Greta Jimenez
Water pollution is a widespread problem that jeopardizes human health and the environment. Rivers, reservoirs, lakes, and seas are being contaminated with chemicals, waste, plastic, and other pollutants. According to the EPA, nearly half of Ireland's rivers are polluted by nitrogen, mainly due to agricultural activities and urban wastewater discharges. In the US, the EPA's National Rivers and Streams Assessment Report found that 47% of river and stream miles were in poor condition, with elevated levels of phosphorus and nitrogen. The EPA also reported that 35% of US river and stream miles were rated good for the fish community indicator, while 19% were in fair condition and 29% were in poor condition. The problem of water pollution extends beyond individual countries, with a variety of chemical pollutants, such as heavy metals, pesticides, and nitrate fertilizers, finding their way into water supplies worldwide.
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What You'll Learn
Nitrogen and phosphorus from agriculture
Nitrogen and phosphorus are essential for crop growth. Farmers apply these nutrients to their fields in the form of chemical fertilizers and animal manure. However, when plants do not fully utilize all the nitrogen and phosphorus, these excess nutrients can leave farm fields and negatively impact air and water quality.
Excess nitrogen and phosphorus can be washed from farm fields into waterways during rain and snowmelt or leach through the soil into groundwater over time. This runoff from agricultural fields is a significant source of river pollution. In Ireland, for instance, agricultural activities are the primary cause of high nitrate levels in rivers, groundwater, and estuaries in the south, southeast, and east of the country.
High levels of nitrogen and phosphorus in water bodies can cause eutrophication, leading to hypoxic "dead zones" that result in fish kills and a decrease in aquatic life. Excess nutrients can also cause harmful algal blooms (HABs) in freshwater systems, disrupting wildlife and producing toxins harmful to human health.
To address this issue, farmers can implement several best management practices (BMPs). These include installing fences along streams, rivers, and lakes to prevent livestock access and excess nutrient runoff. Conservation drainage practices, such as subsurface tile drainage, are also important for managing water movement and reducing nutrient loads while maintaining adequate drainage for crop production.
Additionally, farmers can ensure year-round ground cover by planting cover crops or perennial species to prevent soil erosion and nutrient loss during periods of bare ground. Planting field buffers, such as trees, shrubs, and grasses, along field edges, especially those bordering water bodies, can also help mitigate nutrient runoff.
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Urban wastewater discharges
In the United States, wastewater treatment facilities process approximately 34 billion gallons of wastewater daily. While these facilities play a crucial role in reducing pollutants, the country's aging and overwhelmed sewage infrastructure remains a persistent issue. According to EPA estimates, more than 850 billion gallons of untreated wastewater are released into the environment annually. This untreated sewage contains harmful contaminants such as salmonella, hepatitis, dysentery, and cryptosporidium, posing risks to both human health and the environment.
The problem of urban wastewater discharges is not unique to the United States. In Ireland, for instance, nearly half of the river sites have unsatisfactory water quality, with nitrate levels being too high. This is primarily due to agricultural activities and urban wastewater discharges. The Irish Environmental Protection Agency (EPA) has reported a decline in water quality in 230 rivers in 2020, with nitrogen and phosphorus from urban sources being significant contributors.
To address urban wastewater discharges, it is essential to invest in upgrading and maintaining wastewater infrastructure. This includes replacing aging pipes, improving treatment processes, and ensuring proper management of stormwater to prevent overflows. Additionally, implementing stricter regulations and monitoring programs can help reduce illegal discharges and notify the public about potential health risks associated with contaminated waterways.
While investing in infrastructure is crucial, it is also important to explore nature-based solutions. Expanding natural areas, restoring wetlands, planting trees, and creating green roofs can effectively increase the capacity of sewer systems by reducing stormwater runoff. By combining infrastructure upgrades with nature-based approaches, communities can better manage urban wastewater discharges and protect the health of their local rivers.
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High levels of phosphorus
Phosphorus is an essential element for plant life. However, when there is an excess of phosphorus in water bodies, it can cause eutrophication, or a reduction in dissolved oxygen in water bodies caused by an increase of mineral and organic nutrients. This eutrophication can lead to an explosive growth of aquatic plants and algae, which can cause low dissolved oxygen concentrations, killing fish and harming other aquatic life.
Sources of phosphorus leading to degraded water quality include manure and fertilizer from agricultural practices. In fact, a study by the U.S. Geological Survey found that 68% of 143 river sites had surpluses, meaning that the inputs of phosphorus were greater than outputs. Furthermore, older legacy phosphorus sources, such as manure and fertilizer inputs from the 1980s, were still contributing to the high levels of phosphorus in rivers. This is supported by another study that found that the total phosphorus load in agricultural areas continues to increase.
The impact of high levels of phosphorus in rivers can be seen in Minnesota, where a quarter of the lakes have high levels of phosphorus, causing them to not meet water quality standards for recreation. The excessive phosphorus in these lakes feeds algae growth, making the waters less attractive for swimming and other aquatic recreation, and degrading the conditions necessary for fish, insects, wildlife, and desired plants to thrive. Additionally, phosphorus can fuel toxic blue-green algal blooms, which are harmful to humans and animals.
