The Hydrologic Ensemble Forecast Service - Overview and Future Development

The Hydrologic Ensemble Forecast Service (HEFS) provides probabilistic streamflow forecasts that address the need to quantify uncertainty in hydrologic forecasts for flood risk management, water supply management, streamflow regulation, recreation planning, and ecosystem management, among other applications. In 2023, implementation of the first version of HEFS (HEFSv1) was completed across the US. The national implementation of HEFS has facilitated the NWS goal to move toward probabilistic hydrologic forecasting. In addition, due to HEFS’s implementation and demonstrated skill, Forecast Informed Reservoir Operations (FIRO) is gaining acceptance at more reservoirs. FIRO is a reservoir management strategy using forecasts, as opposed to reacting to current conditions, which allows better water supply management and flood mitigation. With HEFSv1 complete, efforts are underway to improve the HEFS to address the most critical limitations. Over the next three years, the Office of Water Prediction plans to transition to operations existing solutions to forecasting and services limitations. In the longer term, the Cooperative Institute for Research to Operations in Hydrology (CIROH) will explore improved alternatives for meteorological and hydrological post-processing as well as evaluating a centralized approach to meteorological ensemble post-processing, rather than the current River Forecast Center-centric approach.

In this presentation, we provide an overview of the HEFS, describe the current status, and explain the plans for future improvements to the HEFS.