Case Study: Surface Runoff Simulation Using HMS for Arid Watershed

High-intensity and short-duration monsoon rainfall can induce severe flash flood in arid region, especially in Arizona. As climate becomes warmer, climate models predicted more intensified precipitation in arid region, so flood frequency and magnitude will increase. Hydrologic modeling system (HEC-HMS) is the most commonly used rainfall and runoff model incorporated the start-of-art knowledge in hydrology, hydraulics, and sediment transport. This study applied the HEC-HMS model to predict surface runoff from Lucky Hills watershed in Walnut Gulch in southeastern Arizona. The watershed is ungagged and located in a remote mountain area. To explore the applicability of the HMS model, we applied the model to a gaged watershed within the Walnut Gulch experimental watershed. The model was used to simulate multiple precipitation events, and parameters were optimized to match the observed surface runoff. We obtained the relatively large rainfall from Data Access Project of Southwest Watershed Research Center (SWRC) and used SCS distribution function to generate the rainfall hyetograph. Multiple grids were tested until the errors between two simulations’ convergence to nearly zero. This study illustrated the finer delineation for HMS model with observation data from SWRC improves the simulated results.