DEVELOPMENT OF A GROUND-WATER MODEL FOR ACQUISITION OF A WATER RIGHT FOR GREAT SAND DUNES NATIONAL PARK AND PRESERVE, COLORADO

Change in status of Great Sand Dunes National Monument to Great Sand Dunes National Park and Preserve as stated in the Great Sand Dunes National Park and Preserve Act of 2000 includes the specification that the surface water and ground water systems “that are necessary to the preservations of the dunes” are to be protected and that the Interior Department secure a water right for the Park. A ground-water model was constructed of the area in and around Great Sand Dunes National Park and Preserve. The purpose of this model is to assess how stresses on the unconfined or confined aquifers in areas outside of the Park boundary may affect surface and sub-surface water levels within the Park boundary. Model construction of stationary and transient parameters include data from consumptive use, public records, spatial data (for example location of pumping wells, irrigated lands, native vegetation, streams), and data interpolated from a ground-water model of the San Luis Valley. Various tools were used to process the data from different sources for input to the model. Results of simulating pumping the confined aquifer outside of the Park boundary at 100,000 acre-feet per year suggests water levels within the Park boundary could potentially be lowered by up to fifty feet in the confined aquifer in the northern area of the Park, and up to three feet in the unconfined aquifer within the Park boundary. These model results suggest that ground-water pumping outside the Park Boundary may affect water levels within the Park boundary, and as a result may affect the ecosystem within the Great Sand Dunes Park and Preserve.