Year of Award

2026

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Geosciences

Department or School/College

W.A Franke College of Forestry and Conservation

Committee Chair

W. Payton Gardner

Commitee Members

Hilary R. Martens, Andrew Wilcox, Arthur Endsley

Keywords

Groundwater, Geophysics, Hydrology, Hydrogeology, Climate, Colorado River Basin, Arizona

Subject Categories

Geophysics and Seismology | Hydrology

Abstract

Groundwater resources in the Colorado River Basin are critically stressed yet remain under-monitored and under-regulated, creating urgent need for reliable, continuous observations at multiple spatial scales. This study evaluates the performance of the University of Montana Global Navigation Satellite Systems (GNSS) terrestrial water storage dataset as a tool for bridging groundwater monitoring gaps across the Upper and Lower Colorado River Basins between 2006 and 2024. We compare GNSS-derived total water storage and groundwater storage estimates against NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite observations and in-situ groundwater well measurements at regional and sub-regional scales. We employ a Bayesian autoregressive regression model to assess relationships between regional climate anomalies and groundwater storage variability in heavily groundwater-reliant basins in the Lower Colorado River Basin. GNSS and GRACE produce broadly consistent total water storage estimates across the Colorado River Basin, with stronger agreements in the Upper Colorado River Basin than the Lower Colorado River Basin. Differences in performance among GNSS analysis centers indicate that processing methodology of GNSS displacement data meaningfully influences product quality. At the sub-regional scale, GNSS-derived groundwater storage shows strong agreement with well observations in select groundwater basins, particularly those characterized by climate-driven, background groundwater signals, suggesting that GNSS could feasibly fill critical observational gaps where traditional monitoring infrastructure is sparse and basin scales fall below GRACE's effective resolution. The climate model results show that Upper Colorado River Basin snow water equivalent emerged as the most consistent climate predictor of Lower Colorado River Basin groundwater storage, suggesting a broader regional teleconnection between Upper basin hydrological conditions and Lower basin groundwater dynamics. The dominance of the autoregressive term across all modeled basins indicates that prior groundwater conditions are a stronger predictor of current storage than interannual climate forcing, implying that short-term precipitation events may be insufficient to offset sustained pumping-driven depletion. These findings support the integration of GNSS-derived total water storage into groundwater monitoring ensembles across the Colorado River Basin, while highlighting the need for further investigation into the factors governing spatial variability in GNSS-well agreement.

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© Copyright 2026 Michelle Lee Barton