Mohajer et al. (2026) Key natural influences on groundwater storage changes in Central and Southern Arizona

Identification

• Journal: Scientific Reports
• Year: 2026
• Date: 2026-03-24
• Authors: Behshad Mohajer, J. S. Famiglietti, Hrishikesh A. Chandanpurkar, Fengwei Hung, Karem Abdelmohsen
• DOI: 10.1038/s41598-026-44132-0

Research Groups

• School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ, USA
• School of Sustainability, Arizona State University, Tempe, AZ, USA
• Swette Center for Sustainable Food Systems, Arizona State University, Tempe, AZ, USA

Short Summary

This study quantifies the natural hydroclimatic controls on groundwater storage variability in Central and Southern Arizona using GRACE/FO data, revealing that natural factors account for approximately 16% of spatial variance, primarily driven by evapotranspiration, precipitation, and subsurface runoff. The research identifies distinct subbasin clusters based on their hydroclimatic responses, offering a transferable framework for groundwater sustainability assessments.

Objective

• To evaluate and quantify the natural hydroclimatic controls on Groundwater Storage Anomalies (GWSA) variability in Central and Southern Arizona, distinguishing them from anthropogenic influences.

Study Configuration

• Spatial Scale: Central and Southern Arizona, analyzed at the subbasin scale.
• Temporal Scale: 2004 to 2021.

Methodology and Data

• Models used: Principal Component Analysis (PCA), k-means clustering (unsupervised machine learning algorithm), Noah-MP Land Surface Model (within WLDAS).
• Data sources: NASA’s Gravity Recovery and Climate Experiment (GRACE), GRACE Follow-On (GRACE-FO) Mascon data (RL06.3_V4), NASA’s Western Land Data Assimilation System (WLDAS) hydrometeorological data (Noah-MP L4 daily product at 0.01° resolution), and in situ measurements.

Main Results

• The region exhibits substantial spatial heterogeneity in groundwater storage changes.
• Northern and central subbasins are recharge-responsive, primarily influenced by precipitation and subsurface runoff.
• Southern subbasins are loss-dominated, characterized by weaker natural recharge and stronger atmospheric demand.
• Natural hydroclimatic variability accounts for approximately 16% of the inter-subbasin spatial variance in GRACE/FO groundwater storage trends.
• Within this natural component, total evapotranspiration (~29%), precipitation (~23%), and subsurface runoff (~20%) are the largest contributors to the explained variance.
• The remaining spatial variance is attributed to anthropogenic influences, geologic heterogeneity, and observational/modeling uncertainties.
• A diagnostic framework successfully identifies groundwater subbasin clusters driven by shared hydroclimatic modes.

Contributions

• Quantifies the specific contribution of natural hydroclimatic variability to groundwater storage changes in Central and Southern Arizona, providing a clearer understanding of its role relative to anthropogenic drivers.
• Develops a diagnostic framework that identifies groundwater subbasin clusters based on shared hydroclimatic modes, offering a novel approach for regional analysis.
• Provides a transferable tool with potential applications for recharge feasibility analysis, groundwater sustainability assessments, and future local groundwater planning in the Lower Colorado River Basin.

Funding

• Arizona State University College of Global Futures
• Arizona State University School of Sustainability

Citation

@article{Mohajer2026Key,
  author = {Mohajer, Behshad and Famiglietti, J. S. and Chandanpurkar, Hrishikesh A. and Hung, Fengwei and Abdelmohsen, Karem},
  title = {Key natural influences on groundwater storage changes in Central and Southern Arizona},
  journal = {Scientific Reports},
  year = {2026},
  doi = {10.1038/s41598-026-44132-0},
  url = {https://doi.org/10.1038/s41598-026-44132-0}
}