Evaluation of the community WRF-Hydro Modeling System over the NFIE experiment

The fully-distributed, community WRF-Hydro modeling system is scheduled for operational implementation as a nationwide streamflow forecasting needs of the National Water Center (NWC) during the spring of 2016. This paper presents a multi-faceted evaluation of the WRF-hydro modeling system in preparation for operational national streamflow prediction. The testing period encompasses the 2015 warm season which included the National Flood Interoperability Experiment (NFIE) where WRF-Hydro and the RAPID channel routing model were driven by the Multi-Radar Multi-Sensor (MRMS) estimates as the real-time precipitation estimate product and the High Resolution Rapid Refresh (HRRR) for the short term forecast. Precipitation forcing plays a very important role in hydrologic modeling as the precipitation uncertainties propagate nonlinearly into streamflow simulations. Here, we validate the MRMS estimates and HRRR precipitation forecasts at national scale using daily precipitation observations from the Global Historical Climatology Network (GHCN). We assess how much bias is been introduced as a result of regridding the precipitation to the hydrologic model resolution and quantify the impact on the streamflow simulation. WRF-Hydro has several physics options such as surface overland flow, saturated subsurface flow, channel routing as well as conceptual deep groundwater base flow. Here, we evaluate how WRF-Hydro routing options will perform compared to RAPID channel routing model. Streamflow verification data for model simulations and predictions was completed for a subset of GAGES-II reference basins. Multi-temporal and spatial scale verification is performed in order to test the robustness of WRF-Hydro streamflow simulations under different configuration over a wide range of basins sizes and from short-term (hourly) to longer-term (monthly) flow simulations. The goal is to inform WRF-Hydro model configuration for the initial operating capabilities (IOC) project and target processes and parameter estimates for improvement.