three water quality indicators: COD, NH 3 -N, and BOD 5 , and assumed that the concentration of water quality indicators of sewage discharged from each sewage discharge outlet will remain unchanged after the expansion of NSPC, and only the amount of sewage discharge will be changed. The working conditions are set in Table 2 .

Condition 1 (C1): In 2019, the first and second phase of NSPC was in operation stage. NSPC discharged 50,000 m 3 /d untreated sewage from S1 and 200,000 m 3 /d treated sewage from S2; meanwhile, NTWTP discharged 80,000 m 3 /d treated sewage from S3 during this period.

Condition 2 (C2): The future third phase of NSPC has been completed but is not running at full capacity. NSPC did not discharge sewage from S1, and discharging 250,000 m 3 /d treated wastewater from S2, S3 of NTWTP emissions remain unchanged.

Condition 3 (C3): Full-load operation of the third phase of NSPC. NSPC did not discharge sewage from S1, discharged treated sewage 400,000 m 3 /d from S2. Under the condition, NTWTP kept the unchanged discharge from S3.

To sum up, in terms of the amount of water inflow in different hydrology periods, the maximum upstream water inflow in the wet season in 2019 was 41.3 m 3 /d. In the dry season, the minimum upstream water flow was 1.79 m 3 /d. In terms of the water quality of different hydrology periods, the difference between the upstream water quality concentration of the three hydrology periods was small, and the COD concentration was the largest in the dry season, which was 27 mg/L. The concentrations of NH 3 -N and BOD 5 were the highest in the normal season, which were 0.34 mg/L and 3.93 mg/L, respectively. This paper explored the impacts of three working conditions on the water environment in different hydrology periods, which is conducive to the government's better response to the impacts of Nanyang City's wastewater discharge on the Bai River in different stages of development, and to provide effective measures for the management of the water environment.

Water quality evaluation results

In this study, the SMS-Mike21 hydrodynamic-water quality coupling model was employed to simulate variations in COD, NH 3 -N, and BOD 5 concentrations at the assessment section under three distinct operational conditions during different hydrology periods, and the simulation results were showed in Fig.  5 . Based on Fig.  5 , we used the Single-factor evaluation method and single-factor pollution index to evaluate the simulation results of each indicator, and the evaluation results are shown in the Table 3 . In the past, when considering different hydrological periods, water quantity was considered often and water quality was ignored, which would lead to ignoring the influence of incoming water quality on the water environment simulation results and not obtaining sufficient accurate research results 24 , 25 . In this paper, the differences in water quality between different hydrological seasons were considered to make the simulation more realistic.

Simulation value of the pollution factor concentration in the assessment section under different sewage discharge scenarios. ( a ) COD, ( b ) NH 3 -N, ( c ) BOD 5 .

Under C1, the concentration of the three indicators of the assessment section in each hydrological period is higher than the concentration under C2 and C3, because the most pollutants entered the river under C1. The water quality category evaluation results of assessment section in each hydrological period were shown in Table 3 , it can be seen that the water quality evaluation results in the wet season, normal season and dry season were class IV, V and V respectively, and the water quality category was the best in the wet season, which was due to the stronger dilution effect of the largest upstream water volume on the river pollutants. Besides, the most polluted parameter (SI) of the wet, normal and dry season were COD (1.085), BOD 5 (1.725) and BOD 5 (1.51) respectively. Therefore, under C1, the government needs to pay attention to the treatment of COD in the wet season, and the treatment of BOD 5 in the normal and dry season.

Under C2, the concentrations of the three indicators in each hydrological period of the assessment section decreased to varying degrees compared with C1, because the discharge of untreated sewage from S1 was stopped under C2, and the pollutants entering the river were reduced. The water quality category evaluation results of assessment section in each hydrological period were shown in Table 3 , it can be seen that the water quality evaluation results in the wet season, normal season and dry season were class IV, III and II respectively, among which the water quality category in the dry season was upgraded from class V to class II, and the improvement effect is the most obvious, followed by the water quality category in the normal season was upgraded from class V to class III, and the water quality category in the wet season was class IV, which had not changed, because the C2 was to discharge the treated water into the Bai river, diluting the polluted river. The most obvious reason for the dilution effect in the dry season was that the amount of water coming from the upstream is the least, and the dilution pressure is the lowest during the dry season. It can be seen from Table 3 , in the wet season, only the COD concentration exceeded the class III water quality standard, which is the excess multiple of 1.035, showing a slight decrease compared to the COD concentration in C1. Under C2, no pollution factor concentration exceeded the class III water quality standard in the normal and dry season. Compared with C1, the BOD 5 concentration exceeds the standard, it can be seen that the shutdown of S1 had a great positive effect on the pollution prevention and control of BOD 5 , and it can be inferred that the amount of BOD 5 in the untreated sewage in the urban area of Nanyang is higher.

Under C3, the water quality evaluation results in the wet season, normal season and dry season were class IV, III and III, respectively, In the wet season, only the COD concentration exceeded the water quality standard of Class III, which was Class IV, and the excess multiple was 1.015, but there was a slight decrease in the COD concentration relative to C2. In the normal season and the dry season, no pollution indicactor’s concentration exceeded the water quality standard of class III. Compared with C2, the water quality category of C3 did not change in the wet season and normal season, and only the water quality category was reduced from class II to III in the dry season, which was because the concentration simulation value of BOD 5 changed from class II to III. It can be speculated that after the full load operation of the third phase of NSPC, because the purification of BOD 5 by NSPC is not complete, with the increase of sewage discharge, the amount of water inflow decreases, and the concentration of BOD 5 in the assessment section increases. The government needs to increase the treatment of COD in the wet season and BOD 5 in the dry season, and at the same time, the NSPC needs to upgrade the purification technology and purification equipment of BOD 5 . Hence, following the full-load operation of NSPC’s third phase, incomplete BOD 5 purification by NSPC, coupled with rising sewage discharge and decreasing upstream water inflow, leads to BOD 5 concentration increased in the assessment section. Addressing this, the government should intensify COD treatment during the wet season and BOD 5 treatment in the dry season. Simultaneously, NSPC needs to upgrade BOD 5 purification technology and equipment for enhanced efficiency.

In conclusion, the expansion of the NSPC improved the water quality category of the assessment section. In C1, the water quality category of the assessment section was the worst, the water quality category of C2 and C3 had been greatly improved compared with C1. the main reason was the shut down of untreated sewage outlet S1. In C3, at full capacity, the increase of NSPC discharge led to no change in the water quality category of the Bai River during the wet season and normal season compared to C2. However, there was a slight increase in BOD 5 concentration during the dry season, resulting in a marginal decline in the overall water quality of the Bai River. It can be seen that the expansion of NSPC had improved water quality efficiently 24 , 25 , but the purification capability of BOD 5 is weak, and the purification technology needs to be further improved. This provided scientific guidance for the formulation of the Bai River’ water environment problems in the future.

According to the above analysis results, from the operation stage of the first and second phases of NSPC in 2019 to the completion of the construction of the third phase in the future, the BOD 5 concentration in sewage significantly influences the water quality category of the assessment section of the Bai River. Although the simulated value of water quality concentration varied in different hydrological periods, the spatial variation of concentration is basically the same. Therefore, we only chose the dry season as the hydrological background to explore the spatial variation characteristics of BOD 5 concentration under the three working conditions during the dry season, as shown in the Fig.  6 .

Spatial variation characteristics of BOD 5 concentration under three conditions during the dry season (January, February, and December): ( a ) C1, ( b ) C2, ( c ) C3.

Spatially, the concentration of BOD 5 decreased significantly from C1 to C2 during the dry season, but increased slightly from C2 to C3. Under C1, the overall BOD 5 concentration value of the river is too high, and the concentration variation range from 6 to 65 mg/L, which exceeded the class III surface water quality standard of BOD 5 (4 mg/L), the area with elevated pollution levels is situated in the upper reaches of the river, where the overall BOD 5 concentration exceeds 8 mg/L. This is primarily attributed to the presence of sewage outlets S1 and S2 in the upper reaches, with S1 discharging untreated sewage directly, leading to severely degraded water quality and significantly exacerbating the pollution situation in the Bai River section 40 , 41 . Under C2, the overall concentration value of BOD 5 in the river is lower than that of C1, and the variation range of concentration is 3–4.3 mg/L, and the pollution high value area of BOD 5 was located near the sewage outlet S2, and the concentration value exceeded the quality standard of class III surface water, which is due to the large discharge of S2 sewage outlet compared with S1, and the purification capability of NSPC for BOD 5 is weak, resulting in the pollution high value area of BOD 5 near S2. As the pollutants moved away from S2, the BOD 5 in the river channel gradually decreased due to the self-purification capability of the river. However, the closer to S3, the concentration of BOD 5 gradually increased, and then when the pollutant diffused to the downstream of the river, the dilution effect of the upstream to the downstream led to the gradual decrease of the pollutant concentration. In C3, the overall concentration value of BOD 5 in the river was slightly higher than that in C2, and the variation range of BOD 5 concentration was 3.1–4.5 mg/L. BOD 5 near S2 reached the highest value, which exceeded the Class III surface water quality standard. The spatial distribution of BOD 5 concentrations was the same as in C2.

In summary, from the spatial point of view, the overall spatial distribution of BOD 5 concentration under the three working conditions in the dry season showed that the downstream was better than the upstream, which was caused by the dilution from upstream to downstream.

Based on the above analysis, it was found that the BOD 5 concentration of C3 in the dry season was slightly worse than C2, due to the sharp increase in sewage discharge and the insufficient purification capability of BOD 5 by the NSPC. Therefore, BOD 5 is the main pollutant discharged from outlet and the most important factor leading to the deterioration of river water quality, so it is suggested that NSPC should actively fetch in new sewage purification technologies to further improve the sewage purification effect in the future, so as to reduce the concentration of pollution factors in the treated sewage, and improve the removal rate of BOD 5 23 .

Physical, chemical, and biological remediation techniques can be used to improve BOD 5 removal rate 42 . Physical remediation technology: the main principle is to remove pollutants in the river channel by means of dredging sediment, mechanical algae removal, water diversion, dredging and water transfer, etc., in this way to enhance the hydrodynamic conditions of the river, so as to improve the fluidity of the water body and enhance the dilution and degradation ability of pollutants 43 , 44 . Chemical remediation technology: the main principle is to use chemical agents that can react with specific pollutants to coagulate and precipitate pollutants or eliminate algae, and reduce the concentration of pollutants in the river. Bioremediation technology: the main principle is to use the metabolic activities of specific organisms (plants, microorganisms or protozoa) to absorb, transform, eliminate or degrade environmental pollutants to achieve environmental purification and ecological effect restoration 45 . In the actual process of water environment restoration, one kind of technology or a combination of technologies can be selected in combination with the actual situation of the restoration object, so as to achieve the purpose of water environment restoration better and faster 46 . This study pointed out the key treatment points and improvement ideas for the improvement of the water quality category and the overall water environment status of the main sewage discharge area of the Bai River (Nanyang Section).

