Most of the water from the Colorado River goes to agriculture, with sizable allotments going to municipal, industry and commercial uses, a months-long investigation from NPR’s Mountain West News Bureau found. Another large slice of water simply vanishes into the air annually, lost to evaporation from reservoirs dotted across the Colorado River Basin.
There is less water available now in the Colorado River and negotiators are working to figure out how to distribute that water. Now that many users may see their water shares cut, it is important to understand how much water is actually in the system.
The NMWB analyzed data from the federal Bureau of Reclamation (BOR) and best practices established by a team of water scientists published in a prominent environmental journal.
The NMWB found that about 65% of all Colorado River water went to irrigating agriculture from 2000 to 2024 on average. From 2014 to 2024, that’s 9.57 million acre-feet a year, on average. That is slightly down from the previous decade’s average, but only by 2%. An Olympic-sized swimming pool holds about two acre-feet of water.
An acre-foot is commonly defined as enough water to cover a football field one foot deep - or in Arizona, enough water to serve three single-family homes for a year.
Overall, the findings are in step with long-standing expert analysis about the river, but add new detail and nuance. NMWB’s analysis also provides the public and policymakers with a rare, comprehensive look at the federal data, which is viewed as the gold standard but has some shortcomings. NMWB compared national data alongside different data sets from individual Colorado River Basin states, spoke with eight experts, and rebuilt national water use datasets based on scientific findings to get as much detail as possible.
Of all of the consumptive uses tracked by the BOR, 65% of Colorado River water in the United States goes to irrigating agriculture on average. A “consumptive use” occurs when water is withdrawn from the watershed and not returned. That includes evaporation, as well as water for crops, people, livestock and more.
An even higher percentage of Colorado River water, 74% on average, is used by agriculture if one just considers human uses and does not include evaporation in calculations. Those are similar numbers to what the BOR and the Nature Conservancy have documented. The MWNB considered evaporation when considering the total water use.
The Colorado River basin states include Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming. And, all of those states except Nevada use more than half of their total river water consumption towards irrigating agriculture, per the MWNB’s analysis.
Brian Richter, president of Sustainable Waters, a water scarcity education and consulting organization based in New Mexico, said crops take a lot of water to grow, especially in hot climates. The recent warmer regional weather, including the snow drought that earlier this year led U.S. Interior Department officials to take emergency measures to prop up Lake Powell in Utah and Arizona, also means more water will be used because it stretches the growing season.
“Well, it just takes an awful lot of water to grow our food, to put it simply,” Richter said. “And that's just a necessary use of the water.”
Cattle ranching uses a lot of water. Richter and his team previously found in a 2024 Nature study that crops used to feed cattle, like alfalfa and other hay, were the “dominant water-consuming crops” reliant on Colorado River water.
The current pace of water use along the Colorado River is unsustainable, Richter said, adding that a “substantial increase” in water conservation is needed on farms to rightsize the issue.
“Agriculture is such a dominant consumer that we have to have very heavy participation in water conservation efforts in the agricultural community in order to get this system back into some kind of sustainable balance for the long term,” he said.
Some of these strategies include growing different crops that make farmers the same or more money with less water, being more efficient with available water, and the difficult political choice of permanently retiring agricultural land for another use, Richter said. Those varied uses could include reverting the land to wildlife habitat or into a solar farm.
Evaporation takes a slice of water annually
Our data analysis also found that every year, at least 12% of water used along the Colorado River water just vanishes due to reservoir evaporation. Of that, 1.7 million acre-feet evaporated each year on average from 2014 to 2024, which is 6% less than the previous decade’s average.
Richter wrote in an email that this decline is because “less surface area translates into less evaporation.”
Evaporation could be viewed like a “tax” on water use, Richter said, as reservoirs require consistent levels of water, even in dry years. In short, the cost of filling reservoirs comes at the cost of evaporation.
“To be able to use water the way that we're using it is going to require losing some of it to reservoir evaporation,” Richter said.
Michael Cohen, a senior fellow at the Pacific Institute who has been studying Colorado River water use since 1998, said identifying the amount of water that evaporates is an important revelation in the data because policies and cooperation among river basin states hold potential to identify large savings.
