Buckeye, at the western edge of the Phoenix metro region, is the location of a new data center development. (Brett Walton/Circle of Blue)
BUCKEYE, Ariz. – It was supposed to be called Cipriani, a master planned community with more than 9,700 homes at the western fringe of this sprawling desert city in central Arizona.
Plans have changed. One regional growth industry – housing – is being supplanted by another – computing. Even as both carry questions about efficient use of water in one of the driest, fastest-growing areas of the country.
Last August, Cipriani Holdings sold the 2,069-acre land parcel west of the Buckeye Municipal Airport to Tract, a Denver-based data center developer. Instead of housing people, the Cipriani site, now part of the Buckeye Tech Corridor, will incorporate up to 20 million square feet of commercial space to house the cloud.
These are boom times in central Arizona for data centers, particularly in Maricopa County, which is one of the country’s largest data center markets. Factors in its favor, according to Alan Howard, an industry analyst at Omdia, a research firm, include relatively cheap land, tax incentives, low power rates, and proximity to the computing needs of the 5 million people in the Phoenix metro area.
Data centers house the servers and advanced graphics processors that are the foundation of the contemporary internet – and modern life in general. Their purposes range from the small-scale and mundane (storing your beach photos) to the hyperscale and potentially world-changing (training AI models). In aggregate, their power demands and water consumption for cooling have increased exponentially, prompting concerns about the sustainability of data center growth in the Southwest.
Despite the environmental anxieties, there is reason for optimism on water. New data centers are more efficient than older models. Some are using reclaimed water to reduce potable water demand. If the local climate is right, they can use ambient air to cool their servers. Companies like CyrusOne and Microsoft are pioneering cooling systems that consume little or no water in their direct operations, not counting water used to produce their electricity. Though there are tradeoffs involved with energy use, water consumption is increasingly becoming less an absolute constraint and more about the choices companies make.
“I’m far more concerned about energy than water,” said Glenn Williamson, CEO of the Canada Arizona Business Council and chairman of EPCOR Water, a private utility that operates in the state. “For water, we know what we need to do. We just need to pull the trigger.”
New ‘C’ in Arizona’s Economic Geography
The server fervor extends to the highest reaches of government. On January 21, just a day after his inauguration, President Donald Trump hosted a trio of tech industry executives at the White House. Larry Ellison of Oracle, Masayoshi Son of SoftBank, and Sam Altman of OpenAI stood at the president’s side while Trump announced private sector investment in AI infrastructure that could approach $500 billion. For this Stargate Project, he promised the construction of “colossal data centers” to keep America leading the AI race against China.
“I’m going to help a lot through emergency declarations because we have an emergency, we have to get this stuff built,” Trump said.
More and more of this data center “stuff” is being built in Arizona.
School kids learn Arizona’s economic geography via alphabetic repetition. Five C’s were dominant in the state’s early years: cattle, citrus, climate, copper, and cotton. As those industries decline in relative importance, it might soon be time to add a sixth C: computing. Metrics vary, but according to Howard at Omdia, the Arizona data center market is between the fourth and eighth largest in the country. All the big tech companies – Amazon, Google, Meta, and Microsoft – have a presence in the state, as do the less visible names Centersquare, CyrusOne, and QTS.
Arizona encourages the growth of data centers through a sales tax exemption that was approved in 2013. The Arizona Commerce Authority, the regulating agency, says that 64 data centers have received the exemption that covers purchases of hardware and software.
Growth has been accompanied by guardrails. Chandler was the first municipality in the state to regulate data centers. An ordinance adopted in 2022 established siting and noise-reduction requirements, but it did not mention water. The city regulates data center water use through a 2015 policy that limits these facilities to 115 gallons per day, per thousand square feet of space. For additional water needs, the company operating the data center must find an outside source.
Marana, a town 20 miles northwest of Tucson, adopted an ordinance in December that prohibits the water department from supplying data centers with potable water. Companies must find an alternative source and file an application with the town that estimates annual water consumption. No data centers are currently operating in the Marana service area, said Heidi Lasham, the town water director.
In Buckeye, Tract is laying the foundation for a development that could house 40 data centers occupying 20 million square feet at full buildout. Tract’s business model is not to build the data centers, but to acquire land and develop water, wastewater infrastructure, and energy access for the site so that tech companies have a turnkey option for quicker entry into the market.