In this paper, we considered the variation of water quantity and water quality in different hydrological periods, and established a two-dimensional hydrodynamic-water quality coupling model by SMS and Mike21 to make the model simulation results more available. This approach allows for a more comprehensive study into the impact of NSPC expansion on the water environment in the main sewage discharge area of the Bai River (Nanyang section). Therefore, SMS-Mike21 coupling model has good accuracy and applicability for simulating and predicting water environments in similar scenarios.

After the expansion of NSPC, the untreated sewage outlet S1 was closed, and the water quality of the Bai River was significantly improved in the normal season and the dry season, among which the water quality in the dry season was the most obvious. However, with the increase of NSPC sewage discharge, the concentration of BOD 5 in the assessment section increased slightly in the dry season, leading to a slight decrease in the water quality category of the section. Hence, while the expansion of NSPC contributes to enhancing water quality, the weak purification capability for BOD5 highlights the need for further improvements in purification technology.

From a spatial point of view, the water quality in the upper reaches of the river is superior to that in the lower reaches, attributed to the dilution effect of the water. Besides, due to significant pollutant discharges, localized increases in pollutant concentrations were observed near the three outlets 47 .

BOD 5 is the primary factor contributing to the degradation of water quality in the river assessment section, the impact of BOD 5 concentration on the overall water quality category of the river is particularly evident during the dry season. For a large amount of BOD 5 in the Bai River (Nanyang section), we recommend the remediation of BOD 5 by physical, chemical, and biological methods 41 , 42 , 43 .

This study provided SMS-Mike21 coupling model for the water environment simulation, pointed out the water environment simulation in different periods should pay attention to the difference in water quality. It offered targeted insights for improving river water quality, laying a scientific foundation for urban water environment control. Additionally, it provides guiding recommendations for future studies on water environment condition simulations. Future studies can enhance and broaden the model by include non-point source contamination into the model, thus rendering the water environment model more comprehensive.

Data availability

The data that support the finding of this study are available from the corresponding author upon reasonable request.

Luo, P. et al. Exploring sustainable solutions for the water environment in Chinese and Southeast Asian cities. Ambio 2021 , 1–20 (2021).

Google Scholar  

Weyand, M. & Rullich, L. River rehabilitation in urban areas–restrictions, possibilities and positive results. Water Supply 19 (3), 944–952 (2019).

Article   Google Scholar  

Mesquita, J. B. D. F. & Lima Neto, I. E. Coupling hydrological and hydrodynamic models for assessing the impact of water pollution on lake evaporation. Sustainability 14 (20), 13465 (2022).

Article   CAS   Google Scholar  

Mahyari, F. G. et al. Evaluation of a three-dimensional hydrodynamic and water quality model for design of wastewater stabilization ponds. J. Environ. Eng. 149 (4), 05023003 (2023).

Kang, M., Tian, Y., Zhang, H. & Wan, C. Effect of hydrodynamic conditions on the water quality in urban landscape water. Water Supply 22 (1), 309–320 (2022).

Yang, L., Wei, J., Qi, J. & Zhang, M. Effect of sewage treatment plant effluent on water quality of Zhangze Reservoir based on EFDC model. Front. Environ. Sci. 10 , 419 (2022).

Xue, B. et al. Modeling water quantity and quality for a typical agricultural plain basin of northern China by a coupled model. Sci. Total Env. 790 , 148139 (2021).

Pradhan, U. et al. Coupled hydrodynamic and water quality modeling in the coastal waters off Chennai, East Coast of India. Front. Mar. Sci. 9 , 987067 (2022).

Ziemińska-Stolarska, A. & Kempa, M. Modeling and monitoring of hydrodynamics and surface water quality in the Sulejów Dam Reservoir, Poland. Water 13 (3), 296 (2021).

Zhang, Z., Huang, J., Zhou, M., Huang, Y. & Lu, Y. A coupled modeling approach for water management in a river–reservoir system. Int. J. Environ. Res. Public Health 16 (16), 2949 (2019).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Ejigu, M. T. Overview of water quality modeling. Cogent Eng. 8 (1), 1891711 (2021).

Liang, J. et al. MIKE 11 model-based water quality model as a tool for the evaluation of water quality management plans. J. Water Supply: Res. Technol. AQUA 64 (6), 708–718 (2015).

Martin, J. L., Wool, T., & Olson, R. A dynamic one-dimensional model of hydrodynamics and water quality. In EPDRiv1 Version, 1 (2002).

Lu, X. et al. Simulation on TN and TP distribution of sediment in Liaohe estuary national wetland park using mike21-coupling model. Water 15 (15), 2727 (2023).

Man, X., Lei, C., Carey, C. C. & Little, J. C. Relative performance of 1-D versus 3-D hydrodynamic, water-quality models for predicting water temperature and oxygen in a shallow, eutrophic, managed reservoir. Water 13 (1), 88 (2021).

Kadam, P. & Sen, D. Flood inundation simulation in Ajoy River using MIKE-FLOOD. ISH J. Hydraul. Eng. 18 (2), 129–141 (2012).

Wang, Q., Peng, W., Dong, F., Liu, X. & Ou, N. Simulating flow of an urban river course with complex cross sections based on the Mike21 FM model. Water 12 (3), 761 (2020).

Li, X., Huang, M. & Wang, R. Numerical simulation of Donghu Lake hydrodynamics and water quality based on remote sensing and MIKE 21. ISPRS Int. J. Geo-Inf. 9 (2), 94 (2020).

Yan, B., Liu, Y., Gao, Z. & Liu, D. Simulation of sudden water pollution accidents in Hunhe River basin upstream of Dahuofang reservoir. Water 14 (6), 925 (2022).

Wan, L. & Wang, H. Control of urban river water pollution is studied based on SMS. Environ. Technol. Innov. 22 , 101468 (2021).

Zhang, X., Duan, B., He, S. & Lu, Y. Simulation study on the impact of ecological water replenishment on reservoir water environment based on Mike21——taking Baiguishan Reservoir as an example. Ecol. Indic. 138 , 108802 (2022).

Wen, Y., & Wang, Y. Numerical simulation of water environment capacity from wet, normal, and dry years: Taking the Luo River as an example. In AQUA—Water Infrastructure, Ecosystems and Society , 2023318 (2023).

Md Anawar, H. & Chowdhury, R. Remediation of polluted river water by biological, chemical, ecological and engineering processes. Sustainability 12 (17), 7017 (2020).

Zhang, J. et al. Current operation state of wastewater treatment plants in urban China. Environ. Res. 195 , 110843 (2021).

Article   CAS   PubMed   Google Scholar  

Li, J., Chen, Y. & Wang, Z. Effect of pollution load reduction on water quality in rural lakes in the shallow hill water network area. Water Supply 22 (7), 6213–6229 (2022).

Ma, T., Fu, J. & Sun, Y. Study on hydrodynamic optimization and water quality improvement of Yilong Lake based on Mike21. Water Resourc. Power 07 , 54–58 (2023).

Zhou, R., Zheng, H., Liu, Y., Xie, G. & Wan, W. Flood impacts on urban road connectivity in southern China. Sci. Rep. 12 (1), 16866 (2022).

Article   CAS   PubMed   PubMed Central   ADS   Google Scholar  

Hu, Y. & Zhou, L. Numerical simulation analysis on two-dimensional hydrodynamics and water quality of Shifosi Reservoir based on Mike21. Yangtze River 1 , 31–38 (2021).

Lei Sr, S. U. N., Ma, W., Ai Sr, Z., & Qing Sr, Y. Numerical simulation study on water environment of Puzhehei Lake. In 2nd International Conference on Applied Mathematics, Modelling, and Intelligent Computing (CAMMIC 2022), Vol. 12259 1225902 (SPIE, 2022).

Lameche, E. K. et al. Urban flood numerical modeling and hydraulic performance of a drainage network: A case study in Algiers, Algeria. Water Sci. Technol. 88 (7), 1635–1656 (2023).

Article   PubMed   Google Scholar  

Zhang, Y. et al. Prediction of total nitrogen in Miyun Reservoir based on Mike21. J. Arid Land Resourc. Env. 8 , 122–131 (2021).

Yang, J., Dai, J., Gong, X., Chen, M. & Sun, J. Comprehensive evaluation of water quality in small watershed of upper Yangtze River based on multiple methods. Environ. Monit. China 1 , 19–26 (2023).

Haque, M. M. et al. Variability of water quality and metal pollution index in the Ganges River, Bangladesh. Environ. Sci. Pollut. Res. 27 , 42582–42599 (2020).

Ji, X., Dahlgren, R. A. & Zhang, M. Comparison of seven water quality assessment methods for the characterization and management of highly impaired river systems. Environ. Monit. Assess. 188 , 1–16 (2016).

Fan, C. et al. Water quality characteristics, sources, and assessment of surface water in an industrial mining city, southwest of China. Environ. Monit. Assess. 194 (4), 259 (2022).

Xu, C. et al. Study of hydrodynamic and water quality coupling simulation of river network in Nanxun district based on software Mike21. Environ. Sci. Technol. 10 , 51–59 (2022).

Li, H., Wu, J., Liu, J. & Liang, Y. Finite element mesh generation and decision criteria of mesh quality. China Mech. Eng. 23 (3), 368 (2012).

Long, Y. et al. Improving streamflow simulation in Dongting Lake Basin by coupling hydrological and hydrodynamic models and considering water yields in data-scarce areas. J. Hydrol.: Reg. Stud. 47 , 101420 (2023).

Shi, L. & Li, S. Simulation study on water quality of paddy field ditches considering the effects of rainfall and sediment release. Sustainability 16 (3), 1075 (2024).

Lin, F., Li, X., Xu, C. & Shi, H. Temporal and spatial distributions of 5-day biochemical oxygen demand in the Mirs Bay. Ecol. Env. Sci. 5 , 883–889 (2017).

ADS   Google Scholar  

Antonelli, M. et al. Ecotechnologies for Wastewater Treatment-Impacting the environment with innovation in wastewater treatment. Water Sci. Technol. 86 (4), 3 (2022).

Xu, T., Zheng, R., Ban, Y., Wu, F. & Jiang, L. Research on comprehensive management of water environment in Huangjiang River Basin of Haifeng County, Shanwei City, China. Water Wastewater 22 , 137–143 (2023).

