Water quality samples are analyzed monthly for temperature, dissolved oxygen (DO), pH, conductivity, turbidity, total suspended solids, ortho-phosphorus, total phosphorus, ammonia, nitrate-nitrogen, total nitrogen, and fecal coliform (FC) bacteria. Results are compared to State water quality standards. Water quality standards are designed to protect public health and aquatic life. Comparing monitoring results to water quality standards allows an understanding of how safe the creek is for recreational contact as well as for aquatic life (see link at top of page to view current water data).
State water quality standards were revised in 2003. Fairweather Creek is now categorized as “Core Summer Salmonid Habitat” for aquatic life use, and “Extraordinary Contact” for recreational use. As part of the updated water quality standards, portions of Fairweather Creek have been assigned an additional "Supplemental Spawning and Incubation Protection" temperature criteria of 16 ºC. The creek is on the Washington State Department of Ecology’s (Ecology) 303(d) list for violation of DO, water temperature, FC bacteria, and copper standards (Category 5).
See Table 2 below for routine monitoring summary statistics of water quality data collected to date. If stormwater data is available for this site, it will be shown as Table 3. Historical data reviews can be found in the annual reports produced by METRO/King County DNRP.
To view charts of current water quality data, please visit the Data Download webpage.
Long-term Trends
A 33-year (1975 – 2007) trend analysis was conduced with baseflow data collected from Fairweather Creek. The analysis showed some improvements in water quality since 1975 with significant decreases in nitrogen, and FC bacteria. However, as with most streams in the County monitoring program, a significant increase in water temperatures occurred and significant decrease in DO were observed during this same time period. In addition, total phosphorus concentrations increased significantly between 1975 and 2007.
Water Quality Index
A Water Quality Index (WQI) rating system was developed by Ecology that evaluates several water quality parameters and gives a single rating of “high,” “moderate,” or “low” water quality concern. To see how Fairweather Creek ratings compare with other stream sites, please visit the Water Quality Index webpage.