Challenge: To help the City secure a safe and resilient water supply for the future.

Solution: Lake Decatur provides 37,150 acre-feet of water per year to the City of Decatur and its major agribusiness industrial customers. Because the lake is highly vulnerable to drought, INTERA developed an integrated water supply plan to diversify and expand the City’s existing water supplies. Future municipal and industrial demand scenarios were developed based on historical analysis and statistical modeling of demand considering weather, population, rates, and economic indicators. The drought-resilience of existing water supplies was evaluated by recreating the hydrologic record and modeling the reservoir system under future drought conditions and projected water use using a system-level modeling platform (GoldSim). Under design drought conditions, the 2050 supply gap was estimated to be 9,500 acre-feet. INTERA evaluated options including lower lake operating level, deep aquifer wells, existing gravel pits, drought-proof alluvial wells downstream of the water reclamation facility, regional collaboration, and additional conservation. After screening, conceptual-level designs were developed for evaluating the costs, operational benefits, and potential impacts of each alternative.   

Results: Based on our evaluation of alternatives, we developed an implementation plan with recommendations for near, medium and long-term actions designed to secure current supply reliability and resiliency and to prepare the City for adaptive, cost-effective water supply management to 2050 and beyond.