Guo, S., Wen, Y. & Zhang, X. Study on the simulation of reservoir water environment and the optimization of ecological water replenishment effect: Taking Luhun Reservoir as an example. Water Supply 23 (8), 3078–3096 (2023).

Zhang, Y. et al. Aquatic vegetation in response to increased eutrophication and degraded light climate in Eastern Lake Taihu: Implications for lake ecological restoration. Sci. Rep. 6 (1), 23867 (2016).

Wang, S. The distribution pattern and ecological restoration technology of aquatic plants in a eutrophic water landscape belt. Water Supply 23 (1), 860–873 (2022).

Yu, S. et al. Case study of the in-situ restoration of black-odorous water by combined process of forced aeration and biological contact oxidation. Water Sci. Technol. 85 (3), 827–838 (2022).

Jiang, Z. et al. Impact of the second phase of the eastern route of South-to-North water diversion project on distribution of nitrogen and phosphorus in Hongze Lake. Water Sci. Technol. 85 (8), 2398–2411 (2022).

Download references

The National Natural Science Foundation of China (No. 51979107, No. 52209018, No. 51909091), Science and Technology Projects of Water Resources Department of Henan Province, China (GG202332 and GG202334) and the China Scholarship Council (No. 202108410234).

Author information

Authors and affiliations.

School of Management and Economics, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan, China

Huaibin Wei

School of Water Conservancy, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan, China

Yiding Rao, Yao Wang & Yongxiao Cao

School of Water Resources, North China University of Water Resources and Electric Power, Zhengzhou, 450046, Henan, China

The Key Laboratory of Conservation and Intensive Utilization of Water Resources in the Yellow River Basin of Henan Province, Zhengzhou, 450046, Henan, China

You can also search for this author in PubMed   Google Scholar

Contributions

H.W.: Funding acquisition; supervision, project administration. Y.R.: Conceptualization; data curation, methodology; software; validation; formal analysis; writing-original draft. J.L.: Methodology; conceptualization; writing-review & editing. Y.W.: Visualization; writing-review & editing. Y.C.: Resources, Investigation.

Corresponding author

Correspondence to Jing Liu .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Additional information

Publisher's note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

Wei, H., Rao, Y., Liu, J. et al. Impact on urban river water quality and pollution control of water environmental management projects based on SMS-Mike21 coupled simulation. Sci Rep 14 , 6492 (2024). https://doi.org/10.1038/s41598-024-57201-z

Download citation

Received : 31 December 2023

Accepted : 15 March 2024

Published : 18 March 2024

DOI : https://doi.org/10.1038/s41598-024-57201-z

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Hydrodynamic-water quality coupling simulation
• SMS-Mike21 coupling model
• Hydrology period
• Water environmental management projects
• Urban river

By submitting a comment you agree to abide by our Terms and Community Guidelines . If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

An official website of the United States government

Here’s how you know

Official websites use .gov A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS A lock ( Lock A locked padlock ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

JavaScript appears to be disabled on this computer. Please click here to see any active alerts .

Lesson Plans, Teacher Guides and Online Environmental Resources for Educators: Water

Find an array of environmental and science based lesson plans, activities and ideas below from EPA, other federal agencies and external organizations.  ​ Encontrar recursos para estudiantes y maestros.

Topics: Air | Climate Change | Ecosystems | Energy | Health | Waste | Water

Acid Rain: A teacher's guide for grades 6 through 8  (PDF 56 pp, 4.6 MB) A lesson plan and activities from EPA for teachers on acid rain. Grades: 6-8 Type of Resource: Lesson plan

Acid Rain Educational Resources Experiments and activities, a review of basic acid rain concepts, factsheets, and things you can do about acid rain. Grades: K-12 Type of Resource: Lesson plans and experiments

Darby Duck and the Aquatic Crusaders Find seven experiments from EPA to learn about the characteristics of water. Grades: K-5 Type of Resource: Lesson plan and experiments

Drinking Water & Ground Water Kids' Stuff Games, activities, and art projects from EPA about the water cycle and water treatment. Grades: K-12 Type of Resource: Lesson plans

EnviroAtlas: Exploring Your Watershed This interactive lesson-plan module encourages students to explore their local watershed through a hands-on lab, an outdoor exploratory session with maps, and an EnviroAtlas web-mapping session that can be completed with or without internet. Grades: K-6 Type of Resource: Lesson Plans

Ground Water Contamination   (PDF 10 pp, 0.2MB)  Find a general review of groundwater contamination and where it occurs. Grades: 9-12 Type of Resource: Factsheet

How's My Waterway? This tool answers questions about the health of waters in supporting swimming, the eating of fish, drinking water protection and delivery, the health of aquatic communities, and the restoration and protection of waterways. Grades: K-12, College, Adult Learners Type of Resource: Website/tool and lesson plan

How People Get Their Water - Reservoirs: "Holding Tanks" for Drinking Water   Let your students "Ride the Water Cycle" with this activity from EPA. Help them understand the role of reservoirs in maintaining a reliable supply of drinking water. Grades: 4-8 Type of Resource: Lesson plan

Magnificent Ground Water Connection This ground-water activity guide is applicable to a wide range of subject matter and the topics include basic concepts on the water cycle, water distribution, treatment, and stewardship. This page includes five sample lesson activity plans. Grades: K-12 Type of Resource: Curriculum guide and lesson plans

Mercury Messes with the Environment (pdf) (10.57 MB) A children’s activity booklet describing the effects of mercury contamination on humans and the environment. Grades: 6-8 Type of Resource: Activity book

On Your Mark, Set, Evaporate (PDF 4.73 MB, 398 pp) This EPA lesson plan covers transpiration as part of the hydrologic cycle. Grades: 6-8 Type of resource: Lesson plan

Drinking Water Activities for Students and Teachers These resources provide a basic understanding of drinking water terms and where water comes from. Grades: K-12 Type of Resource: Website, Lesson Plans, Teacher Guides, Activities

Thirstin's Groundwater Movement Activity (PDF 332 KB, 2 pp) This class activity demonstrates that ground water must be able to move through underground materials. The students will act as molecules of water and the underground materials. Grades: K-5 Type of resource: Lesson plan

Tracking Pollution - A Hazardous Whodunit A Thirstin lesson plan to teach students to make a topographic map, use it to predict ground water flow and investigate the most likely source of ground water contamination. Grades: 9-12 Type of resource: Lesson plan

Water Sense Resources Resources for educating students about "Fix a Leak Week," EPA's WaterSense Partnership program and water efficiency. Grades: K-8 Type of resource: Lesson plan

Watershed Academy The Watershed Academy is a focal point in EPA's Office of Water for providing training and information on watershed management. The Academy's self-paced training modules and webcast seminars provide current information from national experts across a broad range of watershed topics. Grades: 9-12, College, Adult Learners Type of Resource: Self paced online modules

The following links exit the site

National Wetlands Research Center This site from the U.S. Geologic Survey explores the many factors that affect wetland health, and provides resources for teachers on preserving our wetlands. Grades: 9-12

NOAA's Education Resources Website Explore this site to find the information you need to teach students about weather, climate change, and oceans. You'll find activities, background information, and much more! Grades: 6-12

National Ocean Service Education Find case studies, tutorials, games, and more from NOAA's National Ocean Service. Grades: K-12 Type of Resource: Website

Stormwater Pollution Solutions Challenge In these materials, students will read text and diagrams about the elements of watersheds and learn how stormwater pollution influences children’s health. Then they will develop their own environmental solutions to combat stormwater pollution in a local watershed! Grades: 6-8 Type of Resource: Lesson Plan

Water Science for Schools This site provides extensive background information on a wide variety of water topics. It also includes on-line activities, data tables, maps, and a glossary of terms. Grades: 6-12

EPA Publications

EPA has many publications on every environmental subject that you can download or order. See our predefined searches below on specific search terms to help you view our publication offerings from the National Service Center for Environmental Publications (NSCEP).

Predefined Search Terms:

• Activity Book
• Coloring Books
• Environmental Education
• Science Fair
• Students Home
• Classroom Resources and Project Ideas
• Homework Help and Activities for K-12 Students

Site Search

Securities / matching gifts / planned giving.

We welcome gifts of stock and securities, can help process any matching gifts, and would be honored to discuss Planned Giving with you. Discover more about Planned Giving Please contact our office by clicking below:

Give by Check

The Water Project PO Box 3353 Concord, NH 03302-3353 1.603.369.3858

Donate Cryptocurrency

Water-related education materials for high school.

The following are suggested lesson plans for water-related activities in the high school classroom:

Interactive:

EPA’s Interactive Water Treatment Cycle Learn about the water treatment cycle and appropriate vocabulary words with this interactive poster

EPA’s Build Your Own Aquifer Learn what aquifers are, how they work, and why they are important

Word Games (may be too young for older students):

Water Source Word Search Search for water source vocabulary words

Clean Water Maze Help the children get to the clean water faucet

Water Cryptogram Complete the water-related phrase

Water Challenge Word Search Find vocabulary words from The Water Project’s Water Challenge

Fact Sheets and Quizzes:

Drinking Water Bloopers Learn how much water is wasted when we aren’t thoughtful about water conservation

EPA’s Water Facts of Life Learn some fun facts about the life of water, and water in your life.

EPA’s Water Trivia Learn 45 facts about water

Potomac Watershed Web scavenger hunt

Bulletin Board Ideas:

Water Education Posters from the US Geological Survey: Each poster comes with an educational section describing components of the poster and activities to help children understand the concepts introduced.  All are available either online or as PDF versions.  Click the link for your preferred method of delivery.

• Coastal Hazards Online PDF en Español
• Watersheds Online PDF
• Hazardous Waste Online PDF en Español
• Wetlands Online PDF
• Water Use Online PDF en Español
• Wastewater Online PDF
• Navigation Online PDF
• Ground Water Online PDF
• Water Quality Online PDF

The following activities are comprised of educational lessons, vocabulary words, and instructions for an activity relating to the topic.  Curriculum materials are courtesy of the Water Environment Federation .

