Technical and administrative feasibility of alluvial aquifer storage and recovery on the South Platte River of northeastern Colorado

Increasing population and climate change are causing water managers to reassess water storage. In this context, alluvial aquifer storage and recovery (ASR), in which excess water is stored in the alluvium near a river, offers a plausible option. To investigate this option, a coupled technical-administrative analysis was conducted to investigate the feasibility of alluvial ASR in the semi-arid US state of Colorado, where water rights are governed by the doctrine of prior appropriation. A hypothetical alluvial ASR facility near Brighton, Colorado with a storage capacity of 118,500 cubic meters (96 ac-ft) was considered. This analysis comprises both technical feasibility, using a groundwater model that explicitly accounts for clogging, and administrative feasibility, using a first-of-its-kind analysis of the legal availability of water including both free river and reusable effluent water. This coupled technical-administrative analysis suggests that alluvial ASR facilities present a viable option to meet rising demand for water storage, preventing water loss due to evaporation, reducing the effect of climate stress on water resources, and avoiding the need to purchase land for above-ground water storage facilities. More generally, this study illustrates the crucial importance of placing hydrologic analysis in the broader context of policy constraints.