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Neupauer, Roseanna M ¹ ; Grielbing, Scott A ²

¹ University of Colorado
² University of Colorado

Groundwater withdrawals for drinking water supplies, irrigation, and other uses can lead to depletion of aquifers. If the aquifer is hydraulically connected to a stream or river, groundwater withdrawals can also lead to decreases in stream flow, which is called stream depletion. Limiting stream depletion is important for protecting surface water supplies and riparian habitat. Furthermore, in Colorado, groundwater withdrawals that lead to stream depletion may be subject to water rights. We present a new modeling approach, based on adjoint theory, for quantifying stream depletion due to pumping. The adjoint approach is particularly useful for choosing the location of a new well, if the goal is to minimize stream depletion. For many scenarios, the adjoint model can be solved using standard groundwater flow simulators, such as MODFLOW. We illustrate the application of the adjoint method using MODFLOW.