Wastewater Treatment Learn about wastewater and wastewater treatment with this science tutorial

Water Careers Learn about water-related careers by interviewing people who work in the field

Biography of a River Learn about the history and formation of rivers in your area

Groundwater Basics Develop math skills while calculating volumes of groundwater

From Ground to Water Increase your knowledge about groundwater

What’s the Level? Learn about groundwater and the water table

What Goes on Down Under? Learn the relationship between groundwater and surface water

Do You Drink It? Create an aquifer and use the model to demonstrate well placement and groundwater contamination

Hydraulic Head Relate concepts from physics to hydraulic heads used in the control of groundwater flow and direction

Groundwater: Cleaning Up Create a model and poster board depicting how groundwater becomes contaminated

What is Groundwater Pollution Doing to the Neighborhood? Study the impact of pollution on the environment and human health

Landfills and the Potential for Groundwater Contamination Design a landfill and consider the effects of leaky landfills on the water supply

Leaking Underground Storage Tanks Learn about underground storage tanks and their possible detrimental effects on the water supply

Water Crisis Spotlight Content

• What is Water Scarcity?
• Solving the Crisis
• Stats and Figures
• Teaching Tools

Study Session 7  Pollution: Types, Sources and Characteristics

Introduction.

You were introduced to wastes and pollutants in Study Session 1, where we discussed the interactions between humans and our environment. Pollution was defined as the introduction into the environment of substances liable to cause harm to humans and other living organisms. Many human activities pollute our environment, adversely affecting the water we drink, the air we breathe, and the soil in which we grow food.

In this and the next study session we will look more closely at pollution. In this session you will learn about the different types and sources of pollution and the various human activities that can cause pollution. We will also describe the ways pollution can affect different sectors of the environment: water, air and soil. Study Session 8 describes some of the significant effects of pollution on the environment and on human health. It also discusses options for preventing and controlling pollution.

Learning Outcomes for Study Session 7

When you have studied this session, you should be able to:

7.1  Define and use correctly all of the key words printed in bold . (SAQs 7.1, 7.2, 7.3 and 7.4)

7.2  Describe the main types of pollution. (SAQ 7.3)

7.3  Describe the sources of pollution and the way pollutants reach the environment. (SAQ 7.4)

7.4  Describe the main characteristics of water, air and soil pollution. (SAQ 7.5)

7.1  What is pollution?

If you hold up a glass of water in front of you, how can you tell if it’s polluted? You would expect drinking water to be colourless, odourless and transparent (not turbid with suspended particulates). If it was not all of these things, then it could be polluted. If you were looking at water in a river, it is unlikely to be as clear as drinking water in a glass, but you could deduce it was probably not polluted if you observed that the water did not look dirty or smell bad. You might also observe that animals were drinking the water without ill effects and fish were swimming in it. However, if the water was discoloured or had an unpleasant odour, or you could see dead fish floating on the surface you could conclude that pollution was the problem.

Let us consider the human activity that could have caused the pollution. Imagine a river that flows through an area of land on the edges of a town. The water is used by the community for drinking and other domestic uses and also for vegetable farming. Several residents use this water to irrigate small areas of land where they cultivate vegetables and many of the farmers use fertiliser and pesticide to improve productivity (Figure 7.1). Fertilisers are made of chemicals such as nitrogen, potassium and phosphorus, which are essential plant nutrients. Pesticides are chemicals that destroy pests but can be harmful to other forms of life – including humans.

Imagine that one farmer has finished spreading the chemicals on his crop and decides to wash the empty pesticide sack he has been using in the river. Later that day, it rains heavily and rainwater is seen running off the field into the river. What do you think happens? The river is receiving run-off containing fertiliser and pesticide chemicals that had been applied to the crops, which is made worse by the farmer washing his sack that had contained the pesticide. This could harm fish and other organisms living in the water – possibly killing them. The river is also used by the community so the chemicals could get into drinking water that is consumed by humans. The river has been polluted by the careless action of the farmer washing his sack and by the action of rainwater washing the chemicals into the river.

Pollution always has a source and a recipient. The source is where the pollution comes from, that is, where the pollution is released into the environment. The recipient is where the pollution ends up, which may be a part of the environment or people or animals that become contaminated or damaged.

In the above example about the farmer washing the pesticide sack in the river, what is the source and what is the recipient of the pollution?

The pollution source is the activity of urban farming with pesticides and fertilisers and washing sacks so that pollutants get into the river. In this example, the primary recipient is the water body that receives the pollutants. Other recipients are the people who drink the contaminated water and animals such as fish that also are affected.

There are a number of ways of identifying pollution. These include finding symptoms of damage to aquatic plants and animals (such as dead fish), finding chemicals in the water, comparing the previous history of the quality of water with the present quality, and getting complaints from water users. Even when a problem has been found, investigations to identify the source may take time. For example, water samples from several different points upstream and downstream will need to be analysed to locate precisely where the problem originated.

There are several different ways of classifying pollutants. They can be categorised by their physical nature, by their source, by the recipient or by the sector of the environment affected. In the following sections we will look at each of these classification groups

7.2  Physical nature of the pollutant

Pollutants may be in the form of gas, liquid, solid or energy.

What polluting gases can you think of?

Greenhouse gases are pollutants that contribute to human-induced climate change (mentioned in Study Session 1). The main greenhouse gases are carbon dioxide, methane and nitrogen oxides.

Liquid pollutants usually come from liquid waste. Liquid waste includes human excreta (both faeces and urine), industrial wastewaters and other forms of waste from water-using activities (Figure 7.2). Factories generate liquid waste from activities related to washing in the manufacturing process, cleaning objects and chemical mixing. Sewage is a mixture of human excreta from water-flushed toilets and other wastewater from houses and businesses. Sewage and human waste from overflowing septic tanks and latrines are frequent sources of pollution.

Urban run-off is another type of liquid waste that can cause pollution. Rainwater washes many different types of waste from the land surface into lakes and rivers. Urban run-off can contain a lot of organic matter. This may come from open defecation or inappropriate handling of organic wastes produced from households and businesses. Organic matter includes anything that is derived from living organisms, such as human and animal wastes, decaying plants and food wastes.

Pollutants also come in solid form. Plastic bags are one of the most common solid wastes. Solid waste is any solid material that is assumed not to be useful and is therefore thrown away. Factories, businesses and households produce different kinds of solid waste such as paper, plastics, metals, chemicals in solid form, pieces of cloth or food and animal remains (Figure 7.3). Sometimes you may have observed faecal matter discarded with solid waste, which adds to the problems.

There is a fourth type of pollution that is common in urban communities. This is energy in the form of noise pollution. Noise pollution means unacceptable levels of noise in work, residential and recreational places. Noise makes it difficult to have a conversation and also irritates and disturbs us and in the long term can damage our hearing. Loud music from music shops and clubs in an urban community is a known source of noise disturbance. Such noise may please some, but it disturbs many other people because it interferes with communication in the daytime and sleeping at night.

7.3  Sources of pollution

Another way of classifying pollution is by the sector of human activity that produces it. Before we look at the various sectors, there is an important distinction to be made about pollution sources. Sources of pollution can be categorised as point or non-point sources. Point sources are identifiable points or places that you can easily locate. An example is a diesel truck that produces visible black exhaust fumes from its tailpipe. Liquid waste released from a pipe into a river is another example (Figure 7.4). A non-point source (also known as ‘diffuse pollution’) is one where it is difficult to identify the exact origin of the pollution. A good example is floodwater that washes all types of waste from the land (possibly including faecal matter) into a river. In this situation you cannot identify the individual or household or establishment that has caused the water pollution (Figure 7.5).

Can you think of examples of point and non-point source pollution from earlier in this study session?

The farmer washing his sack is an example of a point source because you could identify where he washed his sack. However, the pesticide washing from the field is an example of a non-point source. The pollutant would wash into the river at several places, and could possibly also have come from other fields. This is an example of how difficult it can sometimes be to accurately identify the source.

7.3.1  Domestic sources

Domestic sources of pollution include toilets, latrines and wastewater from kitchens and bathrooms. If these wastes are properly contained and prevented from getting into the environment, they will not cause pollution. However, frequently this is not the case. Open defecation obviously releases human waste into the environment, which can then be washed into rivers and other surface waters.

What types of organic waste are produced by a typical household?

The organic wastes from domestic sources include human excreta and also food waste and other kitchen waste such as cooking oil residues.

Solid wastes from households and also from shops, markets and businesses include food waste, packaging materials and other forms of rubbish. Domestic sources are also responsible for gaseous pollutants in the form of smoke and carbon dioxide from domestic fires.

7.3.2  Industry

Pollution from the industrial sector in Ethiopia has been on the rise, posing a serious problem to the environment. Many industrial processes produce polluting waste substances that are discharged to the environment, frequently through chimneys (to the air) or through pipes (to surface water) (Figure 7.6). Among the most polluting industries are food processing, tanneries and textiles with processing plants and factories that produce liquid effluents which are discharged into rivers, often without treatment (Ademe and Alemayehu, 2014; Wosnie and Wondie, 2014). In practice, rivers frequently receive polluting discharges from many different sources all at the same time. The Little Akaki River in Addis Ababa, for example, is polluted by several different industrial sources as well as by domestic wastes (Tegegn, 2012).

7.3.3  Agriculture

Like industry, agricultural activities are also increasing in Ethiopia, and changing too. Nowadays, agricultural activities in Ethiopia use more pesticides and fertilisers. Ethiopia imports over 3000 tons of various types of pesticides annually (Federal Environment Protection Authority, 2004). Fertiliser use in Ethiopia has increased from 140,000 metric tons in the early 1990s to around 650,000 metric tons in 2012 (Rashid et al., 2013). Fertiliser contains phosphate and nitrate and if these reach water bodies they can cause excessive plant growth (Figure 7.7).

Agriculture is also responsible for gaseous pollutants in the form of methane produced by livestock and solid pollutants from crop residues, packaging materials and other wastes similar to those produced domestically. Animals also contribute to waste products and potential pollutants with their excrement.

7.3.4  Transport

Do you live in a city or have you visited a city close to where you live? If so you will no doubt be familiar with the variety of vehicles on our roads (Figure 7.8). Some are small cars, others are heavy motor trucks. These vehicles differ not only in their size, but also by using different types of fuel such as petrol, diesel, and blended fuel (10% ethanol and petrol). If you observe the tailpipe of diesel engine vehicles, you will have seen the black exhaust gas produced. The intensity of the black colour is greater for poorly maintained vehicles, to the extent sometimes that it makes the air hazy or smoky and causes coughs and eye irritation. The lack of a policy to remove old vehicles from the roads adds to the problem. Tiwari (2012) found that nearly a third of vehicles in Addis Ababa were over 30 years old, resulting in high levels of tailpipe emissions. Traffic jams, common in all big cities, make the problems worse.

7.4  Pathways of pollution

We said earlier that pollution always has a source and a recipient. The pathway of pollution is the way the pollutant moves from the source, enters into the environment, and finally how it reaches the human body or other recipient. The pathway between source and recipient can take several different forms depending on the type of pollutant. Primary recipients for pollution are water, air, and soil. Pollutants usually reach humans through the consumption of contaminated and polluted water and food, and breathing polluted air.

