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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.

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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.

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We develop and scale technologies to rid the oceans of plastic.

Our cleaning technologies are deployed around the world as we conduct the largest cleanup in history. For over ten years, The Ocean Cleanup has been researching, extracting, and monitoring plastic pollution in oceans and rivers globally – with millions of kilograms removed to date.

A planet-sized problem

Trillions of pieces of plastic pollute our oceans today, and the problem is worsening. This plastic has a devastating impact on marine wildlife and ecosystems. Plastics can persist for many decades, continuously degrading into microplastics. These can be ingested by wildlife and later enter the human food chain. Plastic pollution is a global crisis requiring urgent action.

We aim to clean up 90% of floating ocean plastic pollution

The Ocean Cleanup is a non-profit organization developing and scaling technologies to rid the oceans of plastic. To achieve this objective, we use a dual strategy: intercepting plastic in rivers to cut the inflow of pollution, and cleaning up what has already accumulated in the ocean and won’t go away by itself. When the oceans are clean, we can put ourselves out of business.

Cleaning the ocean

The Ocean Cleanup is cleaning up floating plastics caught swirling in the Great Pacific Garbage Patch, a plastic accumulation zone with over 100,000,000 kilograms of plastic.

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To clean the oceans, we also need to stop new trash from flowing into them. By tackling 1000 rivers around the world, we can halt 80% of riverine pollution reaching our oceans.

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Sustainable Solutions to Water Pollution: The Role of Community Action

A vital human right and prerequisite for sustainable development, access to water is at risk. Unsustainable water management is putting billions of lives at danger in various regions of the world. 

Water use is not being properly coordinated due to inadequate governance, institutional issues, significant data and infrastructure investment gaps, and a lack of a thorough grasp of the issues. lacked sufficient coordination. 

Due to extra pressures brought on by climate change, population expansion, urbanization, and migration, many countries will soon reach a critical point due to water scarcity, pollution, and poor management of water resources. 

The percentage of people who are water-stressed worldwide has gone up from 14% to 60% in less than 100 years. What actions are necessary and feasible to help nations respond to ongoing and impending crises and supply their inhabitants with clean, sustainably managed water?

What Is Water Pollution

Weakening our rivers, lakes, and oceans as well as the water we use at home, water pollution is a serious issue. It takes place when unwelcome objects contaminate the water, making it dangerous for both people and animals as well as vegetation.

What Causes Water Pollution? 

There are many different things that might pollute water. The following are some of the most typical:

• Industrial Pollution: Chemicals and waste can spill into rivers and streams from factories and industries. These chemicals could be harmful to both humans and aquatic life.
• Agricultural Pollution: Farmers use fertilizers and insecticides to help their crops flourish. However, when it rains, these pollutants might contaminate nearby water sources by washing into them.
• Sewage and Wastewater: We produce a lot of wastewater in both our cities and households. This effluent may contain dangerous bacteria and other toxins that end up in our water if it is not adequately treated.
• Oil Spills: Oil can occasionally leak from ships or drilling rigs into the water. For marine life and the purity of the water, this can be quite harmful.

Types of Water Pollutants 

Water pollutants can be of different types:

• Chemical Pollutants: These are substances like pesticides, heavy metals (like lead and mercury), and industrial chemicals that can harm the water and everything in it.
• Biological Pollutants: Bacteria, viruses, and other microorganisms from sewage and human or animal waste can make the water unsafe to drink or swim in.
• Physical Pollutants: This includes things like plastic bottles, trash, and debris that can clog waterways and harm aquatic life.

Why Water Pollution Matters 

Water pollution is a big concern for several reasons:

• Harms Wildlife: Fish, birds, and other creatures may struggle to survive in dirty water due to pollution. Several species suffer, and some may even go extinct.
• Health Risks: People who consume or swim in polluted water risk becoming ill. Diseases and other health issues may result from it.
• Harms Ecosystems: In rivers, lakes, and seas, water pollution can upset the natural order. Problems like algal blooms, which can destroy fish and other aquatic life, can result from this.
• Economic Impact: It can be costly to treat sick people and clean up contaminated water. Moreover, sectors like fishing and tourism can suffer from pollution.

Impacts of Water Pollution

Our environment, health, and economy are all negatively impacted by widespread and severe water contamination. Knowing these effects will help you understand why fighting water pollution is so important.

Environmental Impacts

Disrupted Ecosystems: By destroying fish, plants, and other aquatic life, water pollution can impact aquatic ecosystems. Pollutants upset the balance of life in water bodies when they enter, making it impossible for species to survive.

Algae Blooms: Algal growth can become out of control due to some contaminants, such as excess nutrients from fertilizers. This may result in toxic algae blooms, which lower sea oxygen levels and produce “dead zones” incapable of supporting marine life.

Habitat Destruction: Water pollution can harm the environments that support a wide variety of animal life. This may cause population decreases and potentially the extinction of some species.

Health Impacts

Waterborne Diseases: When humans consume or come in contact with polluted water, hazardous bacteria, viruses, and parasites that can cause diseases like cholera, typhoid, and gastroenteritis may be present.

Contaminated Food Chain: Water contamination can infect the food chain. Fish and other shellfish are unhealthy to eat because they can absorb contaminants. For those who depend on these items as a source of nutrition, this presents health problems.

Skin and Respiratory Problems: Due to exposure to dangerous compounds in the water, swimming or taking a bath in dirty water can cause skin rashes, eye irritations, and respiratory problems.

Economic Impacts

Loss of Industries: When water gets polluted, industries that depend on clean water, such fishing, tourism, and recreation, may suffer. Beach closures and fish kills can hurt local economy.

Treatment Costs: It costs a lot of money and effort to clean up chemically and contaminant-contaminated water. Taxpayers frequently bear the burden of these expenses, which puts a pressure on local budgets.

Reduced Property Values: As fewer people are willing to remain in locations with poor water quality and few recreational options, homes and properties next to polluted water bodies may decrease in value.

Community Action as a Solution

In the struggle against water contamination, community action is a potent and crucial response. Local residents may affect real change and safeguard their water supplies when they band together to confront this issue. Why community involvement is so important is as follows:

Local Empowerment:

• Ownership and Responsibility: Local water bodies have a direct impact on a community’s health. They have the power to own the issue and look for answers by acting.
• Knowledge and Expertise: Locals frequently have specialized knowledge of the water sources, sources of pollution, and environmental difficulties in their community. When tackling particular pollution issues, this local knowledge is priceless.

Awareness and Education:

• Raising Awareness: Community involvement can assist individuals comprehend the significance of and effects of water contamination on their life.
• Education and Outreach: Community organizations can teach locals how to reduce pollution, properly dispose of waste, and preserve water, fostering an environmentally conscious society.

Accountability and Advocacy:

• Holding Polluters Accountable: Initiatives driven by the community can push for stronger rules and make polluters answerable for their deeds.
• Political Influence: Through their combined voice, communities may have an impact on local and regional policy, ensuring that decision-makers give water quality a high priority.

Practical Solutions:

• Local Cleanup Efforts: Communities can organize cleaning efforts to clear up waste and debris from water bodies, improving the water’s beauty and quality.
• Monitoring Programs: Community-based water monitoring initiatives enable locals to closely monitor water quality, spot pollution events early, and notify authorities of their findings.

Partnership Building:

• Collaboration: Communities can pool resources and expertise to combat water contamination by working with local government organizations, environmental groups, and companies.
• Support Networks: Community involvement fosters networks of people and organizations dedicated to the same cause, creating a sense of unity and a shared objective.

Long-Term Sustainability:

• Community-Led Projects: Communities can start and maintain initiatives targeted at long-term ecosystem restoration, water conservation, and pollution reduction.
• Changing Behaviors: By promoting responsible water usage and pollution avoidance at the local level, communities can develop long-lasting habits that contribute to cleaner water.

Types of Community Action

Community action against water pollution takes several forms, all with the goal of protecting local water resources. These ways enable communities to safeguard and improve their water quality on a proactive basis:

Grassroots Initiatives

Hands-on initiatives within communities are part of grassroots efforts. Organizing frequent clean-up events along rivers and lakes to remove pollutants and debris is part of this. Furthermore, communities conduct environmental restoration efforts such as wetland rehabilitation and reforestation in order to restore damaged ecosystems.

Citizen Science Programs

Citizen science involves people of the community in data gathering and research endeavors. Volunteers monitor water quality by collecting data on water conditions and communicating their findings with appropriate authorities. Citizen science also involves biological evaluations, in which people of the community investigate water life and biodiversity in order to detect pollution consequences and restoration needs.

Advocacy Groups

Local environmental organizations are critical to community action. These organizations are concerned with water protection, pollution prevention, and the promotion of clean water policies. Communities also mobilize residents to lobby for tougher pollution legislation and enforcement at the local and regional levels.

Community-Based Water Management

Water management activities at the community level promote sustainable practices. This involves encouraging the installation of rainwater harvesting devices in households and public places in order to reduce reliance on municipal water sources and reduce runoff pollution. Communities also use green infrastructure solutions, such as permeable pavements and rain gardens, to effectively filter and control runoff.

Education and Outreach

Education is an important part of community activism. Schools incorporate water pollution education into their curricula, teaching pupils about responsible water usage and pollution prevention. Furthermore, communities conduct water conservation and sustainable practices workshops, seminars, and informational sessions.

Community Engagement

It is critical to engage the community directly. Residents can discuss water-related concerns, share ideas, and collaboratively explore solutions at regular community meetings. Collaboration with local businesses, government organizations, and nonprofits expands the reach of community participation.

Public Awareness Campaigns

Various methods are used to raise public awareness. Social media campaigns are utilized to educate the public about the concerns of water pollution, highlight success stories, and encourage community involvement. Artistic means such as art, photography, and movies successfully express the necessity of clean water and the repercussions of pollution.

Pollution Reporting Systems

The establishment of reporting channels enables communities to swiftly report pollution problems. Residents can report breaches or suspicious activity to authorities via community hotlines or internet platforms. Furthermore, volunteer patrols monitor polluted regions, assisting in the rapid reporting of environmental violations.

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Discharge from a Chinese fertilizer factory winds its way toward the Yellow River. Like many of the world's rivers, pollution remains an ongoing problem.

Water pollution is a rising global crisis. Here’s what you need to know.

The world's freshwater sources receive contaminants from a wide range of sectors, threatening human and wildlife health.

From big pieces of garbage to invisible chemicals, a wide range of pollutants ends up in our planet's lakes, rivers, streams, groundwater, and eventually the oceans. Water pollution—along with drought, inefficiency, and an exploding population—has contributed to a freshwater crisis , threatening the sources we rely on for drinking water and other critical needs.

Research has revealed that one pollutant in particular is more common in our tap water than anyone had previously thought: PFAS, short for poly and perfluoroalkyl substances. PFAS is used to make everyday items resistant to moisture, heat, and stains; some of these chemicals have such long half-lives that they are known as "the forever chemical."

