Simulation of ground-water flow in Cedar Valley, Utah County, Utah, USA

Cedar Valley is located 35 miles south of Salt Lake City, Utah. Development of new domestic water supplies driven by rapid population growth in and around Cedar Valley has highlighted the need for a better understanding of the valley's ground-water system. In response to this need, we constructed a 2-layer 3-dimensional digital ground-water flow model to simulate the ground-water flow system in the basin-fill aquifer. The model was calibrated for transient flow conditions for the years 1970 through 2007. The last time step of the calibrated transient model (year 2007) showed that the Cedar Valley ground-water system received a total recharge of 26,011 acre-feet/year. The model also indicated that the ground-water system discharged 6,548 acre-feet/year through extraction wells, 3,902 acre-feet/year to Fairfield Spring, 13,103 acre-feet/year subsurface outflow through the bedrock underlying Cedar Pass and Mosida Hills as drains, and 3,430 acre-feet/year through evapotranspiration. The difference between the total recharge into the system and the total discharge out of the system was about 972 acre-feet/year, which represents the net volume of ground-water released from storage. The calibrated model showed an acceptable match between the simulated and the conceptual water flow budgets as well as between the simulated and the measured heads for all observations. We used the model to simulate eight projection scenarios. These scenarios show that water-level declines were greatest with 30% less recharge in the middle 10 years of projection combined with 125% of 2007 withdrawal from wells. Drawdowns ranging from 10 feet to 100 feet were produced in the northern half of the study area under this scenario.