Once released into the environment, the worst effects of many pollutants are reduced by one or more of the following processes:

• Dispersion – smoke disperses into the air and is no longer noticeable away from the source.
• Dilution – soluble pollutants are diluted in the water of a river or lake.
• Deposition – some suspended solids carried in a river settle (are deposited) on the river bed.
• Degradation – some substances break down (degrade) by natural processes into different, simpler substances that are not polluting.

In each case the effect is to reduce the concentration of the pollutant. Concentration is a measure of the amount of the substance in a known volume of water or air. The units used for water pollutants are usually milligrams per litre (mg/l, also written as mg l -1 ), although sometimes you may see ppm which stands for ‘parts per million’.

These processes do not apply to all pollutants. There are some persistent pollutants which remain intact when released into the environment because they do not break down by natural processes. These are described in Study Session 8.

7.5  Sector of the environment affected by pollution

Classifying pollution by the sector of the environment affected – water, air, soil and land – is probably the most commonly used method.

7.5.1  Water pollution

Water pollution can affect surface water such as rivers and lakes, soil moisture and groundwater in aquifers, and the oceans. As you know from Study Session 4, the actions of the water cycle connect all these different reservoirs of water. For example, a polluted river will discharge into the ocean and could damage the marine environment. However, the volume of water in the ocean can disperse and dilute the pollutant so that its worst effects are only felt near the mouth of the river.

Water pollution is characterised by the presence of excess physical, chemical or biological substances that change the qualities of the water and are capable of causing harm to living organisms. We mentioned earlier that natural or unpolluted water is colourless, odourless and transparent. Water that tastes or smells bad or is cloudy can be said to have the symptoms of water pollution. However, some water pollutants cannot be seen or tasted, for example some chemicals, such as pesticides, and most of the micro-organisms that cause waterborne diseases. So, water pollution involves more than just the appearance of the water. Polluted water should not be used for drinking, washing, bathing or agriculture. If polluted water is used by humans, then it can adversely affect the body in different ways, depending on the type and concentration of pollutant.

You also read in Study Session 4 that most rivers and streams in Ethiopia contain significant quantities of suspended solids that are carried along in the flow and make the water look brown in colour, especially in the rainy season (Figure 7.9). Most of the solids are fine particles of soil that have been washed into the river from surrounding land by rain, often following cultivation or construction work. Large quantities of solids in the water can reduce light penetration into the water which can affect the growth of plants.

Biological water pollutants are micro-organisms that are harmful to humans and other forms of life. They are responsible for many different waterborne diseases. The original source of these pollutants is people or animals already infected with the micro-organisms concerned. If faeces from infected people are not correctly contained and treated, the pollutants can get into surface and groundwater. The main groups of biological pollutants are bacteria, viruses, protozoa and helminths (worms).

Chemical water pollutants take many different forms depending on their source. They include plant nutrients (compounds of phosphorus and nitrogen) used as fertilisers which, as you read earlier, can be washed from fields into rivers. These nutrients are also produced by the breakdown of human and animal wastes and are common pollutants of surface waters.

Chemical pollutants also include heavy metals , pesticides and other persistent pollutants. Heavy metals are a group of toxic chemical pollutants that contain compounds of persistent metals such as mercury, cadmium, lead and chromium. The presence of heavy metals in water in excess of acceptable levels can cause illness and death among animals and humans if consumed through drinking and food (Zinabu and Pearce, 2003).

Persistent organic pollutants (POPs) are also toxic to humans and wildlife. They include many different synthetic organic chemicals manufactured for use as pesticides and in industrial processes, e.g. DDT, aldrin and PCBs (polychlorinated biphenyls). Many of these persistent chemicals have been banned in some countries. Their persistence in the environment creates specific problems that are described in Study Session 8.

7.5.2  Air pollution

Air pollution can exist at all scales, from local to global, and can include gases and solid particles. It can affect you in your own home, or in your town or city, and can contribute to global atmospheric changes. The most common sources of air pollution in the urban centres of Ethiopia include the burning of wood, charcoal and other biomass fuel by households, small businesses such as bakeries, manufacturing industries, and vehicles.

Air pollution is defined as the presence in the air of abnormal amounts of chemical constituents capable of causing harm to living organisms. Clean air consists of nitrogen (78% by volume), oxygen (21%) and trace gases (< 1%). Polluted air may contain particulate matter (such as black soot) and many different gaseous chemicals such as carbon monoxide, carbon dioxide, nitrogen oxides, sulphur oxides, ozone, nitrates, sulphates, organic hydrocarbons and many others. Many of these are also found in clean air as trace gases but they become pollutants if present in abnormal quantities.

The emission of black smoke is an indication of intense pollution. However, not all air pollution is visible or can be smelled. Gases such as carbon monoxide and carbon dioxide are invisible and odourless. Carbon monoxide is very dangerous to humans. It can be produced by inefficient burning of fuel (for example a charcoal stove in a home with inadequate air supply) and if breathed in large quantities it can be deadly. Carbon dioxide is an important pollutant that is involved in climate change. (You will learn about in climate change in Study Sessions 9, 10 and 11.)

7.5.3  Soil and land pollution

Soil pollution, also called land pollution, is linked to water pollution. Liquid wastes containing toxic chemicals or pathogenic micro-organisms on the surface of the land can seep slowly into the soil and may percolate down to contaminate groundwater, which can affect people using springs or wells in the area. Possible sources include open defecation, pit latrines or leaking storage containers for industrial chemicals and wastes.

Solid waste can cause soil pollution. A collection of solid wastes in one place or scattered around is unsightly and might smell bad to you as you pass by (Figure 7.10). Household waste typically consists mostly of food waste that will gradually decompose. This produces a bad odour and attracts insects and rats, both of which contribute to the transmission of disease. As the waste decomposes it produces a liquid called leachate which trickles down into the soil. Leachate is a highly concentrated liquid pollutant that may contain toxic chemicals and pathogenic micro-organisms as well as high levels of organic compounds. Rainwater falling on, and washing through, solid waste adds to the problem.

Summary of Session 7

In Study Session 7, you have learned that:

• Environmental pollution is the result of human activity and development that occurs when physical, biological and chemical agents are released to the environment in such quantities that the pollution adversely affects human health and damages the environment.
• Pollution can be classified by its physical nature, by its source, by its recipient, by the sector affected or by its effects.
• Pollution may be in the form of a gas, liquid, solid or energy.
• Sources of pollution may be point sources, which are easily identified, or non-point sources, where the pollution comes from diffuse sources that are not easy to pinpoint.
• There are different types of pollution: water pollution, air pollution, solid waste pollution and noise pollution. All of these can be found in urban areas.
• The main sources of pollution are household activities, factories, agriculture and transport.
• Once they have been released into the environment, the concentration of some pollutants is reduced by dispersion, dilution, deposition or degradation.
• Water can be contaminated by physical pollutants (solid material), biological pollutants (such as bacteria that cause waterborne diseases), and many different chemical pollutants.
• Air pollution can be caused by gases or solid particulates.
• Soil pollution is linked to groundwater pollution. Solid waste can produce highly polluting leachate which contaminates soil groundwater.

Self-Assessment Questions (SAQs) for Study Session 7

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.

SAQ 7.1 (tests Learning Outcome 7.1)

Why is a point source of pollution easier to identify than a non-point source of pollution?

Point sources of pollution are easier to identify because they come from points or places that you can easily locate, such as a pipe discharging waste into a river. A non-point source is more difficult to identify because it does not come from just one place, but can come from a wide area, for example fertiliser washing off a number of fields or floodwater that washes waste from latrines.

SAQ 7.2 (tests Learning Outcome 7.1)

Rewrite the sentences below using terms from the list provided to fill the gaps:

concentration, heavy metals, organic matter, persistent pollutant, sewage.

……………… consists of human excreta and wastewater. It has a high ……………… of ………………

Some pollutants, called ………………, do not break down naturally in the environment. Examples are mercury, cadmium and other ………………

Sewage consists of human excreta and wastewater. It has a high concentration of organic matter .

Some pollutants, called persistent pollutants , do not break down naturally in the environment. Examples are mercury, cadmium and other heavy metals .

SAQ 7.3 (tests Learning Outcomes 7.1 and 7.2)

Describe what is meant by the terms liquid waste and solid waste, using examples from your own experience to illustrate your answer.

Liquid waste is liquid material that is thrown away, or discharged into the environment. From the household you might include human excreta (both faeces and urine) and other wastewaters. In your area you might also see urban run-off when rain washes waste from the land surface. You might also see liquid waste discharged from factories through a pipe into a river.

Solid waste is any solid material that is assumed not to be useful and is therefore thrown away; examples that you might use include food waste, cloth, paper and plastic that are thrown out from your own household or that you see in the area where you live.

SAQ 7.4 (tests Learning Outcomes 7.1 and 7.3)

For the scenarios (a) to (d), fill in the table below to show the pollutant, the source of pollution, the possible pathways and the recipients:

• a. A farmer washes an empty pesticide sack in a river; the river flows into a lake which is used for drinking water by people from a local town.
• b. Rain falls on a waste dump used to collect household waste; the waste dump isn’t properly sealed and liquid percolates down into the soil and into groundwater that is extracted from a nearby well for domestic use.
• c. A tannery based in a town produces liquid waste that contains organic matter and chemicals used in the tanning process; this effluent is discharged into the local river which flows out of the town and through a nature park.
• d. A bus driving through a busy town emits black smoke from its tailpipe.

SAQ 7.5 (tests Learning Outcome 7.4)

Describe how water pollution can change the characteristics of water.

Natural or unpolluted water is colourless, odourless and transparent. Water pollution changes the characteristics of water by the presence of excess physical, chemical or biological substances that change the qualities of the water and are capable of causing harm to living organisms.

Polluted water can taste or smell bad or be cloudy. Polluted water can contain suspended solids that make the water look brown in colour; most of the solids are fine particles of soil that have been washed into the river by rain from surrounding land. Large quantities of solids in the water can reduce light penetration into the water which can affect the growth of plants.

Water pollution changes more than just the appearance of the water. Polluted water can also contain chemicals, such as pesticides, fertilisers and heavy metals that are toxic. Polluted water also can contain biological substances such as organic matter and micro-organisms that cause waterborne diseases.

Copyright © 2016 The Open University

River Pollution

Introduction: River pollution has become a matter of great concern all over the globe in recent times. Rivers are of great use to us. But it is a matter of regret that our rivers are on the verge of extinction. The greedy land grabbers build up buildings along the bank of rivers which create hindrances in the normal flow of water.

