The ground-water system and simulated effects of ground-water withdrawals in northern Utah Valley, Utah

The effects of withdrawals from the principal ground-water reservoir in northern Utah Valley, Utah, were projected by means of a three-dimensional, finite-difference, digital-computer model, which was constructed to study and simulate the ground-water system. The model was calibrated against (1) water levels measured in 1947, which were assumed to represent steady-state conditions; (2) observed water-level changes from 1947-83 for transient-state conditions; and (3) the results of an aquifer test. The calibrated model was used to simulate varying quantities of ground-water withdrawal and recharge and to estimate water-level changes for 1980-2000. The average annual rate of recharge for the area is assumed to be 190,000 acre-feet per year, and the average annual discharge from wells at the end of transient-state calibration was assumed to be 50 ,100 acre-feet per year. Water-level declines of as much as 25 feet are projected for the 20-year period if the average recharge rate is assumed and the discharge from wells is as much as 91,400 acre-feet per year. During transient-state calibration , changes in recharge to the principal ground-water reservoir were shown to be a major cause of the variations in water levels. (USGS)