Tract would not discuss its water plans for the Buckeye development. Graham Williams, chief investment officer, did provide a written statement when asked whether Tract would set water-use requirements for tenants.
“We secure enough water for our sites for a solution that optimizes energy and water use,” Williams wrote. “This is built into our approval process so that our end users are incentivized to maintain these standards since relevant stakeholders have signed off on them.”
In effect, Tract will attempt to balance energy and water demands, since low-water cooling often increases energy consumption.
Terry Lowe, Buckeye water manager, said Tract intends to drill wells on the site to self-supply with groundwater. In the future, he said, Tract will transfer the water system to the city when it no longer wants to be in charge of operating it. A city planning document restricts the site’s groundwater use to 2,000 acre-feet per year.
Tract’s forthcoming groundwater use highlights a loophole in Arizona water law. The state, in 2023, placed a moratorium on new housing developments outside Buckeye whose water source is local groundwater. Existing housing developments that pump groundwater must pay to recharge what they use. Neither provision applies to industrial developments like Tract’s data centers that are located in areas without a renewable surface water supply. This irritates the homebuilding lobby, which complains of unequal treatment.
Amber Walsh, an analyst with Bluefield Research, said that data center water use is a complex topic because of rapid technological change in the industry. Total water demands at present have accelerated, even as individual data centers become more efficient. When viewed nationally, all those drops, in effect, have turned into a flood.
At the state level, data centers are a modest water user, even if they can put pressure on individual utilities. Walsh’s research at Bluefield indicates that data center water consumption in Arizona in 2025 will be roughly 905 million gallons, or 2,777 acre-feet. In the Phoenix area, this is enough water for nearly 10,000 homes annually. It’s less than a tenth of one percent of the state’s annual water use.
Site-specific water data is hard to come by because companies guard the information. Still, researchers and analysts have put together national and regional estimates.
According to Lawrence Berkeley National Laboratory, data centers accounted for 4.4% of U.S. electricity use in 2023, up from 1.9% in 2018. All that power creates heat that needs to be removed. The trend toward hyperscale data centers – the largest of the large, those from the tech titans that are involved in AI computing – has had a similar inflationary effect on water use. Nationally, water consumed in data center operations grew from 21 billion liters in 2014 to 66 billion liters (53,500 acre-feet) in 2023. Indirect water use – the water consumed by the power plants that provide electricity to data centers – amounted to another 800 billion liters.
Sterling Park in Loudoun County, Virginia, is part of the state’s “Data Center Alley,” the country’s largest data center market. (J. Carl Ganter/Circle of Blue)
Water demands are not set in silicon and they involve tradeoffs. They depend on three main factors: type of cooling system, climate conditions, and operational practices. These vary based on location and data center. In favorable climates, using ambient air to cool the equipment results in no water use, but it does require more energy. Evaporative cooling, in which water is the medium for transferring heat, is less energy hungry but consumes more water. Older, water-intensive cooling system designs are being phased out in many places in favor of more efficiency. The Berkeley Lab report, however, notes that the growth of hyperscale data centers using liquid cooling could reverse the efficiency gains.
“Unlike energy, using water to cool a data center is a choice, not a requirement,” according to Alex Setmajer of Equinix, a data center operator. “While all data centers require energy, the decision to use water or not is a decision we make intentionally based on the local climate and long-term sustainability of available water sources.”
Water is becoming a hotter topic in the data center world, but it is still not the main driver for industry decisions, Walsh said. “It’s more or less they select the site that they want and then they’re like, ‘Okay, how can we make whatever water requirements work?’”
For desert areas like Maricopa County, water limits are being met with technological innovation. The eight facilities in the Chandler data center campus operated by CyrusOne do not use water for cooling, and they use a negligible amount overall, only 180,000 gallons a year for humidification. All of the company’s new data centers from 2024 onward will use zero-water cooling.
There are other examples. In December, Microsoft, a computing giant, announced a similar operational innovation for its data centers: a closed-loop cooling system that recycles water, effectively cutting water consumption to zero. The company said in a post on its website that it will pilot the technology in 2026 in data centers in Phoenix and Mount Pleasant, Wisconsin, as it works to make zero-water cooling the “primary cooling method across our owned portfolio.”
