Center for Biological Diversity

For Immediate Release, October 18, 2023


Robin Silver, (602) 799-3275,

Arizona Water Authority Must Reduce Groundwater Use to Protect San Pedro River, Conservation Area

TUCSON, Ariz.— The Center for Biological Diversity called on the Arizona Department of Water Resources today to reduce groundwater use in the Upper San Pedro River Basin in order to accommodate newly established federal water rights for the San Pedro National Riparian Conservation Area.

“For decades the Arizona Department of Water Resources has approved the use of more groundwater than it knew would be available,” said Robin Silver of the Center for Biological Diversity. “By prioritizing the interests of developers, the agency shortchanged the San Pedro River and burdened residents with water use reductions that will inevitably come to pass. The state of Arizona owes each of these residents an apology.”

The reductions would apply to Sierra Vista-area groundwater wells and certificates assuring a 100-year water supply that the department has approved for developments since Nov. 18, 1988. That’s when Congress created the 57,000-acre San Pedro National Riparian Conservation Area and required that federal water rights be reserved to protect the San Pedro River and its globally important aquatic and riparian biodiversity.

The letter also calls on the department to apologize to more than 22,000 Sierra Vista residents for failing to warn them they would inevitably face water-use reductions.

Decades of legal disputes left the exact amount of water rights unclear until August 2023, when an Arizona judge quantified those rights. The ruling by Maricopa County Superior Court Judge Mark H. Brain mandated that groundwater levels be maintained at nine monitoring wells within the conservation area. Two of those wells have already dropped below their required elevation, in violation of the ruling.

The area’s aquifer is being severely depleted. Studies show that without dramatic changes in local water use, the San Pedro River will disappear over the next century.

The Department of Water Resources approved 66 100-year water adequacy certificates for subdivisions in the Sierra Vista area since Congress established the conservation area in 1988, despite the likelihood that pumping too much groundwater from the aquifer would inevitably force local groundwater use reductions once federal water rights were quantified.

During those 35 years the agency also approved more than 2,400 local wells without warning owners that their groundwater pumping would also inevitably need to be reduced.

The amount of water reduction that will be necessary will depend on the well’s location and how much well water is being prevented from reaching the San Pedro River.

The San Pedro River, the Southwest's last free-flowing desert river, is a biodiversity hotspot and international birding mecca. Endangered species that depend on the ecosystem’s lush habitat include southwestern willow flycatchers, Huachuca water umbel, desert pupfish, loach minnows, spikedace, yellow-billed cuckoos, Arizona eryngo and northern Mexican garter snakes.

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.7 million members and online activists dedicated to the protection of endangered species and wild places.

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