Reservoir on the Colorado River in Arizona and Nevada
Lake Mead is a reservoir formed by the Hoover Dam on the Colorado River in the Southwestern United States. It is located in the states of Nevada and Arizona, east of Las Vegas. It is the largest reservoir in the US in terms of water capacity. Lake Mead provides water to the states of Arizona, California, and Nevada as well as some of Mexico, providing sustenance to nearly 20 million people and large areas of farmland.
At maximum capacity, Lake Mead is long, at its greatest depth, has a surface elevation of above sea level, has a surface area of , and contains of water.
The lake has remained below full capacity since 1983 owing to drought and increased water demand. As of May 31, 2022, Lake Mead held of full capacity at , having dropped in June 2021 below the reservoir's previous all-time low of recorded in July 2016, and never returning to that level. By December 2024, following the implementation of water conservation measures, Lake Mead's water levels had risen by 16 feet again over two years.
History.
In the area that was chosen to become Lake Mead, native Americans referred to as Ancestral Puebloans settled in the area. Many archaeological sites were submerged by the creation of Lake Mead, including the most representative, which is referred to as the "Lost City". The lake was named after Elwood Mead, who was the commissioner of the U.S. Bureau of Reclamation from 1924 to 1936, during the planning and construction of the Boulder Canyon Project that created the dam and lake. Lloyd Joseph Hudlow, an engineer with the Bureau of Reclamation, came to Boulder City in March 1933 to assist in the survey, and ended up as the project manager.
Lake Mead was established as the Boulder Dam Recreation Area in 1936, administered by the National Park Service. The name was changed to the Lake Mead National Recreation Area in 1947, and Lake Mohave and the Shivwits Plateau were later added to its jurisdiction. Both lakes and the surrounding area offer year-round recreation options.
The accumulated water from Hoover Dam forced the evacuation of several communities, most notably St. Thomas, Nevada, the last resident of which left the town in 1938. The ruins of St. Thomas are currently visible (as of May 23, 2022) via dirt road and hiking trail, due to Lake Mead's low water level. Lake Mead also covered the sites of the Colorado River landings of Callville and Rioville, Nevada, and the river crossing of Bonelli's Ferry, between Arizona and Nevada. Six years after the dam's construction, the lake filled to an elevation of 1200 feet.
At lower water levels, a high-water mark is visible in photos that show the shoreline of Lake Mead. The high-water mark is white because of the deposition of minerals on previously submerged surfaces.
Geography.
Nine main access points to the lake are available. On the west are three roads from the Las Vegas metropolitan area. Access from the north-west from Interstate 15 is through the Valley of Fire State Park and the Moapa River Indian Reservation to the Overton Arm of the lake.
The lake is divided into several bodies. The large body closest to the Hoover Dam is Boulder Basin. The narrow channel, which was once known as Boulder Canyon and is now known as The Narrows, connects Boulder Basin to Virgin Basin to the east. The Virgin River and Muddy River empty into the Overton Arm, which is connected to the northern part of the Virgin Basin. The next basin to the east is Temple Basin, and following that is Gregg Basin, which is connected to the Temple Basin by the Virgin Canyon.
When the lake levels are high enough, a section of the lake farther upstream from the Gregg Basin is flooded, which includes Grand Wash Bay, the Pearce Ferry Bay and launch ramp, and about of the Colorado River within the lower Grand Canyon, extending to the foot of 240 Mile Rapids (north of Peach Springs, Arizona). In addition, two small basins, the Muddy River Inlet and the Virgin River Basin, are flooded when the lake is high enough where these two rivers flow into the lake. As of February 2015, these basins remain dry.
Jagged mountain ranges surround the lake, offering a scenic backdrop, especially at sunset. Two mountain ranges are within view of the Boulder Basin, the River Mountains, oriented northwest to southeast and the Muddy Mountains, oriented west to northeast. Bonelli Peak lies to the east of the Virgin Basin.
Las Vegas Bay is the terminus for the Las Vegas Wash which is the sole outflow from the Las Vegas Valley.
Drought and water usage issues.
Lake Mead receives the majority of its water from snow melt in the Colorado, Wyoming, and Utah Rocky Mountains. Inflows to the lake are largely moderated by the upstream Glen Canyon Dam, which is required to release around of water each year to Lake Mead under the Colorado River Compact. Releases from Hoover Dam have been over of water each year, which has led to declining levels in Lake Mead since 2000.
Outflow, which includes evaporation and delivery to Arizona, California, Nevada, and Mexico from Lake Mead is generally in the range of , resulting in a net annual deficit of about . Farmers in California's Imperial Valley hold some of the oldest water rights and receive the largest share of water as of 2024.
Before the filling of Lake Powell (a reservoir of similar size to Lake Mead) behind Glen Canyon Dam, the Colorado River flowed largely unregulated into Lake Mead, making Mead more vulnerable to drought. From 1953 to 1956, the water level fell from . During the filling of Lake Powell from 1963 to 1965, the water level fell from . Many wet years from the 1970s to the 1990s filled both lakes to capacity, reaching a record high of in the summer of 1983.
