'A completely new reality': Bolder measures are needed to prevent extreme water shortages in cities like Phoenix and Las Vegas that depend on the Colorado River

A view of Lake Mead from the Hoover Dam. Water levels are much lower than the high-water mark. — Lake Mead, which serves almost 25 million people and cities such as Las Vegas, could drop to 20% full this year, which experts say is incredibly worrying. (Image credit: Christopher Moswitzer via Getty Images)

Share this article 0 Join the conversation Add us as a preferred source on Google Newsletter Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

By submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over.

You are now subscribed

Your newsletter sign-up was successful

Want to add more newsletters?

Join the club

Get full access to premium articles, exclusive features and a growing list of member rewards.

Explore An account already exists for this email address, please log in. Subscribe to our newsletter

Catastrophic water shortages are in store for the 40 million people living in areas fed by the Colorado River, even if cities in the region such as Denver, Phoenix and Las Vegas make dramatic cuts to their usage, recent research suggests.

Water shortages could start as soon as this summer, as snowpack levels reached a record low over Lake Powell and the spring runoff into the Colorado River is expected to be minimal, experts told Live Science. And the region's major cities, which have already slashed their per capita water consumption by up to 58% between 2002 and 2025, can't solve the problem alone.

"We can't just shove it all onto the residents of these cities and tell them to use less water, because it's still not going to be enough [to prevent water shortages]," Renee Obringer, an assistant professor in the Department of Energy and Mineral Engineering at Penn State and the first author of the new study, told Live Science. "Regardless of what mitigation we do, we're still going to have to adapt to this warmer world that is going to have more intense droughts and more frequent droughts."

One piece of the puzzle

Seven states — Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming — pull water from the Colorado River, and the amount allocated to each region is governed by a century-old document called the Colorado River Compact.

But the Colorado River basin, along with the rest of the U.S. Southwest, has been in a megadrought for 25 years. Between 2000 and 2019, the river's flows shrank by 20% due to climate change and water overuse to supply cities, agriculture and industry.

It's unprecedented; it's human-caused; it's scary, frightening, awful.
Brad Udall

Finding new water supplies is unlikely, so Obringer and her colleagues analyzed what would happen if three large cities fed by the river — Denver, Las Vegas and Phoenix — reduced their consumption by around 25% under various climate scenarios, ranging from a global temperature increase of about 2.9 degrees Fahrenheit (1.6 degrees Celsius) to an increase of 7.7 F (4.3 C) compared with preindustrial levels.

Their results were published in December 2025 in the journal Water Resources Research. In most climate scenarios, demand management — which encompasses broad strategies such as raising awareness, offering rebates, and subsidizing low-flow devices — did not make up for lower water storage in urban reservoirs caused by higher temperatures and lower precipitation in the region. Denver, which is technically not located in the Colorado River basin but gets half of its water from the Colorado River, was the lone exception. Demand management compensated for river flow reductions in two high-emissions climate scenarios for the city. However, Obringer suspects some of those more optimistic results could be an artifact of the way the model handles uncertainties.

Cities fed by the Colorado River basin have reduced water use through programs aimed both at demand and reuse. In Las Vegas, for example, residents receive cash rebates for replacing water-heavy lawns with desert plants. The city, which gets 90% of its water from the Colorado River, also returns, after treatment, 40% of the water it uses to Lake Mead, where it can then be reused.

A house in Las Vegas with desert plants in the front yard. — Desert landscaping is replacing grass lawns on Las Vegas private properties, as residents can receive cash rebates for planting drought-tolerant species. (Image credit: Christopher Morris/Corbis via Getty Images)

Cities have taken significant steps to reduce their footprint, and they will likely continue to improve, said Brad Udall, a senior water and climate research scientist at Colorado State University’s Colorado Water Center who was not involved in the study. As a result, some of the region's biggest cities use less water per capita than they did a few decades ago.

But the more efficient cities get, the fewer opportunities they will have to save and reuse water, Udall told Live Science.

Bigger water users

The results highlight a reality scientists have long known: Demand management alone cannot offset the Colorado River's dwindling flows, said Sharon Megdal, a professor and director of the Water Resources Research Center at the University of Arizona, who was not involved in the study.

Cities make up only 18% of water use in the region, while agriculture guzzles more than 70% of the basin's water. "Agriculture's the big user," Megdal told Live Science.

"You can't solve this problem without dealing with agriculture in a major way," Udall agreed. "Because agriculture is 70% of the problem, it needs to be at least 70% of the solution."

Individual farmers have senior water rights to Colorado River water, meaning they receive their full allocation regardless of whether there is a shortage, but political pressure is rising to allocate more water to cities and cut farmers' consumption, Udall said. For example, water managers may decide that farmers in Arizona have to relinquish water to supply the Central Arizona Project canal, which delivers water from the Colorado River to the central and southern parts of the state, including Phoenix and Tucson.

Since 2019, the Colorado River has shrunk so much that it is now 35% smaller than it was on average in the 20th century. "We've never seen flows like this," Udall said. "If these flows continue to drop, I do see agriculture in the Lower Basin not getting the supplies they do [now] and those supplies being reallocated to cities."

