Suspended sediment and water temperature monitoring in the Sauk River, Washington, water years 2012-2016

The Sauk River, a fedrally designated Wild and Scenic River, is one of the few large glacier-fed rivers in western Washington that is unconstrained by dams and drains a relatively pristine landscape which includes Glacier Peak, a glaciated stratovolcano. The U.S. Geological Survey (USGS) conducted a 5-year study (2012-2016 water years) of suspended-sediment and water temperature monitoring for the purpose of determining suspended-sediment loads and identifying sediment production regimes and associated seasonality of sediment transport. Monitoring occurred at three USGS streamgages on the Sauk River, including two long-term gages with more than 90 years of continuous record and a new gage installed for the purpose of the study. Turbidity sensors at each streamgage measured turbidity and water temperature at 15-minute intervals. Suspended-sediment samples were collected at each streamgage over a range of discharge and turbidity conditions. Regression equations were developed to estimate the suspended-sediment concentration (SSC) and the concentration of fine suspended-sediment (fSSC; <0.0625 mm) at each streamgage using turbidity and/or discharge as explanatory variables. A 15-minute timeseries of SSC, fSSC, and the uncertainty of individual estimates (prediction intervals with 90 percent confidence) was computed for each streamgage and is provided. A daily timeseries of suspended-sediment load (SSL) and fine suspended-sediment load (fSSL) derived from either 15-minute, or daily, SSC and discharge data was computed at each streamgage and is provided for the 5-year period. A daily timeseries of water temperature at each streamgage is also provided.