Publication Summary

From June to October 2006, the Department of Ecology (Ecology) conducted a streamflow assessment on the Snoqualmie River and its major tributaries. The assessment was conducted in support of a temperature Total Maximum Daily Load study being developed by Ecology.

A continuous stage height recorder was installed on the Snoqualmie River near its confluence with the Skykomish River. Discrete discharge measurements were also made at four additional sites. For each of these sites, continuous records of discharge were modeled using upstream gages operated by the USGS. Potential error of streamflow data collected from the Ecology monitoring sites ranged from +/- 8% to +/- 27%.

From June to October 2006, the Washington State Department of Ecology (Ecology) conducted a streamflow assessment on the Snoqualmie River and its major tributaries.

This monitoring was conducted in support of a temperature Total Maximum Daily Load (TMDL) study. The purpose of the TMDL study was to (1) characterize summer stream temperature conditions in the Snoqualmie River basin, and (2) establish the heat loading capacity as well as load and wasteload allocations for heat sources in the watershed. These allocations will be set in order for the Snoqualmie River to meet Washington State water quality standards.

The TMDL study was initiated because of federal Clean Water Act 303(d) listings of three reaches of the Snoqualmie River which are water quality impaired for temperature.

A continuous stage height (water surface elevation) recorder was installed at one site, Snoqualmie River near Monroe, and individual discharge measurements were taken to model a continuous record of discharge.

Discrete stage height readings and discharge measurements were taken at four additional sites: Tolt River near Carnation, Raging River at Fall City, North Fork Snoqualmie River near Ellisville, and Middle Fork Snoqualmie River near Ellisville. Each of these four sites was located downstream of a U.S. Geological Survey (USGS) stream gaging station. A continuous record of discharge for each of these sites was modeled using comparative analysis with the respective USGS data sets.

Potential error of streamflow data collected from the five Ecology monitoring sites ranged from +/- 8% to +/- 27%.

Link to EIM data for User Study ID NCRI0001