In all, Ecology assessed 98 percent of the streams, all of the estuaries and 99 percent of the lakes in Washington. The waters were assessed on how well they supported uses that the public expects such as aquatic life, swimming, boating and aesthetic enjoyment. Fecal coliform bacteria are the primary pollution problem harming streams and marine waters. Fecal coliform may enter waters from dairy farms that are not properly managing their dairy waste, failing septic systems, pet waste and stormwater. It's an indicator that other pathogens may be present in the water, pathogens that when ingested may make people very sick.
Excessive nutrients are the primary problem in Washington's lakes.
Excessive nutrients come from sources such as irrigated agriculture, gardening practices and urban and suburban property development. The nutrients cause algae and other aquatic plants to grow in lakes, which rob the aquatic life of the oxygen necessary for survival. In addition, algae and aquatic plants can make lakes unsafe for swimming and boating and cause a lake's aesthetic value to decline. The leading sources of water pollution include some agricultural practices, urban development and failing septic systems. Statewide, pollution from agricultural practices accounts for 33 percent of water pollution problems.