Sharing the River
HISTORY
Las Vegas is located in the Mojave desert.
There are two primary resources that provide the Las Vegas valley with its critical water needs. Ninety percent of it is provided by the Colorado River, renewed by rain and snowmelt from the Rocky Mountains, with the additional 10 percent from groundwater that is pumped from an aquifer beneath the city - fed by rain and snowmelt from mountains surrounding the Valley.
THE COMPACT
Water regulation began in 1922 when Colorado, Utah, Wyoming and New Mexico refused to allow a federal dam project to proceed until those states' water rights were guaranteed against the needs of the lower states including already fast-growing California.
A massive federal flood control and water storage facility couldn’t be built without settling the dispute, so in 1922 the Federal government, split the states that would rely on it into two ‘Basins’ - the ‘Upper’, consisting of Wyoming, Colorado,Utah and New Mexico, and the ‘Lower’ - Arizona, California, Nevada, (and later, part of Mexico).
Under this ‘Colorado River Compact’, allocated 7.5 million-acre-feet* (MAF) of water to each of the two Basins (one acre-foot is the equivalent of a football field in a foot of water). Lower Basin MAF distribution based on estimated needs at the time were California: 4.4, Arizona: 2.8, New Mexico: 1.5 and Nevada 0.3.
The pact was signed in 1928 and the Boulder Canyon Project Act authorized the building of Boulder Dam.
In 1936, Boulder Dam was finished and water began to pool into what now is known as Lake Mead - designed to hold almost 29 million acre-feet of the water (about 9.5 trillion gallons), drawn mostly from Rocky Mountain snowmelt and Lake Powell runoff to the North. (The name changed more than once due to political shifts, with Congress permanently authorizing the name Hoover Dam in 1947).
The lake reached full capacity in 1941 at 1,220 feet above sea level, remaining nearly full and peaking at a record high of 1,225 feet in 1983.
TODAY
The Compact requires the Upper Basin deliver a fixed amount of water to the Lower Basin states and does not provide for restricting their own consumption.
Due to the prolonged drought, Lake Mead is currently only 27% full - 1,039 feet above sea level - 189 feet below capacity and consequently the century-old agreement that had allocated 16 million acre-feet of water can now distribute only 12 million acre-feet.
Additionally, over the past 104 years, the population of the upper basin states has grown by 9 times, and the lower basin is 12 times larger. The Colorado river that feeds Lake Powell and Lake Mead now serves nearly 63 million people - ten times the number of people with far more water needs.
Western state populations have grown by a factor of ten since 1922.
Of the Lower Basin states, Nevada is now 41 times larger, growing from 81,000 to now 3.3 million residents (and 40 million annual visitors in the Las Vegas area alone). Similarly, Arizona is 21 times its 1922 size.
INITIATIVES
Las Vegas has become the nation’s leader in water conservation, recycling 99% of indoor water use. Since 2002 it has reduced the per-capita consumption by 58%, helping to offset a 50% increase in population over the past 24 years.
About 40% of Southern Nevada's total water is used indoors in homes, businesses, and resorts. 200 million gallons of water are processed daily from sinks, showers, and toilets. This wastewater is treated at facilities where organic matter is removed and sent out through the Las Vegas Wash before eventually re-entering Lake Mead.
Outdoor water usage, currently at 60% of the total, mostly can’t be reclaimed, but Vegas still is a leading example of employing conservative methods. The region enacted laws limiting outdoor watering, offering natural foliage replacement incentives and in 2004 banning new residential grass and legislating restrictions on non-functional commercial and multi-family turf, which will evolve into a complete ban in 2027.
Under a 2026 memorandum of understanding, water agencies in Nevada, Arizona, California, and the Federal government established a framework for exchange of this water ‘on paper’. By utilizing surplus output from the Carlsbad Desalination Plant locally, Rather than using it, California will leave a corresponding share of Colorado River water in Lake Mead as storage credits, helping to maintain levels and avoid further Federal cuts to the system to avoid the need for costly new infrastructure.
Additionally, Las Vegas has invested $1.5 billion to build a deep water intake near the bottom of Lake Mead to ensure access even if lake levels drop below current operational limits.
Through these and other measures, as of mid-2026, Las Vegas has banked about 12 years of water supply in Lake Mead and local underground aquifers, where 345,000 acre-feet is stored in a groundwater system accessible by wells.
THE FUTURE
Changes in farming practices along the Colorado River, where about 75% of water is used for agriculture, is also being addressed. The Bureau of Reclamation discussed paying farmers to leave some of their fields unplanted to allow the water that would’ve been used to irrigate crops to stay in the Colorado River.
In 2026, the Southern Nevada Water Authority agreed to not claim some of its Lake Mead allocation in exchange for the U.S. Bureau of Reclamation giving Nevada $16.25 million for conserving an amount equal to one-sixth of its total Colorado River allocation.
Also in 2026, the SNWA will be able to leave 50,000 acre-feet in Lake Mead in anticipation of the expected requirement of 100,000 acre-feet to be left in Lake Mead the following two years.