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| Horse Mesa Dam | |
|---|---|
| Name | Horse Mesa Dam |
| Location | Tonto National Forest, Maricopa County, Arizona |
| Country | United States |
| Status | Operational |
| Construction began | 1924 |
| Opening | 1927 |
| Owner | Salt River Project |
| Dam type | Concrete arch |
| Height | 305 ft |
| Length | 660 ft |
| Reservoir | Canyon Lake |
| Plant capacity | 36 MW |
| Plant operator | Salt River Project |
Horse Mesa Dam Horse Mesa Dam is a concrete arch dam on the Salt River in the Superstition Mountains, located within Tonto National Forest northeast of Phoenix. Constructed in the 1920s by the Arizona Power Company and now owned by Salt River Project, the dam forms Canyon Lake and provides hydroelectric power, flood control, and irrigation service for the Salt River Project system. The facility is part of a series of reservoirs including Roosevelt Lake, Apache Lake, and Saguaro Lake that supply water and power to the Phoenix metropolitan area and surrounding Maricopa County communities.
Horse Mesa Dam sits on the Salt River within the Tonto National Forest near the Superstition Wilderness and is accessible via State Route 88 and the Apache Trail. It impounds Canyon Lake and functions alongside Roosevelt Dam, Horse Mesa Dam's upstream and downstream counterparts such as Mormon Flat Dam in the Salt River Project multipurpose system. The structure contributes to regional water supply and energy infrastructure serving Phoenix, Mesa, Tempe, and other Maricopa County municipalities.
Construction began in 1924 under the direction of the Arizona Power Company and reached completion in 1927 amid the Roaring Twenties period of rapid development in Arizona transitioning to statehood-era growth. The project paralleled contemporaneous works like Roosevelt Dam and drew on engineering practices developed during projects such as Hoover Dam and Glen Canyon Dam planning, while responding to regional needs identified by entities including the Salt River Project. Financing and operations shifted to the Salt River Project after integration of local electric and irrigation interests, reflecting utility consolidation trends seen across the United States in the early 20th century.
The dam is a concrete multiple-arch/arch-gravity structure rising approximately 305 feet with a crest length near 660 feet, designed to withstand hydrologic events on the Salt River and seismic considerations relevant to the Basin and Range Province. Reservoir capacity at Canyon Lake supports seasonal storage managed in coordination with Roosevelt Dam and Mormon Flat Dam; outlet works include gated spillways and sluice tunnels similar in concept to elements at Glen Canyon Dam and Hoover Dam. The power plant houses turbines and generators sized to produce about 36 megawatts, with transmission tied into the Salt River Project grid serving Arizona Public Service Company service areas and municipal utilities in the Phoenix metropolitan area.
Operational control is exercised by Salt River Project personnel who coordinate releases with Roosevelt Dam operations, regional irrigation districts and municipal water suppliers including Phoenix water managers. Water management balances hydroelectric generation, flood control during monsoon and snowmelt seasons, and seasonal irrigation demands for agricultural users in the Salt River Valley and urban water deliveries to Maricopa County. Coordination involves agencies and stakeholders such as the U.S. Bureau of Reclamation-modeled practices, state regulators in the Arizona Department of Water Resources, and regional planning bodies addressing growth in Maricopa County and the Phoenix metropolitan area.
The powerhouse contains Francis-style turbines driving generators to provide peaking and base-load services to the Salt River Project system and municipal utilities including Phoenix and Mesa. Generated electricity historically supported mining, agricultural, and urban expansion in Arizona and remains integrated with regional transmission operated by entities such as the Western Electricity Coordinating Council. Maintenance and upgrades over decades have adapted plant controls and equipment in line with standards promoted by organizations like the Electric Power Research Institute.
By creating Canyon Lake the dam altered riparian and desert ecosystems along the Salt River corridor affecting species native to the Sonoran Desert and habitat in the Tonto National Forest. Recreational opportunities at the reservoir support boating, fishing, camping, and hiking, linking to nearby attractions including the Superstition Mountains, Apache Trail heritage route, and regional tourism focused on the Phoenix metropolitan area. Environmental oversight involves cooperation with the Arizona Game and Fish Department, U.S. Forest Service, and local conservation groups addressing water quality, fish stocking, and habitat restoration projects influenced by federal and state resource policies.
Throughout its service life the facility has undergone periodic inspections, rehabilitation, and maintenance consistent with practices by owners like the Salt River Project and standards referenced by the American Society of Civil Engineers. Notable operational incidents have included transient outages, sedimentation management challenges common to reservoirs in the Southwestern United States, and intermittent maintenance shutdowns coordinated with regional water delivery schedules and emergency response protocols involving agencies such as the Arizona Department of Emergency and Military Affairs. Routine dam safety monitoring, instrumentation upgrades, and periodic concrete assessments ensure continued compliance with state dam safety regulations and utility reliability expectations.
Category:Dams in Arizona Category:Buildings and structures in Maricopa County, Arizona