Drought and climate change
The Colorado River Basin is experiencing the worst drought in recorded history. Since 2000, snowfall and runoff into the basin have been well below normal. These conditions have resulted in significant water level declines at major system reservoirs, including Lake Mead and Lake Powell.
The federal government is projecting a high probability that Lake Mead water levels will continue to decline. Federal, state and municipal water providers in the Colorado River Basin have worked together for more than a decade to slow the decline of Lake Mead water levels. The 2007 Interim Guidelines for the Coordinated Operations of Lakes Mead and Powell and the 2019 Lower Basin Drought Contingency Plan are two agreements that benefit Nevada and other Colorado River water users.
Among other things, these agreements:
- Keep more water in the river for the benefit of all water users and the environment.
- Help slow Lake Mead water level declines to preserve critical reservoir elevations.
- Allow for water banking in Lake Mead in the form of Intentionally Created Surplus.
- Draw participation from new stakeholders, including California and Mexico.
Nevada's combined maximum obligation under these agreements ranges from 8,000 to 30,000 AFY. If at any time Lake Mead is projected to fall below an elevation of 1,030 feet, the Secretary of the Interior will consult with Lower Basin stakeholders to determine if additional actions are needed to protect against the potential for a Lake Mead to decline below 1,020 feet.
The Bureau of Reclamation issued detailed guidelines in 2007 that mandate how Colorado River water stored in Lake Mead would be managed in the event of a shortage.
Under a shortage declaration, the amount of Colorado River water available to Nevada and Arizona would be reduced. The Secretary of the Interior will make a shortage declaration for the following year when the U.S. Bureau of Reclamation’s model projects Lake Mead to be at or below 1,075 feet on January 1 of the following year. The model is run annually in August.
Shortage amounts vary by state and are based on Lake Mead water levels. Nevada's shortage volume ranges from 13,000 to 20,000 AFY.
Drought contingency plan
Congress authorized implementation of the Lower Basin Drought Contingency Plan (DCP) in 2019. Under this agreement, Lower Basin States will begin making DCP contributions when the elevation of Lake Mead is projected to be at or below 1,090 feet.
Contribution amounts vary by state and are based on Lake Mead water levels. Nevada's DCP contribution ranges from 8,000 to 10,000 AFY. This volume of water is in addition to any mandatory reductions associated with a federally declared shortage.
Nevada will receive credit for its DCP contributions. These credits can be recovered when Lake Mead is above 1,110 feet. Below this elevation, Nevada can access or borrow its credits, subject to certain restrictions.
|Lake Mead water level||Shortage amount||DCP contribution||Total|
|Above 1,090 feet||0 acre-feet per year||0 acre-feet per year||0 acre-feet per year|
|At or below 1,090 feet||0 acre-feet per year||8,000 acre-feet per year||8,000 acre-feet per year|
|At or below 1,075 feet||13,000 acre-feet per year||8,000 acre-feet per year||21,000 acre-feet per year|
|Below 1,050 feet||17,000 acre-feet per year||8,000 acre-feet per year||25,000 acre-feet per year|
|At or below 1,045 feet||17,000 acre-feet per year||10,000 acre-feet per year||27,000 acre-feet per year|
|Below 1,025 feet||20,000 acre-feet per year||10,000 acre-feet per year||30,000 acre-feet per year|
Evidence supports the fact that climate change is happening now and that it will have a lasting effect on the availability of Colorado River water supplies. Consistent with global trends, warming has also occurred in the southwestern United States. While climate change models project that warming trends will continue, the magnitude of change at a given location will depend in part on global mitigation efforts to reduce greenhouse gas emissions. Nevada's Clark County is projected to warm between 5 - 10 degrees by the end of the century.
In Southern Nevada, the impacts of climate change are expected to be similar to that of drought. This includes extended durations of low Lake Mead elevations, water quality changes, possible reductions of Colorado River resources, and potential increases in water use to compensate for warmer and drier conditions.
The 2020 State of the Science Report
The Water Authority is responsible for anticipating future water demands and taking the steps necessary to meet them.
Over the years, the agency has taken a number of adaptive management steps to reduce the impacts of drought and climate change on water supplies and facilities.
- Through one of the nation’s most progressive and comprehensive water conservation programs, Southern Nevada has reduced its Colorado River consumption. The community used 35 billion gallons less water in 2019 than in 2002, despite the addition of more than 730,000 residents during that time.
- The Water Authority has constructed a third drinking water intake and a low lake level pumping station at Lake Mead to ensure continued delivery of Colorado River water to Southern Nevada under low reservoir conditions.
- Through compliance and sustainability efforts, the Water Authority seeks a balance between water resource use and environmental stewardship, including species habitat conservation and protection.
- Through water banking efforts in Nevada, Arizona, California and in Lake Mead, the Authority has accrued nearly 2.1 million acre-feet of water. This is nearly nine times Nevada's 2019 consumptive Colorado River water use. Like a savings account, water banking provides the Water Authority with the ability to store water for when its needed.
Continued water conservation and adaptive management are ongoing priorities as our community responds to drought and climate change.
The 1922 Colorado River Compact provided the legal authority to harness the Colorado River. Congress authorized the building of Hoover Dam in 1928, and construction began in 1931.
Completed in 1936, Hoover Dam was designed to regulate Colorado River flows. It also provides water storage and produces hydroelectric power.
The dam created Lake Mead, which stores the Colorado River allocation for Nevada, California, Arizona, and the country of Mexico.
When full, Lake Mead holds almost 9 trillion gallons of water, the equivalent of a 3-year supply for water users in Nevada, Arizona, California, and Mexico.
Ongoing drought has reduced the contents of Lake Mead significantly.