APEX: A New Tool for Predicting the Effects of Climate and CO2 Changes on Erosion and Water Quality

Abstract

Several field scale hydrologic/water quality models have been developed to study the impacts of agricultural management practices. EPIC (Environment Policy Integrated Climate - previously callas as Erosion Productivity Impact Calculator) model is one of the popular models, which was widely applied in US and around the world. But the scope of these field scale models is limited to small field size areas, where the soil, management, crop, and topography are assumed to be homogenous. To extend the capabilities of EPIC to simulate large complex farming systems (multiple fields, soils, rotations, management etc.), a model called APEX (Agricultural Policy/Environmental eXtender) was developed. In addition to the capabilities of EPIC, APEX has components for routing water, sediment, and chemicals (nutrients and pesticides) across complex landscapes and channel systems to the watershed outlet. The subsurface routing routine to APEX is more enhanced than EPIC and could be used to simulate subsurface processes even up to a depth of 30 m. in this paper we present an overview of EPIC and APEX and described in detail the newly added CO2 component of the model.