Environmental Group Sues Arizona Water Regulators Over Benson's Groundwater Designation

The Center for Biological Diversity has taken the Arizona Department of Water Resources to court, alleging the state agency is failing to safeguard groundwater in southern Arizona. The Tucson-based nonprofit filed its suit in Maricopa County Superior Court on Monday.

At issue is the city of Benson, which depends on groundwater and holds a designation from the agency, known as ADWR, certifying a 100-year assured water supply. The center argues that designation should be revoked because groundwater levels in the area are low.

Under state law, ADWR must review assured water supply designations every 15 years and may revoke one if the supply is no longer adequate. Benson City Manager Greg Volker said it has been 17 years since the agency last reviewed the city's designation, though a review is now underway. The lawsuit asks ADWR to complete that review and state definitively whether the designation can be revoked. If the agency declines to revoke it, the center would then have a route to challenge the decision. ADWR declined to comment.

Robin Silver, a co-founder of the center, is bringing the suit. Silver contends that Benson's aquifer is linked to the San Pedro River, so drawing it down harms the northern portion of the San Pedro Riparian National Conservation Area. "That aquifer is connected to the river, so by them sucking their aquifer down, it kills the northern part of the conservation area," Silver said. In Silver's view, "there's not any questions about what the right decision should be, they should just be revoked."

Central to the case is the Villages at Vigneto, a proposed development that has been held up by various issues and environmental concerns for 13 years. Recent Maricopa County Superior Court rulings set minimum stream and groundwater levels to which the conservation area is entitled. The center's complaint claims those rights are already being violated by excessive withdrawals. Silver argues that pumping more from Benson's aquifer to serve the development would inevitably affect the conservation area, because the water is hydrologically connected.

Volker disputed that, saying the city's aquifers can support the development without affecting the basin. "We use our own aquifers which are much deeper," Volker said.

Silver said the concern is less about whether the development would run short of water and more about the millions of songbirds that use the San Pedro Basin as a migration stopover. "If we lose the San Pedro, those are millions of Neotropical songbirds that need that every year in their migration," Silver said.

Silver also criticized Democratic Gov. Katie Hobbs, describing the governor as "very environmentally weak" and accusing the administration of avoiding a decision. Silver said the group had met with the governor nearly every month until recently, calling the meetings a "frustrating waste of time." Silver said the group has been in talks with ADWR and Hobbs since the governor's election in 2022 and believed there was agreement to review the basin designation and protect the groundwater. In Silver's account, Hobbs has created only one new Active Management Area, and it covers a different groundwater basin. Hobbs did not immediately respond to a request for comment.

The filing is the fourth lawsuit against the Hobbs administration over the area's water supply. The Villages at Vigneto is not currently under construction. Volker said the developer is waiting on foundational funding to begin and that litigation does not help, since defending a position in court costs money.