The U.S. Environmental Protection Agency says 55 percent of the streams and rivers in the United States are in poor condition for aquatic life.
The EPA surveyed thousands of kilometers of waterways and found increased levels of mercury and bacteria. Also found were excessive levels of nitrogen and phosphorus, which create too much algae, a plant that uses up oxygen that fish need.
Additionally, the EPA says many of the waterways lack enough vegetation to prevent flooding, erosion and pollution.
The EPA says healthy streams and rivers are vital sources of drinking water and recreation and play a critical role in the economy.