Glen Canyon Dam

Glen Canyon Dam was built on the Colorado River in Arizona by the U.S. Bureau of Reclamation in the late '50's and early '60's (see map).
 

Read about dimensions and other information from the Bureau of Reclamation. Read more about Glen Canyon from the Glen Canyon Natural History Association.

How Water is Released from the Dam

Glen Canyon Dam stores and releases water from Lake Powell, which holds about 24.3 million acre-feet. Water can be released from the dam through the

• power plant (up to 33,200 cubic feet per second, or cfs),
• river outlet works (up to 15,000 cfs), and
• spillways (208,000 cfs).

In order to maximize energy and revenues, releases have generally not exceeded the 33,200-cfs maximum that can flow through the power plant.

Since 1991 (when Interim Operating Criteria were adopted to protect downstream resources pending completion of environmental studies), releases through the power plant have been held at or below 20,000 cfs.

These numbers are exceeded when heavy runoff necessitates releases of extra water, sometimes called floodflows.

Some Spectacular Photographs

Photographs of water being released from Glen Canyon Dam's river outlet works and spillways can be seen at these sites:

• USGS's fact sheet about the controlled flood held during late March and early April of 1996
• USGS Water Resources of Arizona

For more detail...

Read the following passages, taken from "Operation of Glen Canyon Dam--Colorado River Storage Project, Arizona," a Final Environmental Impact Statement published March 1995 by the U.S. Department of the Interior Bureau of Reclamation:

• Powerplant Releases
  "Glen Canyon Powerplant has eight generators with a maximum combined capacity of 1,356,000 kilowatts. The maximum combined discharge capacity of the eight turbines is approximately 33,200 cfs when Lake Powell is full; however, releases during fluctuations are limited to 31,500 cfs. When the reservoir is less than full, maximum possible discharge is reduced. Discharge through the turbines is the preferred method of release because electricity and its associated revenue are produced."
• River Outlet Works Releases
  "The capacity of the river outlet works is 15,000 cfs. The river outlet works are used when there is a need to release more water than can be passed through the powerplant. The outlet works are almost always used in conjunction with powerplant releases, producing combined releases up to 48,200 cfs."
• Spillway Releases
  "Releases through the spillways bypass both the powerplant and the river outlet works. The combined capacity of the right and left spillways is approximately 208,000 cfs. Spillway releases are made only when necessary to avoid overtopping the dam or to lower the level of Lake Powell. Spillway releases are avoided whenever possible, not only to prevent powerplant bypasses, but also because the service life of the spillways is shorter than that of the other release structures."

See suggestions for further reading for the sources of information on this page.