“It's a huge piece of the pie,” Cohen said. “And really, those reservoirs have enabled the system to continue to deliver water to users despite 25 years or 25-plus years of drought. But the cost of that has been a staggering amount of water evaporated and blowing into Nebraska. So that piece of it isn't discussed and how to address that piece of it is definitely off the table.”
Some past proposals to combat evaporation have included adding solar panels on top of exposed water canals to prevent evaporation and by adding “shade balls” to float on the surface of reservoirs. They are expensive and difficult to do without clear results.
The levels of two of the largest reservoirs along the Colorado River, Lake Powell and Lake Mead, have dropped to record lows. The climate has continued to warm and demand for the water held there has not dropped.
“The reservoirs are drying up very fast because we're overusing – we're using more water than the river provides year after year after year,” Richter said. “So we've been dipping into the reservoirs like their savings accounts that we can plunder.”
Richter said the river requires “bold leadership,” likely from the federal government, to change course in this new reality and possibly cap the amount of water that can be pulled from the Colorado River annually.
A chunk of water goes to cities and businesses
More than one-fifth of water from the Colorado River is used by municipal, commercial and industry (MCI) players each year. This includes the water from the facets in cities to businesses along the river. MCI has gone up 1% to an average of 3.4 million acre-feet each year from 2014 to 2024.
This comes as drought ravages the Colorado River Basin and the seven states that rely on the river, and the federal government debates the future of how to distribute a shrinking water source.
Water data difficulties
Identifying how much water is used by each state is a remarkably difficult task. NPR’s Mountain West News Bureau reached out to all of the seven Colorado River Basin states seeking water use data.
Some of the states default to federal Consumptive Use and Loss data from the BOR, but others have their own team of water scientists with their own data at the ready. The MWNB leaned on federal data in order to make apples-to-apples comparisons with similar data definitions.
Richter said chasing down numbers from various sources is the biggest challenge to understanding a full picture of the Colorado River.
“And so that can be very time-consuming and sometimes it almost feels like you're pulling teeth because some of these things are managed by agencies that really aren't required or necessarily in the practice of making their data publicly available, so we have to make special requests in many cases,” he said.
The Colorado River is divided into Upper and Lower Basins. Some states, like Arizona and New Mexico, straddle the basins.
Cohen said the methods for measuring water use differ between the basins, alongside their accuracy.
In the Upper Basin, water use is calculated by how much a stream is depleted compared to how much water was returned to the river. But there can be variability in how much a water headgate is cracked open. A headgate is a measuring device used to identify how much water is used at any given location. In the Lower Basin, users can order the water they are entitled to and an engineer will let that much flow from the Hoover Dam.
“So there's just a very different system in the Upper and Lower Basin. So that leads to a lot of uncertainty into how much water is used, place of use, time of use,” Cohen said.
Cohen also said this uncertainty and possible error range gets “baked” into the values, making identifying exact water use fraught with possible issues.
Another factor in the difficulty of identifying Colorado River water use is an amorphous category known in “BOR” data as exports. Exports are defined by the federal government as “water that is moved from one reporting area to another (intrabasin export) or is removed from the Lower Colorado River System for eventual domestic delivery (interbasin export).”
The bureau identified about a third of all water as an export in an initial BOR analysis. In California, almost all of the state’s water was tagged as an export.
In other words, taking a cup of water from the banks of the Colorado River and bringing it to Denver is considered an export. That process is done on a massive scale all along the river. For example, in Colorado, water is pumped from the river in pipelines, ditches, reservoirs and wells across the state to massive thirsty cities along the Front Range.
A team of researchers led by Richter sought to get more details on where the exports go and established percentage splits for each diversion based on how much Colorado River water went to irrigate agriculture, cities or companies.
However, Cohen has a problem with this approach. He said the percentage of water used by each diversion has changed over time. It is not always exactly an identical split of water use each year between agriculture and municipal, commercial or industry destinations. Cohen said farmland has been absorbed by cities over time.
“Basically, the trend is farmland has been developed,” he said. “They're now growing houses instead of food. And that's particularly true in a lot of the adjacent areas that receive Colorado River Water.”
