Tucannon River Temperature Study, Prepared for : Watershed Resource Inventory Area (WRIA) 35.

This report presents the results of a temperature analysis of the Tucannon River completed for the WRIA 35 Planning Unit. The Tucannon River is located in southeastern Washington and flows approximately 100 kilometers (km) (62 miles) from the Blue Mountains to the Snake River. High water temperature in the Tucannon River has been identified as a limiting factor for salmonid fish habitat (Columbia Conservation District, 2004). Several segments of the Tucannon River are included on Washington State Department of Ecology (Ecology) 303(d) list of impaired waterbodies due to temperature. Ecology is currently conducting scoping for a temperature Total Maximum Daily Load (TMDL) study of the Tucannon River. The WRIA 35 Planning Unit retained HDR Engineering to evaluate water temperature in the Tucannon River. The project objectives are: (1) Review recent and historic data and studies to characterize temperature conditions in the river; (2) Perform field studies and analyses to identify and quantify heating and cooling processes in the river; (3) Develop and calibrate a computer temperature model to determine the sources of heat to the Tucannon River and to predict the temperature of the river that would occur with increased natural riparian shading assuming the current river morphology; (4) Evaluate differences in river temperatures between current and improved riparian shading during the 'critical' period - low river flows and high temperatures; and (5) Determine the potential benefits of riparian shading as a mechanism to decrease river temperature