Use of an Analytical Model to Screen New or Increased Groundwater Withdrawals for Potential Impacts on Streamflow

The State of Michigan recently enacted legislation requiring that new or increased high-capacity withdrawals (greater than 100,000 gallons per day) from either surface water or groundwater be reviewed to prevent Adverse Resource Impacts (ARI). An on-line screening tool was developed as part of the water-withdrawal screening process to identify withdrawals more likely to cause an ARI and recommend site-specific review by the state before the withdrawal is implemented. Proposed withdrawals identified as less likely to cause an ARI are allowed to proceed after registration with the state. The screening tool uses an analytical solution for stream depletion by a pumping well within a risk-based system based on a gradient of risk, ecological response curves, and stream classification. Statewide estimates of aquifer properties are used in the screening tool. Stream depletion is estimated with consideration of capture from adjacent streams and intermittent pumping.