Safeguarding water supplies is important because even though nearly 70 percent of the world is covered by water, only 2.5 percent of it is fresh. And just one percent of freshwater is easily accessible, with much of it trapped in remote glaciers and snowfields.

Water pollution causes

Water pollution can come from a variety of sources. Pollution can enter water directly, through both legal and illegal discharges from factories, for example, or imperfect water treatment plants. Spills and leaks from oil pipelines or hydraulic fracturing (fracking) operations can degrade water supplies. Wind, storms, and littering—especially of plastic waste —can also send debris into waterways.

Thanks largely to decades of regulation and legal action against big polluters, the main cause of U.S. water quality problems is now " nonpoint source pollution ," when pollutants are carried across or through the ground by rain or melted snow. Such runoff can contain fertilizers, pesticides, and herbicides from farms and homes; oil and toxic chemicals from roads and industry; sediment; bacteria from livestock; pet waste; and other pollutants .

Finally, drinking water pollution can happen via the pipes themselves if the water is not properly treated, as happened in the case of lead contamination in Flint, Michigan , and other towns. Another drinking water contaminant, arsenic , can come from naturally occurring deposits but also from industrial waste.

Freshwater pollution effects

Water pollution can result in human health problems, poisoned wildlife, and long-term ecosystem damage. When agricultural and industrial runoff floods waterways with excess nutrients such as nitrogen and phosphorus, these nutrients often fuel algae blooms that then create dead zones , or low-oxygen areas where fish and other aquatic life can no longer thrive.

Algae blooms can create health and economic effects for humans, causing rashes and other ailments, while eroding tourism revenue for popular lake destinations thanks to their unpleasant looks and odors. High levels of nitrates in water from nutrient pollution can also be particularly harmful to infants , interfering with their ability to deliver oxygen to tissues and potentially causing " blue baby syndrome ." The United Nations Food and Agriculture Organization estimates that 38 percent of the European Union's water bodies are under pressure from agricultural pollution.

Globally, unsanitary water supplies also exact a health toll in the form of disease. At least 2 billion people drink water from sources contaminated by feces, according to the World Health Organization , and that water may transmit dangerous diseases such as cholera and typhoid.

Freshwater pollution solutions

In many countries, regulations have restricted industry and agricultural operations from pouring pollutants into lakes, streams, and rivers, while treatment plants make our drinking water safe to consume. Researchers are working on a variety of other ways to prevent and clean up pollution. National Geographic grantee Africa Flores , for example, has created an artificial intelligence algorithm to better predict when algae blooms will happen. A number of scientists are looking at ways to reduce and cleanup plastic pollution .

There have been setbacks, however. Regulation of pollutants is subject to changing political winds, as has been the case in the United States with the loosening of environmental protections that prevented landowners from polluting the country’s waterways.

Anyone can help protect watersheds by disposing of motor oil, paints, and other toxic products properly , keeping them off pavement and out of the drain. Be careful about what you flush or pour down the sink, as it may find its way into the water. The U.S. Environmental Protection Agency recommends using phosphate-free detergents and washing your car at a commercial car wash, which is required to properly dispose of wastewater. Green roofs and rain gardens can be another way for people in built environments to help restore some of the natural filtering that forests and plants usually provide.

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• FRESH WATER
• GROUNDWATER
• WATER QUALITY
• WATER RESOURCES

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Localized water pollution creates opportunities for implementing solutions that foster development and raise community awareness. Governments and companies need to develop incentives and invest in these efforts. Some of our projects offer guidance on how to achieve this.

Students at Chengelpattu Medical College Hospital in Tamil Nadu, India, lived in a foul-smelling and unsanitary environment. Sewage from the 1,300-bed hospital was discharged untreated into the open air at the back of the campus. Medical staff had long complained about the irony of a healthcare facility contributing to pollution affecting both students and the city’s 87,000 residents. After installing a wastewater treatment unit , the sewage discharges ceased, and the hospital gained an unexpected benefit: biogas and organic fertilizers.

Localized water pollution creates opportunities for implementing solutions that foster development and raise community awareness. ©Foto de mali maeder

Point Source and Diffuse Pollution: We Must Understand Them Well

Our intervention, which involved implementing a DEWATS plant, is an excellent example of “point source pollution” in environmental science: the direct and localized release of pollutants from a specific discharge point. Due to its concentrated origin, this type of pollution can be easily identified and observed, as seen with discharges from buildings like hospitals, factories, pig farms, or city landfills.

On the other hand, there is “diffuse pollution”: the dispersed and widespread release of pollutants into the environment without a specific discharge point. A classic example is carbon emissions into the atmosphere. Water includes the runoff of agricultural or urban waters across a river basin, which ultimately discharges various pollutants into the sea and aquifers . Even if the source activity is known, assessing the extent of its geographical dispersion is challenging.

Controlling and reducing diffuse pollution has been a global challenge, prompting various international actions since the 1960s. Significant progress has been made for rivers in industrialized countries through legislation and regulation of industrial activities. However, much remains to be done, particularly in controlling agricultural and livestock practices. In developing countries, this issue is still largely unaddressed. It is crucial to note that approximately 80% of marine pollution is carried by rivers from land-based sources.

Success Stories Against Point Source Pollution

In recent decades, very effective solutions have been developed to fight point-source water pollution, particularly benefiting economically weaker countries. In these countries, sewage pollution has the most direct impact on people’s health. The Chengelpattu Hospital project exemplifies decentralized sanitation : where centralized sewer systems are unavailable, wastewater is treated on-site, providing additional benefits.

In the webinar we organized for World Toilet Day 2021, experts on sanitation in marginal areas highlighted the imperative need to manage feces and the opportunities created from its use. Mona Mijthab , founder of Mosan Sanitation Solutions, explained the development of Mosan, a regenerative circular system in communities in Guatemala, where 500 liters of untreated sewage is dumped every second. The system involves each household collecting its excrement in a simple latrine, which is then manually transported to a collection center and taken to a processing center. There, urine is processed by struvite precipitation, and feces are converted into biochar (biomass of plant origin) through pyrolysis. The resulting mass is carbonized in a reactor, providing the community with valuable fertilizer.

A similar solution is being developed in the Nairobi slum of Kibera , one of the largest in the world, home to an estimated 500,000 to 800,000 people living in shantytowns. The Umande Trust organization was established in Kibera to address the severe sanitation problem. Their solution involves the construction of 19 “biocenters,” facilities where residents can use safe latrines, access clean water, and take showers. The waste is used to produce biogas, which is then supplied to a community kitchen, allowing people to cook with clean water. Some of the waste undergoes anaerobic digestion by microorganisms and is removed once a year to be sold as agricultural fertilizer, with the proceeds reinvested in the community.

The social and economic benefits provide the incentive that ensures the sustainability of these developments, which are grounded in understanding the sources and causes of contamination. The World Bank and the WHO affirm that every dollar invested in basic sanitation saves up to five dollars in medical costs, and this claim remains unchallenged.

The Chengelpattu Hospital project exemplifies decentralized sanitation : where centralized sewer systems are unavailable, wastewater is treated on-site, providing additional benefits.

Point Source Plastic Pollution, Another Opportunity

However, point source and diffuse pollution often overlap, making it difficult to distinguish between them. This is evident with plastic waste, which is scattered throughout the planet’s waters but can be localized and more effectively eliminated on land.

The Umande Trust organization was established in Kibera to address the severe sanitation problem. Their solution involves the construction of 19 “biocenters”. © SuSanA

At the Foundation, we proved this with another innovative project. In the Kabadougou region of Côte d’Ivoire, one of the most neglected areas, we collaborated in building three schools with bricks made from recycled plastic from government-promoted collection programs. Beyond building schools, we achieved three benefits : promoting waste collection, obtaining an inexpensive raw material, and raising community awareness about the importance of plastic control and recycling.

In addition to improving the health of affected communities, studying the success stories in treating point source pollution provides valuable knowledge for designing strategies to combat diffuse pollution. We must win this battle to ensure our survival, and it requires leadership from both governments and companies.

However, point source and diffuse pollution often overlap, making it difficult to distinguish between them. This is evident with plastic waste, which is scattered throughout the planet’s waters but can be localized and more effectively eliminated on land.  © Foto de mali maeder

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Water Pollution

Recent publications and news, sociodemographic factors are associated with the abundance of pfas sources and detection in u.s. community water systems, freshwater fish found to have high levels of ‘forever chemicals’, nitrifying microorganisms linked to biotransformation of perfluoroalkyl sulfonamido precursors from legacy aqueous film-forming foams, soil and water pollution and human health: what should cardiologists worry about, the utility of machine learning models for predicting chemical contaminants in drinking water: promise, challenges, and opportunities., more harvard resources.

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Clean Water

Clean and safe water is essential for good health. how did access change over time where do people lack access.

Access to clean water is one of our most basic human needs.

But, one in four people in the world do not have access to safe drinking water. This is a major health risk. Unsafe water is responsible for more than a million deaths each year.

In this article, we look at data on access to safe water and its implications for health worldwide.

Unsafe water is a leading risk factor for death

Unsafe water sources are responsible for over one million deaths each year.

Unsafe water is one of the world's largest health and environmental problems – particularly for the poorest in the world .

The Global Burden of Disease is a major global study on the causes and risk factors for death and disease published in the medical journal The Lancet . These estimates of the annual number of deaths attributed to a wide range of risk factors are shown here.

Lack of access to safe water sources is a leading risk factor for infectious diseases, including cholera, diarrhea , dysentery, hepatitis A, typhoid, and polio . 1 It also exacerbates malnutrition and, in particular, childhood stunting . In the chart, we see that it ranks as a very important risk factor for death globally.

The global distribution of deaths from unsafe water

In low-income countries, unsafe water sources account for a significant share of deaths.

Globally, unsafe water sources account for a few percent of deaths.

In low-income countries, it accounts for around twice as many deaths .

In the map here, we see the share of annual deaths attributed to unsafe water across the world.

When we compare the share of deaths attributed to unsafe water either over time or between countries, we are not only comparing the extent of water access but its severity in the context of other risk factors for death. Clean water's share depends not only on how many die prematurely from it but also on what else people are dying from and how this is changing.

Death rates are much higher in low-income countries

Death rates from unsafe water sources give us an accurate comparison of differences in mortality impacts between countries and over time. In contrast to the share of deaths that we studied before, death rates are not influenced by how other causes or risk factors for death are changing.

In this map, we see death rates from unsafe water sources across the world. Death rates measure the number of deaths per 100,000 people in a given country or region.

What becomes clear is the large differences in death rates between countries: rates are high in lower-income countries, particularly across Sub-Saharan Africa and Asia. Rates here are often greater than 50 deaths per 100,000 people.

Compare this with death rates across high-income countries: across Europe, rates are below 0.1 deaths per 100,000. That’s a greater than 1000-fold difference.

The issue of unsafe water sources is, therefore, one that is largely limited to low- and lower-middle-income countries.

We see this relationship clearly when we plot death rates versus income, as shown  here . There is a strong negative relationship: death rates decline as countries get richer.

