Lakes In Danger: 46% Pollution Rate And Rising

Water pollution is a widespread problem that jeopardizes human health. Unsafe water kills more people each year than war and other forms of violence combined. The agricultural sector is the biggest consumer of freshwater resources and a serious polluter. A report by the Environmental Integrity Project (EIP) found that around 51% of rivers and streams, 55% of lake acres, and 26% of estuary miles were impaired and unable to meet EPA standards for swimming, fishing, or drinking. Indiana had the worst statistics for rivers, while Florida had the worst for lakes. The leading causes of waterway pollution are agricultural runoff and other indirect sources, such as industrial discharges, stormwater discharges, and nonpoint source runoff. Lakes often contain high pollution levels relative to the surrounding landscapes due to their large drainage basins, and pollutants can have long lifetimes, remaining in the environment for decades.

Industrial and agricultural runoff

Agricultural runoff includes pesticides, fertilizers, and animal manure, which can enter water bodies through rainfall and snowmelt, as well as other factors like cattle loafing in stream corridors and stream channel erosion. These contaminants can cause increased levels of nitrogen and phosphorus in water bodies, leading to harmful algal blooms. Algal blooms can create hypoxic (low oxygen) conditions that are detrimental to aquatic life and can also affect recreational activities and downstream water sources. For example, in 2014, toxic algae contaminated water sources in western Lake Erie, resulting in nearly half a million people losing access to safe tap water.

Soil erosion, nutrient loss, and the runoff of pesticides and other contaminants from agricultural land are leading causes of water quality impairment. The impact of agricultural runoff varies depending on factors such as farm types, conservation practices, soils, climate, and topography. For instance, while about 46% of rivers and streams in the US have excess nutrients, only 28% are considered "healthy" based on biological communities. Similarly, 21% of lakes have high levels of algal growth, and 39% have measurable levels of cyanotoxins, which are byproducts of certain types of bacteria.

To address agricultural runoff, various measures have been proposed and implemented. These include practices such as contour strip cropping, which reduces erosion and runoff, and initiatives like the National Water Quality Initiative (NWQI) by the USDA NRCS. Additionally, organizations like the Alliance for the Great Lakes advocate for regulations at the state and local levels to mandate, incentivize, and prioritize best practices to limit farm runoff and protect water bodies. The Alliance also works with local communities to find community-led solutions to the pollution problem.

Industrial activities also contribute to water pollution, including in lakes. Lake Erie, for example, has been significantly impacted by industrial pollution, with factories dumping chemical pollutants, acids, iron, and oil wastes into the lake and its tributaries. The lack of substantial government oversight in the Great Lakes Basin has allowed industrial waste, sewage, and pesticides to contaminate the lake, leading to ecological and public health issues.

Atmospheric pollutants

Atmospheric deposition is another critical pathway for pollutants to reach lakes. Biomass burning and cooking with charcoal can release pollutants into the atmosphere, which then settle over water bodies. This deposition can include toxic substances such as heavy metals, which are harmful to both aquatic life and human health.

Agricultural practices also play a role in atmospheric pollution affecting lakes. Fertilizers, pesticides, and animal waste from farms can be carried by the wind and deposited over lakes, contributing to nutrient pollution. This type of pollution, caused by excess nitrogen and phosphorus, is the leading threat to water quality worldwide and can lead to harmful algal blooms.

In addition to these sources, industrial activities release pollutants into the atmosphere, which can have long-range transport and affect lakes. These pollutants may include toxic chemicals, heavy metals, and particulate matter, which can contaminate lake water and accumulate in the food chain, impacting both aquatic organisms and humans who consume them.

To address atmospheric pollution affecting lakes, a combination of regulatory measures, improved industrial practices, and agricultural best management practices are necessary. Reducing emissions from vehicles and industries, implementing pollution control technologies, and promoting sustainable agricultural practices can help mitigate the impact of atmospheric pollutants on lake ecosystems.

Non-point source pollution

In agricultural settings, non-point source pollution can occur when fertilizers, pesticides, and animal waste are washed off fields and into nearby water bodies during rainfall or irrigation. This can lead to excessive nutrient enrichment, particularly with nitrogen and phosphorus, causing algal blooms and subsequent oxygen depletion when the algae die and decompose. This process, known as eutrophication, can create "dead zones" in lakes where aquatic life cannot survive due to the lack of oxygen.

