Validation of EPIC for Two Watersheds in Southwest Iowa

S. W. Chung, Philip W. Gassman, L. A. Kramer, Jimmy R. Williams, Roy Gu
March 1999  [99-WP 215]

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Chung, S.W., P.W. Gassman, L. Kramer, J. Williams, and R. Gu. 1999. "Validation of EPIC for Two Watersheds in Southwest Iowa." Working paper 99-WP 215. Center for Agricultural and Rural Development, Iowa State University.


The Erosion Productivity Impact Calculator (EPIC) model is validated using long-term data collected for two southwest Iowa watersheds that have been cropped in continuous corn under two different tillage systems. The annual hydrologic balance was calibrated during 1988-94 by adjusting the runoff curve numbers and residue effects on soil evaporation. Model validation was performed for 1976-87 using both summary statistics and parametric and nonparametric statistical tests. Overall, results show that EPIC was able to replicate the long-term relative differences between the two tillage systems. Also printed in Journal of Environmental Quality 28(3): 971-79. May/June 1999.