Access to safe drinking water

What share of people have access to safe drinking water.

Sustainable Development Goal (SDG) Target 6.1 is to: “achieve universal and equitable access to safe and affordable drinking water for all” by 2030.

Almost three-quarters of the world's population uses to a safely managed water source . One in four people does not use a safe drinking water source.

In the next chart, we see the breakdown of drinking water use globally and across regions and income groups. We see that in countries with the lowest incomes, less than one-third of the population uses safely managed water. Most live in Sub-Saharan Africa.

The world has made progress in recent years. Unfortunately, this has been very slow. In 2015 (at the start of the SDGs), around 70% of the global population had safe drinking water. This has slowly increased over recent years.

If progress continues at these slow rates, we will not reach the target of universal equitable access to safe and affordable drinking water by 2030.

In the map shown, we see the share of people across the world using safe drinking water facilities.

How many people do not have access to safe drinking water?

In the map shown, we see the number of people across the world who do not use safe drinking water facilities.

Improved water sources

What share of people do not use an improved water source.

The definition of an improved drinking water source is: “...those that have the potential to deliver safe water by nature of their design and construction, and include: piped water, boreholes or tubewells, protected dug wells, protected springs, rainwater, and packaged or delivered water.” Note that usage of drinking water from an improved source does not ensure that the water is safe or adequate, as these characteristics are not tested at the time of the survey. However, improved drinking water technologies are more likely than those characterized as unimproved to provide safe drinking water and to prevent contact with human excreta.

In the map shown, we see the share of people across the world who do not use improved water sources.

In the map shown, we see the number of people across the world who do not use an improved water source.

What determines levels of clean water usage?

Usage of improved water sources increases with income.

The visualization shows the relationship between usage of improved water sources versus gross domestic product (GDP) per capita. We see that there is a general link between income and improved water source usage.

Typically, most countries with greater than 90% of households with improved water have an average GDP per capita of more than $10,000 to 15,000. Those at lower incomes tend to have a larger share of the population without access.

Although income is an important determinant, the range of levels of usage that occur across countries of similar prosperity further supports the suggestion that there are other important governance and infrastructural factors that contribute.

Rural households often lag behind in improved water usage

In addition to the large inequalities in improved water usage between countries, there can also be large differences within countries. In the charts, we plotted the share of the urban versus rural population with usage of improved water sources and safely managed drinking water, respectively. Here, we have also shown a line of parity; if a country lies along this line, then access in rural and urban areas is equal.

Since nearly all points lie above this line, with very few exceptions, usage of improved water sources is greater in urban areas relative to rural populations. This may be partly attributed to an income effect; urbanization is a trend strongly related to  economic growth. 2

The infrastructural challenges of developing municipal water networks in rural areas are also likely to play an important role in lower usage levels relative to urbanized populations.

Definitions

Improved water source : "Improved drinking water sources are those that have the potential to deliver safe water by nature of their design and construction, and include: piped water, boreholes or tubewells, protected dug wells, protected springs, rainwater, and packaged or delivered water"

Usage of drinking water from an improved source does not ensure that the water is safe or adequate, as these characteristics are not tested at the time of the survey. However, improved drinking water technologies are more likely than those characterized as unimproved to provide safe drinking water and prevent contact with human excrement.

Safely managed drinking water: "Safely managed drinking water" is defined as an "Improved source located on premises, available when needed, and free from microbiological and priority chemical contamination."

'Basic' drinking water source: an "Improved source within 30 minutes round trip collection time."

'Limited' drinking water source: "Improved source over 30 minutes round trip collection time."

' Unimproved' drinking water source: "Unimproved source that does not protect against contamination."

'No service': access to surface water only.

WHO (2023) – Fact sheet – Sanitation. Updated September 2023. Online here .

Spence, M., Annez, P. C., & Buckley, R. M. (2009).  Urbanization and growth: commission on growth and development . Available online .

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Land & Water Stories

Wastewater Pollution

Turning a Critical Problem into Opportunity

Wastewater is a major threat to nature and human health.

Without adequate treatment, wastewater can contribute to habitat loss and extinction. TNC is actively addressing this through innovative science, strategic communications and policy interventions.

A Scary Status Quo

Every day 80% of the world’s wastewater enters our environment completely untreated, jeopardizing nature and public health, with far-reaching consequences for climate resilience, aquatic biodiversity and food and water security and access. Wastewater introduces a toxic cocktail of contaminants that threaten our food and water security as well as marine species. 

What's in wastewater? Pathogens, pharmaceuticals, microplastics, heavy metals, endocrine disruptors and more.

Our existing wastewater treatment systems allow us to “flush it and forget it,” avoiding the complex reality of wastewater pollution. Ignoring this critical issue leads to dangerous consequences, some of which we are already seeing like closed beaches, collapsed fisheries and algal blooms that suffocate aquatic life. 

Wastewater Pollution is Everywhere

TNC’s Solution

TNC scientists and conservation practitioners are addressing the dangerous impacts of wastewater pollution with a whole-system approach.

In addition to TNC’s on-the-ground projects across the globe, our dedicated wastewater pollution program is working across the Pacific to coordinate partners, develop foundational science and find solutions that work.

• Comms & Policy
• Science & Research
• Green Solutions

Climate Impacts

Eyes on wastewater.

Wastewater can often be a hidden threat. Click through this slideshow to see what's just below the surface.

Ocean Sewage: 2 divers inspect the effects of Delray Beach sewage outfall on the coral reef in Florida. © Steve Spring/Palm Beach County Reef Rescue

Coastal Pollution: Riverine discharges to coastal areas. Studies have linked wastewater pollution to seagrass die-offs, harmful algal blooms and weakened reefs. © Malik Naumann/Flickr

Sewage Contaminated Water: Ignoring wastewater pollution can have dangerous consequences, some of which we are already seeing like closed beaches, collapsed fisheries and algal blooms. © Brian Auer

Wastewater Pollution: Wastewater introduces a toxic cocktail of contaminants that threaten our food and water security as well as marine species. © Tom Fisk

Marin County Sewage: Richardson Bay in Marin County, CA is one of the sites in the Bat Area that has experienced sewage spills. © KQED Quest/Flickr

Strategic Communications & Policy

For too many, wastewater pollution flies under the radar or is simply categorized as someone else’s problem. Cultural taboo, combined with misconceptions about the capacity of oceans and other water systems to absorb wastewater, limits our ability to find and implement solutions. So much of the answer hinges on raising awareness.

It's time the world understood the critical threat wastewater pollution poses to humans and the natural systems we depend on.

That’s why TNC is building awareness and education through partnerships to reach broader audiences and drive campaigns that reduce stigma around wastewater and inspire action. We’re working across sectors to produce and share research, tools, and best practices while highlighting the intersections between wastewater pollution, public health and the environment. 

COLLABORATION IN ACTION

• TNC’s collaboration with the Reef Resilience Network provides wastewater pollution training, tools, and learning resources for coral reef practitioners. 
• Our work alongside partners at the Ocean Sewage Alliance  to build a first-of-its-kind knowledge hub and resource library on marine wastewater pollution. 

POLICY REFORM

If the world is to meet the UN's Sustainable Development Goals , we'll need significant policy reform. Many of the world’s wastewater policies and regulations are inadequate and based on outdated science that neither accounts for modern-day stressors nor recognizes the economic opportunity of wastewater resource recovery. TNC is exploring avenues for policy interventions to reduce and mitigate wastewater pollution for human health and environmental protection.

Coastal Long Island, NY

Nitrogen pollution has had a devastating effect on Long Island’s water quality for decades, causing harmful algal blooms and threatening bivalves, like oysters and mussels, as well as seagrass and salt marsh habitats. TNC’s Long Island team, in collaboration with a myriad of government and private sector partners, knew their restoration work wouldn't be successful without dealing directly with the pollution's source: the island’s half-million septic systems and cesspools. Find out how they worked with policymakers and partners at the federal and local level to secure funding and policy reforms necessary to do just that — from homeowner assistance for upgrading septic systems to building clean water infrastructure across the state that mitigates the effects of wastewater pollution. As of 2024, this coalition continues to work on a major ballot valued at $6B over the next 35 years, to create a county wide water quality restoration act to substantially increase the local funding for clean septic change outs and strategic sewer expansion. This fund would be the key to unlocking federal and state infrastructure funding.

Research & Monitoring

The global scientific community is increasingly recognizing the profound impact that wastewater pollution has on aquatic ecosystems. TNC scientists and field staff are on the front lines monitoring water quality to inform wastewater pollution mitigation and management strategies. 

Studies have linked wastewater pollution to seagrass die-offs, harmful algal bloom events and weakened reefs that can destabilize entire ecosystems. Even coastal wetlands, which naturally absorb nutrients, can become oversaturated when exposed to wastewater pollution over time, making these systems more vulnerable to extreme weather events exacerbated by climate change. 

"Contaminants of emerging concern” (CECs) in wastewater, like  PFAS , pharmaceuticals, and other novel chemicals not only threaten drinking water and human health but are also contaminating coastal waters and fisheries. 

A GLOBAL GOAL FOR OUR OCEANS

TNC’s plan for ocean recovery is expansive. We have a goal of conserving 10 billion acres of ocean worldwide. In order to achieve this goal, we must ensure that wastewater does not threaten the health and quality of the marine waters we protect.

Nature-based Solutions

Nature-based solutions are interventions that harness the power of Earth’s natural features and functions. These can look like dunes and wetlands that insulate coasts from storm surge, or native forest restoration in the face of megafires.

TNC and partners are employing nature-based solutions to address wastewater. One of the most promising solutions our team is studying is constructed wetlands . These are engineered systems designed for wastewater treatment that use natural biological technologies that incorporate wetland vegetation, soils, and microorganisms to remove contaminants.

This can be a cost-effective and sustainable option, and TNC is implementing solutions like these across the globe. From the Dominican Republic to India, our team is demonstrating that constructed wetlands can be an effective, nature-based mitigation strategy to improve water quality and restore wildlife habitat. 

Constructed Wetlands in Lake Sembakkam

In Chennai, the largest city in India’s southern state of Tamil Nadu, a 100-acre wetland has been restored to protect Lake Sembakkam. Rapid urbanization, including increases in wastewater and stormwater pollution, has caused the lake to degrade over time. This is one of many critical natural wetlands that serve as a lifeline for the city’s people and wildlife—including several rare and threatened species of migratory birds. TNC’s India program helped design and restore these wetlands to support biodiversity and to improve habitat, water quality, groundwater storage and recharge, and recreation landscape. Read more about how these constructed wetlands work and why TNC is expanding the project to the broader system of Chennai’s marshland.

Climate change and wastewater pollution are two inextricably linked crises. 

It’s estimated that wastewater treatment plants account for at least 3% of all greenhouse gas emissions, in addition to supplemental emissions from direct discharge into waterways. Beyond the treatment process, wastewater pollution is also a significant threat to some of the key ecosystems we rely on to store carbon, including mangrove forests and seagrass beds. To complicate the matter, the effects of climate change—from sea level rise to the increase in extreme weather events—are overburdening wastewater treatment systems that are already stressed and outdated. 

