Tool for Obtaining Projected Future Climate Inputs for the WEPP and SWAT Models

Abstract

Abstract. Climate change is an increasingly important issue affecting natural resources. Rising temperatures, reductions in snow cover, and variability in precipitation depths and intensities are altering the accepted normal approaches for predicting runoff, soil erosion, and chemical losses from upland areas and watersheds. Previous standards for natural resource planning may no longer apply in the near future, if local weather varies greatly from past long-term historical records. General Circulation Models (GCMs) operate at large scales to estimate changes in atmospheric conditions (temperatures, wind speeds, moisture, etc.) due to projected increases in greenhouse gas concentrations in the atmosphere; however, to utilize this information in typical natural resource model applications at field and watershed scales, considerable efforts at downscaling the GCM predictions are necessary. The project described in this paper utilized the MarkSim DSSAT Weather Generator and a Microsoft Excel VBA Macro to custom build climate input parameter files for the CLIGEN program used with the Water Erosion Prediction Project (WEPP) model, as well as create the direct climate input files needed by the Soil and Water Assessment Tool (SWAT) model. The final product is an automated spreadsheet with a simple user interface which imports, analyzes, and generates climate input files for WEPP and SWAT, and could be easily adapted to produce necessary climate inputs for other natural resource models. The method and software are easy to apply, and make simulation studies exploring effects of projected future climate much quicker and easier to accomplish. This presentation will describe development of the software, use of the tool to generate projected future climate inputs for WEPP and SWAT, and results from model applications in northeastern Indiana. The software tool and documentation are available from the National Soil Erosion Research Laboratory’s website.