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Lake Powell

From Academic Kids

Missing image
Lakepowell2.jpg
Lake Powell above Warm Creek Bay
Facts
Start of storage March 13, 1963
Completion of initial filling June 22, 1980
Elevation 1,127 (3,700 ft)
Volume 26.5 km³ (21,505,000 acre.feet)
Surface area 1627 km² (102.88 mile²)
Length 299 km (186 miles)
Width 40 km (25 miles)
Shoreline 3,057 km (1,900 miles)
Maximum depth 170 m (560 ft)
Mean depth 40 m (132 ft)

Lake Powell is a man-made reservoir on the Colorado River, straddling the border between Utah and Arizona. It was created by the flooding of Glen Canyon by the controversial Glen Canyon Dam, which also led to the creation of Glen Canyon National Recreation Area, a popular summer destination. The reservoir is named for explorer John Wesley Powell, a one-armed American Civil War veteran who explored the river via two wooden boats in 1869. In 1972, Glen Canyon National Recreation Area was established. It is public land managed by the National Park Service, and available to the public for recreational purposes.

Contents

History

Construction on Glen Canyon Dam began with demolition blast keyed by a button push by President Dwight D. Eisenhower at his desk in the Oval Office on 15 October 1956. The filling of the reservoir began in 1963. It reached "Full Pool" (full capacity) in 1980.

More recently, however, several years of drought have reduced it to less than half its capacity. In 2004, Glen Canyon National Recreation Area had to close four of its six boat launching facilities, as the receding water left them high and dry. Some of the closed facilities remain partially available on a "launch at your own risk" basis. Houseboats that are not frequently moved have been stranded by the falling water level.

Geology

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Lake_powell_utah.jpg
Lake Powell from space

Glen Canyon was carved by differential erosion from the Colorado River over an estimated 5 million years. The Colorado Plateau, through which the canyon cuts, arose some 11 million years ago. Within that plateau lie layers of rock from over 300 million years ago to the relatively recent volcanic activity. Pennsylvanian and Permian formations can be seen in Cataract Canyon and San Juan Canyon. Moenkopi Formations from 230 million years ago (Triassic Period), along with Chinle Formations are found at Lees Ferry and the Rincon. Both are the result of the ancient inland sea that covered the area. Once the sea drained, windblown sand invaded the area, creating what is known as Wingate Sandstone. The more recent (Jurassic Period) formations include Kayenta Sandstone, which produces the trademark blue-black "desert varnish" that streaks down many walls of the canyons. Above this is Navajo Sandstone, the result of more compressed sand dunes. Many of the arches, including Rainbow Bridge, lie at this transition point. This period also includes light yellow Entrada Formations, and the dark brown, almost purple Carmel Formation. These latter two can be seen on the tops of mesas around Wahweap, and the crown of Castle Rock and Tower Butte. Above these layers lie the Straight Cliffs Sandstone and conglomerate shales that make up the Kaiparowits Plateau and San Rafael Swell to the north of the lake.

The confluences of the Escalante River and San Juan River lie within Lake Powell. The slower flow of the San Juan has produced incredible Goose Necks, where 5 miles of river are contained within 1 mile on a straight line.

Features

Rainbow Bridge
Enlarge
Rainbow Bridge

The lake's main body stretches up Glen Canyon, but has also filled many (over 50) side canyons. The lake also stretches up the Escalante River and San Juan River where they merge into the main Colorado River. This provides access to many natural geographic points of interest as well as some remnants of the Anasazi culture.

  • Rainbow Bridge National Monument
  • Defiance House ruin
  • Cathedral in the Desert (completely flooded by the filling of the reservoir, but re-exposed in the spring of 2005 as the water level dropped) (photos (http://cathedralinthedesert.org/pages/1/index.htm))
  • San Juan goosenecks
  • Kaiparowits Plateau
  • Hole-in-the-Rock crossing
  • the Rincon
  • Three-Roof Ruin

Development

Because most of the lake is surrounded by steep sandstone walls, access to the lake is limited to developed marinas:

  1. Lees Ferry Subdistrict
  2. Page/Wahweap Marina
  3. Antelope Point Marina
  4. Dangling Rope Marina*
  5. Rainbow Bridge National Monument*
  6. Escalante Subdistrict*
  7. Halls Crossing Marina
  8. Bullfrog Marina
  9. Hite Marina (Currently closed due to low water levels)
*Dangling Rope, Rainbow Bridge, and Escalante are accessible only by boat.

Glen Canyon National Recreation Area draws more than two million visitors annually. Recreational activities include boating, fishing, waterskiing, jet-skiing, and hiking. Prepared campgrounds can be found at each marina, but many visitors choose to rent a houseboat or bring their own camping equipment, find a secluded spot somewhere in the canyons, and make their own camp (there are no restrictions on where visitors can stay). Anyone who camps further than a quarter of a mile from a marina, however, must bring a porta-potty. The burying of human waste in Glen Canyon National Recreation Area is prohibited. Pet waste must also be packed out.