But if we change the status quo, addressing wastewater pollution can provide multiple avenues for tackling climate change. It starts with implementing treatment options that better protect carbon-storing ecosystems. These options are even more effective when coupled with investment in innovative practices that divert waste into valuable resources, such as reclaimed water, biofuel and fertilizer.

In Florida, TNC and partners have helped pave the way for more widespread reuse of wastewater, helping craft legislation that bans the use of ocean outfalls that discharge treated wastewater directly to the coastal zone within Southeast Florida by 2025, instead encouraging reuse. 

Make Transformative Change Possible.

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• Published: 23 May 2024

Current and future global water scarcity intensifies when accounting for surface water quality

• Edward R. Jones   ORCID: orcid.org/0000-0001-5388-7774 1 ,
• Marc F. P. Bierkens   ORCID: orcid.org/0000-0002-7411-6562 1 , 2 &
• Michelle T. H. van Vliet   ORCID: orcid.org/0000-0002-2597-8422 1  

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The inadequate availability of clean water presents systemic risks to human health, food production, energy generation and ecosystem functioning. Here we evaluate population exposure to current and future water scarcity (both excluding and including water quality) using a coupled global hydrological and surface water quality model. We find that 55% of the global population are currently exposed to clean water scarcity at least one month per year, compared with 47% considering water quantity aspects only. Exposure to clean water scarcity at least one month per year increases to 56–66% by the end of the century. Increases in future exposure are typically largest in developing countries—particularly in sub-Saharan Africa—driven by a combination of water quantity and quality aspects. Strong reductions in both anthropogenic water use and pollution are therefore necessary to minimize the impact of future clean water scarcity on humans and the environment.

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Future global urban water scarcity and potential solutions

A triple increase in global river basins with water scarcity due to future pollution

Sub-Saharan Africa will increasingly become the dominant hotspot of surface water pollution

Data availability.

Output data from this study (that is, population exposure to water scarcity) per geographic region are available via Figshare at https://doi.org/10.6084/m9.figshare.24866310.v1 (ref.  53 ). Water quantity and quality data are available via Zenodo at https://doi.org/10.5281/zenodo.7811612 (ref.  54 ).

Code availability

The coupled global hydrological model and water resources model (PCR-GLOBWB 2) and global surface water quality model (DynQual) are freely available via Zenodo at https://doi.org/10.5281/zenodo.7932317 (ref.  55 ) and via GitHub at https://github.com/UU-Hydro/ .

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Acknowledgements

E.R.J. and M.T.H.v.V. were financially supported by the Netherlands Scientific Organisation (NWO) by a VIDI grant (VI.Vidi.193.019). M.T.H.v.V. was also financially supported by the European Research Council (ERC) under the European Union’s Horizon Europe research and innovation programme (grant agreement no. 101039426 B-WEX). E.R.J. acknowledges and thanks the Netherlands Organisation for Scientific Research (NWO) for the grant that enabled us to use the national supercomputer Snellius (project no. EINF-3999).

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The study was designed by E.R.J., M.F.P.B. and M.T.H.v.V. Data processing, analysis and interpretation were led by E.R.J. in consultation with M.F.P.B. and M.T.H.v.V. E.R.J. led the paper writing, and all authors approved the paper.

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Extended data

Extended data fig. 1 population exposure to water scarcity in the east asia & pacific region under uncertain climate and socio-economic change..

a) Number of people exposed to water scarcity from 2005–2100, based on indicators considering water quantity only ( WS ) and including water quality ( WSq ). Thick lines and thin lines display the annual average and monthly average exposure to water scarcity, respectively, while shaded areas represent uncertainty arising from variations in GCM simulations as ±1 s.d. b) Percentage of the population exposed to seasonal (that is at least one month per year) and year-round (>9 months per year) water scarcity from 2005–2100, as indicated by WS and WSq . Lines display the mean average exposure per year averaged over the five GCMs considered, while shaded areas represent uncertainty arising from variations in GCM simulations as ±1 s.d. c) Percentage of the population exposed to water scarcity in each month, as indicated by WS and WSq . Boxplots are made based on monthly exposure to water scarcity across all GCMs for a historical reference period (2005–2020) and under three global change scenarios at the end of the century (2081–2100).

Extended Data Fig. 2 Population exposure to water scarcity in the Eastern Europe & Central Asia region under uncertain climate and socio-economic change.

Extended data fig. 3 population exposure to water scarcity in the latin america & caribbean region under uncertain climate and socio-economic change., extended data fig. 4 population exposure to water scarcity in the middle east & north africa region under uncertain climate and socio-economic change., extended data fig. 5 population exposure to water scarcity in the north america region under uncertain climate and socio-economic change., extended data fig. 6 population exposure to water scarcity in the southern asia region under uncertain climate and socio-economic change., extended data fig. 7 population exposure to water scarcity in the sub-saharan africa region under uncertain climate and socio-economic change., extended data fig. 8 population exposure to water scarcity in the western europe region under uncertain climate and socio-economic change., supplementary information, supplementary information.

Supplementary Figs. 1–4, Tables 1–4 and Discussion.

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Jones, E.R., Bierkens, M.F.P. & van Vliet, M.T.H. Current and future global water scarcity intensifies when accounting for surface water quality. Nat. Clim. Chang. (2024). https://doi.org/10.1038/s41558-024-02007-0

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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.

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• 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).

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What Is Water Pollution?

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When asked what water pollution is, most students can readily explain pollution as trash thrown away by humans that enters our water. Students can readily identify items visible to the naked eye, such as cigarette butts, plastic bottles, and bags. This type of debris is certainly a water-pollution problem. However, when students are asked about other sources of water pollution, they may be lost or not able to identify invisible pollutants. Chemical released by manufacturing, cars, and lawns and farms are large contributors to water pollution but can be hard for students to identify because they may not be visible, or the source of the pollution is not easily connected to the area that is impacted. For example, yard fertilizers and pesticides run into storm drains and simply "disappear" from students' world. Likewise, if students are asked how pollution gets into water, they may point to littering but not identify different types of runoff. It is important that students understand that there are many pollutants that get into the water—in different ways—so they can better understand how to prevent pollution from entering the water systems in the first place. Watch this video of 6th grade students in San Diego, California—a coastal community. The purpose of this classroom video is to see students share their ideas about water pollution. For additional classroom context, video analysis, and reflection opportunities, read the Picture of Practice page for "What Is Water Pollution?" in the Earth's Freshwater Educator Guide , page 80.

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EU continues its engagement in global water cooperation at the 10th World Water Forum

From 18-25 May, EU representatives will be attending the 10th edition of the World Water Forum in Bali, Indonesia which has the theme “Water for Shared Prosperity”.

It is a priority for the EU to accelerate global action to address the water crisis, driven by overdemand, mismanagement and the impacts of climate change, biodiversity loss and pollution. Water resilience is also key to prevent and address the current and future health, food and energy crises. At EU Green Week , the European Commission will launch an awareness-raising campaign on the need to transform the way water is managed, used and valued. This #WaterWiseEU campaign will encourage people to “See Water Differently” and explore solutions to the various water challenges we are facing today. 

At the World Water Forum, the EU will announce joining the Freshwater Challenge , launched at last year’s UN Water Conference. It aims to accelerate the restoration of 300,000 km of degraded rivers and 350 million hectares of degraded wetlands by 2030. By joining this challenge, the EU is showing its commitment to nature-based solutions for ensuring a sustainable water supply. 

The EU will also support water cooperation at global level, by launching a new initiative with the International Network of Basin Organisations supporting peer-learning between Lake and River Basin Organisations. Based on EU experience, this action will strengthen institutional frameworks, human capacities, means for planning and implementation among basin organisations all over the globe. 

EU research and innovation will also be showcased at the Forum, through the co-funded EU partnership Water4All in a dedicated pavilion , and through the Horizon Europe Restore our Ocean & Waters Mission . The EU pavilion will host a one-day event to present EU Research and Innovation on water, the partnerships, the Mission and promoting their various actions. Different international actions with external partners like UNESCO, the International Network of Basin Organisations (INBO) or UNEP will also be presented.  

The EU's participation in the Forum emphasizes its commitment to achieving the United Nations Sustainable Development Goals, notably SDG 6 - ensuring the availability and sustainable management of water and sanitation for all by 2030. The EU aims to keep water high on the global political agenda and to maintain the momentum from the UN 2023 Water Conference, where world leaders committed to accelerate actions for clean water and sanitation for all by 2030. The EU will join high-level discussions on the Water Action Agenda (WAA), Hydro-diplomacy and Peace, Water Governance, One Health approach and Water Information Systems. It will advocate for full implementation of the commitments made to the WAA and for enhancing water cooperation as a tool for security, stability, prosperity and peace. The EU will also showcase its support for the development of water information systems as fundamental tools for providing more comprehensive and valuable information for water resource management and decision-making.  

EU Ambassador to Indonesia Denis Chaibi said: 

The EU commends Indonesia for hosting the 10 th World Water Forum, an important international event to discuss global water issues. The EU sees water cooperation as a vector for peace, security and regional stability. Integrated Water Resources Management enables us to strengthen cross-sectoral cooperation with our partners. The EU has a wealth of experience and tools at its disposal, which it wishes to put to good use with the International Network of Basin Organizations, to a network of technical and institutional exchanges between basin organizations. This initiative is part of a broader approach to implementing the Global Gateway. 

On the Forum   

The World Water Forum is held every three years, and brings the international water sector together, including Heads of State, multilateral institutions, academia, civil society and the private sector. At the Forum, as part of the thematic process, the European Commission will coordinate the topic “Sound water supply and demand” under the sub-theme “Water Security and Prosperity”. A Ministerial Declaration will be adopted on 20 May. 

On the global water crisis  

It is estimated that almost half of the world’s population will suffer acute water stress by 2030. Worldwide, 2.2 billion people still lack access to safe drinking water and more than half of the global population does not have access to safe sanitation. This threatens the health of millions of individuals, especially the most vulnerable groups. Increasing water stress impacts food and energy security and ecosystem health and hampers socio-economic and human development. Increased competition for dwindling freshwater resources threatens stability among and within nations through conflicts, displacement or migration. 

On EU-funded Research and Innovation on water   

Water4All is a joint initiative from the European Commission, the EU Member States and non-EU partnering countries which aims to bring partners together to work towards the sustainable use of water resources in Europe and beyond.Water4All is a co-funded partnership under Cluster 6 of Horizon Europe, the EU research and innovation programme. The partnership’s overall budget is estimated to €400-450 million including an estimated European Union contribution of €126 million over the 10 years duration. It addresses the wider global water emergency crisis, related to water scarcity, water pollution, especially emerging contaminants, like micro-pollutants and micro-plastics, extreme hydro-meteorological events, ecosystems and biodiversity decline. Its vision is to boost the systemic transformation and changes across the entire research – water innovation pipeline, fostering the matchmaking between problem owners and solution providers to ensure water security for all in the long term. 