However, we have a fixed amount of water on earth. It just changes its states and goes through a cyclic order, known as the Water Cycle. The water cycle is a natural process that is continuous in nature. It is the pattern in which the water from oceans, seas, lakes, etc gets evaporated and turns to vapor. After which it goes through the process of condensation, and finally precipitation when it falls back to earth as rain or snow.

Causes of Pollution: River or Water pollution is the contamination of water bodies (like oceans, seas, lakes, rivers, aquifers, and groundwater) usually caused due to human activities. Water pollution is any change, minor or major in the physical, chemical or biological properties of water that eventually leads to a detrimental consequence of any living organism. Drinking water, called Potable Water, is considered safe enough for human and animal consumption.

Chemical fertilizers and pesticides used in the fields are washed away by rain and flood water to the water of river. Mills and factories use many poisonous chemicals. They throw their used and unsold products into the river water and pollute it. All steamers, launches and engine boats pollute water by throwing oil, food waste and human waste into the rivers. The sewerage lines let into the river also pollute water by carrying wastes into the river water especially in the urban areas.

At present, nuclear tests and dumping of nuclear wastes are causing serious river water pollution. We must realize the value of river and this is our duty to keep it fit for our living.

Effects of Pollution of Water –

The effects of Water Pollution are:

• Diseases: In humans, drinking or consuming polluted water in any way has many disastrous effects on our health. It causes typhoid, cholera, hepatitis and various other diseases.
• Eradication of Ecosystem: Ecosystem is extremely dynamic and responds to even small changes in the environment. Increasing water pollution can cause an entire ecosystem to collapse if left unchecked.
• Eutrophication: Chemicals accumulation and infusion in a water body, encourages the growth of algae. The algae form a layer on top of the pond or lake. Bacteria feed on this algae and this event decreases the amount of oxygen in the water body, severely affecting the aquatic life there
• Effects of the food chain: Turmoil in food chain happens when the aquatic animals (fish, prawns, seahorse, etc) consume the toxins and pollutants in the water,  and then the humans consume them.

Prevention: So, we must prevent water pollution at any cost. Industrial wastes must not be disposed of in rivers or lakes. We need to be more careful about disposing of household wastes too. Farmers must be aware of the dangers of using pesticides as they may pollute our rivers, canals, and lakes. It is really very difficult to prevent water pollution, but our awareness is very important. We can purify water by boiling it or by using some medicine. All concerned must be conscious to keep water free from pollution. Govt. should take comprehensive programs to check water pollution. Above all, for a healthier and happier life, massive awareness must be created against water pollution.

Conclusion: Life is ultimately about choices and so is water pollution. We cannot live with sewage-strewn beaches, contaminated rivers, and fish that are poisonous to drink and eat. To avoid these scenarios, we can work together to keep the environment clean so the water bodies, plants, animals, and people who depend on it remain healthy. We can take individual or teamed action to help reduce water pollution. As an example, by using environmentally friendly detergents, not pouring oil down the drains, reducing the usage of pesticides, and so on. We can take community action too to keep our rivers and seas cleaner. And we can take action as countries and continents to pass laws against water pollution. Working together, we can make water pollution less of a problem and the world a better place.

A Rational View Of Industrialization

My Best Friend

Importance of Rivers

My Future Plan of Life

Lecture on Livestock Animals

Results of Using Digestrin

Scientists Uncover Intestinal Bacteria that Boost Bee Memory

Difference between Already and All ready

Lion And His Fear

Lecture on Business Communication

Latest post.

Terbium Monosulfide – a binary inorganic compound

Bismuth Arsenide – an inorganic compound

Gene-related Metabolic Dysfunction may be generating Cardiac Arrhythmia

Controlling Cholesterol Levels with Fewer Negative effects is achievable with new Medicine

Terbium Phosphide – an inorganic compound

Barium Selenide – an inorganic compound

• Class 6 Maths
• Class 6 Science
• Class 6 Social Science
• Class 6 English
• Class 7 Maths
• Class 7 Science
• Class 7 Social Science
• Class 7 English
• Class 8 Maths
• Class 8 Science
• Class 8 Social Science
• Class 8 English
• Class 9 Maths
• Class 9 Science
• Class 9 Social Science
• Class 9 English
• Class 10 Maths
• Class 10 Science
• Class 10 Social Science
• Class 10 English
• Class 11 Maths
• Class 11 Computer Science (Python)
• Class 11 English
• Class 12 Maths
• Class 12 English
• Class 12 Economics
• Class 12 Accountancy
• Class 12 Physics
• Class 12 Chemistry
• Class 12 Biology
• Class 12 Computer Science (Python)
• Class 12 Physical Education
• GST and Accounting Course
• Excel Course
• Tally Course
• Finance and CMA Data Course
• Payroll Course

Interesting

• Learn English
• Learn Excel
• Learn Tally
• Learn GST (Goods and Services Tax)
• Learn Accounting and Finance
• GST Tax Invoice Format
• Accounts Tax Practical
• Tally Ledger List
• GSTR 2A - JSON to Excel

Are you in school ? Do you love Teachoo?

We would love to talk to you! Please fill this form so that we can contact you

• MCQ Questions (1 Mark)
• Assertion Reasoning
• Picture Based Questions
• True or False
• Match the following
• Correct and rewrite the sentences
• Map Based Questions
• Fill in the blanks
• NCERT Questions
• Past Year Questions - 3 Marks
• Past Year Questions - 5 Marks
• Case Based Questions

River Pollution - Concepts - Chapter 3 Class 9 Geography - Drainage - Geography

Last updated at April 16, 2024 by Teachoo

River Pollution 

• Th e increasing domestic, municipal, industrial, and agricultural demand for river water has a natural impact on water quality. 
• As a result, more and more water is being drained out of the rivers reducing their volume.
• On the other hand, untreated sewage and industrial effluents are dumped into rivers in large quantities causing river pollution.
• This affects not only the water quality but also the river's ability to self-clean.
• For example, given the adequate streamflow, the Ganga water is able to dilute and assimilate pollution loads within 20 km of large cities.
• However, i ncreasing urbanization and industrialization make this impossible, and the pollution level of many rivers has been rising.
•  Concerns about rising pollution in the rivers, the government, and environmentalists launched various action plans to clean the rivers.

National River Conservation Plan (NRCP)

• The river cleaning program in the country was initiated with the launching of the Ganga Action Plan (GAP) in 1985. 
• In 1995 , the Ganga Action Plan was expanded to include other rivers as part of the National River Conservation Plan (NRCP). 
• The goal of the NRCP is to improve the water quality of the country's rivers , which are major water sources, through the implementation of pollution abatement work .

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

Hi, it looks like you're using AdBlock :(

Please login to view more pages. it's free :), solve all your doubts with teachoo black.

The Impact of Human Activities on River Pollution and Health-Related Quality of Life: Evidence from Ghana

• October 2022
• Sustainability 2022(14):13120
• 2022(14):13120
• This person is not on ResearchGate, or hasn't claimed this research yet.

• Jiangsu University

• Hohai University

• University of California, Santa Barbara

Abstract and Figures

Discover the world's research

• 25+ million members
• 160+ million publication pages
• 2.3+ billion citations
• Y. Danurrachman
• Maryono Maryono
• Fuad Muhammad
• P. Van der Maas
• ENVIRON MONIT ASSESS

• José Agustín García-Romero

• Mijail Arias-Hidalgo
• Anthony KolaOlusanya
• Ezekiel Oyeyemi

• Olubukola Omobuwa

• Bruno Pinto

• Anyizi Bertha Nkemnyi
• Lucy Mange Ndip
• Benedicta Oshuware Oben
• Mbeng Ashu Arrey
• SOC INDIC RES
• Shaojun Chen

• COMPUT ELECTRON AGR
• Yongchun Zheng

• Emmanuel Kwesi Nyantakyi

• Ebenezer Abokyi
• J CLEAN PROD

• Kari Heiskanen
• SENSORS-BASEL

• Adili Mvena

• Enock L. Chambile

• David A. Keiser
• Joseph S. Shapiro
• DRUG ALCOHOL DEPEN

• Isabelle Etting

• CHEMOSPHERE

• Luís Fernando Cusioli

• Recruit researchers
• Join for free
• Login Email Tip: Most researchers use their institutional email address as their ResearchGate login Password Forgot password? Keep me logged in Log in or Continue with Google Welcome back! Please log in. Email · Hint Tip: Most researchers use their institutional email address as their ResearchGate login Password Forgot password? Keep me logged in Log in or Continue with Google No account? Sign up

• Biology Article
• Water Pollution Control

Water Pollution And Its Control

Water is one of the most vital natural resources on earth and has been around for a long time. In fact, the same water which we drink has been around in one form or the other since the time of the dinosaurs.

The earth has more than two-thirds of its surface covered with water. This translates to just over 1 octillion litres (1,260,000,000,000,000,000,000 litres) of water distributed in the oceans, rivers, lakes and streams.

That is a lot of water, however, less than 0.3% is accessible for human consumption. As commercialization and industrialization have progressed, that number continues to dwindle down. Furthermore, inefficient and outdated practices, lack of awareness and a plethora of other circumstances have led to water pollution.

Also Read: How Can We Conserve Water?

• Water pollution
• Modern Epidemic

Minamata Incident

• Ganges River

What is Water Pollution?

Water pollution can be defined as the contamination of water bodies. Water pollution is caused when water bodies such as rivers, lakes, oceans, groundwater and aquifers get contaminated with industrial and agricultural effluents.

When water gets polluted, it adversely affects all lifeforms that directly or indirectly depend on this source. The effects of water contamination can be felt for years to come.

Also Refer:  Types of Pollution

Sources Of Water Pollution

The key causative of water pollution in India are:

• Urbanization.
• Deforestation.
• Industrial effluents.
• Social and Religious Practices.
• Use of Detergents and Fertilizers.
• Agricultural run-offs- Use of insecticides and pesticides.

Water Pollution – A Modern Epidemic

One of the primary causes of water pollution is the contamination of water bodies by toxic chemicals. As seen in the example mentioned above, the dumped plastic bottles, tins, water cans and other wastes pollute the water bodies. These result in water pollution, which harms not just humans, but the whole ecosystem. Toxins drained from these pollutants, travel up to the food chain and eventually affect humans. In most cases, the outcome is destructive to only the local population and species, but it can have an impact on a global scale too.

Nearly 6 billion kilograms of garbage is dumped every year in the oceans. Apart from industrial effluents and untreated sewage, other forms of unwanted materials are dumped into various water bodies. These can range from nuclear waste to oil spills – the latter of which can render vast areas uninhabitable.

Effects Of Water Pollution

The effect of water pollution depends upon the type of pollutants and their concentration. Also, the location of water bodies is an important factor to determine the levels of pollution.

