Rethinking a groundwater flow system using a multiple-tracer geochemical approach: A case study in Moab-Spanish Valley, Utah

Journal of Hydrology
By: , and 

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Abstract

The Glen Canyon Group Aquifer (GCGA) is the sole source of public water supply for the city of Moab, Utah, a domestic and international tourist destination. Population and tourism growth are likely to target the GCGA for future water resources, but our analysis indicates that additional withdrawals would likely be sourced from groundwater storage and not be sustained by recharge. A quantitative estimate of groundwater discharge from the GCGA is problematic because the downgradient aquifer boundary is the Colorado River, and groundwater discharge to the river is very small compared to the river flow. A water budget based on a conceptual model of GCGA discharging into an adjacent alluvial Valley-Fill Aquifer (VFA) was reported by Sumsion (1971) and numerous subsequent studies have repeated and utilized this water budget. The GCGA contains stable isotopes, tritium, 3He/4He ratios, dissolved solids, and sulfate concentrations that contrast with the VFA, indicating it is instead recharged by local streams rather than from the GCGA. Water-budget calculations, based on: (1) measured spring discharge and streamflow gains, (2) horizontal gradients in VFA groundwater age, and (3) GCGA outcrop area vadose-zone pore waters are all less than previously thought. Using a lumped parameter model and 14C groundwater ages, we estimate recharge to the deeper GCGA (DGCGA) to be 4.2 ± 2.3 × 106 m3/yr, which is approximately equal to the measured discharge from wells and springs.


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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Rethinking a groundwater flow system using a multiple-tracer geochemical approach: A case study in Moab-Spanish Valley, Utah
Series title Journal of Hydrology
DOI 10.1016/j.jhydrol.2020.125512
Volume 590
Year Published 2020
Language English
Publisher Elsevier
Contributing office(s) Nevada Water Science Center, Utah Water Science Center
Description 125512, 18 p.
Country United States
State Utah
Other Geospatial Moab-Spanish Valley
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