LINKING GROUNDWATER WITHDRAWALS TO POTENTIAL ECOLOGICAL IMPACTS IN GLACIAL SETTINGS: CHALLENGES, SCIENCE, AND LEGISLATION

A risk-based system was developed to assess the potential for causing an adverse resource impact by new or increased water withdrawals as part of the State of Michigan implementation of the Great Lakes-St. Lawrence River Basin Water Resources Compact. The science underpinnings of this risk-based system include: estimation of ungaged streamflows, stream classification, development of flow-ecology relations for stream classes, and assessment of streamflow depletion by pumping wells. Regression was used to estimate streamflow for ungaged streams. Fish, temperature, and streamflow data were used to develop response curves predicting the change in fish species presence and abundance in response to water withdrawals. Glacial deposits dominate much of the landscape and the resulting streamflow and potential for groundwater/surface-water interaction was quantified in the development of the assessment procedures through an analytical model for streamflow depletion by a pumping well. These components were integrated into a screening tool that serves as the first step of the risk-based evaluation of new or increased uses.