In these decades prior to 2000, Glen Canyon Dam frequently released more than the required to Lake Mead each year. That allowed Lake Mead to maintain a high water level despite releasing significantly more water than it is contracted for. Since 2000, the Colorado River has experienced the southwestern North American megadrought, with average or above-average conditions occurring in only five years (2005, 2008–2009, 2011 and 2014) in the first 16 years of the 21st century. Of any 16-year period in the last 60 years, 2000-2015 had the lowest water availability.
In June 2010, the lake was at 39% of its capacity, ;ref name="Lake Levels/River Flow" ; ;/ref ; and on November 30, 2010, it reached , setting a new record monthly low. From mid-May 2011 to January 22, 2012, Lake Mead's water elevation increased from after a heavy snowmelt in the Rocky Mountains prompted the release of an extra from Glen Canyon into Lake Mead.
In 2012 and 2013, the Colorado River basin experienced its worst consecutive water years on record, prompting a low Glen Canyon release in 2014 – the lowest since 1963, during the initial filling of Lake Powell – in the interest of recovering the level of the upstream reservoir, which had fallen to less than 40% capacity as a result of the drought. Consequently, Lake Mead's level fell significantly, reaching a new record low in 2014, 2015 and 2016.
In 2014, its record low was on July 10, 2014. On June 26, 2015, Lake Mead reached another new record low when it fell to for the first time since the lake was filled, which risked triggering drought restrictions. If the lake is below the elevation of 1,075 feet at the beginning of the water year, an official shortage declaration by the Bureau of Reclamation will enforce water rationing in Arizona and Nevada. The water year begins October 1 to coincide with seasonal Rocky Mountain snowfall, which produces most of the Colorado River's flow.
Lake Mead's water level rebounded a few feet by October 2015 and avoided triggering the drought restrictions. The water level started falling in Spring 2016 and fell below the drought trigger level of 1,075 feet again in May 2016. It fell to a new record low of on July 1, 2016, before beginning to rebound slowly. Drought restrictions were narrowly avoided again when the lake level rose above 1,075 feet on September 28, 2016, three days before the deadline, and the Bureau of Land Reclamation did not issue a shortage declaration.
A reprieve from the steady annual decline occurred in 2017, when lake levels rose throughout the year due to heavier than normal snowfall in the Rocky Mountains. As a result of the large snowmelt, the lake regained the water levels it had in 2015 with a seasonal high of . The seasonal low of in 2017 was close to that experienced in 2014, safely above the drought trigger. That level was still below the seasonal low experienced in 2012, and the lake was projected to begin falling again in 2018.
Despite those and other predictions of an impending shortage determination by 2020, snowpack of 140% of average in the Upper Colorado River basin as of April 2019 resulted in 128% above average inflow into Lake Powell, resulting in water level on Lake Mead. In December 2019, Lake Mead water level reached , about above projections. As of April, 2020, the water level stood at , again benefiting from above average mountain snowpack (107% of average).
From 2018 to early-2021, Lake Mead water levels remained well above the level that would trigger a shortage determination. However, by mid-2021 its level fell below the trigger elevation and was projected to keep falling through 2022, which led the Bureau of Reclamation to declare a water shortage in August 2021. On July 28, 2022, the level was , the lowest level since 1937 when the reservoir was initially filled. The lake has rebounded somewhat from its low point in 2022, but its level still remains below the drought threshold as of June 2024.
As a result of the decreasing water level, marinas and boat launch ramps have either had to be relocated to another area of the lake or have closed down permanently. The Las Vegas Bay Marina was relocated in 2002 and the Lake Mead Marina was relocated in 2008 to Hemenway Harbor. Overton Marina and Echo Bay Marina have been closed due to low levels in the northern part of the Overton Arm. Government Wash, Las Vegas Bay, and Pearce Ferry boat launch ramps have been closed. Las Vegas Boat Harbor and Lake Mead Marina in Hemenway Harbor/Horsepower Cove remain open, along with Callville Bay Marina, Temple Bar Marina, Boulder Launch Area (former location of the Lake Mead Marina) and the South Cove launch ramp.
Changing rainfall patterns, climate variability, high levels of evaporation, reduced snow melt runoff, and current water use patterns are putting pressure on water management resources at Lake Mead as the population relying on it for water, and the Hoover Dam for electricity, continues to increase. To lower the minimum lake level necessary to generate electricity from to , Hoover Dam was retrofitted with wide-head turbines, designed to work efficiently with less flow in 2015 and 2016.
If water levels continue to drop, Hoover Dam would cease generating electricity when the water level falls below and the lake would stabilize at a level of when the water reaches the lowest water outlet of the dam. In order to ensure that the city of Las Vegas will continue to be able to draw its drinking water from Lake Mead, nearly $1.5 billion was spent on building a new water intake tunnel in the middle of the lake at the elevation of . The tunnel took seven years to build under the lake and was put into operation in late 2015.
According to a 2016 estimate, about 6% of Lake Mead's water evaporates annually. Covering 6 percent of Lake Mead with floating photovoltaics has a potential generating capacity of 3,400 megawatts, which is comparable to the capacity of Hoover Dam, and would reduce water lost to evaporation in the covered area by as much as 90%. A 2021 estimate stated that covering 10% of the lake's surface with foam-backed floating photovoltaics could result in "enough water conserved and electricity generated to service Las Vegas and Reno combined."
In December 2021, with Lake Mead at 35% of capacity, Arizona, California, Nevada, and