An Evaluation of Potential Aquifer Storage in Eastern Colorado

A growing population in Colorado and recent years of drought has placed an ever greater strain on Colorado's water resources. One solution is to increase water storage, including use of natural reservoirs associated with groundwater aquifers.  The State of Colorado is actively working to manage its water supplies in a sustainable and environmentally beneficial manner. In 2006 the Colorado State Legislature authorized the Colorado Water Conservation Board, the water resources planning agency of the Department of Natural Resources, to identify underground water storage sites within the South Platte and Arkansas River drainage basins.  These watersheds contain alluvial and bedrock aquifers that underlie much of the eastern third of the State.  The aquifer regions were subdivided into 44 areas for detailed analysis.  The study included developing criteria and weighting factors by which to evaluate potential storage sites, compiling and mapping relevant information for each of the evaluation criteria, and identifying the highest-ranking sites in each basin and aquifer setting.  The criteria included ten hydrogeologic, environmental and implementation considerations. This evaluation showed that a number of areas for potential underground water storage exist in both basins, in both alluvial and bedrock settings.  Alluvial aquifer areas located away from the mainstems of the South Platte and Arkansas Rivers scored the highest due to larger storage volumes and longer residence times.  Several bedrock aquifer areas also received high scores due to their suitable characteristics for infrastructure, proximity to demand and minimal adverse impacts despite scoring low on the hydrogeologic characteristics.  Further investigations on a more local scale along with an examination of several issues that were not considered in this study were recommended. The results of this study were submitted to the State legislature and serve as the foundation for additional study.