|Pierson, Frederick - Fred|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2009
Publication Date: 6/15/2009
Citation: Wei, H., Nearing, M.A., Stone, J.J., Guertin, D.P., Spaeth, K., Pierson Jr, F.B., Nichols, M.H., Moffet, C.A. 2009. A new Splash and Sheet Erosion Equation for Rangelands. Soil Science Society of America Journal. 73:1386-1392. Interpretive Summary: Erosion rates predicted from models for rangelands have the potential to be important quantitative indicators for rangeland health and for assessing conservation practice effects by government agencies, rangeland managers, conservationists and rangeland scientists. Process-based erosion models are preferred to empirical models because of their ability to capture the physical erosion processes in the field. However, the equations of existing process-based erosion models were all developed from experiments carried out in cropland fields, which make them unsuitable for rangeland applications because of differences in soils and plants species. Rangelands also have relatively greater spatial heterogeneity than croplands, which make modeling the processes a bit more problematic. The splash and sheet erosion equation is one of the core relationships needed for rangeland soils. It is very important because splash and sheet erosion is the dominant soil loss process on most rangelands with good vegetation cover. In this paper we developed a new splash and sheet erosion equation based on an extensive rangeland database from rainfall simulator experiments, which covers a wide range of rangeland soils and plant systems from across the western United States. Our proposed equation quantifies the splash and sheet erosion rate as a combined function of rainfall intensity and runoff rate, and is the first one that has been developed from rangeland experiments. The new equation should enable improved estimation of water erosion on rangelands in the western U.S. and perhaps on other rangelands of the world.
Technical Abstract: Soil loss rates predicted from erosion models for rangelands have the potential to be important quantitative indicators for rangeland health and for assessing conservation practice effects. Splash and sheet erosion processes on rangelands differ in substantial ways from those in croplands, where the process is conceptualized as interrill erosion: 1) most of the previous interrill equations were developed from cropland soils; 2) interrill erosion was conceptualized and modeled for small size plots, which are not large enough to encompass the relative high spatial heterogeneity of rangelands; and 3) interrill erosion is usually modeled as a function of rainfall intensity (I) and runoff rate (q) such that I and q are independent. Splash and sheet erosion combined is the dominant type of erosion on most undisturbed rangeland hillslopes where there is adequate vegetation, and these important erosion processes need to be addressed to develop an appropriate rangeland erosion model. In this study we developed a new equation for calculating the combined rate of splash and sheet erosion (Dss) using a large set of rainfall simulation data from the western U.S.. The equation we proposed: Dss = Kss I 1.052q0.592,where Kss denotes the splash and sheet erosion coefficient, takes into account a key inter-relationship between I and q revealed in the data. This equation was better at predicting observed erosion rates than the Water Erosion Prediction Project (WEPP) model. The new equation should enable improved estimation of water erosion on rangelands in the western U.S. and on other rangelands of the world.