The shift to less water-intensive cooling is not without a penalty. The tradeoff is more energy use. Microsoft says this energy increase will be “nominal” due to more efficient cooling equipment. The company declined to respond to questions about how it would implement the new zero-water cooling system designs.
Shutting the Bedroom Door
For Buckeye officials, the Tract development is another step in its rapid demographic evolution. At the turn of this century, Buckeye was a quiet farm town of 8,000 people. Now, it holds almost 120,000. By the turn of the next century, city officials are planning for more than 1 million.
Every weekday morning Buckeye witnesses an exodus. Workers flow out, leaving for jobs elsewhere. City officials reckon that 90 percent of working residents leave town to earn a paycheck, many joining the Interstate 10 caravan east into Phoenix. Peak drive times can be 30 minutes longer than in the off hours.
In the evening, the flow reverses. This is the standard definition of a bedroom community: sleep there, work elsewhere. Eric Orsborn, the mayor, said he wants to change that pattern. Buckeye’s future is aimed at developing not only its residential plots but also its business sector.
The Tract development, though it will generate only a modest number of non-construction jobs, is part of this plan.
“If you’re going to build a city of let’s say 300,000 by 2040, we don’t want everybody leaving the city every day to go to work,” Orsborn said. “So it is one of our highest priorities is to attract those jobs out this way.”
This story was produced by Circle of Blue, in partnership with The Water Desk at the University of Colorado Boulder’s Center for Environmental Journalism.
Lake Powell at Wahweap Marina as seen in December 2021. Dwindling streamflows and falling reservoir levels have made it more likely that what some experts call a Colorado River Compact “tripwire” will be hit in 2027. (Heather Sackett/Aspen Journalism)
Time is ticking for states that share the shrinking Colorado River to negotiate a new set of governing rules. One major sticking point, which has the potential to thrust the parties into a protracted legal battle, hinges on differing interpretations of a few sentences in a century-old agreement.
In a recent letter, the river’s Lower Basin states – California, Nevada and Arizona – asked federal officials to analyze the effects of a hypothetical legal concept known as a “compact call.”
The problem? The 1922 Colorado River Compact says nothing about a compact call. And although the phrase often looms like a threat over Colorado River discussions, there is no agreed-upon definition of the term, what would trigger a compact call nor how one would play out. In fact, the Upper Basin states – Colorado, New Mexico, Utah and Wyoming – don’t believe the laws governing the river even contemplate it.
The February letter comes as water managers from all seven Colorado River Basin states are in the midst of deciding how Lake Powell and Lake Mead will be operated and cuts will be shared after 2026 when the current guidelines expire. In March 2024, each basin submitted competing proposals to the U.S. Bureau of Reclamation. In January, federal officials with the outgoing Biden administration released their analysis of five different potential ways forward and did not include either basin’s proposal, but a “basin hybrid” that incorporated elements from both.
In essence, the Lower Basin states have identified a potential opening with the Trump administration, and asked new leaders at the Interior Department to adopt the Lower Basin’s view on some of the most contentious and disagreed-about parts of Colorado River management.
“I believe that under the law, the compact requires delivery of 7.5 million acre-feet of water on a 10-year rolling average, plus one-half of the Mexico Treaty obligation to the Lower Basin,” said Tom Buschatzke, director of Arizona’s Department of Water Resources. “So we want to see Reclamation, as our request indicated, incorporate that outcome into the modeling for any alternative to look at. That includes how reductions in the Upper Basin states might have to occur.”
Over a century ago, the compact split the river’s water evenly, with half (7.5 million acre-feet a year) going to the Upper Basin and half to the Lower Basin. Another 1.5 million acre-feet a year was later allocated to Mexico.
The crux of the dispute comes from how the Upper Basin states and the Lower Basin states each interpret a key phrase in the compact: “The States of the Upper Division will not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 75,000,000 acre-feet for any period of ten consecutive years…”
To the Upper Basin states, “will not cause” means that their use won’t be the reason the Lower Basin doesn’t get its allocation. They see it as a “non-depletion” obligation.
