Types, Sources, and Solutions for Lake Pollution

In an extensive sampling effort, the Environmental Protection Agency, with the help of state and tribal agencies, coordinated water quality assessments for the country’s lakes. They evaluated 43% of the lake surface area or about 17.3 million acres of water. The study concluded that:

• Fifty-five percent of the study’s water acreage was judged to be of good quality. The other 45% had waters impaired for at least one type of use (for example as drinking water supply, for recreational fishing, swimming, or aquatic life support). When considering man-made lakes alone, the proportion that was impaired jumped to 59%.
• Water quality is sufficiently high to allow swimming in 77% of the waters assessed.
• Aquatic life was not supported adequately by 29% of lake waters.
• For 35% of the lake waters surveyed, fish consumption was not recommended.

For the impaired lakes, the top types of pollution were:

• Nutrients (problematic in 50% of impaired waters). Nutrient pollution occurs when excess nitrogen and phosphorus make their way into a lake. These elements are then picked up by algae, allowing them to grow rapidly to the detriment of the aquatic ecosystem. Overabundant cyanobacterial algae blooms can lead to toxin build-up, oxygen level drops, fish kills, and poor conditions for recreation. Nutrient pollution and the subsequent algae blooms are to blame for Toledo’s drinking water shortage in the summer of 2014. Nitrogen and phosphorus pollution comes from inefficient sewage treatment systems and from some agricultural practices.
• Metals (42% of impaired waters). The two main culprits here are mercury and lead. Mercury accumulates in lakes mostly from atmospheric deposition of pollution coming from coal-fired power plants. Lead pollution is often the result of accumulated fishing tackle like sinkers and jig heads, and from lead shot in shotgun shells.
• Sediment (21% of impaired waters). Fine-grained particles like silt and clay may occur naturally in the environment but when they enter lakes in large quantity, they become a serious pollution problem. Sediments come from the many ways soil can be eroded on land and carried into streams then lakes: erosion can originate from road construction, deforestation, or agricultural activities.
• Total Dissolved Solids (TDS; 19% of impaired waters). TDS measurements can be interpreted as how salty the water is, generally due to high concentrations of dissolved calcium, phosphates, sodium, chloride, or potassium. These elements most often enter the roadways as road salt, or in synthetic fertilizers.

Where do these pollutants come from? When assessing the source of pollution for the impaired lakes, the following findings were reported:

• Agriculture (affecting 41% of impaired waters). Many agricultural practices contribute to lake water pollution, including soil erosion, manure and synthetic fertilizer management, and the use of pesticides,
• Hydrologic modifications (18% of impaired waters). These include the presence of dams and other flow regulation structures and dredging activities. Dams have extensive effects on a lake’s physical and chemical characteristics, and on aquatic ecosystems.
• Urban runoff and storm sewers (18% of impaired waters). Streets, parking lots, and rooftops are all impervious surfaces that do not allow water to percolate through. As a result, water runoff speeds up to storm drains and picks up sediments, heavy metals, oils, and other pollutants, and carries it into lakes.

What Can You Do?

• Use soil erosion best practices whenever you disturb soil near a lake.
• Project lake shorelines on your property by preserving the natural vegetation. Replant shrubs and trees if needed. Avoid fertilizing your lawn close to a lake’s edge.
• Encourage the use of sustainable farming methods like cover crops and no-till farming. Talk to farmers at your local farmers market to find out more about their practices.
• Keep septic systems in good working order, and have regular inspections conducted.
• Encourage local authorities to use alternatives to road salt in winter.
• Consider your nutrient inputs from soaps and detergents, and reduce their use whenever possible.
• In your yard, slow down water runoff and allow it to be filtered by plants and soil. To accomplish this, establish rain gardens, and keep drainage ditches well vegetated. Use rain barrels to harvest roof runoff.
• Consider using pervious pavement in your driveway. These surfaces are designed to let water percolate into the soil below, preventing runoff.
• Choose alternatives to lead when selecting a fishing tackle. 

Sources

• EPA. 2000. National Lake Assessment Report.
• EPA. 2009. National Lake Assessment: A Collaborative Survey of the Nation’s Lakes.