What Influences Water Quality

Natural Influences

Washington is affected by recurring floods and droughts. Floods range from fairly common high flows that barely go over a stream channel to unusually high flows that cover large areas and cause extensive damage.

Droughts either may be seasonal and have an undesirable effect on agriculture or may be long lasting to affect our water supplies.

Most of the 70 inches of average precipitation in western Washington and 20 inches in eastern Washington is brought to the State in the fall and winter by prevailing southwesterly and westerly winds from the Pacific Ocean.

Lots of winter rainfall over snow at low elevations causes most of the flooding in western Washington. In eastern Washington, floods can be caused by:

• winter rainfall over snow in the lower elevations
• spring snow melt runoff
• local summer thunderstorms (source: National Water Summary)

Atmospheric changes due to El Nino affects the weather, which affects our water. Abnormally high sea-surface temperatures cause torrential rains. The term El Nino, at the present, is associated with ecological and economic disasters, due to floods and losses in the fishing industry.
Volcanic eruptions can affect our water by producing sulfur dioxide gas, which returns to the ground in the form of sulfuric acid, or acid rain. Acid rain is also caused by humans.

Riparian Zones

These buffers created by plants and trees along a stream, lake or wetland are a critical part of the aquatic ecosystems.
Riparian zones;

• keep out excess soil, debris and pollutants from entering the water by slowing the speed of the water moving from the land to a stream or lake. This also provides an initial filtering of sediments and other pollutants.
• serve as a habitat connector by providing a protective pathway for wildlife.
• contribute large woody debris in the streambed which creates deep pools where fish can hide and rest.
• cool the water temperature by providing a canopy from tree branches.

Beaver dams are one of nature's ways of creating a wetland. If a beaver dam is destroyed, plants like reed canary grass may invade. This grass usually forms a thick, choking mass that obstructs water flow. So, instead of the wetland absorbing the water, water runs off and can cause the rapid filling of nearby streams and wetlands.

The threats to water quality may come from naturally occurring elements such as iron, manganese, arsenic, chloride, and radon.