Hydrogeology and Water Budget for Goshen Valley, Utah County, Utah

Abstract

Goshen Valley contains extensive areas of agriculture, significant wetlands, and several small municipalities, all of which rely on both groundwater and surface water. The objective of this study is to characterize the hydrogeology and groundwater conditions in Goshen Valley and calculate a water budget for the groundwater system. Based on the geologic and hydrologic data presented in this paper, we delineate three conceptual groundwater zones. Zones are delineated based on areas of shared hydrogeologic, geochemical, and potentiometric characteristics within the larger Goshen Valley. Groundwater in Goshen Valley resides primarily in the upper basin fill aquifer unit (UBFAU) and lower carbonate aquifer unit (LCAU) hydrostratigraphic units. Most wells in Goshen Valley are completed in the UBFAU, which covers much of the valley floor. The UBFAU is the upper part of the basin fill, which is generally less than 1500 feet thick in Goshen Valley. Important spring discharge at Goshen Warm Springs issues from the LCAU. Relatively impermeable volcanic rocks (VU) occur along much of the upland parts of the southern part of Goshen Valley. Large sections of the southwest part of the Goshen Valley basin boundary have limited potential for interbasin flow. Interbasin groundwater flow is likely at several locations including the Mosida Hills and northern parts of Long Ridge and Goshen Gap in areas underlain by LCAU. Depth to groundwater in Goshen Valley ranges from at or just below the land surface to greater than 400 feet. Groundwater is within 30 feet of the land surface near and north of Goshen, in areas of irrigated pastures and wetlands that extend east toward Long Ridge and Goshen Warm Springs, and to the north towards Genola. Groundwater movement is from upland parts of the study area toward the valley floor and Utah Lake. Long-term water-level change is evident across much of Goshen Valley, with the most significant decline present in conceptual zone 2 and the southern part of conceptual zone 1. The area of maximum groundwater-level decline—over 50 feet—is centered a few miles south of Elberta in conceptual zone 2. Groundwater in Goshen Valley spans a range of chemistries that include locally high total dissolved solids and elevated nitrate and arsenic concentrations and varies from calcium-bicarbonate to sodium-chloride-type waters. Overlap in chemistry exists in surface water samples from Currant Creek, the Highline Canal, and groundwater. Stable isotopes indicate that groundwater recharges from various locations that may include local recharge, from the East Tintic Mountains, or far-traveled groundwater recharged either in Cedar Valley or east of the study area along the Wasatch Range. Dissolved gas recharge temperatures support localized recharge outside of Goshen. Most groundwater samples in Goshen Valley are old, with limited evidence of recent groundwater recharge. An annual water budget based on components of recharge and discharge yields total recharge of 32,805 acre-ft/yr and total discharge of 35,750 acre-ft/yr. Most recharge is likely from interbasin flow and lesser amounts from precipitation and infiltration of surface water. Most discharge is from well water withdrawal with minor spring discharge and groundwater evapotranspiration. Water-budget components show discharge is greater than recharge by less than 3000 acreft/yr. This deficit or change in storage is manifested as longterm water-level decline in conceptual zone 2, and to a lesser degree, in conceptual zone 1. The primary driver of discharge in conceptual zone 2 is well withdrawal. Conceptual zone 3 is broadly in balance across the various sources of recharge and discharge, and up to 1830 acre-ft/yr of water may discharge from conceptual zone 3 into Utah Lake. Minimal groundwater likely flows to Utah Lake from zones 1 or 2.