The bureau decided to utilize Richter’s approach as the best possible method available, but with caveats. Also, the BOR data from 2021 to 2024 is the most recent available but has been deemed “provisional” by the bureau.
State-by-state findings
States along the Colorado River use the water to help residents, farms and businesses flourish. Richter, however, said they use more water than is replenished.
“The seven states that share the Colorado River system are gonna have to find a way to get by with using a lot less of the Colorado River in the coming decades,” he said. “They're on the brink of disaster right now.”
Because of the uncertainty throughout the Colorado River system, it is difficult to get precise water use numbers by category and the state. So the bureau relied on averages to be able to gauge trends between decades.
ARIZONA
Arizona is one of the highest users of water to irrigate agriculture by sheer volume. On average, 3.5 million acre-feet of water were used annually for agriculture from 2014 to 2024, down 6% from the previous decade. Agriculture comprised 67% of the state's total Colorado River water consumption on average from 2014 to 2024.
Almost 1.3 million acre-feet of water was used by MCI from 2014 to 2024, on average, 27% of the annual water use in that time period for the state. The average amount of MCI water blossomed by 15% in a decade-to-decade comparison of averages.
The average reservoir evaporation in Arizona grew 14% to 279,082 acre-feet from 2014 to 2024. This applies only to Arizona evaporation documented by BOR data in the state and does not take into account some of the evaporation that happened at large reservoirs.
CALIFORNIA
California is another massive water user. More than three-quarters of the water used in California went towards irrigating agriculture. That was 3.1 million acre-feet on average for agriculture from 2014 to 2024, a dip of 4% from the previous decade’s average.
The other quarter of water went to city, industry and commercial uses: 1 million acre-feet on average from 2014 to 2024.
COLORADO
The Centennial State used 74% of its water towards irrigating agriculture, or 1.4 million acre-feet on average from 2014 to 2024. That is a growth of 4% from the previous decade.
Twenty-one percent of Colorado’s water went to MCI. The 401,689 average acre-feet each year is a decrease of 8% from the previous decade.
A portion of the state’s water, 5%, went to reservoir evaporation from 2014 to 2024, amounting to 89,114 acre-feet.
WYOMING
Wyoming used the highest percentage of water for irrigating agriculture of the Colorado River states at 87% on average. An average of 559,626 acre-feet went to agriculture in Wyoming from 2014 to 2024, an increase of 16% from the previous decade.
A mere 7% of the state’s water went to MCI on average. The 45,294 acre-feet for MCI on average from 2014 to 2024 dropped 23% from the previous decade.
NEVADA
Nevada is the only Colorado River state to use more of its water for MCI than for agriculture. The state put 313,243 acre-feet on average, or 79%, of the acre-feet towards municipalities, commercial and industry uses. That is a 7% decrease from the previous decade.
About one-fifth of the state’s water went to agriculture. The 75,964 acre-feet average for irrigating agriculture from 2014 to 2024 decreased 27% from the average of 2003 to 2013.
NEW MEXICO
More than two-in-three acre-feet of Colorado River use in New Mexico went to irrigating agriculture. On average, that is 257,097 acre-feet per year from 2014 to 2024. The agricultural average increased 5% from the previous decade’s average.
About one-third of New Mexico’s water use went to MCI, or 119,643 acre-feet, on average from 2014 to 2024. MCI water use decreased by 13% when compared to the 2003-to-2013 average.
A bit of water evaporated in the state each year. Just over 28,000 acre-feet on average evaporated from reservoirs in New Mexico from 2014 to 2024 — slightly less than the earlier decade. That is still 7% of the state’s average annual water use.
UTAH
Seventy-three percent of Utah’s Colorado River water went towards irrigating agriculture on average from 2014 to 2024. That is an annual average of 787,778 acre-feet — a growth of 9% from the previous decade.
Nearly one-fifth of the water went towards MCI on average from 2014 to 2024 and was 190,725 acre-feet on average. That grew by 4% compared to the 2003 to 2013 average.
About 8% of Utah’s Colorado River water went to evaporation — 90,761 acre-feet on average from 2014 to 2024. That is a slight increase of 3% from the previous decade’s average.