SPATIAL VARIABILITY IN THE GROUND WATER MOVEMENT IN DELAWARE COUNTY, IN: A GIS BASED MODEL

Groundwater flow modeling is an important component of most aquifer resource studies. This task becomes time consuming when the modeler is required to analyze complex heterogeneous aquifers and to face manipulation of large amounts of input and output data structures specific to the model. Geographic Information Systems (GIS) provide a platform in which layered, spatially distributed databases can be manipulated with ease, thereby significantly simplifying the implementation of data management tasks of model building and model calibration As an aid to modelers a GIS integrated groundwater flow modeling platform is developed here using Arc View 8.3 software. The GIS platform facilitates the time consuming task of preparing data input and output structures for multilayer groundwater flow. Delaware County, Indiana, the chosen study area, has more than 3000 located water supply wells, which are either in the near surface glacial sand and gravel outwash deposits or in the carbonate bedrock below. The depth to bedrock in the county varies between 10 feet to 300 feet with preglacial bedrock valleys that contain a number of different sand and gravel aquifers at various depths. It has been observed that approximately 50% of the wells are glacial and the other 50% are in bedrock. The bedrock contained active preglacial karst systems that have lead to areas of high transmissivity solution features which adds further interest to modeling this region. Arc View GIS 3D and geospatial analysts are used to study the flow patterns by developing a 3D model of major aquifers in the county, both glacial and bedrock. The appropriate sub surface and surface layers, including soil and land-use, shall be overlaid to identify the framework for groundwater flow. It is expected that this study will be beneficial to improve the understanding of groundwater in Delaware County, including both vertical and horizontal flow and interaction of flow between glacial and bedrock aquifers. In addition, major recharge and discharge zones will be identified and assessed for impacts regarding water quality.