Numerical simulation of ground-water flow in basin-fill material in Salt Lake Valley, Utah

Abstract

A three-dimensional, finite-difference, numerical model was developed to simulate ground-water flow in the basin-fill material in Salt Lake Valley, Utah. The model was calibrated to steady-state and transient-state conditions. The steady-state simulation was developed and calibrated using hydrologic data defining average conditions for 1968. The transient-state simulation was developed and calibrated using hydrologic data from 1969-91. Areally the model grid is 94 rows by 62 columns, with each cell 0.35 mile on a side. Vertically, the aquifer system is divided into seven layers. The model simulates recharge to the basin-fill ground-water flow system from (1) consolidated rock, (2) streams and canals, (3) precipitation on the valley floor, (4) irrigated land, (5) reservoirs and evaporation ponds in the southwestern part of the valley, and (6) underflow at Jordan Narrows. Estimated discharge to wells, canals, and springs is incorporated in the model. During simulation, the model computes (1) ground-water flow to and seepage from the Jordan River and the lower reaches of its principal tributaries, (2) recharge from consolidated rock at the northern end of the Oquirrh Mountains, (3) discharge to drains, and (4) discharge by evapotranspiration. During steady-state calibration, calibration variables were adjusted within probable ranges to minimize differences between model-computed and measured water levels, model-computed and estimated ground-water discharge to the Jordan River, and simulated and measured vertical hydraulic gradients. The transient-state simulation was calibrated to measured water-level changes and estimated annual gains in the Jordan River.