A peakflow forecast for Payette Lake using SNOTEL data

Flow into Payette Lake, Idaho has been regulated within natural range since at least 1923. The goal is to capture the maximum volume of runoff without causing high water damage to the lakeshore. Flow restriction is by tainter gates and removable stoplogs, a method which allows only a minimal flow adjustment once the stoplogs are placed. If outflow is stopped too far ahead of peak flow, the risk for high water around the lakeshore increases; if peak flow is missed, the maximum runoff volume may not be captured. A large proportion of runoff to Payette Lake is contributed by the late lying, high elevation snowpack in the surrounding mountains. The snow water equivalent in the pack is available on a daily basis from Soil Conservation Service SNOTEL sites in the basin. Climatic data is recorded at several NWS CLIMATE stations in the basin and daily runoff flows are generated by the Bureau of Reclamation using lake levels. This is combined to forecast the date of peak runoff and a volume flow and provides an operational tool for efficient reservoir regulation.