The Rangeland Hydrology and Erosion Model (RHEM) is a newly conceptualized model that was adapted from relevant portions of the Water Erosion Prediction Project (WEPP) Model and modified to specifically address rangelands conditions. RHEM is an event-based model that estimates runoff, erosion, and sediment delivery rates and volumes at the spatial scale of the hillslope and the temporal scale of a single rainfall event. It represents erosion processes under normal and fire-impacted rangeland conditions. Moreover, it adopts a new splash erosion and thin sheetâ€“flow transport equation developed from rangeland data, and it links the model hydrologic and erosion parameters with rangeland plant community by providing a new system of parameter estimation equations based on 204 plots at 49 rangeland sites distributed across 15 western U.S. states. Recent work on the model was focused on representing intra-storm dynamics, using stream-power as the driver for detachment by flow. RHEM simulations for multiple management practices can be run separately and then compared side-by-side within the model interface. The model produces graphical and tabulated output for annual precipitation, runoff, and erosion based on a CLIGEN-generated 300 year record of precipitation events. A new feature was developed that allows the user to configure a baseline scenario to represent conservation practices or a reference state of a state-and-transition model within an Ecological Site. Then, the user can run several scenarios and compare them against the soil loss base line scenario and estimate the soil loss probabilities of occurrence of each scenario. Furthermore, a new approach was developed for the parameterization of the splash and sheet flow erodibility parameter to enhance RHEM applications on disturbed rangelands. The improved splash and sheet flow erosion modelling and the probabilistic approach in RHEM creates a practical management tool for quantifying erosion and assessing erosion risk following rangeland disturbance.
OVERVIEW OF RANGELAND HYDROLOGY AND EROSION MODEL
Society for Range Management
SRM Sacramento, CA