Historic American Engineering Record: Granite Reef Diversion Dam, Salt River, Mesa Vicinity, Maricopa County, Arizona

Historic American Engineering Record (HAER) No. AZ-51 presents a written historical summary and relevant historical documentation about the construction and use of Granite Reef Diversion Dam, which diverts Salt River water released from upstream storage dams into canal irrigation systems for agricultural, industrial, and municipal uses. The report contains a narrative description, photographs, drawings, and maps.

The Granite Reef Diversion Dam is the principal structural mechanism by which the Salt River Project diverts stored waters into canals for delivery and use throughout the Salt River Valley. The dam was built in the northeastern portion of Mesa, Arizona near the Usery Mountains, where the Salt River flows into the Salt River Valley below the confluence of the Verde River. It controls the flow of river water into the Arizona Canal (see HAER No. AZ-19 at https://core.tdar.org/document/393523) on the north side of the Salt River, and into the South Canal (see HAER No. AZ-52 at https://core.tdar.org/document/393535) on the south side of the river. The Arizona Canal provides irrigation water to the cities of Scottsdale, Phoenix, Glendale, and Peoria, and historically delivered water for the generation of hydroelectric power (which provided the first electricity to Phoenix). The South Canal carries irrigation water to the cities of Mesa, Gilbert, Chandler, and Tempe; it also delivered water to a series of hydropower plants (which provided electricity to Salt River Project customers and cities on the south side of the Salt River).

Historically, Granite Reef Diversion Dam was constructed at approximately the same time as the Salt River Project's Theodore Roosevelt Dam as a response to an urgent request to support water storage and delivery along the Salt River below the mouth of the Verde River. After the formation of the US Reclamation Service in 1902, officials recognized that the implementation of a successful irrigation project in the Valley would require a permanent dam to channel stored and released water into canals on the north and south side of the Salt River. The simultaneous construction of the Granite Reef Diversion Dam and the Roosevelt Dam allowed engineers working on the projects to develop designs and construction strategies that defined U. S. Reclamation Service practices in the earliest irrigation projects funded under the Newlands Act.