Using hydrologic forecasts from the Hydrologic Ensemble Forecast Service for Forecast Informed Reservoir Operations (FIRO)

Accurate hydrologic forecasts are crucial for mitigating natural disasters such as floods or droughts and optimizing reservoir operations for diverse and sometimes competing users. To provide reliable and skillful ensemble forecasts for Forecast Informed Reservoir Operations (FIRO) and other applications, the U.S. National Weather Service (NWS) developed the Hydrologic Ensemble Forecast Service (HEFS). The HEFS uses "raw" precipitation and temperature forecasts from the Global Ensemble Forecast System version 12 (GEFSv12) and provides bias-corrected ensemble forcing and streamflow forecasts at forecast locations across the NWS's thirteen River Forecast Centers (RFCs). Currently, several organizations use the HEFS forecasts, including New York City Department of Environmental Protection, Sonoma Water, and California Nevada (CN), Middle Atlantic (MA), and Northeast (NE) RFCs to support their FIRO. Streamflow forecasts from the HEFS consistently show higher accuracy compared to those produced by the RFCs' climatologically-based Ensemble Streamflow Prediction (ESP), which is being replaced by the HEFS. This implies potential performance gains in reservoir operations when incorporating HEFS forecast products into operating rules and decision making for reservoirs, compared to using ESP. This presentation reports the most recent HEFS validation results compared to ESP, and discusses the experience of utilizing HEFS products for reservoir operations, and future enhancements for the HEFS.