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Title: Evaluating the WEPP rangeland hillslope model using cesium-137 estimated spatial soil erosion data

Author
item LIU, BIN - China Institute Of Water Resources
item Zhang, Xunchang
item STORM, DANIEL - Oklahoma State University
item BROWN, GLENN - Oklahoma State University
item CAO, WENHONG - China Institute Of Water Resources
item DUAN, XINGWU - Yunnan University

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2017
Publication Date: 11/10/2017
Citation: Liu, B., Zhang, X.J., Storm, D.E., Brown, G.O., Cao, W., Duan, X. 2017. Evaluating the WEPP rangeland hillslope model using cesium-137 estimated spatial soil erosion data. Vadose Zone Journal. 16(11). doi:10.2136/vzj2017.03.0067.

Interpretive Summary: Soil erosion is a serious environmental problem worldwide. Extensive research has been conducted identifying and quantifying erosion processes, measuring soil erosion, and evaluating the effectiveness of soil conservation practices. The radionuclide 137Cs from nuclear bomb tests has been used to estimate soil erosion and sediment sources in many studies, but uncertainties exist in reference site variability, erosion conversion models, etc. The purpose of this study was to use the 137Cs method to quantify erosion/deposition rates at a hillslope scale, and to compare the results with those predicted by the Water Erosion Prediction Project (WEPP) model. Seven samples along the contour line at 2-3 meter intervals were composited to represent the 137Cs inventory for that slope position. Since there was only one soil type for all the transects, soil erosion rates predicted by WEPP was highly related to slope and land uses/cover. Compared with the WEPP hillslope model, the 137Cs method predicted the same soil erosion and deposition trend, although the 137Cs method predicted lower soil erosion rates but greater variance. The results showed that the 137Cs method can be used to estimate long-term soil erosion rates under the native tallgrass prairie when measured soil loss is unavailable. This work showed a useful tool to erosion scientists and soil conservationists for estimating soil erosion rates under the native prairie conditions.

Technical Abstract: Soil erosion is a serious environmental problem worldwide. Extensive research has been conducted identifying and quantifying erosion processes, measuring soil erosion, and evaluating the effectiveness of soil conservation practices. The 137Cs method has been used to estimate soil erosion and sediment sources in many studies, but uncertainties exist in reference site variability, Gama Spectrometry measurement, conversion models, etc. The purpose of this study was to use the 137Cs method to quantify erosion/deposition rates at the hillslope scale, and to compare the results with those predicted by the Water Erosion Prediction Project (WEPP) model. Seven samples along the contour line at 2-3 meter intervals were composited to represent the 137Cs inventory for that slope position. The study area for this research was the Bull Creek watershed, located in west central Oklahoma, USA. Since there was only one soil type for all the transects, soil erosion rates predicted by WEPP was highly related to slope, and reflected the change of land cover. Compared to the WEPP hillslope model, the 137Cs method predicted the same soil erosion and deposition trend. However, the 137Cs method predicted significant lower soil erosion rates than the WEPP and the results had larger variance. The 137Cs method provided more information on the integrated spatial and temporal changes in erosion/deposition at hillslope scale compared to WEPP.