Evaluating the Water Quality Impacts of Discharges from Proposed Fish Acclimation Ponds in a 303(d) Listed Water Body in Central Washington

Acclimation ponds for coho salmon are being proposed at several sites in the Wenatchee River watershed, which is a tributary of the Columbia River. The lower section of the Wenatchee River is currently listed on the Washington State's 303(d) list for temperature, dissolved oxygen (DO), and pH excursions. A methodology was developed for assessing the nutrient load from proposed sites based on data collected in discharges from active acclimation ponds. A QUAL-2K model developed by the Washington State Department of Ecology (WDOE) for developing phosphorus load allocations for the Wenatchee watershed was adapted to evaluate the Wenatchee River water quality impacts due to the discharges from the proposed ponds. Mechanistic modeling indicated that water quality impacts from the discharges are likely to be negligible even when existing point sources continue to discharge nutrient loads at their maximum load allocations.