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Title: The Rangeland Hydrology and Erosion Model: A dynamic approach for predicting soil loss on rangelands

item Hernandez, Mariano
item Nearing, Mark
item AL-HAMDAN, O. - Texas A&M University
item Pierson Jr, Frederick
item Armendariz, Gerardo
item Weltz, Mark
item SPAETH, K.E. - Natural Resources Conservation Service (NRCS, USDA)
item Williams, Christopher - Jason
item Goodrich, David - Dave
item Unkrich, Carl
item Nichols, Mary
item Holifield Collins, Chandra

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2017
Publication Date: 9/12/2017
Citation: Hernandez Narvaez, M.N., Nearing, M.A., Al-Hamdan, O., Pierson, F.B., Armendariz, G.A., Weltz, M.A., Spaeth, K., Williams, C.J., Goodrich, D.C., Unkrich, C.L., Nichols, M.H., Holifield Collins, C.D. 2017. The Rangeland Hydrology and Erosion Model: A dynamic approach for predicting soil loss on rangelands. Water Resources Research. 53:1-24.

Interpretive Summary: The Rangeland Hydrology and Erosion Model (RHEM) is a USDA-developed tool for assessing runoff and soil erosion rates on western rangelands of the United States. In this article, we presented an improved version V2.3 of the RHEM model. This model was developed to fill the need for a process-based rangeland erosion model that can function as a practical tool for quantifying runoff and erosion rates specific to western U.S. rangelands to provide reasonable runoff and soil loss prediction capacity for rangeland management and research. The capability of RHEM V2.3 for simulating flow and soil erosion was tested on a small watershed in Arizona and on 124 NRI plots placed in Arizona and New Mexico. The improvement made in model efficiency was significant in comparison with the original version RHEM V1.0 when the new equations for estimating soil erodibility are used, especially with respect to low-sediment yield simulation. The analysis of the 124 NRI points in Arizona and New Mexico suggests that the parameter estimation equations conveyed coherent information to the model. Evaluation of the model predictions undertaken in this study demonstrates that RHEM V2.3 produces results of satisfactory quality when simulating large flow and soil erosion events, but a greater degree of uncertainty is associated with predictions of small runoff and soil erosion events. This model will provide USDA with a tool that will have significant impact on helping to understand, assess, and manage western rangelands in the United States.

Technical Abstract: In this study we present the improved Rangeland Hydrology and Erosion Model (RHEM V2.3), a process-based erosion prediction tool specific for rangeland application. The article provides the mathematical formulation of the model and parameter estimation equations. Model performance is assessed against data collected from 23 runoff and sediment events in a shrub-dominated semiarid watershed in Arizona, USA. To evaluate the model, two sets of primary model parameters were determined using the RHEM V2.3 and RHEM V1.0 parameter estimation equations. The test indicated that RHEM V2.3 parameter estimation equations provided a 60% improvement over RHEM V1.0 parameter estimation equations. Second, the RHEM V2.3 model was calibrated to measurements from the watershed. The parameters estimated by the new equations were within the lowest and highest values of the calibrated parameter set. These results suggest that the new parameter estimation equations can be applied for this environment to predict sediment yield at the hillslope scale. Furthermore, we also applied the RHEM V2.3 to demonstrate the response of the model as a function of foliar cover and ground cover for 124 data points across Arizona and New Mexico. The dependence of average sediment yield on surface ground cover was moderately stronger than that on foliar cover. These results demonstrate that RHEM V2.3 predicts runoff volume, peak runoff, and sediment yield with sufficient accuracy for broad application to assessing and managing rangeland systems.