Lake Powell


Lake Powell is a reservoir on the Colorado River in Utah and Arizona, United States. It is a major vacation destination visited by approximately two million people every year. It holds of water when full, second in the United States to only the downstream reservoir of Lake Mead – though Lake Mead has fallen below Lake Powell in size several times during the 21st century in terms of volume of water, depth and surface area.
Lake Powell was created by the flooding of Glen Canyon by the Glen Canyon Dam, which also led to the 1972 creation of Glen Canyon National Recreation Area, a popular summer destination of public land managed by the National Park Service. The reservoir is named for John Wesley Powell, a Civil War veteran who explored the river via three wooden boats in 1869. It lies primarily in southern Utah, with a small portion in northern Arizona.
Lake Powell is a water storage facility for the Upper Basin states of the Colorado River Compact. The Compact specifies that the Upper Basin states are to provide a minimum annual flow of to the Lower Basin states.
According to US Geological Survey and the Bureau of Reclamation report, in addition to water loss, Lake Powell faced an average annual loss in storage capacity of about 33,270 acre-feet, or 11 billion gallons, per year between 1963 and 2018 because of sediments flowing in from the Colorado and San Juan rivers. Those settle at the bottom of the reservoir and decrease the total amount of water the reservoir can hold. Environmentalists have pushed to drain Lake Powell and restore Glen Canyon to its natural, free-flowing state.

History

Planning

In the 1940s and early 1950s, the United States Bureau of Reclamation planned to construct a series of Colorado River dams in the rugged Colorado Plateau province of Colorado, Utah, and Arizona. Glen Canyon Dam was born of a controversial damsite the Bureau selected in Echo Park, in what became Dinosaur National Monument in Colorado. A small but politically effective group of objectors, led by David Brower of the Sierra Club, succeeded in defeating the Bureau's bid, citing Echo Park's natural and scenic qualities as too valuable to submerge.
Glen Canyon Dam was built to solve the downstream delivery obligations of the Upper Basin states. Lake Powell is an "aquatic bank" built to fulfill the terms of the "Compact Calls" of Lower Basin.

Construction

Construction on Glen Canyon Dam began with a demolition blast keyed by the push of a button by President Dwight D. Eisenhower at his desk in the Oval Office on October 1, 1956, which started clearing tunnels for water diversion. On February 11, 1959, water flowed through the tunnels so dam construction could begin. Later that year, the bridge was completed, allowing trucks to deliver equipment and materials for the dam and also for the new town of Page, Arizona.
Concrete placement started around the clock on June 17, 1960. The last bucket of over 5 million cubic yards was poured on September 13, 1963. The dam is 710 feet high and the surface elevation of the water at full-pool is approximately 3700 feet. Construction cost $155 million, and 18 lives were lost. On September 22, 1966, Glen Canyon Dam was dedicated by Lady Bird Johnson. From 1970 to 1980, turbines and generators were installed for hydroelectricity.

Filling and operations

Upon completion of Glen Canyon Dam on September 13, 1963, the Colorado River began to back up, no longer being diverted through the tunnels. The newly flooded Glen Canyon formed Lake Powell. Sixteen years elapsed before the lake filled to the level on June 22, 1980. The lake level fluctuates considerably depending on the seasonal snow runoff from the Rocky Mountains. The all-time highest water level was reached on July 14, 1983, during one of the heaviest Colorado River floods in recorded history, in part influenced by a strong El Niño event. The lake rose to above sea level, with a water content of. It lies primarily in parts of Garfield, Kane, and San Juan counties in southern Utah, with a small portion in Coconino County in northern Arizona. The northern limits of the lake extend at least as far as the Hite Crossing Bridge.

