The Arizona Supreme Court ruled that the Arizona Department of Water Resources (ADWR) does not have to consider unquantified federal reserved water rights when determining whether a developer has an adequate water supply under state law.

The case – Silver v. Pueblo Del Sol Water Company – involved the ADWR's approval of an application by Pueblo Del Sol Water Company to supply water to a proposed 7,000 unit development in Cochise County, approximately 5 miles from the San Pedro River. Arizona law requires developers to receive an adequate water supply designation from the ADWR in certain circumstances.

The ADWR's 2013 approval prompted a lawsuit by the U.S. Department of Interior, Bureau of Land Management, and environmentalists Robin Silver and Patricia Gerrodette, based on the 1988 designation of the San Pedro Riparian National Conservation Area (SPRNCA) by Congress that reserved water rights to fulfill the unspecified purposes of SPRNCA. A Maricopa County Superior Court ruled that the ADWR should have considered the federal government's reserved water rights; that ruling was overturned by an appeals court in 2016 and both sides appealed to the Arizona Supreme Court.

In its August 9, decision, the Arizona Supreme Court vacated the Superior Court's decision and affirmed ADWR's approval of Pueblo Del Sol Water Company's application. The Court held that under the state law as currently written, the ADWR is not required to consider unquantified federal reserved water rights in its analysis.

The Water Systems Council (WSC) filed an amicus brief supporting the position of the ADWR that such a requirement would entail speculative analyses not within the scope of ADWR's duties.

“This decision reinforces the principle that federal reserved water rights must be quantified prior to impacting state water rights,” said Margaret Martens, WSC Executive Director. “Given the huge number of unquantified federal reserved water rights, this principle provides important protection to private water wells and supports the notion that the right to a private water well is an important property right.”

The Water Systems Council is the only national, nonprofit organization solely focused on household wells and small water well systems. WSC is committed to ensuring that Americans who get their water from household private wells have safe, reliable drinking water and to protecting our nation's groundwater resources.

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