The Direct Causes of Freshwater Pollution

Nearly 70 percent of the earth is covered by water, yet freshwater makes up a very small fraction --- only 2.5 percent of total volume. The Clean Water Act of 1972 regulates the release of pollutants into U.S. waterways and prohibits the discharge of pollutants unless the discharger obtains a permit first. An amendment in 1987 was directed at eliminating point-source pollution, a single, identifiable, localized source of pollution. A great deal of the pollution affecting freshwater, however, comes from nonpoint sources.

Storm Water Runoff

• Flooding can lead to freshwater pollution.

  Storm water runoff is generated when precipitation from rain and melting snow flows over land and does not seep into the ground. As the water flows over paved streets, parking lots and building rooftops, it accumulates debris, chemicals, sediment and other pollutants. If the storm water runoff is left untreated before reaching waterways, lakes and streams, the pollutants present can affect the ecosystem functions and biological diversity in freshwater.

Raw Sewage

• Raw sewage can cause diseases if found in freshwater.

  The U.S. Environmental Protection Agency estimates that the amount of untreated sewage that enters the environment is enough to fill both the Empire State Building and Madison Square Garden every year. Raw sewage is untreated waste materials that carry infectious bacteria, viruses, parasites and toxic chemicals. It is supposed to be carried to wastewater treatment plants for processing, but during severe weather, rainwater can overflow the system and force raw sewage back onto the streets. Aging sewer systems also cause sewage to run untreated into freshwater sources.

Agricultural Runoff

• Farm runoff is the leading source of impairments to surveyed rivers and lakes.

  The United States has more than 330 million acres of agricultural land, and in 2000, the National Water Quality Inventory reported that agricultural pollution was the leading source of water quality impacts on surveyed rivers and lakes and the second largest source of impairments to wetlands. Pollutants that result from farming include sediment, pesticides, metals and salts. Animal waste that is carried into freshwater contains viruses and bacteria that can contaminate areas and cause water quality problems.

Solutions

• New approaches must be employed that prevent pollution. Low-impact development and storm water management practices can offer small-scale treatment of polluted water at the source of runoff. Storm water can also be collected for reuse on construction sites. City governments need to take a more active role in repairing broken sewer systems and replacing outdated pipes to avoid overflow during heavy rainfall. Farmers and ranchers can apply better management practices to control the volume and flow rate of runoff water and reduce soil transport into nearby freshwater.