Casa Grande, AZ

Water talk: In light of drought issues, here’s the history and future of the Coolidge Dam

Nicole Underwood

By Nicole Underwood / NewsBreak Pinal County, AZ

(CASA GRANDE, AZ) - The Coolidge Dam has long been one of the many historic sites in our state that has affected the area’s growth and legacy of irrigation. Ahead of its time, the dam is a site to behold. But, current water shortages in Arizona add to the growing concerns on the sustainability of existing water systems for future populations.

Famously named after the 30th President of the United States, Mr. Calvin Coolidge, the Coolidge Dam was built between 1924 and 1928, and was dedicated by President Coolidge on March 4, 1930. The dam itself regulates the distribution of part of Pinal County’s irrigation water and is governed by the U.S. Bureau of Indian Affairs (BIA), the entity which currently oversees the dam’s operations since the 1920s.

Part of the San Carlos Irrigation Project, the Coolidge Dam is approximately 250 feet feet high, impounding the Gila River for 23 miles when full. The project was designed to irrigate a massive span of 100,000 acres. Unlike other dams in the state, the history of this dam is directly connected to the story of nearby Native communities, where conflicts over water allocation and use ultimately concluded with the restoration of water access back to Native peoples.

Prior to the dam being built, Indigenous communities relied on the flow of the Gila River to support their agriculture. The arrival of anglo settlers, however, strained these valuable resources and could not sustain the needs of both communities. As a result, conflict grew and water shortages began to increase for the existing tribal communities for nearly six decades, into the early 1900s. The Coolidge Dam was finally authorized to resolve conflicts created by the settlers.

The water access supported the existing Salt River Pima-Maricopa Indian Communities of the two pre-American Sovereign Indian tribes: the Pima (​​known as Akimel O'odham, the river people) tribe and the Maricopa tribe, both descendants of the Hohokam peoples, who farmed the Salt River Valley and originated our current canal irrigation system (Inter Tribal Council of Arizona.) Today, the San Carlos Apache Indian Reservation spans across three counties — Gila, Graham, and Pinal — encompassing 1.8 million acres.

The design of the dam is also historically significant. According to the Library of Congress, the Coolidge Dam was built by the U.S. Indian Service and was perhaps the first and possibly only dam to use a multiple dome design. In addition to the three reinforced multiple concrete domes, its design includes massive buttresses on 100-foot centers, with the buttresses supporting three inclined egg-shaped domes. During this time, its design was challenged on the grounds of patent infringement. After seven rejections, George Sydney Binckley received a patent in 1913, specifically regarding the horizontal curvature of the cone design principles of the construction. The project itself had a strong art deco style, making a bold statement of modern relishments and details, noticed in the design choice of its tiles, lamps and the iconic concrete eagle.
The early stages of the dam being builtThe Digital Archaeological Record

While the history of the dam was a marvel of modern engineering at its time, it has also gone through many phases of upgrades and construction in the past century. Some of these many changes include the dam originally having electricity sourced from a hydroelectric plant (no longer operable due to flood damage in the 1980s.) It has also experienced additional flood damage due to snow and heavy rainfall in the early 1990s, with structural modifications to the tune of $46.5 million in 1995 (nearly $75 million dollars in today’s economy.)

These days, according to a recent article published in YaleEnvironment360, the nearby reservoir is usually dry and plugs the flow of water to the Gila River. Although the nearby lake can hold nearly 20,000 acres of water, it typically holds only 50 acres. Since the reservoir is built to hold 19,500 acres of water, its lack of water creates mounting concern around the sustainability of the area and the needs of wildlife dependent on the water supply. Allyson Siwik, executive director of the Gila Conservation Coalition, was quoted as saying in YaleEnviroment’s research stating: “We’re not going to have rivers with native species in the Southwest unless we can protect and restore these systems.”

Recreation does exist nearby, where residents and visitors can explore the Gila River, just south of the Coolidge Dam and the San Carlos Lake, where the San Carlos Apache Tribe Recreation and Wildlife Department keeps many fish species stocked during fishing seasons.

Overall, however, there is a serious groundwater shortage, due to Arizona’s rapidly growing businesses and residential areas. To meet demands, water well drilling companies are stressing the San Carlos Reservoir, formed by the Coolidge Dam, now almost 100 years old. According to, the state of Arizona has “promised $40 million to drill or rehabilitate groundwater wells to make up a portion of the loss” of water.

It is a high alert moment for the area, to allow our growing desert population to have access to needed water and existing wildlife to exist for another 100 or more years.

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