Publication Summary

The status and trends in water quality in the Spokane River system in Washington State is mixed. Cadmium, lead, and zinc enter the system from upstream, but significant amounts of nutrients and fecal bacteria are added to the mainstem Spokane, and Hangman Creek contributes large quantities of sediment. There are preliminary indications of declining metals concentrations, and sediment in Hangman Creek has declined. Ammonia and phosphorus concentrations have been falling; other nitrogen forms, including total nitrogen, have been increasing. Fecal coliform bacteria also have been increasing, especially during the low-flow months.

Among the 62 long-term stations monitored by the Washington State Department of Ecology′s Freshwater Monitoring Unit are 16 sets of upstream/downstream stations that delineate stream reaches. Stations at the Spokane River at Riverside State Park and at Stateline comprise one of these sets. This report is the second in a series that presents results of an analysis of water quality monitoring data from these 16 reaches.

The status and trends in water quality in the Spokane River system in Washington is mixed. Cadmium, lead, and zinc enter the system from upstream, but significant amounts of nutrients and fecal coliform bacteria are added to the mainstem Spokane River, and Hangman Creek contributes large quantities of sediment. There are preliminary indications of declining metals concentrations, and sediment in Hangman Creek declined. Though ammonia and phosphorus concentrations also fell, other nitrogen forms, including total nitrogen, increased. Fecal coliform bacteria also increased, especially during the low-flow months.