An electric engine is hauling cars filled with clay for use in the construction of Roosevelt Dam. The tracks are adjacent to the power canal that was built to divert water from the Salt River and carry it to a penstock near the dam site where it fell 220 feet to power a water turbine. The penstock and turbine were temporarily located in small cave south of and below the dam site. Electricity generated by the turbine provided power for this engine and a host of other tools and appliances at the dam site and the nearby town of Roosevelt, 1905. (Restoration photograph)
In the late 1800s, Phoenicians enjoyed the wonders of Arizona Falls, gathering there to picnic, socialize and dance near the cool water. Located on the Arizona Canal between 56th and 58th Streets, Arizona Falls, built in 1902, was the first hydroelectric plant in Phoenix. Here the Arizona Canal drops 20 feet, and it was this falling water that was harnessed to produce power. The hydroelectric plant was one of four such plants located on canals in the valley. Along with the challenge aridity presented in much of the West, the development of Western power generation was an equally formidable task. In the Salt River Valley, the inaccessibility of traditional power sources, such as timber and coal deposits, caused developers to look for alternatives for energy. The development of federal government reclamation projects provided glimpses of the dividends that water storage could provide in energy production and revenues. The first reclamation projects, including the Salt River Project, used hydroelectric power in dam construction. The energy produced at Roosevelt Dam could not only be used for construction, but also wholesaled to the nearby Globe area mines, sent to the Valley as power for pumping, or transmitted to Phoenix as a municipal energy source. Roosevelt Dam was the catalyst that made the Salt River Project the first multipurpose project under the Reclamation Act.
Constructed by the Salt River Valley Water User's Association between 1923 and 1925, Mormon Flat Dam was the first facility in the Association's privately-funded hydropower expansion program. It was built for the dual purposes of generating hydroelectric power and for storing approximately 57,000 acre-feet of water in its reservoir, Canyon Lake, for agricultural and urban/commercial uses in the Salt River Valley. In a radical departure from the design used by the U. S. Reclamation Service for Roosevelt, C.C. Cragin designed a concrete, thin-arch structure with a height (streambed to crest) of 224 feet. The dam's crest is 380 feet long, with a top width of 8 feet and a maximum base width of 20 feet.In 1917, the USRS turned over the operation and maintenance of the dams, canals, and lateral ditches of the Salt River Project to the Salt River Valley Water Users' Association, although there was hesitation on part of some Association proponents to assume the responsibility. The future of hydropower development and the sales generated from it were important factors in rallying local support for the Association's assumption of project control. Revenues created by hydropower sales could be used to pay off government debt and subsidize the cost of water storage and transmission.
In addition to power from Roosevelt Dam, four hydro plants on valley canals such as the one at Arizona Falls on the Arizona Canal and the recently built hydro plant on the new Crosscut Canal also provided power to valley farms, homes, and businesses. Roosevelt and the four smaller generating plants had a total capacity of 27,000 horse power. By 1920, demand for power was beginning to exceed supply.
As the second dam constructed from 1924 to 1927 by the Salt River Valley Water Users Association, Horse Mesa Dam was to provide inexpensive power to the copper mines of Globe and Miami. Financing from Inspiration Consolidated Copper Co. allowed for construction, and the Company agreed to purchase all the Horse Mesa's power. The dam was designed by C. C. Cragin and Bureau of Reclamation engineers. The result was a concrete thin-arch dam standing 305 feet high from bedrock to the top of the coping and a crest length of 660 feet. Thickness at the base varies from 43 to 57 feet, with the dam being 8 feet thick at the top. The arch's maximum span is 450 feet.Project leadership recognized that a ready and accessible market needed new power sources, and the unused hydropower potential of the Salt could provide the answer. C.C. Cragin, the general superintendent and chief engineer of the Association in the 1920s and a proponent for expanding hydropower, had a bold vision: additional reservoir construction along the Salt. The first of three new dams to be built by the Association, with blessing of the Reclamation Service, was Mormon Flat Dam about 17 miles downstream of Roosevelt. Built between 1923 and 1925, Mormon Flat Dam began the fundamental shift on the project from one designed exclusively for irrigation to one for irrigation and hydropower. Two more dams followed in quick succession, Horse Mesa Dam located between Roosevelt and Mormon Flat (1924 to 1927) and Steward Mountain Dam located between Mormon Flat and Granite Reef Diversion Dam (1928 to 1930).
In the early days of reclamation, power generation was intended primarily for construction and pumping. By the third decade of the 20th century, power was now being supplied to towns, homes, cotton gins, and mines. Project generating capacity was increased to 103,000-horsepower, and gross annual power revenues escalated from around $500,000 annually to nearly $2,500.000. The additional revenue proved important in many ways: it subsidized water delivery costs; it paid portions of cost for expanding the system; and it helped repay the government debt.
Stewart Mountain Dam is a 207-foot-high, reinforced concrete radius, thin-arch dam consisting of a single arch flanked on both sides by gravity buttresses or abutments, with a gravity overflow spillway on the east side. The main arch stretches 480 feet from buttress to buttress and varies in thickness from eight feet at the crest to 33 feet at the deepest foundation. Built between 1928 and 1930, it was the last of the dams built by the Salt River Valley Water Users Association to provide both power and irrigation water to Valley residents.Expansion of the power system increased electricity to both the urban and rural areas of the Salt River Valley. For the valley farmer, the benefits provided by the new development were many. By 1930, 2,000 farms had electricity with approximately 50 new connections per week. Power was used not only for pumping, but for cooking ranges, water heaters, ensilage cutters, milking machines, cream separators, feed grinders, incubators, brooders and a host of other farm appliances. Advertisements for the latest in home electrical appliances were prevalent in local newspapers as retailers championed the ways in which new products such as the vacuum cleaner and the washing machine could lessen manual work and improve the quality of life in the Valley.
Water and power have always had an intricate relationship in the history of the American West. These two elements were the cornerstone for the creation of the Salt River Valley and modern Arizona. Without the development of each of these resources in the early twentieth century, the reality of the post World War II Valley boom would have been impossible.
(Taken and adapted from "Irrigation and Early Hydropower Development in the Salt River Valley," by Stephen Sloan. In RECLAMATION Managing Water in the West pg. 375-384. U.S. Department of the Interior, Bureau of Reclamation. Government Printing Office, Washington D.C. 2008)