According to Colorado officials, they’re not delivering water downstream, but rather they’re not causing the flows to be depleted.
“What this means is that if the flows were to drop below 75 million acre-feet over a ten-year period, there would be an inquiry into what caused that to occur,” Michael Elizabeth Sakas, Colorado River communications specialist with the Colorado Water Conservation Board said in a written response to questions from Aspen Journalism.
On the other hand, the Lower Basin states say they’re owed the water, with the Upper Basin states required to send the 75 million acre-feet over 10 years, plus half of the Mexico Treaty obligation (which works out to 82.5 million acre-feet every 10 years) downstream to the Lower Basin.
Colorado River expert Eric Kuhn says that the latest report from the U.S. Bureau of Reclamation is a major caution sign for the basin. An anemic snowpack this past winter could be setting the basin on the road to a compact call (as defined by the Lower Basin). The most recent federal forecast predicts that in 2027, the 10-year cumulative flow at Lee Ferry could drop below 82.5 million acre-feet, a threshold Kuhn calls the first “tripwire” for a compact call.
“If flows were to go below 82.5 million, then that’s the first time, in theory, the lower division states could point to the Upper Basin and say, ‘You’re not complying with your compact obligations,’” Kuhn said. “This is not going to sneak up on us. I think most of the modeling shows that it’s almost inevitable we will drop below 82.5 in the next three or four years.”
But Upper Basin officials disagree. In their interpretation, this tripwire doesn’t exist. A compact call is a concept recognized only by the Lower Basin.
They also point out that calls for water apply to situations where there is a senior rights holder and a junior rights holder. Under the prior appropriation system, the oldest water rights get first use of the river, and senior rights can force junior rights to stop using water so seniors can get the full amount they are entitled to. But Upper Basin officials say there is no priority between the two basins; they are on equal standing.
That may be true, but the three Lower Basin states are also home to the basin’s biggest water users and cities, with more political power than the sparsely populated Upper Basin states.
Navajo Bridge spans the Colorado River downstream from Lake Powell near Lee Ferry, the dividing line between the upper and lower basin. Some federal forecasts predict that in 2027, the flow at Lee Ferry could drop below a critical threshold that some experts call a “compact tripwire.” (Heather Sackett/Aspen Journalism)
River headed for “wildly uncharted territory”
So what would happen if and when the river shrinks enough to trigger the first compact tripwire?
In practice, a compact call could mean the Lower Basin states would sue the federal government to get them to send more water downstream from Lake Powell. (The U.S. Bureau of Reclamation is responsible for making releases from Lake Powell and Lake Mead.) The Lower Basin states could also demand that the Upper Basin states implement cuts to get more water into Lake Powell. But the Upper Basin states will almost certainly argue they are in compliance with the compact and don’t need to make cuts. The Supreme Court could then decide whether the Upper Basin states are in compliance with the compact.
“It’s wildly uncharted territory,” said Chuck Cullom, the executive director of the Upper Colorado River Commision. “It’s not a straightforward path to say: ‘We need you to release more water out of Glen Canyon Dam and curtail uses.’”
The Upper Basin’s argument hinges on what is causing the flows at Lee Ferry to drop. The four states say it’s not their fault, because they only use between 3.5 and 4.5 million acre-feet a year, far less than their allocation of 7.5 million acre-feet. The culprit, they say, is climate change, which according to scientists has contributed to a 20% decline in flows from the 20th century average. They have also shown that every 1 degree Celsius of warming results in a 9% reduction in flows.
With a fixed number for how the river is shared, and a slowly dwindling amount of water available, the Upper Basin has been bearing the brunt of the effects of climate change, a phenomenon that Kuhn calls the “Upper Basin squeeze.” But the climate change argument could open a can of worms.
“There are numerous other water compacts between states,” Kuhn said. “Are we reopening every one of those? It could mean that other states do not have to comply with their compact obligations.That would be a precedent decision that would affect every compact in the western United States.”
How would cuts work?
Water users on Colorado’s Western Slope are eager to know how cuts could play out and over the past few years they have asked state officials repeatedly for more clarity on this issue. One reason is because most of the big transmountain diversions that take water from the mountainous headwaters of the Colorado to Front Range cities date to after the 1922 compact, meaning they would likely be cut first. But as the population centers and economic engines of the state, it’s unlikely a plan to cut water use would include turning off the taps to Denver.
