GEOLOGIC AND GROUNDWATER INTERPRETATION IN EAST CENTRAL INDIANA BY STUDY OF STATIC WATER LEVELS FROM A LARGE WATER WELL DATABASE

Static water level information from a large computer database of water well records can yield new perspectives on subsurface geology and groundwater flow configurations. We have expanded on earlier work using the Indiana Department of Natural Resources water well records. The study now encompasses a ten county 17,000 km2 area involving 33,000 UTM located water well records for east central Indiana. This area is particularly interesting since glacially buried bedrock valleys with over 700 feet of relief have produced a situation where there are essentially equal numbers of glacial and bedrock wells spread throughout the area and groundwater flows through bedrock from one glacial valley to another.

Maps using all static water elevations reflect the ground topographic surface as expected. However, a map of static water level depths reveals four distinctively different regions of contour pattern including the Trafalgar loamy mix till plains to the south, the Lagro clay till plains, the Lagro end moraines, and the Wabash valley to the north. Static water level maps are constructed for the typically three highest water table months versus the lowest and the difference is taken between those data. The average difference is a reasonable 1 meter, but there are local areas of distinctly higher, lower, or reverse contrasts to be explained. Static water level maps are also constructed for shallow wells versus deeper wells and the difference is taken between these data. The resulting maps show areas of vertical downward or upward gradient which indicate three dimensional flow directions. The major upward gradients from deep wells appear to be under the Wabash and Whitewater River valleys to the northwest and southeast and not under the White, Mississinewa, and Salamonie Rivers in the middle. Static water level information provided on GIS maps looking at local issues near known buried cavern areas, large capacity pumping operations, areas of shallow bedrock, and contrasting soil associations are also discussed.