Particle-tracking analysis of flow paths and travel times within the capture areas of well fields in Salt Lake Valley, Utah

A particle-tracking analysis was done to estimate capture zones for selected public-supply wells in Salt Lake Valley. Twenty-five- and 50-year capture zones were estimated using a regional, finite-difference, ground-water flow model in conjunction with a particle-tracking program. Three sets of wells currently discharging ground water of adequate quality for public use, but located near areas of ground water with high dissolved-solids concentrations, were selected for the analysis. These included five wells in central Salt Lake Valley near the former Vitro chemical-processing site, four wells in southwestern Salt Lake Valley northeast of Copperton, and five wells in southeastern Salt Lake Valley between Midvale and Sandy. Capture zones were estimated for the wells for current average pumping and projected increased pumping. The quality of ground water within the estimated capture zones was evaluated by comparing the extent of the zones with the distribution of dissolved solids in the ground water surrounding the selected wells.

Results of the analysis of wells in central Salt Lake Valley indicate that most of the volume of ground water within the well’s capture zones is characterized by dissolved-solids concentration of less than 500 milligrams per liter. Estimated capture zones of wells in southwestern and southeastern Salt Lake Valley contain ground water with higher dissolved-solids concentrations than ground water currently being discharged by those wells. Estimated 50-year capture zones of selected wells in southwestern Salt Lake Valley contain ground water with dissolved-solids concentrations exceeding 5,000 milligrams per liter. Estimated 50-year capture zones for wells in southeastern Slat Lake Valley, based on simulation of projected increased pumping, indicate flow toward the wells from an area of ground water west of the Jordan River characterized by dissolved-solids concentrations exceeding 1,000 milligrams per liter.