Abstract

1. Development of an Open Source GIS Interface to the USDA Soil and Water Assessment Tool (SWAT) Jeyakanthan (Jey) Veluppillai1, Daniel P Ames2, Raghavan ("Srini") Srinivasan3 Abstract The Soil and Water Assessment Tool (SWAT) is a physically-based watershed and landscape simulation model developed by the USDA-ARS and particularly suited to non-point source pollutant analysis. The Idaho State University Geospatial Software Lab is developing an interface to SWAT using MapWindow GIS which is a free and open source product that can be redistributed to modelers, developers, and end-users free of charge. Results and Sample Output The major outputs of OpenSWAT are stored in the form of raster grids, MS Access database tables, and text files. Example raster operation outputs are shown in the figure below, including delineated watersheds, soil definitions, etc. The next important form of OpenSWAT output is reports, in the end of each and every raster operation OpenSWAT produces specific watershed reports used for evaluation of land use, and ultimately streamflow and water quality in the watershed. Hydrologic Balance Evaporation and Transpiration Precipitation The important steps involved in OpenSWAT Modeling Methods OpenSWAT is dependant on the existing desktop MapWindow GIS application and the development is purely based on Microsoft products. MS VB.Net is the language used to develop the graphical user interfaces and Microsoft Access is the database management system used to store the output and input data sets. Many GIS operations can be done with the aid of OpenSWAT including automatic watershed delineation, soil definition, land used land cover definition, reclassification, slope definition, and weather data definition. Simulation, calibration and other advanced operations (e.g. parameter sensitivity analysis) can be done using the SWAT Editor tool which was developed by Texas A&M University. SWAT Editor is launched from the OpenSWAT toolbar. Surface Runoff Root Zone Infiltration/plant uptake/ Soil moisture redistribution Lateral Flow Vadose (unsaturated) Zone Delineated Watershed Delineated Watershed with IDs After Soil Definition Revap from shallow aquifer Percolation to shallow aquifer Shallow (unconfined) Aquifer Return Flow Confining Layer Flow out of watershed Deep (confined) Aquifer Recharge to deep aquifer The hydrological life cycle of OpenSWAT Introduction OpenSWAT is free and open source software (FOSS) plug-in for the existing MapWindow GIS desktop application (www.mapwindow.org). The main purpose of OpenSWAT is to perform watershed modeling and analysis tasks using an automated software toolkit. The main components of OpenSWAT are; project setup, automatic watershed delineation, land use and land cover definition, soil definition, slope definition, and weather data definition. After Land Use Definition After Slope Definition Final Output Conclusions and Discussion The input raw data sets for OpenSWAT can be automatically or manually retrieved from many different online and other sources. OpenSWAT supports a large number of raster and vector data formats, although most of the underlying processes use raster grids. MapWindow GIS has proven to be a suitable GIS platform for an open source implementation of SWAT because it supports all of the required data formats and necessary operations. It is expected that this effort will result in a tool that can be used throughout the world because it does not require license fees. Watershed Delineation Window of OpenSWAT Project Setup Window of OpenSWAT Land Use Definition Window of OpenSWAT HRU Definition Window of OpenSWAT MapWindow GIS Application and a sample project MapWindow GIS Based BASINS (BASINS 4.0) Sample simulation output results 1.) Graduate Student Veluppillai (“Jey") Jeyakanthan Idaho State University Geospatial Software Laboratory, Idaho Falls, Idaho velujeya@isu.edu 2.) Primary Advisor Dr. Daniel P Ames Idaho State University Geospatial Software Laboratory, Idaho Falls, Idaho amesdani@isu.edu 3.) Mentor Dr. Raghavan ("Srini") Srinivasan Texas A&M University and Texas Agricultural Experiment Station Department of Biological and Agricultural Engineering r-srinivasan@tamu.edu