GROUND-WATER AVAILABILITY IN TURKEY CREEK BASIN, CO

Turkey Creek Basin is a mountainous watershed located in Jefferson County, CO, approximately 20 miles west of Denver. Rapid development and population growth in the basin has raised concerns regarding water quantity and quality. Published values for available ground-water storage in the basin are poorly constrained, ranging from 1.5 to 150 years at present rates of water use. Assuming each of the approximately 5000 homes consumes 10% of their daily pumping (i.e. the remainder is returned through septic drain fields), residential use represents an overall decrease in ground-water recharge of 0.07 in/year. Published values of precipitation and evapotranspiration rates indicate that water retained in the basin is on the order of 3 inches/year, implying residential consumption of available water is small, about 2%. However, estimation of ground-water recharge from a very short record of stream flow and estimates of ground-water outflow from the basin suggest that water retention in the basin may be much lower and that ground-water recharge is a small fraction of the retained water, thus consumption may be on the order of 20% of ground-water recharge. This assessment is under investigation. If this is the case, then accurate values of ground-water storage in the aquifer are critical because the storage will support the residents in times of drought

Basin storage is estimated using water budgets, ground water modeling, and residence time based on measured tritium age-dates of ground-water samples that suggest rapid turnover of ground water in the basin. The evolving ground-water model will evaluate sustainable ground-water use and simulate the impacts of potential growth, represented as increased water consumption, in the basin.