Availability of water from the Outwash Aquifer, Marion County, Indiana

The outwash aquifer in Marion County, Indiana is a continuous, unconfined sand and gravel deposit containing isolated boulder, till, silt, and clay deposits along the White River, Fall Creek, and Eagle Creek. Flow in the aquifer is from the boundaries of the aquifer with the Tipton till plain toward the streams and major pumping centers in the aquifer. A two-dimensional, finite-difference model of the outwash aquifer was calibrated to water levels of October 6 to 10, 1980 and used to estimate availability of water in the aquifer. A drawdown limit of 50-percent saturated thickness applied to 78 simulated-pumping wells assumed to be 1 foot in diameter produced 97 cubic feet per second from the outwash aquifer. Streamflow reductions caused by 97 cubic feet per second simulated pumpage and constant-flux boundaries were estimated to be 85 cubic feet per second in the White River and 12 cubic feet per second in Fall Creek. In comparison, the 7-day, 10-year low flows were 83 cubic feet per second in the White River near Nora and 23 cubic feet per second in Fall Creek at Millersville. Simulated pumpage of 115 cubic feet per second and constant-flux boundaries produced streamflow reductions of 101 cubic feet per second on the White River and 13 cubic feet per second on Fall Creek. (USGS)