Glen Canyon Dam is a concrete arch-gravity dam on the Colorado River in northern Arizona, near the town of Page (about 15 miles upstream from Lees Ferry and roughly 8 miles south of the Utah-Arizona border). It stands 710 feet high above bedrock (583 feet above the original riverbed), with a crest length of 1,560 feet. It forms Lake Powell, one of the largest reservoirs in the United States (capacity roughly 24–27 million acre-feet at full pool of about 3,700 feet elevation). The dam is a key unit of the Colorado River Storage Project (CRSP).
Origins and Why It Was Built
Interest in a dam in Glen Canyon dates to the early 20th century. U.S. Geological Survey hydrologist E.C. LaRue proposed a site as early as 1916–1921, initially more for flood control than long-term storage. Studies continued in the 1920s, but priority went to Hoover Dam (completed 1936) farther downstream.
The decisive driver was the 1922 Colorado River Compact, which apportioned the river’s waters roughly equally between the Upper Basin (Colorado, Utah, Wyoming, New Mexico) and Lower Basin (California, Arizona, Nevada), with measurement at Lees Ferry. The Upper Basin states needed large upstream storage to develop their share for irrigation, municipal, and industrial use without risking failure to meet delivery obligations to the Lower Basin during droughts. Without storage, Upper Basin development would be constrained because water would simply flow downstream to Hoover Dam/Lake Mead.
By the 1940s–1950s, rapid population and economic growth in the West intensified the need. The Bureau of Reclamation advanced the Colorado River Storage Project, a system of dams and reservoirs to regulate flow, store water for beneficial use, provide flood control, reclaim arid lands, and generate hydropower. Hydropower revenues were essential: they would repay construction costs and help finance other Upper Basin projects. Glen Canyon Dam was the centerpiece—the largest storage feature—providing the bulk of the system’s capacity to hold water during wet years for release in dry ones while guaranteeing Lower Basin deliveries.
Congress authorized the CRSP (including Glen Canyon Dam) on April 11, 1956. The project was never primarily a local irrigation scheme; its core purposes were basin-wide storage and power generation.
Site Selection
Engineers and geologists evaluated multiple sites in lower Glen Canyon from the 1920s through the late 1940s (intensive work 1946–1948). Key criteria included:
- A large reservoir basin capable of holding an immense volume of water.
- Strong, stable canyon walls and bedrock foundation able to support a high dam.
- Proximity to quality aggregate (rock and sand) for concrete—available nearby on Wahweap Creek.
- Economic feasibility and constructability.
An early favored site was about 4 miles upstream from Lees Ferry (which could have held more water), but the chosen site—roughly 15–16.5 miles upstream—was selected for superior foundation rock (Navajo Sandstone cliffs rising nearly vertically) and easier access to gravel deposits. The remote location presented challenges: no nearby rail, and a 200-mile drive to cross from one rim to the other. This necessitated new access roads and the Glen Canyon Bridge (a 1,271-foot steel-arch bridge completed 1959, then among the world’s highest).
The final site sits in a narrow gorge of sandstone and shale, ideal for an arch-gravity design that transfers load into the abutments.
Construction and Filling
Construction began almost immediately after authorization. On October 15, 1956, President Dwight D. Eisenhower triggered the first blast by remote control from the White House. The prime contract went to Merritt-Chapman & Scott in April 1957 (winning bid about $108 million). Work included diversion tunnels to reroute the river, deep excavation to bedrock (about 137 feet), and shaping the canyon walls.
Concrete placement started in June 1960 (first formal pour around June 16–17) and continued around the clock. The dam contains roughly 4.9 million cubic yards of concrete in the structure itself (over 5.3 million including the powerplant)—enough for a multi-lane highway from Phoenix to Chicago. It was built in large blocks and topped out on September 13, 1963, at 710 feet. About 18 workers died during construction. The remote site required creating the town of Page, Arizona, for the workforce.
The river was diverted; the last diversion tunnel was closed on March 13, 1963, and Lake Powell began filling. First power generation occurred in September 1964. First Lady Lady Bird Johnson dedicated the dam on September 22, 1966. Filling to capacity took until June 22, 1980 (about 17 years). Glen Canyon National Recreation Area was established in 1972.
Controversy
The dam was highly controversial. Early CRSP plans included dams at Echo Park and Split Mountain in Dinosaur National Monument. A major campaign by the Sierra Club (led by David Brower), Wilderness Society, and others successfully blocked those, framing them as a threat to national parks. In the political compromise, Glen Canyon Dam proceeded (and was made larger to compensate for lost storage). Many environmentalists later regretted the trade-off, viewing the flooding of Glen Canyon’s scenic, archaeological, and ecological treasures as a major loss—“the place no one knew.” Archaeological salvage projects documented sites before inundation. The dam also fundamentally altered the Colorado River’s flow, temperature, and sediment regime through the Grand Canyon, leading later to the 1992 Grand Canyon Protection Act and adaptive management programs.
Operations and Later History
Lake Powell stores water for Upper Basin use and regulated releases to the Lower Basin. The powerplant (eight generators, original rating ~1,320 MW) has produced billions of kilowatt-hours annually in good years, with revenues supporting CRSP operations, environmental programs, and repayment. Notable events include 1983 floods that damaged the spillways (requiring major repairs) and ongoing adaptive management for downstream ecosystems and recreation.
Current Struggles with Low Water
Prolonged drought, aridification linked to climate change (warmer temperatures, reduced snowpack efficiency, higher evaporation and soil absorption), and overallocation have sharply reduced inflows. Lake Powell has declined dramatically from full-pool levels last seen in the early 1980s.
As of late August 2026, the lake has set new record lows, hovering around 3,518 feet elevation—roughly 22–23% of live capacity and about 180+ feet below full pool. It sits only tens of feet above minimum power pool (3,490 feet), the level at which the penstocks lose adequate submergence and the turbines can no longer generate hydropower reliably. Dead pool (the point at which water can no longer be released by gravity through the outlets) is at approximately 3,370 feet.
Projections in 2026 have warned of potential drops toward or below minimum power pool in 2027 under continued dry conditions, with reduced generation already occurring (output has fallen substantially from historical peaks). Managers have implemented emergency measures: reduced releases from Glen Canyon, increased upstream releases (e.g., from Flaming Gorge), and operational adjustments under drought contingency plans and interim guidelines to protect elevations near or above ~3,500–3,525 feet. Below minimum power pool, releases shift solely to the smaller river outlet works (not designed for sustained primary use), raising concerns about capacity, reliability, sediment, and downstream water delivery. Recreation (marinas, boat ramps) has been heavily impacted, with many facilities unusable.
The situation threatens hydropower for roughly millions of customers in the West, water supplies for agriculture and cities in the Lower Basin, and the broader Colorado River system’s stability. It has prompted study of potential dam modifications for lower-level operations and underscores the original assumptions about hydrology that no longer fully hold. Lake Powell and Lake Mead together hold far less water than in earlier decades, highlighting the ongoing Colorado River crisis.
In summary, Glen Canyon Dam was engineered as a linchpin of 20th-century Western water development—securing Upper Basin rights, enabling growth, and generating power—chosen for its geology and storage potential after careful evaluation. Decades later, it faces the limits of that vision under a drier climate and strained allocation system.