A mathematical erosion model to simulate soil losses in agricultural watersheds

A deterministic conceptual model which simulates detachment, entrainment, transport and deposition of eroded soil particles by rainfall impact and flowing water is presented. Both upland and channel phases of sediment yield are incorporated into the erosion model. The algorithms for the soil erosion and sedimentation process including land and crop management effects are taken from the literature and then solved using a digital computer;The erosion model is used in conjunction with the modified Kentucky Watershed Model which simulates the hydrologic characteristics from watershed data. The two models are linked together by using the appropriate computer code. The watershed and erosion model provides the streamflow rate and suspended sediment yield at each time step;Calibrations for both the watershed and erosion model parameters are made by comparing the simulated results with actual field measurements in the Four Mile Creek watershed near Traer, Iowa using 1976 and 1977 water year data. Two water years, 1970 and 1978, are used as test years for model verification;There is good agreement between the mean daily simulated and recorded streamflow and between the simulated and recorded suspended sediment load. A correlation coefficient of approximately 80% is obtained between the recorded data and the simulated results from both the watershed and erosion models. The results obtained demonstrate the validity of the model and its ability to predict soil loss and sediment yield from small agricultural watersheds;Futhermore, by further modification and expansion with additional data, the watershed and erosion model developed through this study can be used as a planning tool for watershed management and for solving non-point pollution problems