Controversy

When several dams were proposed for the Colorado River in the 1950s, the Sierra Club opposed the plan, but a compromise was reached when the plan was reduced to the Glen Canyon Dam. In hindsight, environmentalists greatly regret this compromise, and continue to call for the decommissioning of the dam and the draining of Lake Powell. Others, including the local governments in the area, strongly oppose this idea. No state or national office has given any consideration or resources toward planning a decommissioning, partly because, in every year since 1996, the appropriations bill for the Department of the Interior has prohibited any use of federal funds to study decommissioning.

Water storage

Though Lake Powell was created as a "water bank" for the desert southwest, which is the fastest growing area in the United States, the only city using water directly from it is Page, Arizona, a town of 8000. Lake Powell is functioning exactly as it was intended to, even in the 6th year of drought in the soutwest. Lake Powell ensures that Lake Mead downstream will exist, as most of the water in the Colorado River System gets delivered to the lower basin states, California, Nevada, and Arizona. Under the Colorado River Compact of 1922, this water supports 80% of the produce grown in the U.S. Opponents counter that millions of acre-feet are lost to evaporation because of the dam, and that Lake Mead (created by the Hoover Dam further down the Colorado river) can better manage the water resources of the river. However, with Lake Mead being a lake at lower elevation with more exposed surface and hotter temperatures, Lake Mead's evaporation rate is around 6% to 7% each year. In contrast, Lake Powell's evaporation rate is only around 2%, since it is a higher elevation lake, and the deep canyons keep the water cooler.

Power generation

The power plant at Glen Canyon Dam can generate up to 1,300 megawatts of hydroelectric power. This represents approximately three percent of the power supply in the six states that it serves. Though Lake Powell also serves as a source of water for the coal fired Navajo Generating Station, critics contend that the Colorado River could still supply the necessary water without the reservoir if the intakes were moved upstream several hundred meters. The total amount of power generated by these two facilities provides electrical power for 5,000,000 people in the western United States.

As at Hoover Dam pylons of special designs are required to run the powerlines away from the transformer station of the dam.

Other economic effects

Proponents of Lake Powell's current status point to the economic impact of more than two million visitors each year who come for the recreational opportunities. Many sites on the reservoir are easily accessible by boat. Other tourists are attracted by a trout fishery below Glen Canyon Dam. Supporters of decommissioning envision a revised (though smaller) tourist economy based on the restoration of Glen Canyon, supplemented by a major restoration research facility at the site.

Impact on the Grand Canyon

Before the construction of the dam, the Colorado River, as it flowed through the Grand Canyon, was comparatively warm and carried large amounts of sediment. Floods, especially in the spring, deposited the sediment on beaches. The effects of the dam have been the removal of about 95% of the sediment, a drop in the temperature of the water, and an end to the natural flooding. (In 1996 the Bureau of Reclamation released an artificial spring flood in an attempt to counteract the dam's effect on the Grand Canyon.)

Supporters of maintaining the dam argue that the Grand Canyon now has lush green vegetation along the river corridor, supporting many species of birds and insects, including the endangered California Condor and Southwest Willow Flycatcher. They contend that, before the dam, virtually no vegetation could exist in the canyon, as flood waters continually wiped it out. Environmentalists counter that the changes in the river's flow have altered the ecosystem of the Grand Canyon, endangering many native plant and wildlife species.

Under the federal Grand Canyon Protection Act of 1992, damages to the ecosystem of the Grand Canyon must be mitigated. The federal government has spent more than $200 million toward compliance with this statute. Nevertheless, some species, such as the Colorado pikeminnow and the bonytail chub (both of which are officially listed as endangered) and the Southwest river otter, have been eliminated from the Grand Canyon. Others, such as the humpback chub (also endangered), are in severe decline. In 2004 the Grand Canyon Trust, represented by Earthjustice, filed suit against the federal government over its failure to protect the humpback chub from the effects of the Glen Canyon Dam and other Colorado River dams.

External links

Colorado River system
Dams and aqueducts (see US Bureau of Reclamation)
Shadow Mountain Dam | Granby Dam | Glen Canyon Dam | Hoover Dam | Davis Dam | Parker Dam | Palo Verde Diversion Dam | Imperial Dam | Laguna Dam | Morelos Dam | Colorado River Aqueduct | San Diego Aqueduct | Central Arizona Project Aqueduct | All-American Canal | Coachella Canal | Redwall Dam
Natural features
Colorado River | Rocky Mountains | Colorado River Basin | Grand Lake | Sonoran desert | Mojave desert | Imperial Valley | Colorado Plateau | Grand Canyon | Glen Canyon | Marble Canyon | Paria Canyon | Gulf of California/Sea of Cortez | Salton Sea
Tributaries
Dirty Devil River | Dolores River | Escalante River | Gila River | Green River | Gunnison River | Kanab River | Little Colorado River | Paria River | San Juan River | Virgin River
Major reservoirs
Fontenelle Reservoir | Flaming Gorge Reservoir | Taylor Park Reservoir | | Navajo Reservoir | Lake Powell | Lake Mead | Lake Havasu
Dependent states
Arizona | California | Colorado | Nevada | New Mexico | Utah (See: Colorado River Compact)
Designated areas
Glen Canyon National Recreation Area | Lake Mead National Recreation Area

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