21st century drought and push to drain

Colorado River flows have been below average since 2000 as a result of the southwestern North American megadrought, leading to lower lake levels. In winter 2005 the lake reached its then-lowest level since filling, an elevation of above sea level, which was approximately below full pool. After 2005, the lake level slowly rebounded, although it has not filled completely since then. Summer 2011 saw the third largest June and the second largest July runoff since the closure of Glen Canyon Dam, and the water level peaked at nearly, 77 percent of capacity, on July 30. However, water years 2012 and 2013 were, respectively, the third and fourth-lowest runoff years recorded on the Colorado River. By April 9, 2014, the lake level had fallen to, largely erasing the gains made in 2011.
Colorado River levels returned to normal during water years 2014 and 2015 by the end of water year 2015. The Bureau of Reclamation in 2014 reduced the Lake Powell release from 8.23 to 7.48 million acre-feet, for the first time since the lake filled in 1980. This was done due to the "equalization" guideline which stipulates that an approximately equal amount of water must be retained in both Lake Powell and Lake Mead, in order to preserve hydro-power generation capacity at both lakes. This resulted in Lake Mead declining to the lowest level on record since the 1930s.
Long-term water level decline continued, forcing an emergency release of water from the Flaming Gorge Reservoir in July 2021. By April 22, 2022, Lake Powell was at in elevation – just of capacity. This marks the lowest water level for Lake Powell since it was filled in 1963.
The capacity of Lake Powell has decreased by 7% since 1963, facing an average annual loss of 33,270 acre-feet of storage, due to the inflow of sediments from Colorado and San Juan rivers.
Peer-reviewed studies indicate that storing water in Lake Mead rather than in Lake Powell would yield a savings of 300,000 acre feet of water or more per year, leading to calls by environmentalists to drain Lake Powell and restore Glen Canyon to its natural, free-flowing state.

Climate

These data are for the Wahweap climate station on Lake Powell just south of the Utah-Arizona border.

Geology

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. The Moenkopi Formation, which dates from 230 million years ago, and the Chinle Formation are found at Lees Ferry and the Rincon. Both formations 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 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. Many of the arches, including Rainbow Bridge, lie at this transition point. This period also includes light yellow Entrada Sandstone, 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 sandstone, conglomerate and shale of the Straight Cliffs Formation that underlies the Kaiparowits Plateau and San Rafael Swell to the north of the lake.
The confluences of the Escalante, Dirty Devil and San Juan rivers with the Colorado lie within Lake Powell. The slower flow of the San Juan river has produced goosenecks where of river are contained within on a straight line.

Landmarks and features

The lake's main body stretches up Glen Canyon, but has also filled many 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.

Development

Access to the lake is limited to developed marinas because most of the lake is surrounded by steep sandstone walls:
The following marinas 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.
The Castle Rock Cut is one of the most important navigational channels in the lake; it was blasted as early as the 1970s to allow boaters to bypass the winding canyons between the Glen Canyon Dam and reaches of Lake Powell further upstream – saving, on average, one hour of travel time. The cut has been deepened several times since then, to allow the use of the channel during droughts. During the protracted 21st-century drought, however, the lake has dropped so quickly on several occasions that the cut dried up during the summer tourist season, most recently in 2013. Continued deepening of the Castle Rock cut has been criticized for its high cost, but boaters and the National Park Service argue that it improves safety, saves millions of dollars in fuel, and improves emergency response time. In September 2021 the level of Lake Powell was 45 feet below the bottom of the Castle Rock cut.
Currently, most marinas on the lake don't have Automatic Identification System monitoring stations that transmit boat positions to the AIS websites for the boating community. A substantial number of vessels on the lake do not have AIS transponders as there currently are no mandatory requirements for AIS usage for this body of water. Extra precautions must be taken with respect to boating safety, as the fractal nature of the lake's hydrologic surface area can allow vessels with limited charting equipment to become easily lost.
The burying of human waste in Glen Canyon National Recreation Area is prohibited. Anyone who camps farther than a quarter of a mile from a marina must bring a portable toilet. Pet waste must also be packed out.
The southwestern end of Lake Powell in Arizona can be accessed via U.S. Route 89 and State Route 98. State Route 95 and State Route 276 lead to the northeastern end of the lake in Utah.