In a crisis situation where cuts are mandatory, the strict prior appropriation system would probably not hold.
“They’re going to have to make hard decisions, and they are going to primarily meet the human health and safety needs of people first,” Kuhn said. “It’s an open secret that the priority system works under normal conditions; it doesn’t work in emergencies.”
Western Slope water users also want to know the state’s plan for cuts, because some areas may be more at risk of forced cutbacks than others. The Yampa/White/Green River basin in the northwest corner of the state, for example, developed later than other places, with lots of more junior water rights. Would they be first on the chopping block?
“We believe that regardless of where things stand on the river, clarity can’t hurt water users,” said Peter Fleming, general counsel with the Colorado River Water Conservation District. “In the long run, clarity will help people to plan better.”
But state officials have been reluctant to provide clarity about how cuts could be implemented, saying now is not the time to plan for it and that the Upper Basin states have always been in compliance with the compact.
“Colorado is not at risk of any compact curtailment scenario in the near future,” Sakas said in a written response to Aspen Journalism. “For the last 20 years, the Upper Basin has been using half of what we are allowed to use under the 1922 Compact while our downstream neighbors use significantly more than their apportionment.”
Figuring out who would be the first to take cuts and tracking that water to the state line would not be an easy task, said Colorado River expert Jennifer Gimbel. Gimbel is the senior water policy scholar at the Colorado State University Water Center and is the former director of the Colorado Water Conservation Board.
“It would be a tremendous headache and a huge undertaking,” she said. “But I don’t know if that means we shouldn’t be doing it.”
The Colorado Division of Water Resources, in a first step, has been developing measurement rules and requiring measurement devices for water users across the Western Slope. According to state officials, the goal of this effort is to accurately measure diversions so that if necessary, Colorado sends downstream only the water that is required to maintain compact compliance and not a drop more.
Trying to stay out of court
One thing most water managers agree on is that finding a seven-state consensus is better than the potentially protracted litigation possible under some kind of compact call scenario. Some are hoping for the best but preparing for the worst. The Arizona Department of Water Resources requested about $1 million last year for Colorado River litigation from the state budget. Buschatzke said the Upper Basin states might fare worse under a compact call than they would by adopting the Lower Basin proposal.
“Because there are a lot of moving parts, litigation — a compact call — is a possibility,” he said. “It’s not a possibility I want to see occur. But I’ll have to do what I have to do to protect the state of Arizona.”
If the states can come up with new guidelines that fairly share the river, the threat of a compact call, which has long hung over Colorado River management discussions, could evaporate like water from the surface of Lake Mead. Cullom said that in 2007 when the seven states implemented the soon-to-expire guidelines that are currently in place, they agreed that if the two basins made good on their commitments outlined in those guidelines, they would set aside the issue of compact compliance — at least until after 2026.
“If they can figure out a way to live within the means of the river in such a manner that both the Upper Basin and Lower Basin agree, hopefully addressing a compact call again won’t be needed because it’s been addressed,” Gimbel said.
This story was produced by Aspen Journalism, in partnership with The Water Desk at the University of Colorado’s Center for Environmental Journalism.
Sleepy Bear Mobile Home Park resident Renee Hoffman washes dishes at her kitchen sink on January 21, 2025. After learning that her neighborhood water system is contaminated with PFAS, Hoffman started to distrust her tap and stopped using tap water for most household purposes. After washing the dishes, she carefully wipes them down, out of an abundance of caution. (Rae Solomon/KUNC)
Renee Hoffman was never thrilled about the water quality at her house in Sleepy Bear Mobile Home Park on the outskirts of Steamboat Springs.
“It just didn’t taste great,” she said. “It had that kind of calcium buildup and stuff.”
But one day in 2023, she got a letter from the mobile home park management that made her distrust her tap in a whole new way.
“This drinking water notice came through, telling us that there was PFAS in the water,” she said.
Polyfluoroalkyl Substances, or PFAS, are a class of compounds sometimes called “forever chemicals” because they don’t break down naturally in the environment.
