- Groundwater levels are declining fastest in rural, unregulated areas.
- Tribal oversight reduces groundwater decline risk but has mixed quality outcomes.
- Nitrate and arsenic levels rise with groundwater recharge, posing new risks.
- Communities with more Black residents face double the odds of groundwater loss.
- Domestic well areas are more prone to arsenic exceedances than regulated systems.
Thursday, April 17, 2025 — A new study published on April 6 in the journal Water
provides a sobering snapshot of Arizona’s groundwater reality, revealing significant disparities in water access, contamination risk, and aquifer sustainability across the state. The research—conducted by experts at the University of Arizona—analyzes groundwater trends in 1,881 drinking water service areas using two decades of data and a framework that links water availability, quality, and access.
The findings highlight stark geographic and demographic divides in groundwater decline. Areas outside of Arizona’s Active Management Areas (AMAs), which are subject to less regulation, experienced widespread declines in groundwater levels over the last 20 years—up to 52 feet in some regions. In contrast, groundwater levels have risen in parts of urban and managed areas, thanks in part to targeted recharge efforts.
But that recharge comes with a hidden cost.
“Rising groundwater levels are associated with higher nitrate and arsenic detection,” the authors reported. This counterintuitive finding reflects a phenomenon where recharge—while stabilizing supply—can also mobilize naturally occurring and human-introduced contaminants into the drinking water supply.
Socioeconomic disparities also play a critical role. The study found that groundwater declines were twice as likely to occur in communities with higher Black populations (OR = 2.01), while Hispanic and Latino communities had slightly lower odds of decline (OR = 0.92). Meanwhile, tribal areas generally saw fewer groundwater declines (OR = 0.62), but had mixed results in terms of contamination, with reduced nitrate exceedances but variable arsenic levels.
One of the more troubling revelations concerns domestic well areas—unregulated clusters of private wells. These systems, often found in rural and low-income areas, showed higher odds of arsenic exceedances than community water systems regulated under the Safe Drinking Water Act. The study authors suggest that gaps in monitoring and infrastructure may contribute to these risks.
Aquifer type also mattered. Karst systems—complex underground networks common in rural Arizona—showed long-term stability but short-term vulnerability. Alluvial aquifers, typically found in urban areas, are more prone to fluctuations but benefit from more consistent monitoring.
The study, which used geostatistical tools, regression analysis, and spatial clustering, underscores the need for more nuanced groundwater governance. The authors called for “expanded managed aquifer recharge, targeted regulatory interventions, and strengthened Tribal water governance” to address growing risks and inequities.
With Arizona facing ongoing drought, population growth, and Colorado River shortages, the study serves as both a warning and a guidepost. The data suggest that solutions must not only address quantity, but also quality and equitable access, especially for the most vulnerable communities.
🔗 Full study: https://doi.org/10.3390/w17071097
Citation:
Williams, S. A., Zuniga-Teran, A. A., Megdal, S. B., Quanrud, D. M., & Christopherson, G. (2025). Assessing the Relationship Between Groundwater Availability, Access, and Contamination Risk in Arizona’s Drinking Water Sources. Water, 17(7), 1097. https://doi.org/10.3390/w17071097
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