Robin Silver, M.d.; United States of America, U.S. Department of the Interior, Bureau of Land Management; And…

Summary

The Court held that the Arizona Department of Water Resources was not required to consider unquantified federal reserved water rights when determining whether a proposed development had an adequate water supply. The agency's physical-availability regulation addressed existing uses affecting the groundwater supply, not the effect of a proposed use on other water rights, and its legal-availability regulation was consistent with the statute because the legislature adopted the agency's preexisting framework. The Court vacated the lower courts' decisions and affirmed approval of the developer's application.