“PFAS are ubiquitous,” said Zach Schafer, director for policy at the Environmental Protection Agency’s Office of Water. “They’re used in countless products that we use every day, whether it’s nonstick cookware or waterproof clothing. It’s used in stain resistant carpets. It’s used in firefighting foam. And it’s very useful, which is why it’s been used since the 1940s.”
But PFAS are also very harmful. Exposure to even a small amount of some PFAS compounds, like Perfluorooctanoic acid, or PFOA, and Perfluorooctanesulfonic acid, or PFOS, can disrupt immune response, liver and thyroid function and cause heart disease and cancer. They can also affect developing fetuses.
“We’re increasingly learning that some PFAS that we’ve studied a great deal have pretty serious adverse health effects at very, very low levels,” Schafer said. “Based on the latest science, there really is no safe level in drinking water.”
The notice that Hoffman received included information from the Colorado Department of Public Health and Environment informing her that the shallow water well supplying her small neighborhood had tested positive for PFOA and PFOS and warning about the potential health impacts of exposure.
“I almost threw it out,” she said. “But I’m glad I opened it, because I wouldn’t have heard of it any other way.”
The shallow well at the Sleepy Bear Mobile Home Park on the western edge of Steamboat Springs sources water from the Yampa River to supply the 54-lot neighborhood. The water system tested positive for PFAS in 2023. (Rae Solomon/KUNC)
The letter offered some recommendations for reducing exposure but stopped short of telling residents to stop drinking their tap water, “as current health advisories are based on a lifetime of exposure.”
That did little to reassure Hoffman that the water was safe for her family.
“We stopped giving it to our animals, stopped using it to cook noodles and things like that. We just stopped using it altogether,” she said.
New drinking water standards
Last year, the EPA created new drinking waterstandards that limit PFOA and PFOS to less than 4 parts per trillion, which is the smallest concentration tests can reliably detect. But PFAS have already worked their way from industrial sources into drinking supplies across the country. The EPA estimates between 6 and 10 percent of the nation’s utilities are contaminated. They have until 2029 to fix the problem.
“We are going to save thousands of lives, prevent tens of thousands of avoidable illnesses, and reduce the levels of PFAS in more than 100 million people’s drinking water nationwide,” Schafer said.
The new rules will require all water systems across the country to start monitoring PFAS by 2027. But some states are ahead of the curve. The Colorado Department of Public Health and Environment launched a free, voluntary testing program in 2020 and state officials report that so far, about two-thirds of the state’s water utilities have opted in.
Through that program, the state has already identified 29 water systems, in communities large and small, with a PFAS problem that needs to be addressed.
For the most part, the point of contamination remains a mystery and public health officials are more focused on removing the chemicals than discovering their source.
“Rarely can we trace the levels we detect in drinking water back to specific sources of PFAS contamination,” a CDPHE representative wrote in an email. “Our focus is to help our public water systems assess PFAS levels in their drinking water and reduce exposure.”
The good news, according to Schafer, is that the technology to remove PFAS from drinking water already exists and is readily available.
“Those include activated carbon ion exchange and reverse osmosis,” he said.
But for some utilities, it might make more sense to reduce their reliance on or to simply stop using a contaminated water source.
“Depending on the specific characteristics, the size and the needs of a water system, they can choose how to meet the standard,” Schafer said. “It’s going to vary based on what PFAS are in their water, at what levels, and what the design of the water treatment system already is. So, it really isn’t going to be a one-size-fits-all approach.”
Costly fixes for small water systems
No matter the approach, dealing with PFAS contamination is bound to be a major undertaking. According to John DeGour, regulatory affairs specialist with the National Rural Water Association, smaller communities are likely to find it a struggle.
“You have to pay for sampling, you have to install treatment if necessary, or find a new source,” he said. “But if you’re a small system, you obviously have less resources to do that.”
When PFAS turned up in one of the wells supplying rural Keenesburg, on Colorado’s Eastern Plains, public works director Mark Gray was surprised.
Well 11, one of several wells supplying water to rural Keenesburg, Colo. from the Lost Creek Alluvial, first tested positive for PFAS contamination in 2019. The small water system serving about 860 users has until 2029 to reduce PFAS levels to new federal standards adopted last year. (Rae Solomon/KUNC)
“I never anticipated us to have any PFAS in our wells,” he said. “It’s the biggest problem we have. It’s the only problem we have.”
