Publication Summary

From June 2005 through November 2006, the Washington State Department of Ecology (Ecology) conducted a streamflow assessment on the East Fork Lewis River. The assessment was conducted in support of a temperature and fecal coliform Total Maximum Daily Load study being developed by Ecology.

Continuous stage height recorders and staff gages were installed at two sites. In addition, data were used from one long-term Ecology streamflow monitoring site and one U.S. Geological Survey streamflow monitoring site, both located on the E.F. Lewis River. Potential error of streamflow data collected from the Ecology monitoring sites ranged from +/-14% to +/-30%.

From June 2005 to November 2006, the Washington State Department of Ecology (Ecology) conducted a streamflow assessment on the East Fork Lewis River.

The assessment was conducted in support of a temperature and fecal coliform Total Maximum Daily Load (TMDL) study. The purpose of the TMDL study was to (1) characterize water temperatures and fecal coliform concentrations in the East Fork Lewis River basin, and (2) establish loading capacity, and load and wasteload allocations, for heat and fecal coliform sources in the watershed. These allocations will be set in order for the East Fork Lewis River to meet Washington State water quality standards.

Continuous stage height (water surface elevation) recorders and staff gages were installed at two sites for this study. 1. The lower site, which was impacted by the Columbia River tidal bulge, collected tide-impacted stage height data until the station was flooded in December 2005. 2. At the upper site, 11 discharge measurements were taken over the duration of the study, and a discharge rating curve was developed by relating the stage heights to their corresponding discharges. A continuous discharge record was developed for this site by applying the rating curve over the range of stage heights encountered.

In addition to the two sites established in support of the TMDL study, data were used from one long-term Ecology streamflow monitoring site and one U.S. Geological Survey streamflow monitoring site.

Potential error of streamflow data collected from the three Ecology monitoring sites ranged from +/- 14% to +/- 30%.