Publication Summary

Between May and November 2002, the Department of Ecology conducted a streamflow assessment on two tributaries to the Walla Walla River in support of a temperature Total Maximum Daily Load study. Continuous stage height recorders were installed at four sites, and several discharge measurements were taken at each site. Discharge rating curves were developed by relating discrete stage height values to corresponding discharge measurements, and a continuous discharge record was developed for each site. Channel aggradation, aquatic weed growth, and human interference were the primary causes of error in discharge data.

Between May and November 2002, the Department of Ecology conducted a streamflow assessment on two tributaries to the Walla Walla River: the Touchet River and Yellowhawk Creek.

The assessment was conducted in support of a temperature Total Maximum Daily Load (TMDL) study developed by Ecology′s Environmental Assessment Program. The purpose of the TMDL study was to characterize the water temperature in the basin and to establish load and wasteload allocations for the heat sources to meet water quality standards for surface water temperature.

Continuous stage height recorders and staff gages or bridge reference points were installed at four sites, and at least six discharge measurements were taken at each site. Discharge rating curves were developed by relating several stage height values to corresponding discharge measurements. Applying these rating curves over the range of stage height enabled a continuous discharge record to be developed at each site.

Only one of the four sites monitored in this study produced discharge data that are accurate to within 10%. Channel aggradation, aquatic weed growth, and human interference were the primary causes of error in discharge data.