METHODOLOGY FOR GROUNDWATER RESOURCE ASSESSMENT IN UTAH'S VARIABLE HYDROGEOLOGIC TERRAINS

Increasing pressures from drought and land use changes on groundwater resources in Utah necessitates a robust methodological framework for aquifer characterization and sustainable management. Here, we detail the approach taken by the UGS Groundwater Program to investigate groundwater across Utah's diverse hydrogeologic settings, from the Basin and Range Province to the Colorado Plateau.

Our methodology integrates multiple investigative techniques: (1) high-resolution remote sensing surveys, including NDVI, InSAR, and ET, to assess aquifer depletion, management changes, and land-surface changes; (2) USGS Soil-Water-Balance (SWB) model to estimate groundwater recharge by processing readily available soil property, land use, and climate datasets through a modified Thornthwaite-Mather methodology that calculates water balance components including ET, runoff, and recharge on a daily time step; (3) environmental tracer analysis utilizing major ion chemistry and stable and radiogenic isotopes to determine groundwater age and flow paths; (4) analysis of model outputs versus historical and current monitoring data to validate results; and (5) exhaustive field work.

Studies in three representative basins—Pahvant Valley, Bryce Canyon, and the Matheson Wetlands Preserve—demonstrate the effectiveness of this integrated approach. Each study area employs the methods distinctly: Pahvant Valley focuses heavily on NDVI and InSAR to track agricultural impacts on groundwater levels, Bryce Canyon emphasizes SWB modeling to understand recharge processes in its unique geological setting, and Matheson Wetlands Preserve utilizes environmental tracers to characterize groundwater-surface water interactions. The methodology has successfully identified previously unknown fault-controlled groundwater flow paths and areas of surface water-groundwater interaction.

This systematic approach provides a template for future groundwater studies in intermountain regions and offers crucial insights for water resource management in semi-arid environments. The results will directly inform state water management policies and support the development of sustainable groundwater management plans across Utah's diverse landscapes.