ASSESSING REGIONAL AQUIFER MANAGEMENT EFFECTIVENESS WITH A COLLABORATIVELY BUILT MODEL ON THE EASTERN SNAKE RIVER PLAIN, IDAHO

The Eastern Snake Plain Aquifer (ESPA) supports a robust agricultural economy, contributing an estimated 21% to Idaho's goods and services with an estimated value of $10 billion as of 2009. However, this economic prosperity comes with inherent challenges. Groundwater pumping combined with increased surface water irrigation efficiency and more frequent drought have led to diminished recharge rates and a consistent decline in both aquifer storage and spring discharge since the 1950s. To address these issues, water users and the State of Idaho have implemented various aquifer management methods, such as managed aquifer recharge and pumping reductions, aimed at halting and reversing the decline of the aquifer.

To evaluate the effectiveness of these management strategies, we utilize a calibrated MODFLOW-USG groundwater flow model, developed by the Idaho Department of Water Resources along with a cohort of government agencies, known as the Enhanced Snake Plain Aquifer Model version 2.2 (ESPAM 2.2). This model serves as a crucial tool for evaluating the impacts of different aquifer management approaches on key metrics, such as aquifer storage and spring discharge. Additionally, a numerical superposition version of ESPAM 2.2 enables rapid assessment of management impacts. Through this approach, we can discern variations in magnitude, timing, and spatial distribution resulting from distinct management efforts. Furthermore, we can test novel implementations and optimize their spatial distribution to achieve favorable outcomes that reconcile competing resource allocations.