Five EU Missions have been launched under Horizon Europe programme. They aim to deliver concrete solutions to big societal challenges by putting research and innovation into a new role, combined with new forms of governance and collaboration, as well as by engaging citizens.  

The Horizon Europe Mission “Restore our Ocean and Waters“ is restoring the health of one of our most precious shared resources: our ocean and waters. This means protecting and restoring marine and freshwater biodiversity and ecosystems, eliminating pollution, and making the blue economy carbon-neutral and circular. The Mission will look at the whole water system from rivers to the seas and ocean. To support the Mission objectives and its related lighthouses, two cross-cutting enablers will be enhanced: the digital ocean and water knowledge system and broad public mobilisation and engagement. 

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Funding A Water Secure Future

• Infographic

The World Bank's groundbreaking new report, " Funding a Water-Secure Future: An Assessment of Public Spending ," quantifies for the first time how much governments spend on water and the size of the financing and funding gaps that must close to meet people's needs.

Full Report   I  Executive Summary

* Translations coming soon

Annual spending on water is $164.6 billion in developing countries, which amounts to roughly 0.5 percent of their GDP. While roughly 91 percent of the annual spending on water above comes from the public sector, including public spending by the government and the SOEs; only less than 2 percent comes from the private sector. Countries need to increase their spending in the WSS subsector by US$131.4 to US$140.8 billion annually—almost tripling current expenditure levels.

This global average, however, masks the stark heterogeneity across different regions and country groups. Sub-Saharan Africa and South Asia face the largest spending gaps. The report identifies critical weaknesses in the sector, such as low budget execution rates and inefficiencies. To bridge these gaps and attract private investment, the report emphasizes the necessity for governments to enhance spending efficiency, catalyzing long term financing, and reforming the water sector towards achieving Sustainable Development Goals for water access by 2030.

KEY HIGHLIGHTS

• To achieve the SDG targets for universal access to safe water and sanitation, the world is experiencing an annual spending shortfall of between US$131.4 billion and US$140.8 billion.
• Overall, annual spending in the water sector for developing countries is about US$164.6 billion, which is just about 0.5% of the total GDP.
• Despite large spending gaps, the water sector is not able to spend all the allocated budget. The annual budget execution gap is about 72%.

To overcome all these deficits, Funding a Water-Secure Future underscores the importance of governments spending more and better. These and other measures outlined in the report will go a long way toward achieving a more water-secure future that the world needs. Key recommendations include:

Increase budget execution rates through enhancing the sector’s absorptive capacity by reforming public investment management and public financial management.

Raise the productivity of public spending in the sector by improving efficiency at various levels.

Reduce the inefficiencies of water service providers by prioritizing cost-effective utility operations and improving investment planning for infrastructure development and technology upgrades.

Minimize disparities in access to water services by targeting investments and water subsidies to poorer and rural communities.

Catalyze the flow of long-term private and international finance by using risk-pooling arrangements, public sector guarantees, and catalytic capital to invest more, and more often, in water resources.

Implement reforms including improving cost recovery and demand management; developing government capacity and human capital; and strengthening data access, transparency, and communications.

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Closing the Funding and Financial Gap: The Quest for Water Security

Funding a water-secure future: How governments can spend better to spend more on ...

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The global clean water crisis looms large

Water scarcity will intensify with climate and socioeconomic change, disproportionately impacting populations located in the Global South. So concludes a new Utrecht University article published in Nature Climate Change on 23 May 2024, which used a state-of-the-art global water quantity and quality model to estimate clean water scarcity until the end of the century.

Humans require clean water for drinking and sanitation purposes, but also for the production of food, energy and manufactured goods. As communities and policymakers grapple with water scarcity issues on the ground, researchers at Utrecht University aim to shed light on the escalating global clean water crisis.

Current and future water scarcity

Using simulations from a state-of-the-art water quantity and quality model, the authors assess present-day and future global water scarcity. "Climate change and socioeconomic developments have multi-faceted impacts on the availability and quality of, and demands for, water resources in the future," says lead author Dr. Edward Jones. "Changes in these three aspects are crucial for evaluating future water scarcity."

The study estimates that 55% of the global population currently lives in areas that experience a lack of clean water in at least one month per year. "By the end of the century, this may be as high as 66%," remarks Jones.

Strong regional differences in future water scarcity

While global water scarcity is projected to intensify in the future, both the changes and impacts will not occur equally across all world regions. Future increases in water scarcity in Western Europe and North America, for example, are concentrated in just a few months of the year -- predominantly driven by water quantity aspects. Conversely, water scarcity increases in developing countries are typically more widespread in space and persist for a larger portion of the year.

Jones remarks, "Increases in future exposure are largest in the Global South. These are typically driven by a combination of rapid population and economic growth, climate change and deteriorating water quality."

Quality: the invisible part of water scarcity

Water quality -- despite being crucial for safe water use -- remains an under-represented component of water scarcity assessments. "Previous assessments still predominantly focus on water quantity aspects only," explains Jones. "Yet, the safe use of water also depends on the quality."

Therefore, a key aim of this study was also to normalise the inclusion of water quality in water scarcity assessments -- and in the design of management strategies for alleviating water scarcity.

Jones concludes, "The lack of clean water presents a systemic risk to both humans and ecosystems, which is becoming increasingly difficult to ignore. Our work highlights that, alongside substantially reducing our water demands, we must place an equally strong focus on eliminating water pollution in order to turn the tide on the global water crisis."

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May 24, 2024

Cape Cod Weighs Big-Ticket Pollution Solutions

Toxic algal blooms are forcing Cape Cod communities to consider expensive sewer and septic system projects.

By Rachel Feltman , Barbara Moran , Kathleen Masterson , Madison Goldberg & Jeffery DelViscio

Anaissa Ruiz Tejada/ Scientific American

This story was co-published with WBUR in Boston and produced with assistance from the Pulitzer Center . Read WBUR’s coverage of efforts to improve Cape Cod’s water pollution , including a “ pee-cycling ” project being considered by one innovative town. And check out a documentary short exploring these issues that was co-produced by WBUR and Scientific American.

[CLIP: Theme music]

Rachel Feltman: Cape Cod’s ponds and bays have suffered from decades of pollution. But scientific detective work has finally pinpointed the worst culprit: human urine. When household septic systems flush nitrogen and other nutrients into the water, they provide an all-you-can-eat buffet for algae blooms. More algae means less sunlight and oxygen for other marine life, which means trouble for the people of Cape Cod.

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If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

For Science Quickly , I’m Rachel Feltman. Today we’re bringing you the second installment in our three-part Fascination series on Cape Cod’s yellow tide. In this episode WBUR environmental correspondent Barbara Moran looks at some of the big-ticket pollution solutions up for consideration—and unpacks why they’re so controversial.

So without further ado, here’s part two: “Sticker Shock.”

[CLIP: Gerard Martin speaks at a Massachusetts Department of Environmental Protection (MassDEP) hearing: “All right, excuse me, everybody, I think we’re gonna get going.”]

Barbara Moran: Starting in late 2022 and continuing into the next year, concerned residents gathered for a series of public meetings with representatives from the Massachusetts Department of Environmental Protection. The residents were there to share their thoughts.

[CLIP: Martin continues to speak at the hearing: “The hearing is being recorded and conducted in a hybrid format.”]

Moran: The state was proposing new rules that would require communities to reduce their nitrogen pollution. In some places that meant people would potentially have to install new $35,000 septic systems. Here’s what Frank King of Brewster, Massachusetts, had to say about that.

[CLIP: Frank King speaks at the MassDEP hearing: “If that is correct, you are looking at a massive protest on the scale of another Boston Tea Party.”]

[CLIP: Chris Shanahan speaks at the MassDEP hearing: “Thirty or thirty-five thousand dollars a year? That’s a complete misrepresentation.”]

Moran: That’s Chris Shanahan of Falmouth, Massachusetts.

[CLIP: Shanahan continues to speak at the hearing: “You can buy a system for that. You gotta maintain it. You gotta fix parts. It just never ends. So lifetime expense is more like eighty or a hundred thousand over 30 years.”]

[CLIP: Joan Hutchings speaks at the MassDEP hearing: “I’m not somebody that has a McMansion. I’ve got a three-bedroom home that’s been in my family for a bazillion years.”]

Moran: Joan Hutchings of North Truro, Massachusetts. She said her town already made her upgrade her septic system.

[CLIP: Hutchings continues to speak at the hearing: “Now the state’s gonna have me do something else? I don’t know, I might put an outhouse out back—seriously.”]

Moran: People are concerned about the cost, as you heard. But they’re also concerned about whether these new systems even work. Can they actually prevent water pollution? I wondered the same thing. So I went to see an expert.

Brian Baumgaertel: My name is Brian Baumgaertel. I’m the director of the Massachusetts Alternative Septic System Test Center.

Moran: You met Brian briefly in Episode One. Now we’re on his home turf: a two-and-a-half acre outdoor laboratory on Cape Cod known as MASSTC.

Brian’s team is on a mission to find the best septic systems in the world—and it’s not a job for the squeamish.

[CLIP: Sound of wastewater channel]

Moran (tape): All right, so I’m looking into this hole, and there’s, like, water pouring in and some scummy stuff floating around there.

Baumgaertel: Yeah, that’s the raw wastewater coming in from Joint Base Cape Cod. And it doesn’t look like what most people would think of when—you know, when you’re thinking of wastewater, you think it’s pretty disgusting. I—you know, maybe I’ve just gotten so used to it. I don’t know.

Moran (tape): It is a little disgusting. [Laughs]

Baumgaertel: It’s got kind of a smell. You know, it’s one of the less glorious parts of MASSTC, but it’s a necessity. [Laughs] It’s brown gold, brown gold for us.

Moran: MASSTC uses that brown gold to test prototype septic systems from all over the world. I ask Brian to show me one—although it’s hard to see much at the facility.

Baumgaertel: A lot of what we do here is underground because of course, for the most part, septic systems in homes would be underground.

Moran: Brian walks over to a grassy mound that looks weirdly like a burial site—which it is, actually. He says that buried underneath our feet is a new kind of septic system that removes nitrogen from wastewater.

Here’s how it works: Wastewater flows into a tank, and all the solid stuff sinks to the bottom. The liquid left floating on top includes our pee, which is rich in nitrogen, phosphorus and other nutrients. This liquid flows out of the tank …

Baumgaertel: And then flows into the actual unit itself …

Moran (tape): Another tank that’s under our feet.

Baumgaertel: Yep, yep. There’s another tank that’s about 12 feet long right here.

Moran (tape): Okay.

Baumgaertel: And inside that tank are a number of compartments.

Moran: The compartments contain limestone rocks and wood chips. These ingredients create a breeding ground for bacteria that eat nitrogen. They convert it into harmless nitrogen gas before it gets into the groundwater.

Other systems remove nitrogen in different ways. Brian and his team test the water coming out of each system to see how well it works. And he says this one has been working pretty well.

