DEVELOPMENT OF A GIS TOOL FOR GROUNDWATER RECHARGE AND DISCHARGE ESTIMATION

Recharge and discharge result from a set of complex, uncertain processes that generally are difficult to study. Understanding recharge and discharge is important to define the relationships among groundwater, precipitation, and surface water, thus resulting in more efficient management options for water supply. Conventional recharge and discharge estimation methods require time-consuming small-scale field experiments or data collection. As one potential alternative, we are developing a Geographic Information System (GIS) software package to facilitate the estimation of shallow recharge and discharge patterns and rates using advanced image processing. Advantages of this approach are that it has a relatively short preparation time and use readily available hydrogeologic data. The overall goal of this research is to provide an efficient recharge and discharge estimation tool that allows the user to select variable degrees of zonation. The software is programmed in Visual Basic using the ArcObjects environment. After the current code development stage, this GIS-based software will associate with the existing groundwater modeling code, MODFLOW, and parameter estimation code, PEST, for a linked recharge and discharge analysis and calibration procedure. The procedure design is modular, however allowing the incorporation of other image processing algorithms, recharge and discharge estimation methods and parameter estimation methods as they become available. During development, the software has been verified using a hypothetical model and will be tested on field sites in Wisconsin which have been well-studied by the USGS. The final version of this software will be applied to ongoing ISWS studies of groundwater in Illinois. This is a two-year joint research by the Illinois State Water Survey, University of Illinois at Urbana-Champaign and the U.S. Geological Survey. This project is supported by National Institutes for Water Resources and the USGS.