The glacial deposits underlying a 260 square-mile area near Logansport, Indiana, range in thickness from 0 to 300 feet and consist of three semiconfined sand and gravel aquifer units separated and overlain by three semiconfining till units. The ground-water development potential of the lowest of the sand and gravel aquifers is considerable. Thickness of the aquifer is generally about 80 feet along the axis of the narrow buried valley that it fills. Maximum and average transmissivities of the aquifer are about 38,000 and 13,000 square feet per day, respectively. Withdrawal of 10 million gallons per day from the aquifer was simulated by a four-layer digital model of the study area. Simulated pumping centers were located in areas of high transmissivity and proximity to ground-water discharge. Results indicate an absence of hydrologic constraints to development of the quantities of ground water simulated in the model. However, the simulation of water-level declines of as much as 35 feet in the lowest aquifer indicates that interference with the operation of domestic wells is likely.
