Quantifying Stream Depletion Due To Groundwater Pumping Using Adjoint Methodology
Griebling, Scott A 1 ; Neupauer, Roseanna M 2
1 University of Colorado
2 University of Colorado
Water scarcity has become a common topic, especially in the western United States, stemming from concerns over higher demands from increasing populations as well as lower supplies from changes in climactic patterns. Rivers and streams hydraulically connected to aquifers where groundwater pumping occurs or might occur in the future are likely to feel the impact of increases in groundwater extraction as wells are pumped to meet new and higher demands. Stream depletion associated with pumping wells has been quantified by both analytical and numerical approaches; however, methods for identifying the stream depletion caused by new wells remain inefficient and require separate simulations for each potential well location. This work develops an efficient adjoint method for finding stream depletion throughout a domain corresponding to a new well. The adjoint equations couple river and aquifer flow using Manning’s equation, allowing for the head in the river to change. The adjoint equations are solved using MODFLOW and an adapted form of the stream package. We employ test cases to show the applicability of the approach and the increase in computational efficiency it produces.