Abstract
Sustained pumping of groundwater can lead to declining water levels in wellfields and concerns regarding the sustainability of groundwater resources. Aquifer Storage and Recovery (ASR) is a promising approach for maintaining water levels in wells and increasing the sustainability of groundwater resources. Herein, an analytical model relying on superposition of the Theis equation is used to resolve water levels at 40 wells in three vertically stacked ASR wellfields operating in the Denver Basin Aquifers, Colorado (USA). Fifteen years of dynamic recovery/recharge data are used to estimate aquifer and well properties, which are then used to predict water levels at individual wells. Close agreement between modeled and observed water levels supports the validity of the analytical model for ASR wellfield applications. During the study period, 45 million m(3) of groundwater is produced and 11 million m(3) is recharged, leading to a net withdrawal of 34 million m(3) of groundwater. To quantify the benefits of recharge, the analytical model is applied to predict water levels at wells absent the historical recharge. Results indicate that during recovery and no-flow periods, recharge has increased water levels at wells up to 60 m compared to the no-recharge scenario. On average, the recharge increased water levels during the study period by 3, 4, and 11 m for wells in the Denver, Arapahoe, and Laramie Fox-Hills Aquifers, respectively. This study demonstrates the utility of analytical modeling to quantify the effects of long-term ASR at wells.