To address this issue, Minnesota has adopted a nutrient reduction strategy that outlines goals and action steps for reducing phosphorus and nitrogen. This includes recommendations such as using less fertilizer on lawns and cropland, implementing buffer strips that filter runoff, and following feedlot operation and manure application rules to prevent runoff. Similar efforts have been made in Atlanta, Georgia, where voluntary and mandatory restrictions on phosphorus detergents have led to a decrease in the amount of phosphorus in the Chattahoochee River.
In Ireland, nearly half of the river sites were found to have unsatisfactory nitrate concentrations, with nitrogen and phosphorus from agriculture and urban wastewater discharges being significant contributors to water pollution. The Irish Environmental Protection Agency (EPA) has published an indicators report on the quality of water in various water bodies, and local organizations such as the Rivers Trust are working to deliver nature-based solutions and provide practical advice to land managers to improve river health.
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Fish community health
The health of fish communities is a critical component of river and stream health. The US Environmental Protection Agency (EPA) has developed a fish community index to evaluate the condition of fish communities in these water bodies. The index takes into account various factors, including taxonomic richness, taxonomic composition, pollution tolerance, habitat and feeding groups, spawning habits, and the percentage of migratory and native taxa.
According to the EPA's National Rivers and Streams Assessment, only about one-third (35%) of river and stream miles in the United States had healthy fish communities. This assessment was conducted in collaboration with state and tribal partners during the spring and summer of 2018 and 2019, utilizing standardized sampling procedures to collect data on biological, chemical, physical, and human health indicators.
Chemical pollution is another major threat to fish communities. Contaminants such as mercury, pesticides, and industrial chemicals can accumulate in fish tissues, posing risks to both the fish themselves and humans who consume them. These contaminants can enter rivers through various sources, including agricultural runoff, sewage treatment plants, and chemical spills.
It is important to note that the presence of pollutants in a river or stream may not always be apparent through visual inspection. Laboratory testing is often required to determine the levels of chemical pollutants in fish. The EPA provides resources such as the "How's My Waterway" tool to help the public access information about water quality and make informed decisions about fishing and recreational activities.
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Groundwater pollution
Agricultural activities are a major contributor to groundwater pollution. The use of chemical and organic fertilisers, pesticides, and animal waste in farming and livestock production can contaminate groundwater. When it rains, these pollutants are washed into waterways, leading to nutrient pollution, which is the number-one threat to water quality worldwide. Excess nitrogen and phosphorus in water or air can cause algal blooms, which are harmful to both people and wildlife. In Ireland, for instance, almost half of the river sites have unsatisfactory nitrate concentrations, and 38% of the sites have rising concentrations, largely due to agricultural activities.
Point source pollution is another form of groundwater pollution, where contamination originates from a single source, such as wastewater discharged by a manufacturer, oil refinery, or wastewater treatment facility. Other examples include leaking septic systems, chemical and oil spills, and illegal dumping. While the EPA regulates point source pollution by establishing limits on what can be discharged, it can still affect miles of waterways.
Nonpoint source pollution, on the other hand, comes from diffuse sources and can also impact groundwater. For instance, in the Upper Midwest of the United States, nutrient pollution from farm fields can bypass buffers meant to protect waterways and eventually end up in streams.
Once groundwater becomes polluted, it can be extremely difficult and costly to rid it of contaminants. A polluted aquifer may be unusable for decades or even thousands of years, and the contamination can spread far from its original source as it seeps into streams, lakes, and oceans.
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Frequently asked questions
Water pollution occurs when harmful substances contaminate a body of water, degrading water quality and making it toxic to humans or the environment.
Rivers can be polluted by a variety of substances, including chemicals, waste, plastic, and other pollutants. More specifically, rivers can be polluted by nitrogen and phosphorus from agriculture and urban wastewater discharges, pesticides, fertilizers, waste leached from landfills, and septic systems.
River pollution can have a range of negative effects on both human health and the environment. According to the EPA, 3.5 million Americans contract health issues such as skin rashes, pink eye, respiratory infections, and hepatitis from sewage-laden coastal waters each year. River pollution also harms aquatic ecosystems, which rely on a complex web of animals, plants, bacteria, and fungi.
River water quality is monitored through programmes such as the National River Monitoring Programme and the Water Quality Monitoring Programme, which assess the ecological and chemical status of surface waters and groundwater. Parameters such as nutrient levels, biological elements, and riparian vegetation cover are measured to evaluate the health of river ecosystems.
Various organizations, such as the Environmental Protection Agency (EPA) and The Rivers Trust, are working to improve river water quality through initiatives such as the National Rivers and Streams Assessment and by providing practical advice to land managers. Additionally, the EPA publishes assessments of water quality every three years to track progress and identify areas in need of improvement.
