Comparison of Simulated and Observed Runoff and Soil Loss on Three Small United States Watersheds

Abstract

The use of mathematical models has been proven to be cost-effective in determining soil productivity changes due to various agricultural management practices. Nevertheless, many models need to be validated prior to their application. Though many models are physically based, calibration is often needed to better explain weather and land use change effects. In this study, runoff and soil loss simulated by the EPIC (Environmental Policy Integrated Climate — previously known as Erosion Productivity Impact Calculator) model are presented for three small watersheds in the United States, which had different land use and cropping systems. Each data set was divided temporally into testing and training periods. The EPIC model was calibrated using the observed weather, runoff, and soil loss data. Outputs from the model (runoff and soil loss) from the three watersheds for the testing period are presented.

In general, the long term predictions of EPIC were close to the observed values. Furthermore, the model was found to perform satisfactorily for fields under conventional crops like wheat, corn, and sorghum, but the soil loss predicted for a watershed under native grass land was not satisfactory. Information on observed biomass and residue coverage might improve the model performance.