Enhancements to the WRF-Hydro Hydrologic Model Structure for Semi-arid Environments

Timothy M. Lahmers1, Hoshin Gupta1, Pieter Hazenberg1, Christopher L. Castro1, David J. Gochis2, David Yates2, Aubrey Dugger2, David C. Goodrich3

1Department of Hydrology Atmospheric Sciences

The University of Arizona, Tucson, Arizona

2National Center for Atmospheric Research, Boulder, Colorado 

3USDA-ARS, Southwest Watershed Research Center, Tucson, Arizona

The NOAA National Water Center (NWC) implemented an operational National Water Model (NWM) in August 2016 to simulate and forecast streamflow and soil moisture throughout the Contiguous US (CONUS). The NWM is based on the WRF-Hydro hydrologic model architecture, with a 1-km resolution Noah-MP LSM grid and a 250m routing grid. The operational NWM does not currently resolve infiltration of water from the beds of ephemeral channels, which is an important component of the water balance in semi-arid environments common in many portions of the western US. This work demonstrates the benefit of a conceptual channel infiltration function in the WRF-Hydro model architecture following calibration. The updated model structure and parameters for the NWM architecture, when implemented operationally, will permit its use in flow simulation and forecasting in the southwest US, particularly for flash floods in basins with smaller drainage areas. Our results show that adding channel infiltration to WRF-Hydro can produce a physically consistent hydrologic response with a high-resolution gauge based precipitation forcing dataset in the USDA-ARS Walnut Gulch Experimental Watershed. NWM WRF-Hydro is also tested for the Babocomari River, Beaver Creek, and Sycamore Creek catchments.