His first instinct was to look for ways to pay for potentially expensive fixes.
“We have made applications to every grant available — grants for engineering, grants to build filtration. We are very actively looking at everything that’s available to us,” Gray said.
Congress set aside billions in the Bipartisan Infrastructure Law of 2021 to address PFAS in drinking water. That includes $6 billion specifically for small and disadvantaged communities. According to the CDPHE, Colorado has already received $31 million out of a promised $189 million for PFAS remediation. But with a cloud of uncertainty over how the new Trump administration plans to dole out federal funds, it’s suddenly unclear whether and when the balance will ever reach its intended users.
It’s still too soon to know which PFAS removal approach will be right for Keenesburg, or what the price tag will be. And while any grant funding that is made available can help cover the initial costs, utilities will ultimately be on the hook for the cost of ongoing operations.
“We’re being tasked from the EPA to try to come up with an almost impossible standard,” Gray said. “You almost have to anticipate the increased cost in treatment.”
Those increased costs will likely raise the rate that consumers pay for water. But utilities will have little choice.
“We’re a small town and we’re one of the few communities that provides its own water,” Gray said. “We want it to be safe.”
As for the Sleepy Bear Mobile Home Park, the easiest solution just might be to abandon the neighborhood well altogether and tap into the municipal system in Steamboat Springs.
Renee Hoffman no longer gives her dog and cats tap water after learning that the local water system contains PFAS. Now she hauls in extra filtered water from a private treatment plant down the road. (Rae Solomon/KUNC)
“We support that and we want to work with Sleepy Bear to make that happen,” said Steamboat Springs water distribution and collection manager Michelle Carr. “It’s really just a matter of figuring out the logistics.”
Those logistics would have to include extending the city water main westward, a project Carr said the city has already planned and budgeted for as they eye future developments on the city’s western edge.
But even that could come at “significant cost,” according to Thomas Morgan, manager of KTH Enterprises, which owns Sleepy Bear Mobile Home Park. Via text message, he wrote that he has been meeting with city officials, “to see if costs and requirements could be lessened.”
Indeed, there might be some appetite among city council members to subsidize a connection to the city water system for the mobile home park, “because of their interest in supporting affordable and low-income housing,” Carr said.
But from resident Renee Hoffman’s perspective, the park management needs to make clean water a priority, whether or not those subsidies come through.
”There’s a lot of young kids here,” She said. “To think that they were drinking that water from infancy — what levels they might have in their bodies.”
And she just wants her family to be able to do normal things again, like brush their teeth and wash the dishes without worrying that the water could make them sick.
“Nobody wants their rent to be raised, right?” she said. “But if we were to secure a better water source for our long-term health, I think you just have to weigh the benefits of it and ante up, I guess.”
This story was produced by KUNC, in partnership with The Water Desk at the University of Colorado’s Center for Environmental Journalism.
Buckeye, Arizona, has plans to become one of the Southwest’s largest cities in the next decades. (Brett Walton/Circle of Blue)
BUCKEYE, Ariz. – Beneath the exhausting Sonoran sun, an hour’s drive west of Phoenix, heavy machines are methodically scraping the desert bare.
Where mesquite and saguaro once stood, the former Douglas Ranch is being graded and platted in the first phase of a national real estate developer’s gargantuan plan that foresees, in the next few decades, as many as 100,000 new homes to shelter 300,000 people. In late October 2024, dozens of trees, salvaged from the land and potted as if they had just arrived from the nursery, watched over the quiet construction zone.
This remote site in western Maricopa County, between the stark White Tank Mountains and frequently dry Hassayampa River, is the location of Teravalis, the largest master planned community in Arizona and one of the largest in the country. It is part of a constellation of roughly two dozen master planned communities in the area – with names like Tartesso, Festival Ranch, Sun City Festival, and Sun Valley – that could propel upstart Buckeye in the coming decades to one of the largest cities in the Southwest. Buckeye planning documents anticipate a city population later this century between 1 million to 1.5 million if all the master planned communities are fully built out.
