INQUIRY-BASED EXCERCISE IN HYDROGEOLOGY USING GIS AND ANALYTICAL MODELS: WHY DID GROUNDWATER LEVELS DECLINE IN STERLING, OHIO

Private residential wells in the village of Sterling, Ohio, started going dry in the 1980's after the nearby City of Rittman established a municipal well field 0.25 miles west-southwest of Sterling in 1978. A lawsuit filed by a group of Sterling residents claimed that Rittman's pumping of its three large diameter production wells caused the lowering of water levels and the subsequent drying up of many domestic wells in Sterling. Could fundamental hydrogelogic theory, borehole logs and aquifer test analysis, and analytical modeling techniques prove this, or were other factors (drought, domestic consumption, etc.) the reason for the decline in water levels? This was the challenge presented to a class of hydrogeology students. Sterling lies along Chippewa Creek, in north-central Ohio. The 350-foot deep buried glacial valley underlying the village contains a 40-foot thick sand aquifer confined by up to 60 feet of clay. Well log information going back to 1956 was plotted in GIS format and used to establish trends in water-level decline. An analytical model was developed based on analysis of an aquifer test. Precipitation records and historic water levels from a USGS monitoring well revealed no evidence of drought conditions. The groundwater demand from Sterling's 200 domestic wells was found to be insignificant based on model-predicted drawdowns using an estimated water demand of 100 gpd per person. Model-predicted drawdowns based on Rittman's municipal well production were compared to observed water-level declines of 1978-1980, 1981-1985, 1986-1990, and 1991-995 at radial distances of 400, 800, and 1200 feet from the pumping wells. These results indicated that the Rittman wells were the most likely reason for declining water levels over time. A final presentation of the findings was made in a simulated courtroom setting with students as expert witnesses and a panel of professors as judges.