New research into the groundwater flow system of Moab-Spanish Valley, Utah, suggests that the Glen Canyon Group Aquifer (GCGA), which serves as the sole public water supply for the city of Moab, may face sustainability challenges. The analysis indicates that additional water withdrawals would likely be drawn from groundwater storage instead of being supported by recharge.
Study methodology and geochemical findings
The study utilized a multiple-tracer geochemical approach, examining stable isotopes, tritium, 3
He/4
He ratios, dissolved solids, and sulfate concentrations. These findings show that the GCGA is recharged by local streams rather than from the adjacent Valley-Fill Aquifer (VFA).
Comparing new results to previous models
Previous water-budget models, including those used in studies dating back to 1971, suggested a different relationship between the aquifers. However, this analysis found that water-budget calculations based on measured spring discharge, streamflow gains, horizontal gradients in groundwater age, and outcrop area pore waters are all less than previously thought.
Estimated recharge rate calculations
Using a lumped parameter model and 14C groundwater ages, researchers estimated the recharge to the deeper Glen Canyon Group Aquifer (DGCGA) to be approximately 4.2 ± 2.3 × 10^6 m3/yr. This estimated recharge rate is roughly equal to the measured discharge from springs and wells.