Baumgaertel: So far the data look very encouraging. Every day we get a little bit more data, we get a little bit more confidence that the technology can work.

[CLIP: “We Are Giants,” by Silver Maple ]

Moran: Others are also heartened by the data, including Zenas Crocker, who goes by Zee. He’s executive director of the nonprofit Barnstable Clean Water Coalition.

Zenas Crocker: And this system is so successful that in the data that we’re seeing now, it will remove between 95 and 97 percent of nitrogen going into the groundwater.

Moran: Zee’s group was so impressed with how well these systems remove nitrogen that it launched a pilot project. The group is installing more than a dozen in a neighborhood by Shubael Pond in Barnstable, Massachusetts—including one when I visited last September.

[CLIP: Sound of chains being attached to a tank, followed by it being lifted]

Moran: As we watch, a crane operator uses chains to lift a concrete tank and lower it into a hole in the ground.

[CLIP: Sound of the tank being lowered and men talking]

Moran: Zee’s group is working with the Environmental Protection Agency and the U.S. Geological Survey to monitor how well the new systems keep nitrogen out of the groundwater.

Crocker: We chose this location in particular because these are all small lots. We’re also in a working-class community. Generally we’re looking at full-time residents here and people who really can’t afford, necessarily, to upgrade their septic systems.

Moran: The Barnstable Clean Water Coalition paid to install the systems in this neighborhood; the homeowners paid nothing—which won’t be an option for the whole cape.

But there is another approach to stopping wastewater pollution: switching from septic tanks to sewage pipes, which would bring the waste to a treatment plant. And that’s what Barnstable is doing in other parts of the town.

I went to Barnstable’s town hall to meet the guy in charge.

Moran (tape): Hi, how’re you doing? I have a nine o’clock interview with Mark Ells.

Receptionist: Okay, sure, he’ll be right with you.

Moran: Mark Ells is Barnstable’s town manager.

Mark Ells: We’ve seen a significant deterioration of our bays to the point where we don’t have shellfish, we don’t have finfish. So we want to make sure that we put in place solutions that help us to address not only what we know today but what we’re anticipating tomorrow.

Moran: Barnstable is the largest town on the cape, and parts are pretty urban, with houses and commercial buildings relatively close together. In places like this, sewer systems are a practical and cost-effective choice.

So the town has begun a massive expansion of its sewer system, planning to extend service to almost 12,000 properties.

[CLIP: “Let There Be Rain,” by Silver Maple ]

It’ll take 30 years and cost more than $1 billion. The town got local, state and federal funding to help cover the expansion costs. But homeowners will still have to pay.

First there’s a town assessment of up to $10,000 . Then homeowners have to pay to get their house hooked up to the sewer line and pay for someone to deal with their old septic tank. And then they’ll have a monthly sewer bill. The final cost, spread over decades, is probably in the range of $20,000 to $30,000—or more—per house.

[CLIP: Construction sounds]

Moran: And there’s another cost to installing sewer lines: seemingly constant roadwork and traffic jams.

One day last fall cars crawled along as superintendent Mike Donovan’s crew dug up the main road into Barnstable.

Moran (tape): Is this going to be, like, what your company does for, like, the next three decades?

Mike Donovan: We—well, hopefully, yeah. That’s what we do for a living. We’re installing sewer all over the cape right now.

Moran: But even this ambitious, expensive sewer expansion will take decades to reach some neighborhoods in Barnstable.

Pat Uhlman lives across the street from Shubael Pond. And she’s seen it turn green with toxic algae. She says a few decades is too long to keep polluting the water.

Pat Uhlman: If we don’t start cleaning it up now, you know, you might not even want to walk down by that pond by then.

Moran: Luckily Pat is part of the neighborhood pilot project that got new septic systems installed for free. She says she understands that other homeowners are feeling sticker shock, but the pollution has to stop.

Uhlman: The cape economy is still people coming here in the summer. So if they can’t swim in our ponds, they can’t swim in our ocean, they can’t boat, there’s not gonna be any reason for them to come here.

Moran: There may be another solution, a cheaper one. It won’t solve all the cape’s water problems, but it could help—a lot. We’ll talk about that next week in the final part of this Scientific American–WBUR Fascination miniseries.

Feltman: Thanks for listening. Tune in next Friday for the final installment in this miniseries—which, spoiler alert, involves a little something called “pee-cycling.” You don’t want to miss it.

Can’t wait for next Friday to get here? Don’t worry. We are taking Monday off for Memorial Day, but we’ll be back in your feed on Wednesday with some tips for protecting wildlife from the comfort of your own backyard.

This series is a co-production of WBUR and Scientific American . It’s reported and hosted by WBUR’s Barbara Moran.

Science Quickly is produced by Jeff DelViscio, Kelso Harper, Madison Goldberg and Rachel Feltman. Our theme music was composed by Dominic Smith. Shayna Posses and Aaron Shattuck fact-checked this series, and Duy Linh Tu and Sebastian Tuinder contributed reporting and sound. WBUR’s Kathleen Masterson edited this series. Additional funding was provided by the Pulitzer Center .

For Scientific American ’s Science Quickly , I’m Rachel Feltman.

The world’s benchmark climate monitoring station passes a major milestone

• May 20, 2024
• Download Cover Image

On May 17, 1974, staff of the new National Oceanographic and Atmospheric Administration’s Geophysical Monitoring for Climatic Change program took their first atmospheric measurements for what would become one of the most scientifically significant records of humanity’s impact on Earth’s climate.

Since then, NOAA’s Global Monitoring Laboratory’s continuous measurements of atmospheric carbon dioxide (CO 2 ) at the Mauna Loa Observatory have contributed to the longest modern datasets of this important greenhouse gas. NOAA’s daily measurements provide independent observations that complement measurements taken by the University of California San Diego’s Scripps Institution of Oceanography, which started sampling in 1958. The sustained, collaborative effort has helped educate scientists and the public about the relentless rise of CO 2 caused primarily by fossil fuel pollution. 

The concentration of carbon dioxide, or CO 2 , in that first sample was 333.46 parts per million (ppm). This month, as the annual CO 2 cycle peaks, concentrations have been averaging 427 ppm, more than 90 ppm above the 1974 level.  

“The long-term measurements at Mauna Loa have given us an accurate and unmistakable record of humans’ impact on the only atmosphere we have,” said Vanda Grubišić, director of the Global Monitoring Laboratory (GML).

This graph shows the full record of monthly mean carbon dioxide measured at Mauna Loa Observatory, Hawaii, by NOAA and the Scripps Institution of Oceanography. Credit: NOAA Global Monitoring Laboratory

Perched high on the barren slopes of the Mauna Loa volcano in the middle of the Pacific Ocean, the observatory protrudes through the strong marine boundary layer temperature inversion that separates the more polluted lower portions of the atmosphere from the much cleaner free troposphere. The 11,135-foot elevation above sea level is ideal for sampling well-mixed air undisturbed by the influence of local pollution sources or vegetation, producing measurements that represent the average state of the atmosphere in the northern hemisphere. 

The characteristics that make the site ideal for measuring CO 2 also provide ideal conditions for a wide variety of other atmospheric research efforts. The observatory’s 10 buildings house instruments that collected up to 250 climatological measurements for NOAA and partner agency scientists and engineers every day before the eruption of the volcano cut off access to the site in November 2022. 

In the beginning

The Mauna Loa Observatory was established by the U.S. Weather Bureau , the precursor to NOAA’s National Weather Service, on June 28th, 1956, but not to monitor climate. Instead, scientists made routine weather observations and studied atmospheric circulation. They also made observations of solar radiation, cosmic radiation, fallout from atomic tests, snow crystals, meteors, the Sun’s corona, even the atmosphere of Mars. 

Charles David Keeling was the first to observe that CO 2 levels rose and fell every year in concert with the seasons, a dynamic which is now known as the Keeling Curve . The highest monthly mean CO 2 value of the year occurs in May, just before plants in the northern hemisphere start to remove large amounts of CO 2 from the atmosphere during the growing season. In the northern fall, winter, and early spring, plants and soils give off CO 2, causing levels to rise through May. 

Keeling was also the first to recognize that despite the seasonal fluctuation, average CO 2 levels were increasing every year. Not only has that trend continued, but the rate of the annual increase has also risen – sharply – in recent decades. (Keeling’s son, geochemist Ralph Keeling, runs the Scripps program at Mauna Loa.)

This aerial photograph shows the dominant fissure erupting on the Northeast Rift Zone of Mauna Loa, taken at approximately 8 a.m. Hawaii Standard Time on November 29, 2022. Lava fountains were up to 25 m (82 ft) that morning as the vent was feeding the main lava flow to the northeast. Credit: M. Patrick/USGS photo

The volcano awakes

On Nov. 27, 2022, lava flows from the erupting Mauna Loa volcano buried more than a mile of the access road and destroyed power poles, temporarily interrupting all scientific activity at the observatory. NOAA and Scripps scientists were able to quickly set up alternative sampling sites for some measurements, including CO 2 , at Maunakea. 

In 2023, MLO staff visiting the site once a week via helicopter restored limited power to four key observatory buildings by augmenting existing solar generation and adding battery systems. Approximately 33 percent of the atmospheric measurements on the mountain site have been restored, including consistent measurements for greenhouse gases, halocarbons and trace gases, ozone, aerosols and global radiation. Reconstruction of the access road to the observatory is anticipated in 2025.

The Mauna Loa Observatory is one of four NOAA atmospheric baseline observatories strategically situated from the Arctic to the South Pole, each of which collects numerous daily in situ and remote atmospheric and solar measurements. Continuous measurements of atmospheric CO 2 at the Barrow Observatory near the ​​village of Utqiaġvik, Alaska began in July 1973, at the South Pole Atmospheric Research Observatory in January 1975, and at the American Samoa Atmospheric Baseline Observatory in January 1976.

To explore more information about the CO 2 record at Mauna Loa Observatory, visit the GML website’s Trends in CO2 page. 

For more information, contact Theo Stein, NOAA Communications: [email protected] .

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Mexico’s drought, heatwave and water shortage are so bad even police are blocking traffic in protest

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MEXICO CITY (AP) — Mexico’s drought, heatwave and water shortages have gotten so bad that even police blocked traffic in protest Wednesday.

In recent months, residents of some Mexico City neighborhoods have regularly taken to forming human chains to block boulevards to demand water. In April, complaints about contaminated water sparked a weeks-long crisis in one upscale neighborhood.

Normally, police seek to redirect traffic, but on Wednesday some officers were themselves manning a protest blockade, near the capital’s iconic Independence Monument.

The officers stood blocking six lanes of traffic, saying their barracks hadn’t had water for a week, and that the bathrooms were unusable.

“We don’t have water in the bathrooms,” said one female officer who would not give her name for fear of reprisals, adding that conditions in the barracks were intolerable. “They make us sleep on the floor,” she said.

The lack of water has worsened longstanding tensions between police officers and their supervisors over issues like sexual harassment and unfair working conditions.

