HYDROGEOLOGIC AND GROUNDWATER-CHEMISTRY EVALUATION OF CONCEPTUAL MODELS OF INTERBASIN GROUNDWATER FLOW: RESULTS FROM UTAH GEOLOGICAL SURVEY’S WEST DESERT GROUNDWATER-MONITORING NETWORK, WESTERN UTAH

The Utah Geological Survey established a groundwater-monitoring network (68 wells and 6 springs) in Snake Valley and adjacent basins, west-central Utah in 2009, in response to proposed large-scale groundwater development in eastern Nevada and western Utah. We apply new groundwater-level and chemical data from the UGS network to test conceptual models of regional groundwater flow. Previous workers proposed that groundwater flows from the Snake Range and adjacent recharge areas, NE to Tule Valley (32,000 ac-ft/yr, spring & evapotranspiration [ET] discharge) and Fish Springs (35,000 ac-ft/yr, spring & ET discharge), by deep flow through carbonate-rock aquifers.

Potentiometric-surface contours support regional SW-to-NE groundwater flow from Snake Valley to Tule Valley and Fish Springs, and S-to-N flow from nearby basins to Fish Springs. To reach Fish Springs from Snake Valley, groundwater must traverse structurally complex carbonate-rock aquifers and cross several range-bounding normal faults. Feasible flow paths based on hydraulic potential and aquifer permeability exist that can accommodate flow rates from previous conceptual and numerical models based on water-budget analysis. Trends in solute composition, groundwater temperature, stable isotope and radiogenic-isotope composition along these flow paths are complicated, but lend support to these flow paths with a number of caveats. Model recharge temperatures from dissolved-gas compositions suggest different recharge sources for groundwater in Tule Valley and Snake Valley, and mixing of different sources of discharge at Fish Springs and Coyote Spring in Tule Valley. The chemical data and hydrogeologic setting support flow to Fish Springs and Tule Valley from basins to the S and SE.

On the whole, hydrogeologic and groundwater-chemical data support limited interbasin flow from Snake Valley to Tule Valley and Fish Springs, through carbonate-rock aquifers, along a long, structurally complex but permeable flow path. Data do not support a simple, closed-system flow path, and instead indicate the major discharge areas in these desert basins are sourced by several flow paths having different recharge conditions and residence times, potentially including sources in Snake Valley and basins S and SW of Fish Springs and Tule Valley.