A comprehensive evaluation of RHEM in the WGEW watersheds with long-term data

The Rangeland Hydrology and Erosion Model (RHEM) developed in the 2000s has been a popular tool for predicting runoff and erosion in rangelands. However, RHEM has not been evaluated with long-term (>20y) or large set of runoff and sediment data (>30 events). In this study, the Lucky Hills watershed (10.24ha) located in the Walnut Gulch Experiment Watershed (WGEW) was selected for RHEM evaluation, because long-term monitoring data since 1960s are available for areas only subject to overland-flow erosion and areas subject to both overland-flow and channel erosion. A python script was developed to pull and screen all available runoff events from the WGEW Data Access Project and find the corresponding rainfall, sediment and soil moisture data. Then RHEM was evaluated, calibrated and validated from the hillslope scale to the watershed scale systemically. Results from this study provide a comprehensive evaluation of RHEM performance at the hillslope and small-watershed scale.