Project Number: 5362-13610-011-02
Project Type: Specific Cooperative Agreement

Start Date: Sep 26, 2012
End Date: Sep 25, 2014

Objective:
The Rangeland Hydrology and Erosion Model (RHEM) is a new process-based model developed by the USDA-ARS. The model has been developed for assessing the runoff, soil erosion rate, and sediment delivery rate and volume on rangelands at the hillslope scale for a rainfall event. Evaluation of RHEM performance is a key element for its acceptance as a useful tool. Therefore, the objective of the research work is to evaluate the performance of RHEM and its new components especially when it is applied in disturbed rangelands.

Approach:
In order to accomplish the objective of the research, the following tasks will be performed: 1. Evaluate the new width (w) and hydraulic friction (ft) equations for concentrated flow in RHEM using independent plot-scale data. 2. Evaluate the current parameterization equation for splash and sheet erodibility (Kss), and hydraulic conductivity (Ke) in RHEM on disturbed rangeland, and if necessary develop new parameterization equations specifically for disturbed rangeland. 3. Evaluate the RHEM concentrated flow erodibility approach (Kw(max)) and its parameterization equations using independent data. 4. Evaluate the performance of RHEM for disturbed rangelands. The performance of the model will be evaluated without calibration as well as by optimizing some of the sensitive parameters such as Ke .The new probabilistic approach for partitioning overland flow into concentrated and sheet flow as well as parameterization of hydraulic friction (ft) for routing the overland flow will be also tested.