Improving Groundwater Management in the South Platte Alluvial Aquifer

Groundwater pumping from high capacity wells located in the South Platte alluvial aquifer in northeast Colorado was estimated to be nearly 500,000 AF annually prior to significant administrative changes that occurred in the early 2000s. Currently, it is estimated that closer to 450,000 AF are pumped annually in the basin, while augmentation of pumping has increased dramatically over the past decade. Concerns have arisen in recent years about well curtailments and possible over-augmentation leading to high water tables. In 2012 the Colorado Legislature passed House Bill 12-1278, titled Concerning the Authorization of a Study of the South Platte River Alluvial Aquifer. The Act directed the Colorado Water Institute at Colorado State University to conduct a study of the South Platte alluvial aquifer to identify and delineate areas within the basin adversely impacted by high groundwater levels and to conduct a feasibility-level evaluation of the causes of high groundwater levels in the affected area, and determine if expanded utilization of the aquifer is feasible. HB1278 did not authorize modeling studies, but rather an evaluation of the available data to address the objectives of the Act. Our general plan of work for this study was to use the existing data tools in the South Platte Decision Support System (SPDSS) developed for CWCB as part of the Colorado DSS (CDSS). We used the SPDSS to develop datasets on groundwater levels, surface and groundwater diversions, river flow, call records, stream gain and loss, augmentation, artificial recharge, phreatophytes, and other factors for analysis. While high groundwater levels are found throughout the basin, problems impacting homeowners are observed to be localized and care must be exercised not to overreach when applying solutions.