In light of specific concerns over the clarity of the water in the Walla Walla River, the turbidity component of the Washington State Department of Ecology's (DOE) Water Quality Index (WQI) is treated separately in this indicator. In potable water use, the higher the turbidity level, the higher the risk of that people may develop gastrointestinal diseases. This is especially problematic for immune-compromised people because contaminants like viruses or bacteria can become attached to the suspended solid. The suspended solids interfere with water disinfection with chlorine because the particles act as shields for the virus and bacteria. Similarly, suspended solids can protect bacteria from ultraviolet (UV) sterilization of water.
A high turbidity level can also harm the flora and fauna in the rivers because it blocks light from reaching lower depths of water bodies, which inhibits the growth of submerged aquatic plants. That, in turn, affects other species dependent on those plants, such as fish and shellfish.
Turbidity in open water may be caused by the growth of phytoplankton. Human activities that disturb the land, such as construction, can lead to high sediment levels entering water bodies during rain storms, due to stormwater runoff, and create turbid conditions. Urbanized areas contribute large amounts of turbidity to nearby waters, through stormwater pollution from paved surfaces such as roads, bridges, and parking lots.
This indicator measures the level of turbidity in the Walla Walla River and the Snake River. Turbidity is one component of the overall Water Quality Index (WQI), (See: Indicator 3.1.1). Specifically, the Walla Walla River is measured near Touchet (approximately three river miles upstream from U.S. Hwy. 12), and the Snake River is measured near Pasco (on U.S. Hwy. 12 near Burbank at Hood Park).