“The bosses have water in their offices, but we’re not allowed to go in there,” said the female officer. “They don’t give us solutions. Today they brought in a water truck, after they saw the news media show up.”

In the midst of record temperatures and a severe drought, many buildings in the capital have to get water brought in by tanker trucks, but they have been in short supply and are expensive.

About 85 percent of the country was expected to see highs of at least 104 degrees (40 Celsius) Wednesday, with about a third of the country reaching 113 degrees (45 Celsius) or more.

Almost 40% of the country’s dams are below 20% of capacity, and another 40% are between 20 and 50% full. Mexico City has been forced to reduce water supplies because the reservoirs that feed the city are drying up. Some stores are running of mineral water.

Nationwide, authorities have had to truck in water for everything from hospitals to fire-fighting teams. Low levels at hydroelectric dams have contributed to power blackouts in some parts of the country.

Consumers are feeling the heat as well. On Monday, the nationwide chain of OXXO convenience stores — the nation’s largest — said it was limiting purchases of ice to just two or three bags per customer in some places.

Meanwhile, the heatwave has been so bad that in the Gulf coast state of Tabasco, howler monkeys are falling from the trees due to apparent heat stroke.

At least 138 of the midsize primates, who are known for their roaring vocal calls, were found dead in Tabasco since May 16, according to the Biodiversity Conservation of The Usumacinta group.

Environmental Pollution in the Moscow Region According to Long-term Roshydromet Monitoring Data

• Published: 02 November 2020
• Volume 45 , pages 523–532, ( 2020 )

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• G. M. Chernogaeva 1 , 2 ,
• L. R. Zhuravleva 1 ,
• Yu. A. Malevanov 1 ,
• N. A. Fursov 3 ,
• G. V. Pleshakova 3 &
• T. B. Trifilenkova 3  

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Long-term Roshydromet monitoring data (2009–2018) on the pollution of the atmosphere, soil, and surface water are considered for the Moscow region (Moscow city within its new boundaries and the Moscow oblast). The air quality in the megacity (Moscow) and in background conditions (Prioksko-Terrasny Reserve) is compared.

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G. M. Chernogaeva, L. R. Zhuravleva & Yu. A. Malevanov

Institute of Geography, Russian Academy of Sciences, 119017, Moscow, Russia

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Chernogaeva, G.M., Zhuravleva, L.R., Malevanov, Y.A. et al. Environmental Pollution in the Moscow Region According to Long-term Roshydromet Monitoring Data . Russ. Meteorol. Hydrol. 45 , 523–532 (2020). https://doi.org/10.3103/S1068373920080014

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A hidden threat

Fast-rising seas could swamp septic systems in parts of the south.

On the worst days, when the backyard would flood and the toilet would gurgle and the smell of sewage hung thick in the air, Monica Arenas would flee to her mother-in-law’s home to use the bathroom or wash laundry.

“It was a nightmare,” Arenas, 41, recalled one evening in the modest house she shares with her husband and teenage daughter several miles north of downtown Miami.

She worried about what pathogens might lurk in the tainted waters, what it might cost to fix the persistent problems and whether the ever-present anxiety would ever subside.

Residents in neighborhoods around Arenas’s have similar tales to share — of out-of-commission toilets, of groundwater rising through cracks in their garage floors, of worries about their own waste running through the streets and ultimately polluting nearby Biscayne Bay.

For all the obvious challenges facing South Florida as sea levels surge, one serious threat to public health and the environment remains largely out of sight, but everywhere:

Septic tanks.

Millions of them dot the American South, a region grappling with some of the planet’s fastest-rising seas, according to a Washington Post analysis . At more than a dozen tide gauges from Texas to North Carolina, sea levels have risen at least 6 inches since 2010 — a change similar to what occurred over the previous five decades.

One village’s risk

Officials worry about the threat of rising groundwater along the Little River in and around El Portal, where many homes rely on septic systems

Septic systems

Elevation above king tide*

Profile along NW Second Avenue

Above king tide

Below king tide

Little River

Officials worry about the threat of rising

groundwater along the Little River in and

around El Portal, where many homes rely

on septic systems

Unincorporated

Miami Shores

To Biscayne

King tide shown is the highest observed tide at Virginia Key on Oct. 28, 2023 (1.96 ft.)

Source: Miami-Dade County

Northwest 2nd AVe

BISCAYNE BAY

Along those coastlines, swelling seas are driving water tables higher and creating worries in places where septic systems abound, but where officials often lack reliable data about their location or how many might already be compromised.

“These are ticking time bombs under the ground that, when they fail, will pollute,” said Andrew Wunderley, executive director of the nonprofit Charleston Waterkeeper, which monitors water quality in the Lowcountry of South Carolina.

To work properly, septic systems need to sit above an adequate amount of dry soil that can filter contaminants from wastewater before it reaches local waterways and underground drinking water sources. But in many communities, that buffer is vanishing.

How rising waters threaten

septic systems

The most common type of septic systems rely on gravity to move sewage through a tank where solids settle and liquid waste is slowly released into the soil through a series of perforated pipes called a drain field.

Normal operation

DRAIN FIELD

Sewage enters

Wastewater filters

through soil

GROUNDWATER

The soil acts as a natural filter, neutralizing germs and pollutants before they can contaminate groundwater.

Rising water table

Contamination

Sea level rise and extreme rainfall are raising groundwater levels, resulting in more shallow buffers of soil that help protect local waterways and underground aquifers.

System failure

If a conventional septic system becomes submerged, wastewater will not be properly treated. Toilets can stop working and sewage can flood yards.

The most common type of septic systems rely on gravity to move sewage through a tank where solids settle and liquid waste is slowly released into the soil through a series of perforated pipes called a drainfield.

How rising waters threaten septic systems

An estimated 120,000 septic systems remain in Miami-Dade County, their subterranean concrete boxes and drain fields a relic of the area’s feverish growth generations ago. Of those, the county estimated in 2018, about half are at risk of being “periodically compromised” during severe storms or particularly wet years.

Miami, where seas have risen six inches since 2010, offers a high-profile example of a predicament that parts of the southeast Atlantic and Gulf coasts are confronting — and one scientists say will become only more pervasive — as waters continue to rise.

Virginia Key, Biscayne Bay, Fla.

sea level rise since 2010

0.4 inches per year

0.1 inches per year

Annual mean

Here, expensive repairs afflict homeowners as septic systems falter. Fetid water increases the risk of gastrointestinal diseases and other health hazards as floodwaters fill yards and streets. Profound worries persist about the environmental toll — which, researchers in Miami say, means submerged septic tanks are leaking nutrients into the porous limestone, potentially fueling algae blooms that kill fish .

“It’s really pretty gross,” said Michael Sukop, a hydrogeologist at Florida International University.

Rising seas will only exacerbate the problem, he added. “As the water table gets higher, all bets are off.”

Miami-Dade County is racing to replace as many septic tanks as possible, as quickly as possible. But it is a tedious, expensive and daunting task, one that officials say will ultimately cost billions of dollars they don’t yet have.

It also is far beyond a Florida problem.

In Georgia, officials have documented more than 55,000 septic tanks in counties near the Atlantic Coast in an ongoing data gathering effort. In North Carolina, researchers estimate, the discharge from approximately 1 million septic systems drains to waterways that eventually reach the ocean. In South Carolina, the issue has been the subject of legal fights and proposals in the state legislature.

In numerous states, researchers are studying the potential effects of what they call a largely unseen and unquantified environmental and public health threat.

“We don’t even know the scale of the problem,” said Rob Young, director of the Program for the Study of Developed Shorelines at Western Carolina University. “I think it’s everywhere. And it can’t get better as long as sea levels are rising. The only question is how quickly it can get worse.”

An environmental mess

More than 700 miles north of Miami, Mike O’Driscoll is among the scientists trying to decipher just how quickly rising seas are driving water tables higher, and why that matters.

O’Driscoll, a coastal studies professor at East Carolina University, and several colleagues have spent recent years documenting how rising groundwater is altering the hydrology along the Outer Banks in North Carolina.

In Nags Head, the group installed technology to monitor nearly a half-dozen aquifer wells for fluctuations in groundwater levels. They compared their findings to similar data from the North Carolina Department of Environmental Quality stretching back to 1983, and a clear trend emerged: Rising sea levels are raising the groundwater.

“If you look around the Outer Banks, the groundwater has risen one and a half feet in some places,” O’Driscoll said.

North Carolina requires about a foot to a foot and a half of separation between septic drain fields and the seasonal high-water table, depending on the soil type. But in places, that cushion is dwindling.

The Drowning South

“Rising groundwater has started to inundate systems in low-lying areas,” O’Driscoll said. “Some may be failing right now, but within a couple of decades, in some places, it won’t be viable to use conventional septic systems anymore.”

Beyond the environmental concerns, O’Driscoll worries about the financial impact for coastal communities and residents. It can cost homeowners $30,000 or more to install more advanced on-site wastewater treatment systems, and it costs localities many millions to expand existing infrastructure.

The Environmental Protection Agency estimates that roughly 20 percent of households in the United States rely on septic systems to treat their wastewater. That figure rises to more than one-third of homes in the Southeast, according to the agency . Florida is home to an estimated 2.6 million such systems.

In some places, such as rural areas not served by a centralized sewer and not threatened by encroaching groundwater, the approach can work well and be cost effective .

When conventional systems work as designed, solids from a home or business’s waste settle within the septic tank, while liquid waste is discharged into a drain field — usually a set of perforated pipes designed to slowly release effluent into the ground. The soil acts as a natural filter, neutralizing disease-causing pathogens, and reducing nitrogen, phosphorus and other contaminants before it reaches groundwater.

But that process is under increasing strain as seas push higher in the region and torrential rainfalls become more common, a combination that can inundate buffers that once existed.

EPA-funded research in Maryland has shown that many coastal properties with septic systems, which already face significant flood risk, will become far more vulnerable in the coming decades. As more septic systems fail, said Allison Reilly, a University of Maryland civil and environmental engineering professor, the more widespread the consequences will become, disproportionately harming low-income and minority residents.

“Right now it’s an environmental issue,” she said, “but as we warm, we’d expect it to become more of a public health issue.”

‘W e know what’s coming ’

Roy Coley , Miami-Dade County’s top sewer and water official, stood in the backyard of a home on NE 87th Street one afternoon. Nearby, workers had dug a trench as they prepared to connect the house and others nearby to a municipal sewer line.

“You’ve got so many thousands to do, where do you start? You start with one,” he said. “These houses are the low-hanging fruit.”

Over the past several years, leaders in Miami-Dade have aggressively pursued federal and state funding to decommission septic tanks and connect homes to sewage lines. The homes along NE 87th Street, not far from the Little River, just off Biscayne Bay, were converted in part using a grant from the Florida Department of Environmental Protection.

Miami-Dade County said it has so far been awarded about $280 million in grants. About 100 homes have been converted, and workers have put in place the public infrastructure to connect another 775. Coley said the county also is trying various approaches to offset connection costs for homeowners, which average around $15,000.

