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Historical Development and Applications of the EPIC and APEX models

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  042097,  2004 ASAE Annual Meeting . (doi: 10.13031/2013.17074) @2004
Authors:   Philip W. Gassman, Jimmy R. Williams, Verel W. Benson, R. Cesar Izaurralde, Larry M. Hauck, C. Allan Jones, Jay D. Atwood, James R. Kiniry, Joan D. Flowers
Keywords:   EPIC, APEX, soil erosion, water quality, carbon sequestration, climate change, modeling

The development of the field-scale Erosion Productivity Impact Calculator (EPIC) model was initiated in 1981 to support assessments of soil erosion impacts on soil productivity for soil, climate and cropping conditions representative of a broad spectrum of U.S. agricultural production regions. The first major application of EPIC was a national analysis performed in support of the 1985 Resources Conservation Act (RCA) assessment. The model has continuously evolved since that time and has been applied for a wide range of field, regional, and national studies both in the U.S. and in other countries. The range of EPIC applications has also expanded greatly over that time including studies of: (1) surface runoff and leaching estimates of nitrogen and phosphorus losses from fertilizer and manure applications, (2) leaching and runoff from simulated pesticide applications, (3) soil erosion losses from wind erosion, (4) climate change impacts on crop yield and erosion, and (5) soil carbon sequestration assessments. The EPIC acronym now stands for Erosion Policy Impact Climate, to reflect the greater diversity of problems that the model is currently applied to. The Agricultural Policy EXtender (APEX) model is essentially a multi-field version of EPIC that was developed in the late 1990s to address environmental problems associated with livestock and other agricultural production systems on a whole farm or small watershed basis. The APEX model also continues to evolve and to be utilized for a wide variety of environmental assessments. The historical development will be presented for both models as well as example applications at several different scales.

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