‘Megadrought’ intensifies water shortage in the Lake Mead reservoir

The effects of climate change are taking their toll on Lake Mead.

Ymaup | CC-BY-SA-3.0
Lake Mead in the midst of a drought.
Mackenzie Brown

Global Warming Associate

Matt Casale

Former Director, Environment Campaigns, PIRG

Lake Mead, the largest reservoir in the United States, provides water to almost 25 million people, three  states and two countries. It recently hit a worrying milestone: The lake dipped below 30% of its capacity for the first time in its 86-year lifespan, prompting the Bureau of Reclamation to declare a Category 1 water shortage

These dire conditions at Lake Mead are the result of a “megadrought” that has gripped the American West. A recent study in the journal Nature Climate Change found that the region is the driest it has been in 1,200 years. A study estimated that 42% of these drought conditions can be attributed to human-caused climate change, which has been primarily caused by burning fossil fuels for energy.

The megadrought, and ongoing aridification of the American West, is one example of climate change’s impact on our lives. The Earth’s atmosphere is a delicately balanced system, and a change in temperature by a few degrees can have a major impact on weather and ecosystems. Without addressing climate change, we can expect wildfires, hurricanes, floods, heat waves, droughts and even extreme winter storms to increase frequency and intensity. 


The Bureau of Reclamation’s Lake Mead water shortage declaration requires Arizona to reduce its water usage by 18%, Nevada by 7% and Mexico by 5%. The receding water level at Lake Mead also puts the Hoover Dam’s ability to produce electricity at risk: If the water level drops 100 more feet, the electricity-generating hydroelectric turbines will no longer function. Due to the low water level, the dam is already producing less electricity than usual- 3.3 billion kilowatt-hours, as opposed to 5.3 in 2000.

In the American West, researchers suggest we may be seeing a permanent change toward a drier climate through a process known as aridification. The combination of reduced precipitation and higher temperatures are causing moisture to evaporate before it can reach larger bodies of water. But even once the water reaches lakes and rivers, the heat and dryness continue to decrease the water supply.

Warming temperatures cause drought in a few ways. Hotter temperature causes evaporation, leading to drier soils and sapping moisture from plants. It also reduces snowfall, a crucial source of water in the West. The rapid, early melting of snowpack caused by warming further moist soil. Climate change is also shifting storms and precipitation towards the poles, reducing rainfall in other regions.

In addition to Lake Mead, other water sources, such as the Great Salt Lake and Lake Powell, are reaching worrying lows as a result of the drought. Forty states overall are experiencing drought in some form, and the situation is not expected to improve in the near future. 

California, with the region’s largest water allotment, hasn’t been forced to make cutbacks yet. The state, however, has voluntarily enacted an emergency order aimed at conserving water. The order bans the watering of non-essential grass, among other outdoor uses. California grows over half of the nation’s fruits, vegetables, and nuts. The state’s Central Valley, the agricultural heart of the state, is a major user of water (sometimes to the detriment of nearby residents), but is seeing its allocation from the state slashed in the face of continued drought. 

Neighboring Arizona, on the other hand, has taken the lion’s share of the cuts. Arizona officials are trying to avoid mandatory water conservation orders and instead have tried to encourage residents to make “culture change.” Cities such as Scottsdale, Tucson and Phoenix have begun to implement their own municipal water conservation plans. Despite these water conservation strides, questions remain about the sustainability of Arizona’s pace of development, where irrigation-dependent agriculture continues to expand and exurban builders skirt regulations to build homes with no reliable water supply

In Nevada, the Southern Nevada Water Authority, the entity that provides water to the Las Vegas region, has implemented a plan restricting water use by golf courses, and bans grass lawns on new homes. 

In the Southwest, cutbacks so far have typically focused on ornamental vegetation such as lawns and trees. But as shortages continue, states are beginning to look at agriculture as a target for cuts. This industry brings jobs and money to the region, but at a cost: agriculture is responsible for 79% of the region’s water use. 

The crisis in Lake Mead and the West is another reason why we must transition away from fossil fuels. As long as we keep using coal, gas and oil to heat and cool our homes, drive our cars and cook our food, these severe changes will only continue to deepen, further threatening food systems and water supplies in the West. 

The West’s water woes are yet another example of the challenges ahead if we fail to address climate change. In the years to come, the residents of the states that draw from Lake Mead will need to create new systems to manage and allocate water but in the meantime there is work to do to stop the problem from getting any worse.


Mackenzie Brown

Global Warming Associate

Matt Casale

Former Director, Environment Campaigns, PIRG

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