• Water bodies in the vicinity of urban areas are extremely polluted. This is the result of dumping garbage and toxic chemicals by industrial and commercial establishments.
• Water pollution drastically affects aquatic life. It affects their metabolism, and behaviour, and causes illness and eventual death. Dioxin is a chemical that causes a lot of problems from reproduction to uncontrolled cell growth or cancer. This chemical is bioaccumulated in fish, chicken and meat. Chemicals such as this travel up the food chain before entering the human body.
• The effect of water pollution can have a huge impact on the food chain. It disrupts the food chain. Cadmium and lead are some toxic substances, these pollutants upon entering the food chain through animals (fish when consumed by animals, humans) can continue to disrupt at higher levels.
• Humans are affected by pollution and can contract diseases such as hepatitis through faecal matter in water sources. Poor drinking water treatment and unfit water can always cause an outbreak of infectious diseases such as cholera, etc.
• The ecosystem can be critically affected, modified and destructured because of water pollution.

The Minamata Incident marked one of the worst cases of water pollution

In 1932, a factory in Minamata City, Japan began dumping its industrial effluent – Methylmercury, into the surrounding bay and the sea. Methylmercury is incredibly toxic to humans and animals alike, causing a wide range of neurological disorders.

Its ill effects were not immediately noticeable. However, this all changed as methylmercury started to bioaccumulate inside shellfish and fish in Minamata Bay. These affected organisms were then caught and consumed by the local population. Soon, the ill effects of methylmercury were becoming apparent.

Initially, animals such as cats and dogs were affected by this. The city’s cats would often convulse and make strange noises before dying – hence, the term “dancing cat disease” was coined. Soon, the same symptoms were observed in people, though the cause was not apparent at the time.

Other affected people showed symptoms of acute mercury poisoning such as ataxia, muscle weakness, loss of motor coordination, damage to speech and hearing etc. In severe cases, paralysis occurred, which was followed by coma and death.  These diseases and deaths continued for almost 36 years before they could be officially acknowledged by the government and the organisation.

Since then, various control measures for water pollution have been adopted by the government of Japan to curb such environmental disasters in the future.

Pollution of the Ganges

Some rivers, lakes, and groundwater are rendered unfit for usage. In India, the River Ganges is the sixth most polluted river in the world. This is unsurprising as hundreds of industries nearby release their effluents into the river. Furthermore, religious activities such as burials and cremations near the shore contribute to pollution. Apart from the ecological implications, this river poses a serious health risks as it can cause diseases like typhoid and cholera.

Pollution of the Ganges is also driving some of the distinct fauna to extinction. The Ganges River shark is a critically endangered species that belong to the order Carcharhiniformes. The Ganges River dolphin is another  endangered species of dolphin that is found in the tributaries of the Ganges and Brahmaputra rivers.

As per a survey, by the end of 2026, around 4 billion people will face a shortage of water. Presently, around 1.2 billion people worldwide do not have access to clean, potable water and proper sanitation. It is also projected that nearly 1000 children die every year in India due to water-related issues. Groundwater is an important source of water, but unfortunately, even that is susceptible to pollution. Hence, water pollution is quite an important social issue that needs to be addressed promptly.

Control Measures of Water Pollution

Water pollution, to a larger extent, can be controlled by a variety of methods. Rather than releasing sewage waste into water bodies, it is better to treat them before discharge. Practising this can reduce the initial toxicity and the remaining substances can be degraded and rendered harmless by the water body itself. If the secondary treatment of water has been carried out, then this can be reused in sanitary systems and agricultural fields.

A very special plant, the Water Hyacinth can absorb dissolved toxic chemicals such as cadmium and other such elements. Establishing these in regions prone to such kinds of pollutants will reduce the adverse effects to a large extent.

Some chemical methods that help in the control of water pollution are precipitation, the ion exchange process, reverse osmosis , and coagulation. As an individual, reusing, reducing, and recycling wherever possible will advance a long way in overcoming the effects of water pollution.

Further Reading:

Frequently Asked Questions

What is sewage treatment.

Wastewater treatment or sewage treatment generally refers to the process of cleaning or removing all pollutants, treating wastewater and making it safe and suitable for drinking before releasing it into the environment.

What are the main steps in sewage treatment?

There are four main stages of the wastewater treatment process, namely:

• Stage 1: Screening
• Stage 2: Primary treatment
• Stage 3: Secondary treatment
• Stage 4: Final treatment

What are the main causes of water pollution?

The main causes of water pollution are attributed to

• Industrial activities
• Urbanization
• Religious and social practices
• Agricultural runoff
• Accidents (such as oil spills, nuclear fallouts etc)

What are the effects of water pollution?

Water pollution can have disastrous consequences on the ecosystem. Furthermore, toxic chemicals can travel through the food chain and get into our bodies, causing diseases and death.

To learn more about water pollution, causes, effects, preventive measures and other important environmental concerns (such as eutrophication), visit us at BYJU’S Biology.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

Visit BYJU’S for all Biology related queries and study materials

Your result is as below

Request OTP on Voice Call

Leave a Comment Cancel reply

Your Mobile number and Email id will not be published. Required fields are marked *

Post My Comment

I like this paper

Best source for obtaining detailed information about anything

Nice and useful site

i know right

Best platform for gaining accurate solutions of Maths And Science

can u tell me what are the preventions and control of river pollution important for India ???

The best platform for study purposes Really very helpful 😊 Thanks to Byjus 🙏

Elaboration is beautiful

really helpful for my semester report 🙂

Byjus is my best education platform, this bring revolutinise the educatuon, thanks to byjus

Really it is best knowledge source

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.

Maryland sues Harford County developer over mud pollution in Gunpowder River

Acting after years of complaints from residents, Maryland authorities have filed suit against the developer and builders of a Harford County housing project, accusing them of polluting the Gunpowder River and one of its tributaries by failing to control muddy runoff from the construction site.

More than 30 inspections since May 2022 of the 388-home Ridgely’s Reserve development and a related sewer line project in the Joppa area found numerous violations of state sediment pollution and nontidal wetlands laws, according to the 94-page complaint filed Sept. 6 in Harford County Circuit Court.

On behalf of the Maryland Department of the Environment, the state’s attorney general is seeking penalties against Texas-based homebuilder D.R. Horton, its development subsidiary Forestar Real Estate Group, and a York, Pennsylvania, contractor, Kinsley Construction.

“The repeated violations at Ridgely’s Reserve demonstrate a blatant disregard for our environmental laws and the welfare of Marylanders,” said Attorney General Anthony Brown.

The Baltimore Banner thanks its sponsors. Become one.

In addition to fines of up to $25,000 per day per violation, the state’s complaint seeks a court order requiring the defendants to repair the damage done by the pollution to the Gunpowder and its tributary, Foster Branch.

Sediment pollution is a major threat to the ecological health of the Chesapeake Bay and its tributaries. Rainfall and snowmelt can wash clay, silt and sand off exposed soil. The muddy runoff turns streams and rivers murky, smothering fish eggs and bottom-dwelling aquatic life. It also blocks sunlight that underwater grasses need to grow.

Gas-powered leaf blowers of Baltimore, your days are numbered

Once a polluter, c.p. crane will become a waterfront park in baltimore county, offshore wind was approved in maryland. here’s what it could look like..

Aerial surveys have found marked declines in submerged aquatic vegetation in the Gunpowder the last two years, even as grass beds providing critical habitat for fish and crabs have increased elsewhere in the Bay.

“Inspection after inspection has documented problems with this project, and this pollution has caused real harm to our waterways,” MDE Secretary Serena McIlwain said in a release announcing the lawsuit . “It is past time for this pollution to stop. We are asking the court to not only impose a financial penalty but also require that the affected waterways be restored.”

The three companies did not respond to emails seeking comment on the lawsuit.

The state’s lawsuit comes a month after the Gunpowder Riverkeeper formally notified the same companies that it intended to file a federal lawsuit against them for “ongoing and continuous” Clean Water Act violations at the Joppa construction site. Residents have been complaining for more than two years about muddy runoff from the 121-acre development turning Foster Branch and the Gunpowder murky shades of orange and brown. They have collected about 1,000 signatures on a petition demanding action that was posted on a website titled “Mad about Mud.”

In the news release announcing the lawsuit, MDE acknowledged that it began inspecting Ridgely’s Reserve and its sewer construction sites in response to complaints from residents and the riverkeeper. Each inspection found repeated violations, including failing silt fences and bare soil that during rainstorms could become muddy runoff into Foster Branch and the Gunpowder downstream.

Although the sewer line project is finished, the lawsuit says the construction site still needs to be stabilized to prevent muddy runoff. Work continues at the housing development, though most of the homes have been built and some sold, according to MDE’s lawsuit.

A Harford County spokesman said county officials welcomed the state’s lawsuit, noting that County Executive Bob Cassilly had walked the construction site and discussed it with the MDE secretary. The county levied $20,000 in fines against the developer and stopped work at the site seven times over the past two years to require repairs to runoff controls. MDE inspections continued to find violations, most recently in July.

Bill Temmink, a Joppatowne resident who has filed multiple complaints with the county and state over muddy runoff from Ridgely’s Reserve and the sewer project, lodged another complaint the day MDE filed its lawsuit. He contended that the housing development still has a large area of bare ground that could erode away in a rainstorm.

Temmink and some other local residents who’ve complained about the muddy runoff welcomed the state lawsuit. Gunpowder Riverkeeper Theaux Le Gardeur likewise said he was encouraged.

He urged the state to insist on restoration of the damaged waterways as the focus of any resolution of its lawsuit.

“That’s low-hanging fruit,” he said, noting that the county has a preexisting watershed restoration plan for Foster Branch.

But Jack Whisted, a retired engineer who lives along Foster Branch, said it was too little too late for him.

“The Gunpowder has been brown all summer. I feel the damage is irreparable,” he said by email.

“My disappointment over this has made me extremely sad,” Whisted added, “and makes me want to move away to better water.”

Tim Wheeler is a reporter for Bay Journal , a media partner of The Baltimore Banner.

More From The Banner

Ravens vs. Raiders: 5 things to watch, including Lamar Jackson, Maxx Crosby and Justin Tucker

Vote: Pick a side in Baltimore’s war of the Italian subs

Residents want Baltimore City Council to slow down Amtrak’s tunnel project. But can they?

Towson woman charged with vandalizing property during protests over Netanyahu’s DC visit

Community issues.

• Criminal justice
• Environment
• Transportation

Something went wrong. Please try again in a few minutes. If the problem persists, please contact customer service at 443-843-0043 or [email protected] .

