Estimating rangeland runoff, soil erosion, and salt mobility and transport processes

Authors: Weltz, Mark; NOUWAKPO, SAYJRO - University Of Nevada

Submitted to: International Rangeland Congress
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2015
Publication Date: 7/18/2016
Citation: Weltz, M.A., Nouwakpo, S.K. 2016. Estimating rangeland runoff, soil erosion, and salt mobility and transport processes. In:Proceedings of the X International Rangeland Congress, July 18-22, 2016, Saskatoon, Saskatchewan, Canada. p.407-409.

Interpretive Summary: Over 55% of sediment and salts entering the Colorado River are derived from accelerated soil erosion from federal rangelands with damages estimated to be $385 million per year. About 55% of the loading is derived from rangelands. This suggests a significant opportunity to reduce dissolved-solids loading to the Colorado River through implementing rangeland management conservation practices. Rainfall simulation was used to quantify the hydrologic, erosion, and salt mobilization and transport processes on 2 ecological sites in central Utah, U.S. The rainfall simulation data was used to evaluate the ability of the Rangeland Hydrology and Erosion Model (RHEM) to predict runoff, sediment yield, and salt transport from saline rangelands. A governing principle of rangeland management is that changes in land cover result in changes in watershed condition and response. Rangeland management practices influence runoff, soil erosion, and salt transport because they affect plant distribution, biological diversity, canopy and ground cover, and soil properties. The RHEM model did an excellent job in predicting runoff at the 2 sites over all 4 rainfall intensities applied. RHEM predicted sediment yield reasonably well with no significant bias in the predicted sediment yield. For saline and sodic sites, such as these, the soils are highly dispersive and the RHEM model slightly under predicted sediment yield. New parameterization equations designed specifically for saline and sodic soils should improve sediment yield predictions. There was a very strong correlation between observed sediment yield and observed total dissolved solids at these 2 sites. This indicates that we can predict salt transport and changes in total dissolved solids entering the Colorado River as a function of sediment yield.

Technical Abstract: Over 55% of sediment and salts entering the Colorado River are derived from accelerated soil erosion from federal rangelands with damages estimated to be $385 million per year. About 55% of the loading is derived from rangelands. This suggests a significant potential to reduce dissolved-solids loading to the Colorado River through land- and water-management activities on rangelands. Rainfall simulation was used to quantify the hydrologic, erosion, and salt mobilization and transport processes on 2 ecological sites in central Utah, U.S. The rainfall simulation data was used to evaluate the ability of the Rangeland Hydrology and Erosion Model (RHEM) to predict runoff and sediment yield from saline rangelands. A governing principle of rangeland management is that changes in land cover result in changes in watershed condition and response. Rangeland management practices influence runoff and soil erosion because they affect plant distribution, biological diversity, canopy and ground cover, and soil properties. The RHEM model did an excellent job in predicting runoff at the 2 sites (R2 0.90) over all 4 rainfall intensities applied. RHEM predicted sediment yield (R2 0.58) reasonably well with no significant bias in the predicted sediment yield. For saline and sodic sites, such as these, the soils are highly dispersive and the RHEM model slightly under predicted sediment yield. New parameterization equations designed specifically for saline and sodic soils should improve sediment yield predictions. There was a very strong correlation (R2 0.84) between observed sediment yield and observed total dissolved solids at these 2 sites.