For more than a decade, Dr. Barry Evans and his group at PSIEE have been improving AVGWLF, a GIS-based watershed modeling tool that uses hydrology, land cover, soils, topography, weather, pollutant discharges, and other critical environmental data to model sediment and nutrient transport within a watershed. AVGWLF has been used for federally-mandated "total maximum daily load" (TMDL) studies in Pennsylvania since 1999, and “regionalized” versions of this software have been developed for EPA Region 6 in the southwestern part of the U.S., in New York state, and for New England. AVGWLF has been used by the Mexican Institute of Water Technology (IMTA) for various watershed studies since 2000, and it has been used by other governmental agencies and scientists located throughout the world.
To extend the utility of this software, a major revision was recently undertaken to move the tool from a commercial GIS software package to a free one called MapWindow (see www.mapwindow.org). It is believed that this new software, called MapShed, will expand the use of this type of modeling tool to a much larger number of users, many of whom do not have the means to purchase the commercial GIS software needed for AVGWLF. In addition to the GIS platform upgrade, numerous analytical tools have been enhanced to provide additional modeling capabilities such as the simulation of pathogen loads, better simulation of pollutant transport processes in urban settings, and improved assessment of the effects of best management practice (BMP) implementation on pollutant load reduction.Like AVGWLF, MapShed is a customized GIS interface that is used to create input data for an enhanced version of the GWLF watershed model originally developed at Cornell University. In utilizing this interface, the user is prompted to identify required GIS files and to provide other information related to “non-spatial” model parameters. This information is subsequently used to derive values for required model input parameters which are then written to the input file needed for model execution. Also accessed through the interface is regional climate data stored in Excel-formatted files that is used to create the necessary “weather” input file for a given watershed simulation. With MapShed, a user selects areas of interest, creates model input files, runs the simulations model, and views the output in a series of seamless steps.