• Skip to primary navigation
• Skip to main content
• Skip to footer

7-DAY UNLIMITED ACCESS

Trump Tower found liable for Chicago River pollution

By Miranda Willson | 09/12/2024 04:29 PM EDT

The building’s HVAC system likely sucked up thousands of fish, environmental groups say.

Kayakers on the Chicago River paddle toward Trump Tower in Chicago on Aug. 1. Tannen Maury/AFP via Getty Images

A judge this week found Trump Tower in Chicago liable for polluting the Chicago River without the proper permits and failing to prevent fish from being sucked into the building’s HVAC system.

Cook County Judicial Circuit Court Judge Thaddeus L. Wilson sided with environmental groups and Illinois Attorney General Kwame Raoul, who say the building owners created “a public nuisance” for years through the operation of the water intake system used to cool the property.

The environmental offenses at Trump Tower began in 2008 and likely killed thousands of fish, according to the Sierra Club, one of the groups involved.

The alleged facts in the case are “well founded,” Wilson wrote, and the building owners failed to take steps required to minimize the property’s impact on aquatic life. The building was also found liable for discharges of heated water and for misreporting its discharge levels, among other complaints.

“Defendant has created and continues to create a public nuisance in violation of Illinois law by operating its [cooling water intake system] in a manner that substantially and unreasonably interferes with the public right to fish and otherwise recreate in the Chicago River,” Wilson wrote in his order.

Steven Cheung, a spokesperson for Donald Trump’s reelection campaign, directed questions on the ruling to the Trump Organization. An email to the Trump Organization’s press team on Thursday was not immediately returned.

The building is owned by 401 North Wabash Venture, LLC, doing business as Trump International Hotel & Tower.

Albert Ettinger, an attorney representing Friends of the Chicago River and the Sierra Club in the case, said the problems at Trump Tower are particularly frustrating given that the groups have been trying to increase fish count and improve water quality. Once heavily polluted, the Chicago River has more recently been “recovering,” he said. The building is one of the largest users of Chicago River water for heating and cooling, the groups say.

“Frankly, it’s kind of aggravating to be stocking fish into the river while Trump Tower is sucking them out,” Ettinger said.

There could be more hearings in the case to determine the exact remedies and how much the penalties will be, unless the parties reach a settlement, he added.

The transformation of the energy sector.

Policy. Science. Business.

Congress. Legislation. Politics.

The leader in energy and environment news.

Late-breaking news.

© POLITICO, LLC

A major Colorado River water transfer has some asking for more details

A Front Range water distributor is pushing back on a planned transfer of rights to water from the Colorado River. It has led to a disagreement between two major water agencies — a minor flare-up of longstanding tensions between Eastern Colorado and Western Colorado, which have anxiously monitored each others’ water usage for decades.

Northern Water, which serves cities and farms from Fort Collins to Broomfield, is asking for more data about the future of the Shoshone water right. Meanwhile, the Colorado River District, a powerful taxpayer-funded agency founded to keep water flowing to the cities and farms of Western Colorado, says Northern Water may be attempting to stymie its purchase of the water rights.

In early 2024, The Colorado River District announced it would spend nearly $100 million to buy rights to the water that flows through the Shoshone power plant, near Glenwood Springs. Shoshone’s water right is one of the oldest and biggest in the state, giving it preemptive power over many other rights in Colorado.

Even in dry times, when water shortages hit other parts of the state, the Shoshone power plant can send water through its turbines. And when that water exits the turbines and re-enters the Colorado River, it keeps flowing for a variety of users downstream.

Since t hat announcement, the river district has rallied more than $15 million from Western Colorado cities and counties that could stand to benefit from the water right changing hands. Those governments are dishing out taxpayer money in hopes of helping make sure that water stays flowing to their region, even if demand for water goes up in other parts of the state.

The river district plans to leave Shoshone’s water flowing through the Colorado River. It’s an effort to help settle Western Colorado’s long-held anxieties over competition with the water needs of the Front Range, where fast-growing cities and suburbs around Denver need more water to keep pace with development.

The water right is classified as “non-consumptive,” meaning every drop that enters the power plant is returned to the river. The river district wants to ensure the water that flows into the hydroelectric plant also flows downstream to farmers, fish and homes. The agency plans to buy rights to Shoshone's water and lease it back to the power company, Xcel Energy, as long as Xcel wants to keep producing hydropower.

Almost all of the $98.5 million for the river district’s purchase of Shoshone’s water will come from public funds. In addition to money from its own coffers and Western Colorado governments, the river district also plans to apply for federal funding to pay for its purchase of Shoshone's water. It is planning to seek $40 million from the Inflation Reduction Act.

Despite decades-long tensions between water users on the Western Slope and the Front Range, leaders on the East side of the mountains have stayed mostly quiet about the Shoshone transfer.

Northern Water’s recent statements about Shoshone perhaps mark the most notable public pushback to the pending deal. The agency supplies water to Front Range cities such as Loveland and Greeley, as well as farms along the South Platte River all the way to the Nebraska border.

The agency outlined its concerns in a letter to elected representatives, including Colorado Senators Michael Bennet and John Hickenlooper and congresspeople Joe Neguse, Lauren Boebert, Yadira Caraveo and Greg Lopez.

In short, Northern said it supports the concept of the transfer, but wants an independent study of how much water the Colorado River District plans to send down the river each year.

“We want to make sure that we're all going into this with the same data to make sure that everyone's interests are being addressed,” said Jeff Stahla, Northern Water spokesman.

Northern posits that the Western Slope could pull more water than the amount that has been historically used by Shoshone – enough to increase strain on upstream reservoirs that also supply the Front Range.

The River District calls that claim a “gross mischaracterization” of its plans.

"Their points ignore the stated intent of the effort and are counter to the stated values,” said Matthew Aboussie, a spokesman for the River District, “And they 100% know that.”

The River District published its own letter about the matter. The agency’s director said Northern Water’s efforts “were received as intentional obstacles intended to threaten the viability of the Shoshone Permanency Project,” and said Northern’s calls for more data collection could require a time-intensive study of the project and tie it up in litigation for up to a decade.

“We are not looking to change the historic flows,” Aboussie said. “So the intention is to protect the status quo.”

The River District is currently compiling data about the history and future of the Shoshone water right and plans to present it in Colorado’s water court, which is part of the state’s normal process to approve the transfer or sale of water rights.

This story is part of ongoing coverage of the Colorado River, produced by KUNC and supported by the Walton Family Foundation. KUNC is solely responsible for its editorial coverage.

This story has been updated to note the amount of money that the Colorado River District expects to request from the federal government.

Copyright 2024 KUNC

• nagpur News

NMC, Tata to sign ₹1,927cr deal to clean up Nag river

About the Author

Proshun Chakraborty is a Senior Correspondent at The Times of India, Nagpur. He covers news on traffic, the zilla parishad, the district collectorate, the divisional commisionarate and fire control. His hobbies include surfing the net, reading and travelling. Read More

Visual Stories

Pollution still an issue in the Jukskei river, especially with rain season coming

Jukskei river stakeholders were asked for an assessment ahead of rainy season in sandton..

As rainy season looms, concern over Sandton residents residing near or along the Jukskei river built into an enquiry towards finding out what solutions emerged through winter for managing pollution in the river system.

Known to be active in efforts to clean the Jukskei, Buccleuch resident Lauren Nightingale was contacted on August 15 towards finding out what state the river was in, ahead of the rainy season.

Read more:  Morningside resident puts river spruit first

“So much litter, and so much rubbish [in there]; people are clueless about our most precious commodity – water,” Nightingale lamented. “Pollution gets discharged along the way from source to end, unfortunately. Many years ago, there were resident fish and crabs; now, there’s only chickens that get released during traditional healing ceremonies.”

Nightingale elaborated that the state of the Jukskei is of major concern, as the river joins the confluence of the Crocodile and Hennops rivers in the Rhenosterspruit area.

“At the moment, it appears as if non-profit organisations are the only ones who do anything about our rivers,” Nightingale said. “There are supposed to be 3 000 plus green warriors working for the Gauteng government. The last time we heard them do anything was when they went to Mpumalanga to do something about the Cholera outbreak. They should be working on the river crises.”

The founder of Hennops River Revival, Taryn Johnston, was contacted for more information on the Jukskei’s former glory, before humans began mistaking it for a dumping site of convenience. Johnston reminisced on how the Jukskei river formed from a natural spring in Ellis Park, to flow through various regions, including Alexandra, Buccleuch 1, and Morningside.

“The river was relatively clean and supported a variety of aquatic life,” Johnston reflected on September 8, painting a beautiful scene. “In former times common fish species including yellowfish and tilapia would swim, be caught, and eaten. The riverbanks were lined with indigenous plants like reeds and various grasses. Fascinatingly, crabs were also a part of this past ecosystem, highlighting the river’s once-thriving biodiversity.”

Also read:  The Jukskei River sorely needs cleaning up

Johnston discourages anyone from ever drinking the water of the Jukskei river. She went on to describe a scene she once witnessed while collecting test water samples from the Jukskei.

“We witnessed a man undressing, he proceeded to throw numerous buckets full of Jukskei River water over himself; it appeared to be part of a ritual; we also noticed many candles, red, blue, and white,” said Johnston. “So, no, please do not drink the river water, even if you have boiled it. You’d be at risk of contracting an illness or disease if you come into contact with the water.”

In conclusion, Johnston celebrated some of the groups actively working towards rehabilitating the state of the Jukskei river:

• Alexandra Water Warriors: A community group which has been actively involved in cleaning the river, setting up pollution traps to catch plastic and other debris. Alex Water Warriors have recently partnered with Suncasa, funded by Global Affairs Canada through the Partnering for Climate Programme, with a focus on nature based solutions

• WaterCAN: An initiative by OUTA. WaterCAN is a growing network of citizen science activists who are committed water guardians and willing stewards advocating for clean, safe, and sustainable water.

• Deep Water Movement: Citizen science monitoring of water quality in numerous rivers. These are cross-sector educational activities, from schools to board rooms, with the most recent: ‘Crisis Intervention Convention’ – a pivotal event dedicated to addressing the pressing water and waste issues facing South Africa.

Follow us on our  Facebook ,  X ,  Instagram  and  TikTok  pages. Join our  WhatsApp group  for any story ideas you may have.

Related article:  Bryanston river water unsafe to drink

Print Content

Discovery reap the benefits of vitality day run, related articles.

Celebrating Athol’s 250th parkrun

A successful Crawford International Sandton College Fun Run and Walk despite cold weather in Sandton

Sandton CPF seeks dedicated community members for Sector 1 committee

Entertainment on the square – One week was funny, the next absolutely magical