Seasonal Streamflow Forecasting in the Columbia River Basin
Climate and hydrologic fluctuations in the Pacific Northwest lead to large year-to-year variations in the strength of the Columbia River hydropower resource. We describe and present results from a seasonal hydrologic prediction system for the Columbia River basin that gives insight into the seasons-ahead behavior of this resource starting near the beginning of each water year. The forecast system is based on the real-time application of a state-of-the-science, macroscale hydrologic model coupled with ensemble climate forecasts. Estimates of initial land surface conditions, primarily in the form of snow water equivalent, are improved via the assimilation of snowpack observations, and forecast biases are reduced through statistical forecast calibration. The forecast system produces graphical forecast products designed to help water and energy managers understand the current state of the Columbia River basin, the climate outlook for the water year, and the implications of both for future streamflow.