Many municipal water supplies come from groundwater pumped from wells that are set near surface water to take advantage of induced infiltration. By inducing surface water to enter the groundwater system, drawdown in the wells is minimized and the pumping capacity is increased. There are two potential problems that can result, however. First, there is the possibility that surface-water contaminants might enter the aquifer and pollute the water supply. Second, inducing infiltration can reduce flow in the stream which could negatively affect the ecological health of the stream system as well as the downstream communities. Understanding the groundwater/surface-water connection is thus important to managing both the groundwater and surface-water systems. This study investigates the use of stable isotopes of ¹⁸O and ²H for quantifying the amount of infiltration induced by municipal pumping and compares those results to the hydraulic connection between surface and groundwater. The technique is applied in the Four Mile Creek alluvial buried aquifer of Oxford, Ohio. Surface water and groundwater have different isotopic signatures; surface-water samples have greater variability and higher average ¹⁸O and ²H concentrations. The results show that municipal well water from Production Well 3 (PW3) has an isotopic signature of groundwater while Production Well 1 (PW1) has average isotope concentrations that indicate an even mix of groundwater and induced infiltration. Hydraulic gradients between the creek and groundwater system are downward near PW1 and PW3, but the gradients near PW3 do not respond to changes in pumping rates while they do near PW1. We are currently continuing the study near PW1 and expanding it to Production Well 2 (PW2). The study highlights the use of multiple techniques (stable isotopes, hydraulic head measurements) to better understand and manage groundwater systems.
Authors: Sarah Eick and Jensen Fass
Faculty Advisor: Jonathan Levy, Geology and Environmental Science
Graduate Student Advisor: Idah Ngoma, Geology and Environmental Science
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