- Environmental groups are suing Arizona over a large housing project in Benson.
- The development would rely on groundwater now legally reserved for a federal conservation area, plaintiffs allege.
- Complaint says officials failed to review a 2008 water designation despite a legal requirement to do so every 15 years.
- The San Pedro River is already losing flow due to over-pumping in the area.
Tuesday, August 5, 2025 — The Center for Biological Diversity, along with the San Pedro 100 and Dr. Robin Silver, filed a lawsuit in Arizona Superior Court accusing the Arizona Department of Water Resources (ADWR) and its director, Thomas Buschatzke, of failing to uphold legal duties concerning groundwater management. The suit centers on the 28,000-home Villages at Vigneto development in Benson and its reliance on groundwater that may no longer be legally or physically available.
Background: What the Lawsuit Alleges.
At issue is a designation issued in 2008 by ADWR that granted the City of Benson a “100-year adequate water supply” under Arizona law. That designation enabled the city to pursue large-scale developments like the Villages at Vigneto, but it has not been reviewed in the 17 years since it was issued. State law requires such designations to be revisited at least every 15 years.
In the years since the designation, several hydrological studies and legal rulings have drastically changed the water landscape in the Upper San Pedro River Basin. Notably, court rulings in 2023 and 2024 quantified federal reserved water rights for the San Pedro Riparian National Conservation Area (SPRNCA), guaranteeing minimum stream flows and groundwater levels essential to the last free-flowing desert river in the Southwest.
The San Pedro River at Risk.
The lawsuit alleges that continued groundwater pumping for projects like Vigneto will intercept water that legally belongs to SPRNCA. According to the plaintiffs, monitoring data show groundwater levels have already dropped below legally mandated thresholds in several wells near the conservation area. Streamflows have also declined, violating the rights confirmed in the adjudication.
Hydrological studies cited in the complaint, including those by Prucha (2016), Eastoe (2017), and Meixner (2018), indicate that pumping for Vigneto and a newly proposed $190 million aluminum plant in Benson will further divert groundwater away from the river and conservation area.
Legal Claims and Requested Action.
The plaintiffs are seeking two forms of relief:
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A court order directing ADWR to review and possibly revoke Benson’s 100-year water designation.
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A declaratory judgment stating that ADWR’s failure to act violates Arizona’s Groundwater Code and its responsibilities under administrative rules.
The lawsuit argues that ADWR has ignored overwhelming evidence showing the groundwater supply is no longer adequate. Further, the plaintiffs claim that the Department’s inaction could mislead homebuyers who assume a secure long-term water supply exists.
Broader Implications for Arizona Water Law.
The case brings into focus the tension between development pressures and Arizona’s legal obligations to protect groundwater and surface water resources. Although Benson is located outside of an official Active Management Area, the legal standards still require any proposed development to show that water will be available, legally and physically, for at least 100 years.
Critically, the lawsuit underscores the connection between groundwater pumping and federal reserved rights—an evolving and increasingly relevant area of water law in the West. If the court agrees with the plaintiffs, it could set a precedent for stronger oversight of groundwater use near federally protected lands.
A Wait for the Court.
As of August 4, 2025, the court has not yet ruled on whether it will grant the plaintiffs’ request for immediate review. Regardless of the outcome, the case raises significant questions about Arizona’s future water planning and its responsibility to balance development with environmental stewardship.
Sources.
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Full complaint (PDF): Download
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Court Order Quantifying SPRNCA Water Rights: https://biologicaldiversity.org/programs/public_lands/rivers/san_pedro_river/pdfs/20230825-ORDER-QUANTIFYING-W1-11-232-ORDER-QUANTIFYING-FEDERAL-RESERVED-WATER-RIGHTS-FOR-SAN-PEDRO-RIPARIAN-NATIONAL-CONSERVATION-AREA.pdf
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Clarifying Order (2024): https://biologicaldiversity.org/programs/public_lands/rivers/pdfs/20241212-CLARIFYING-ORDER-12.12.24-W1-11-232-OR-quantify-fed-res-rights.pdf
