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Page A-6 <br /> TASK 5. Evaluation of Potentia) Sources — Mahomet Aquifer Alternative <br /> Operational experience suggests that the benefits provided by emergency wells at the DeWitt and <br /> Cisco wellfields are tempered by costs associated with interference effects on neighboring wells <br /> (DeWitt), loss of water to dry streambeds (DeWitt and Cisco), or inefficiencies due to recycling of <br /> stream water(Cisco). We will examine the costs and benefits of operating these wells during drought <br /> and near-drought conditions and formulate operational schemes that optimize use of the wells. Our <br /> analysis will examine the timing and tradeoffs associated with using these emergency wells, with a <br /> focus on maximizing the net benefits. <br /> Subtasks: <br /> 1. Conduct interviews with ISWS and develop focused groundwater model runs for ISWS <br /> 2. Develop conceptual model of transmission from DeWitt well field to Lake Decatur <br /> 3. Develop mathematical model of losses and lag time for transmission to Lake Decatur <br /> 4. Model operation of DeWitt well field focusing on interaction with Sangamon River and the Mahomet <br /> aquifer with well-defined predictive modeling scenarios to bound the drought yield of the aquifer(latter <br /> to be performed by the ISWS) <br /> 5. Assess alternative Mahomet Aquifer well locations <br /> 6. Develop operating rules for DeWitt well field <br /> Results and Products: <br /> • Conceptual model of transmission from DeWitt well field to Lake Decatur <br /> � Mathematical model of losses and lag time for transmission to Lake Decatur <br /> • Groundwater modeling of operation of DeWitt well field focusing on interaction with Sangamon River <br /> and the Mahomet aquifer—well defined predictive modeling scenarios to bound the drought yield of <br /> the aquifer(to be performed by the ISWS) <br /> • Operating rules for DeWitt well field: <br /> o Mahomet triggers for drawdown and recovery at the well field <br /> o Rate and duration of pumping and resting during drought defined <br /> o Drought yield—production from Mahomet aquifer <br /> o Drought yield—inflow to Lake Decatur <br />