ABSTRACTThe City of Columbus, Ohio, obtains nearly 15 percent of its municipal water supply from four radial‐collector wells located along the Scioto River and Big Walnut Creek. Upstream from the three wells located adjacent to the Scioto River are five uncontrolled landfills and two aggregate mines that operate quarry‐dewatering systems. Flow paths along which leachate could migrate from the landfills, under existing conditions and under various hypothetical conditions related to the cessation of quarry dewatering, were simulated with a two‐layer, steady‐state, ground‐water flow model incorporating spatially variable recharge, transmissivity, and hydraulic conductivity. The model was calibrated with two sets of water‐level data and with the results of a seepage study along the Scioto River and Scioto Big Run. Results of simulations indicate that water levels near the quarries and landfills will rise to an altitude sufficient to saturate some of the landfill wastes. Predicted flow directions associated with all the hypothetical conditions indicate that leachate migrating from the landfills will not discharge directly into the capture zones of the collector wells; rather, the leachate will be diverted into one or the other quarry‐dewatering systems and/or into the Scioto River. The model simulations also indicate that approximately 60 percent of the ground water discharged within the study area is by quarry dewatering, and about 13 percent of the yield of the collector wells under normal pumping rates is from induced stream