“We are seeking every way in the world to ease that pain,” he said.

But it remains a herculean task. The county estimates that about 9,000 septic tanks already are vulnerable to compromise or failure under current conditions — a number expected to climb as sea levels rise. Coley said roughly 11,000 septic tanks are on the priority list for removal.

Eradicating septic entirely could cost more than $4 billion, the county estimated in 2020. And the future of the effort, officials said in an email, “is strongly dependent on identifying and securing funding sources.”

But Coley said there has been a key shift over time: buy-in from elected officials and residents.

“I think up until now, there was just a general lack of understanding about how failing septic tanks impacted the environment,” he said. But that’s no longer the case. “When you know better, you do better.”

The problem of leaky and failing septic tanks is hardly a new one in Miami, and the area’s geography and geology have always made them a risky proposition.

The author of a 1949 article in Look Magazine titled “Florida’s Polluted Paradise” detailed the estimated 150,000 septic tanks already around greater Miami, many wedged side-by-side in a region that is “prairie-flat” and hardly above sea level.

Even then, South Florida’s heavy rains often overwhelmed them. “I, myself, have seen septic tanks in numbers back up and overflow into lawns and onto sidewalks in residential areas, owning to the fact that the underlying ground was too burdened with sewage and water to contain any more,” wrote the author, Philip Wylie.

Two decades later, little had changed.

A 1970 report from the Federal Water Quality Administration found that as many as 800,000 people around the county relied on septic tanks, and that many waterways suffered from low oxygen concentrations and startling levels of coliform bacteria, which can signal the presence of fecal waste.

“Septic tanks, widely used in Dade County, are public health hazards,” the report concluded.

The federal government insisted the county develop a master plan to reduce sewage pollution and combat leaking waste from septic tanks.

Using hundreds of million dollars of federal money along with public bonds, the county did build new wastewater treatment plants to ease some of the pollution, but it was not a panacea. Today, there remain neighborhoods that are surrounded by municipal sewer service, but where most homes still rely on septic tanks.

“They were intended to be temporary in Miami, and here we are 50, 70 years later,” said Rachel Silverstein, executive director of Miami Waterkeeper, which has campaigned to end septic pollution.

“There’s water everywhere, and there’s nowhere for it to go,” she said one sunny morning as a high tide sent water sloshing over the bulkheads along Biscayne Bay.

As bad as the problem has been historically, there is one aspect long-ago planners did not factor in: sea-level rise.

“Septic systems were not designed with the assumption that groundwater levels would rise gradually over time,” found a 2018 county report , “and as a result many are not functioning as they were originally designed.”

That report emphasizes how elevated groundwater levels are creating an “immediate” public health risk. “There are also many financial and environmental risks, including contamination of the freshwater aquifer, which is the community’s sole source of potable water,” the study found.

In recent years, Miami-Dade Commissioner Raquel Regalado has led the charge toward trying to phase out failing septic systems in the county.

“I hate them all. I want to get rid of all of them,” the Republican lawmaker said of the old concrete tanks.

She spearheaded a moratorium on any new septic systems on county-owned properties, pushed to ensure that development within a certain distance of sewer lines be required to connect, oversaw rules that require more sophisticated, self-monitoring septic tanks when outdated ones must be replaced and supported trying to offset costs of sewer conversions for homeowners.

“We have to get ahead of this, because we know what’s coming,” Regalado said. “It’s an environmental disaster waiting to happen.”

‘It will keep happening’

The lawsuit came from two South Carolina environmental groups — the Charleston Waterkeeper and the Coastal Conservation League.

Amid a building boom, the groups claim, state regulators have failed to adequately consider the effects of sea-level rise and stronger storms when approving growing numbers of septic tank permits across eight coastal counties.

“[Their] failures place the public’s health at risk and expose our state’s waterways, marshes, beaches, and fisheries to significant, documented harms that can be traced to untreated sewage from malfunctioning, ill-maintained, and/or ill-placed septic systems,” one filing read .

The lawsuit, filed in late 2022, cites existing or planned housing developments in vulnerable areas, including several near the town of Awendaw, about 25 miles northeast of Charleston. There, the suit states, hundreds of homes built close together would rely on septic tanks, all near the Cape Romain National Wildlife Refuge.

“A large percentage of the developed land is actually comprised of septic drain fields,” one filing argues , saying that such a situation risks “significant, irreparable harms” to public health and that of nearby marshes, beaches and fisheries. That includes the possibility of diseases such as hepatitis A and salmonellosis, which can be transmitted through fecal matter, and degradation of water quality, the filing said.

The groups want state officials to give special consideration to the cumulative impact of such clusters of septic permits. Already, they argue, South Carolina has no comprehensive inventory of existing septic tanks and little way for the public to challenge permits before they are approved.

“Sea level rise is happening. It will keep happening,” said Leslie Lenhardt, a senior managing attorney for the South Carolina Environmental Law Project, which is working on the case. “It’s steady, and it’s coming for these developments.”

In legal filings and in an email to The Post, the South Carolina Department of Health and Environmental Control said that it follows current law, which requires the agency “to conduct a coastal zone consistency review of only those wastewater treatment systems and septic tanks that handle more than 1,500 gallons per day or handle other than domestic waste.”

The agency acknowledged that there is no database of all septic tanks in the state, and said there is “no legal authority” that requires public notice about pending septic permits — though anyone can request such information by email.

Data provided by the agency shows it has approved increasing numbers of septic permits in the state’s coastal counties: nearly 16,000 from 2018 through 2023, with the largest numbers in Charleston County.

Beyond the courtroom, other South Carolina officials also are attempting to change the status quo.

“Everyone is very proud of the natural resources around here, but it’s fragile,” said state Rep. Joe Bustos (R), whose district encompasses a coastal swath of Charleston County, an area where seas have risen 7 inches since 2010, according to The Post’s analysis.

Bustos has co-sponsored a bill, unpassed by the legislature, that would ban new septic permits within two miles of the coast.

Wunderley, the Charleston Waterkeeper, supports that legislation and has watched both sea-level rise and the area’s growth accelerate in recent years. “It’s creating this dual pressure that’s really hard to deal with,” he said.

The legal and legislative efforts in South Carolina offer a glimpse at the tensions that states and localities face as they confront the legacy of conventional septic tanks in coastal areas where seas are rising fast.

There are success stories, but none are cheap or fast.

In 1999, with evidence that water quality was deteriorating along parts of the Florida Keys, the state mandated that the island chain eliminate the use of tens of thousands of septic tanks and other outdated waste systems. The cost reached roughly $1 billion as Monroe County built centralized sewage and hooked up thousands of homes and businesses.

“There was a huge change in water quality,” said Coley, who spent a decade working for the Florida Keys Aqueduct Authority.

For years, Georgia has worked to compile one of the most robust databases of where its remaining septic systems are — an effort that at times has involved digging through handwritten permits in dusty county filing cabinets. The result is a detailed list that allows state officials to better understand the risks that exist, both now and as groundwater rises over time.

“There are places where septic systems are clearly unsuitable, and that needs to be factored into future land planning,” said Scott Pippin, an attorney and environmental planner at the University of Georgia’s Carl Vinson Institute of Government.

Skip Stiles, a senior adviser at the Norfolk-based group Wetlands Watch, said septic failures are “like a blinking yellow light” that foreshadow a wider set of problems. As waters rise, he said, it will raise wrenching questions where the problem already is shifting from a nuisance to a persistent hazard.

“It’s forcing that decision that all of us in coastal communities are going to face eventually, but some are already facing now: Do I stay or do I go?”

Buying time

Arenas and her family are among the first homeowners to benefit from Miami-Dade County’s race to replace the most vulnerable systems.

Last year, crews removed their septic tank and hooked their house into a nearby municipal sewer line. Overnight, the nightmare vanished. No more monthly calls to have her underground tank pumped out. No more fretting over toxic water in the yard, or racing to a relative’s house to use the bathroom.

“It is 100 percent changed,” Arenas said.

That remains far from the case everywhere.

Less than a mile away, in the quaint village of El Portal, where peacocks lounge on the steps of the municipal building and Spanish moss hangs from giant oaks, Elizabeth Fata Carpenter spent years worried about water rising underneath the community she loves.

Carpenter and her husband moved to the neighborhood in 2019, and their yard flooded on multiple occasions, undermining the septic system behind their 87-year-old house. Especially after heavy rains, water oozed from the cracks in their garage floor. Their overmatched drain field overflowed into their yard and across the patio. They carried their 70-pound dog to higher ground for walks, and kept boots nearby to wade to their cars.

“We know the floodwater on our property is septic tank water,” Carpenter said one morning last fall outside her home, steps from the Little River. “I know it’s flowing into the river, and not just from my house, but everybody’s homes.”

Earlier this spring, the couple sold the house and moved to Fort Lauderdale. But Carpenter remains as chair on El Portal’s sustainability and resilience task force . And as an environmental attorney, she continues to fret about the collective pollution caused by septic tanks.

El Portal Mayor Omarr Nickerson shares those worries, and is working to end his community’s reliance on septic systems. But there is an inescapable obstacle: money.

Nickerson estimates that it would take roughly $50 million to convert the homes of El Portal to the municipal sewer system. The village’s annual budget is about $2 million, he said, more than half of which goes to the police department.

The county has designated roughly $6 million to help kick-start the effort, Nickerson said, but El Portal also must compete for funding with dozens of other local governments.

He worries that the issue, if left unsolved, might not only pollute the bay, but eventually drive people from his community.

Walking the streets on a postcard-perfect morning, Nickerson points to houses where unseen troubles lie. Where toilets back up. Where sewage-tainted water sometimes swamps yards and driveways. Where homeowners keep sandbags close at hand.

“It’s just going to continue,” Nickerson said.

The mayor points out an easily overlooked clue about the changing landscape of his village. Outside some houses, unnatural mounds of earth rise from the otherwise pancake-flat ground — an unmistakable sign that an old septic tank has been replaced with a newer, elevated version.

Some mounds are unadorned. Others are neatly landscaped. One resident built an entire deck around what she called the “mountain” in her backyard.

Several years ago, the septic system behind Kristen McLean’s home along the Little River failed as groundwater filled the tank and rendered her plumbing useless. For weeks, she relied on a composting toilet while she had a new engineered system installed.

“When we dug the hole for that septic system, the groundwater was 18 inches below my lawn,” she said. “This little area is a microcosm of what South Florida is up against.”

McClean sold the house in 2021 and jokes that she moved two miles away but seven feet higher.

These days, the mound rising in her old front yard is ringed with native plants.

It’s now a butterfly garden.

About this story

Design and development by Emily Wright .

Photo editing by Sandra M. Stevenson . Video editing by Alice Li and John Farrell . Design editing by Joseph Moore .

Editing by Anu Narayanswamy , Katie Zezima and Monica Ulmanu . Additional editing by Juliet Eilperin . Project editing by KC Schaper . Copy editing by Phil Lueck .

Additional support from Jordan Melendrez, Erica Snow , Kathleen Floyd and Victoria Rossi.

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