Urban areas also contribute to non-point source pollution through runoff from impervious surfaces such as roads, parking lots, and rooftops. When rainwater flows over these surfaces, it picks up pollutants such as oil, grease, heavy metals, and trash, carrying them directly into storm drains and nearby water bodies without any treatment. This can have detrimental effects on aquatic ecosystems and also impact human health if the polluted water is a source of drinking water.

Atmospheric deposition is another significant source of non-point pollution. Air pollutants, such as nitrogen oxides and sulfur dioxide emitted from power plants, industries, and vehicles, can be carried over long distances and deposited onto land and water surfaces through rainfall or dry deposition. These pollutants can contribute to acidification of lakes and the excess nutrient loading discussed earlier.

Managing non-point source pollution is challenging and often requires a combination of regulatory measures, best management practices, and public education. Encouraging farmers to adopt sustainable land management practices, such as precision fertilizer application, conservation tillage, and the use of buffer strips and riparian zones, can help reduce the amount of pollutants entering water bodies. In urban areas, implementing green infrastructure, such as rainwater gardens and permeable pavements, can help capture and treat stormwater runoff before it reaches lakes and rivers.

Overall, addressing non-point source pollution requires a holistic approach that involves stakeholders from various sectors, including agriculture, urban planning, industry, and environmental protection agencies. By working together to implement preventative measures and best practices, it is possible to minimize the impact of non-point source pollution on our precious water resources and ensure the health and longevity of lakes and other aquatic ecosystems.

Nitrogen and phosphorus pollution

Nitrogen pollution is a significant concern for Great Lakes coastal wetlands, as these ecosystems are naturally sensitive to nitrogen loading. Excess nitrogen can stimulate algal growth, leading to a buildup of organic matter and a decrease in oxygen levels, making the habitat less suitable for fish populations. Experiments conducted on lakes Michigan and Huron revealed that nitrogen had a more pronounced effect on algal growth compared to phosphorus.

Phosphorus loading has traditionally been considered a more significant issue in Great Lakes habitats. However, the experiments showed that nitrogen played a more critical role in stimulating algal growth. Phosphorus, when combined with nitrogen, can further exacerbate the problem. This combination of nutrients creates favourable conditions for excessive algal blooms, which can produce toxins harmful to both humans and aquatic life.

The impact of nitrogen and phosphorus pollution extends beyond the ecological consequences. The presence of these pollutants in drinking water sources increases the cost of treatment, resulting in higher water bills for consumers. Additionally, the odour and aesthetic concerns associated with algal blooms can affect the recreational value of lakes and rivers, making them less appealing for swimming and other activities.

Addressing nitrogen and phosphorus pollution requires a multifaceted approach. It involves implementing better management practices in agriculture and urban planning, reducing nutrient runoff, and enforcing stricter pollution limits. By understanding the sources and impacts of these pollutants, effective strategies can be developed to protect and rehabilitate affected ecosystems, ensuring the sustainability and quality of water resources for both human and ecological needs.

Algal blooms

Excess nitrogen and phosphorus in the water cause an overgrowth of algae in a short period of time. This overgrowth of algae consumes oxygen and blocks sunlight from reaching underwater plants. When the algae eventually die, their decomposition uses up the remaining oxygen in the water, creating "'dead zones'" where there is not enough oxygen for aquatic life to survive. These dead zones are a significant problem for bays, lakes, and coastal waters as they receive excess nutrients from upstream sources.

The increase in nutrient levels that contribute to algal blooms can be attributed to various factors. Agricultural practices, including the use of fertilizers and pesticides, are a significant source of nutrient pollution. Additionally, factors that decrease water flow, such as drought, water extraction, and the construction of dams and canals, can contribute to the formation of algal blooms by creating stagnant or slow-moving water conditions that favour algal growth.

The impacts of algal blooms are far-reaching. They can affect aquatic ecosystems, leading to the loss of fish and other aquatic life. They also have economic consequences, impacting local industries and recreational activities. Furthermore, they pose a risk to public health, with the potential for illness and unknown long-term health effects in both humans and animals.

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