Okanogan Subbasin Water Quality and Quantity Report for Anadromous Fish in 2006.

Abstract

Fish need water of sufficient quality and quantity in order to survive and reproduce. The list of primary water quality indicators appropriate for monitoring of anadromous fish, as identified by the Upper Columbia Monitoring Strategy, includes: discharge, temperature, dissolved oxygen, pH, turbidity, conductivity, nitrogen, phosphorus and ammonia. The Colville Tribes Fish and Wildlife Department began evaluating these water quality indicators in 2005 and this report represents data collected from October 1, 2005 through September 30, 2006. We collected empirical status and trend data from various sources to evaluate each water quality indicator along the main stem Okanogan and Similkameen Rivers along with several tributary streams. Each water quality indicator was evaluated based upon potential impacts to salmonid survival or productivity. Specific conductance levels and all nutrient indicators remained at levels acceptable for growth, survival, and reproduction of salmon and steelhead. These indicators were also considered of marginal value for monitoring environmental conditions related to salmonids within the Okanogan subbasin. However, discharge, temperature, turbidity, dissolved oxygen and pH in that order represent the water quality indicators that are most useful for monitoring watershed health and habitat changes and will help to evaluate threats or changes related to salmon and steelhead restoration and recovery. On the Okanogan River minimum flows have decreased over the last 12 years at a rate of -28.3CFS/year as measured near the town of Malott, WA. This trend is not beneficial for salmonid production and efforts to reverse this trend should be strongly encouraged. Turbidity levels in Bonaparte and Omak Creek were a concern because they had the highest monthly average readings. Major upland disturbance in the Bonaparte Creek watershed has occurred for decades and agricultural practices within the riparian areas along this creek have lead to major channel incision and bank instability. High sediment loads continue to threaten Omak and Bonaparte sub-watersheds. Major rehabilitation efforts are needed within these sub-watersheds to improve salmonid habitats. We found that for the past 12 years dissolved oxygen levels have been on a slightly downward trend during summer/fall Chinook egg incubation. Dissolved oxygen readings in early October, for summer/fall Chinook and from June through early July for summer steelhead can occasionally drop to the range from 8 to 10 mg/L and therefore warrant continued monitoring. Levels of pH represent an indicator that has little monitoring value throughout most of the subbasin. The Similkameen River drainage showed dramatic annual changes in the mean pH values and a declining trend for pH thus warranting continued monitoring. Average daily temperatures, in 2006, exceeded 25 C for eight days in July in the Okanogan River at Malott. Due to increased warm water temperatures, delays in migration have increased at a rate of 1.82 days per year over the last 10 years. Increases in water temperature can be linked to many anthropogenic activities. Increasing water temperatures within the Okanogan River watershed represent the single most limiting factor facing salmonids in main-stem habitats.