A stretch of dry lakebed on the shores of Lake Granby, Colorado. — Lake Granby in Colorado is fed by the Colorado River, but much of the lakebed is exposed this year due to low water levels. (Image credit: RJ Sangosti/MediaNews Group/The Denver Post via Getty Images)

The problem is that farmers in the Lower Basin grow crops that benefit the region economically through exports, including alfalfa, cotton, vegetables and citrus fruit. In Arizona, roughly 20% of cropland is used to grow alfalfa for cattle feed. The state is also the biggest cotton producer in the Colorado River basin, and it grows up to 90% of leafy greens consumed in the U.S. and Canada.

To cut their water consumption, farmers can change their irrigation techniques and crop patterns, Megdal said. Drip irrigation, which delivers water directly to the roots, cuts evaporation and reduces water use by up to 50% compared with methods such as flood irrigation used for cotton and alfalfa. Thirsty crops such as alfalfa could be replaced with low-water forage mixes consisting of wheat, barley, oats, rye and peas. Recently, there has also been a focus on guayule, which is a substitute for rubber, as an alternative crop for farmers, Megdal said.

But farmers respond to demand and may have long-term contracts with buyers. "It has to be economical," Megdal said.

Agriculture should switch to more efficient irrigation, but it's also important to realize that some seemingly wasteful methods, such as furrow or flood irrigation, can replenish aquifers, which are also being depleted, Udall said.

Some farmers are letting their fields go fallow, which could happen more and more as water shortages intensify, Megdal added.

Renegotiating water rights

The Colorado River Compact is up for renewal this year, meaning there is an opportunity to devise a more sustainable agreement, Obringer said. But negotiations have stalled between the Upper Basin, which includes Colorado, New Mexico, Utah and Wyoming; and the Lower Basin, which encompasses Arizona, Nevada and California. While officials wrangle over the precise wording in the document, the underlying problem is that the Lower Basin needs more water than it's getting, even though the Upper Basin already uses less water than it was allocated in the compact.

Officials in the Upper Basin have argued that cuts should now fall exclusively upon the Lower Basin. But that can't happen, Udall said, because cuts need to be deep across the Colorado River basin to make a difference. No matter what the Upper Basin thinks it is entitled to, it must accept reductions in water use, he said.

Reality check

Solutions must be found and implemented immediately, because the Colorado River's future has never looked bleaker.

Winter brought barely any snow, and the little that fell melted in early March instead of April, meaning river flows this spring and summer could hit record lows. "It's unprecedented; it's human-caused; it's scary, frightening, awful," Udall said.

Graph showing the snowpack measured above Lake Powell. We see that 2026 snowpack was much lower, and melted sooner, than snowpack in other years. — This graph shows snowpack levels above Lake Powell, measured across more than 100 stations. The dark blue line is 2026, and the other lines are the lowest snowpack years so far in the 21st century (2000, 2001, 2002, 2003, 2012, 2013, 2018, 2021, 2022 and 2025). The data shows that 2026 "is so much worse than these other terrible years," Udall said. (Image credit: NOAA / Colorado Basin River Forecast Center)

Udall estimates that Lake Mead, which serves almost 25 million people in cities such as Las Vegas and Los Angeles, and Lake Powell, which supplies Lake Mead and Indigenous tribes, will be only about 20% full over the coming months. Without adjustments in reservoir release, water levels could drop low enough to prevent energy production at Glen Canyon Dam, which usually produces enough electricity to power over 350,000 homes.

"We're close to dead pool," Udall said. This is when the water level in a reservoir falls so low that it can't flow downstream. "That's never happened, and it's very serious."

It would take years of unusually high precipitation and runoff to recover from the current state, according to Megdal. "It is a challenging situation," she said. "You really have to adjust to a new normal."

The Colorado River flows below the Glen Canyon Dam in Page, Arizona. — Extremely low precipitation this winter means spring and summer runoffs into the Colorado River will be minimal. (Image credit: L.E. Baskow/Las Vegas Review-Journal/Tribune News Service via Getty Images)

To make matters worse, "data centers are popping up everywhere in this region," Obringer said. A midsize data center uses up to 300,000 gallons (1.4 million liters) of water per day for cooling, and this number will only increase as temperatures rise. Much of the water that runs through the system can be reused, but some is consumed to generate the electricity to power data centers.

'A completely new reality': Bolder measures are needed to prevent extreme water shortages in cities like Phoenix and Las Vegas that depend on the Colorado River

One piece of the puzzle

Bigger water users

Renegotiating water rights

Reality check

Схожі новини

Inside the evidence revolution — how decision-making became data driven

Cosmic-ray detection heralds era of mega-observatories for neutrinos

Fossil-Fuel Funded GOP Leaders Claim a Renowned Scientific Institution Has ‘Potential Conflicts of Interest’

У Steam вийшов горор Lysa Hora: The Haunted Hill від колишнього розробника STALKER 2