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Aquapedia background February 11, 2014 Colorado River Basin Map Layperson's Guide to the Colorado River Elwood Mead Colorado River Hoover Dam

Lake Mead

Aerial view of Lake Mead

Lake Mead is the main reservoir formed by Hoover Dam on the border between Southern Nevada and northwestern Arizona.

Created in the 1930s as part of Hoover Dam [see also Elwood Mead], Lake Mead provides water storage in the Lower Basin of the Colorado River. The reservoir is designed to hold 28,945,000 acre-feet of water and at 248 square miles its capacity is the largest in United States.

Most of the water in Lake Mead is drawn from Rocky Mountain snowmelt and runoff. The water is drawn from a vast storage and distribution network, including Lake Powell on the Utah-Arizona border. Lake Powell serves a bank account for the Upper Basin states of Colorado, New Mexico, Utah and Wyoming, and helps regulate the required delivery of water to the Lower Basin states of Arizona, Nevada and California through Lake Mead.

However, one of the largest droughts on record in the region dating back to 2000 has lowered Lake Mead’s water level. The combined storage at Lake Powell and Lake Mead is expected to drop below 30 percent by late 2022 due to declining inflows of runoff. In addition, Lake Mead loses about 800,000 acre-feet of water annually through evaporation.

The water supply crunch in the Colorado River Basin has a ripple effect, including on recreation and on water allocation to Arizona, California and Nevada.

Due to the sharp decline of water storage in Lake Mead, the Bureau of Reclamation in August 2021 declared the first-ever shortage at the pivotal reservoir. Reclamation’s declaration triggered mandatory curtailments to water users in Arizona and Nevada. The impact has been felt chiefly by Arizona farmers reliant on Colorado River water delivered by the Central Arizona Project. Further declines in Lake Mead’s elevation would spur additional water cuts to users in Arizona, Nevada and California, as well as Mexico under binational agreements.

The Bureau of Reclamation oversees Lake Mead as well as Hoover Dam. The National Park Service oversees recreational activities as part of the Lake Mead National Recreation Area.

Lake Mead Agreements

In 2007, the Seven States Agreement established new guidelines for both Lake Powell and Lake Mead. The agreement includes rules to allow Arizona, California, and Nevada to store conserved water in Lake Mead.

In 2012, Minute 319 was signed between the United State and Mexico. Minute 319 established new rules for sharing Colorado River water. Under the 5-year agreement—one in a series of U.S.-Mexico Colorado River agreements dating back to 1944—Mexico may store some of its of Colorado River water in Lake Mead. However, if a water shortage is declared in the Lower Basin, less water is sent to Mexico. 

In 2017, U.S. and Mexican representatives with the International Boundary and Water Commission signed Minute 323, which enables Mexico to continue to store its water in Lake Mead, helping to keep reservoir levels high enough to avoid triggering dramatic cuts to Colorado River water users.

In 2019, a Drought Contingency Plan was enacted for both the Lower and Upper Basin states. The Upper Basin plan centers on reduced water demand. In the Lower Basin, cities and farms in Arizona, California and Nevada agreed to scale back and take deeper cuts as Lake Mead reaches threshold elevations that trigger those cutbacks.

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Aquapedia background September 1, 2016 Lake Tahoe Lake Mead Mono Lake Diamond Valley Lake

Lakes

Definition

Lake TahoeA lake is an inland standing body of water.

Lake, Pond or Wetland?

Scientifically and legislatively, lakes are indistinguishable from ponds, but lakes generally are considered to be longer and deeper lentic, or still, waters. In the 18th and 19th centuries, scientists attempted to distinguish the two more formally, stating that ponds were shallow enough to allow sunlight to penetrate to the bottom, but this exists today as an unofficial point.

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Aquapedia background February 11, 2014 Colorado River Basin Map Layperson's Guide to the Colorado River Elwood Mead Colorado River Hoover Dam
Maps & Posters May 20, 2014 Colorado River Bundle

Colorado River Basin Map
Redesigned in 2017

Redesigned in 2017, this beautiful map depicts the seven Western states that share the Colorado River with Mexico. The Colorado River supplies water to nearly 40 million people in Arizona, California, Colorado, Nevada, New Mexico, Utah, Wyoming and the country of Mexico. Text on this beautiful, 24×36-inch map, which is suitable for framing, explains the river’s apportionment, history and the need to adapt its management for urban growth and expected climate change impacts.

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Cover page for the Layperson's Guide to the Colorado River .
Publication May 20, 2014 Colorado River Basin Map

Layperson’s Guide to the Colorado River
Updated 2018

The Colorado River provides water to 40 million people and 4 million acres of farmland in a region encompassing some 246,000 square miles in the southwestern United States. The 32-page Layperson’s Guide to the Colorado River covers the history of the river’s development; negotiations over division of its water; the items that comprise the Law of the River; and a chronology of significant Colorado River events.

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Aquapedia background February 3, 2014

Elwood Mead

Elwood Mead (1858-1936) was the commissioner of the U.S. Bureau of Reclamation during the era of the development of Hoover Dam on the Colorado River between Arizona and Nevada, Grand Coulee Dam in Washington and Owyhee Dam in Oregon, among other large water projects.

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Aquapedia background January 30, 2014 Colorado River Basin Map Layperson's Guide to the Colorado River Layperson's Guide to the Colorado River Delta

Colorado River

Colorado RiverThe turbulent Colorado River is one of the most heavily regulated and hardest working rivers in the world.

Geography

The Colorado falls some 10,000 feet on its way from the Rocky Mountains to the Gulf of California, helping to sustain a range of habitats and ecosystems as it weaves through mountains and deserts.

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  • Colorado River Timeline
Aquapedia background February 4, 2014 Dams Layperson's Guide to the Colorado River

Hoover Dam

Hoover DamHoover Dam, one of the tallest dams in the United States and a National Historic Landmark that draws tourists from across the globe, is a key reservoir providing flood control, water storage and irrigation along the lower Colorado River. It also is one of the nation’s largest hydroelectric facilities, generating on average about 4 billion kilowatt-hours of hydroelectric power each year, enough electricity to serve more than 1.3 million people in Nevada, Arizona and California.

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