The Phoenix metro area is expanding ever outward, riding the decades-long wave of a nationwide redistribution of people toward warmer, sunnier states. That population growth – the state added nearly 1.2 million people in the last 15 years – has driven up home prices and pushed single-family home buyers into lands farther removed from the center. Buckeye is about as far removed as it currently gets.
All the while, the state’s water supply has declined. The Colorado River, shrinking due to a warming climate, has been in shortage condition since 2022, a situation that has cut Arizona’s allocation from the river by at least 18% annually. Groundwater, which has nurtured Buckeye to this point, is no longer sufficient for new growth in the area, the state says. Arizona Department of Water Resources decisions in 2023 about groundwater availability in the region sent shockwaves through the housing industry, halting new subdivisions in Buckeye and certain other locations around Phoenix that would have used local groundwater. The decisions affected only proposed developments that had not yet received permits to pump groundwater.
“We’re in an era of limits,” Tom Buschatzke, director of the Arizona Department of Water Resources, reiterated during a January 16, 2025, meeting to discuss new policies that could unlock homebuilding in the area. The Arizona Municipal Water Users Association echoed that sentiment weeks earlier: “Arizona’s future is not secure if we continue to depend only on groundwater.”
The Home Builders Association of Central Arizona, an influential trade group, reckons that 200,000 homes in the greater Phoenix area for which builders thought they had sufficient water are now in limbo. On January 22, 2025, the association announced a lawsuit against the state over its restrictions on groundwater use that have held up home construction.
Howard Hughes Holdings, the national real estate company that is developing the 37,000-acre Teravalis site, has secured water for only the first 8,500 homes, some of which are scheduled to be ready by next year. Where will the rest of the water come from? Deals could be made with nearby tribal nations to lease their senior rights. Ag land could be bulldozed and the water given over to housing. Wastewater can be cleaned up and reused. Groundwater could be pumped from designated “transport” basins from which water can be moved outside its natural watershed. Many options are on the table – even a farfetched pipeline carrying desalinated water from Mexico – but they require delicate political negotiation, wads of money, or both.
The exurban growth is a clash between Old Arizona, with its cotton fields and cattle ranches, and New Arizona’s subdivisions and silicon chip manufacturers. In Buckeye, the two eras often occupy adjacent parcels, each representing different ways of irrigating the Arizona Dream. Behind all the political maneuvering is one overriding question: How should Arizona’s limited water be used?
Growing Pains
Until this century, Buckeye was a tiny farm town known for its cotton fields and rodeo. Its story since then has been one of audacious growth. In the last 25 years, the number of residents has climbed from roughly 8,000 to now almost 120,000. And that’s just the start.
The Buckeye Planning Area, designated by the city, encompasses 639 square miles. Phoenix, by comparison, spreads across 519 square miles. Not all of the Planning Area is within the current Buckeye city limits, but city officials do anticipate that those lands, prior to development, will be incorporated in order for them to access city services. At present, just 15% of the Planning Area is developed and the city boundaries are a patchwork of annexations.
“Water and infrastructure are really the two most significant challenges I think that we have moving forward,” said Eric Orsborn, mayor of Buckeye.
Orsborn, an enthusiastic municipal booster who owns a construction business, knows the importance of the homebuilders. “You’re the fuel that helps us grow,” Orsborn told a representative from the Home Builders Association of Central Arizona at a Buckeye City Council meeting on October 15, 2024.
Because of its farming history, Buckeye is latticed with irrigation canals. (Brett Walton/Circle of Blue)
To understand the current brouhaha over housing development, turn back the clock 45 years. At the time, groundwater extraction was so rampant that the land surface was sinking and wells were going dry. The state needed to rein in its use. Lawmakers did so through the Groundwater Management Act of 1980, which established four “active management areas,” or AMAs, in which groundwater would be regulated. Now there are seven AMAs. Municipalities in the AMAs could become “designated water providers” if they proved a 100-year renewable supply of water such as treated wastewater or a surface water source like the Salt River or Colorado River, which began to be delivered to the Phoenix area via the Central Arizona Project canal in 1985.
Buckeye, because it still relies almost exclusively on groundwater, is one of the few cities in the Phoenix AMA that is not a designated provider. This has consequences. The city’s three water providers pump groundwater and residents pay the Central Arizona Groundwater Replenishment District, a state-created agency, to recharge a portion of that pumping. Meanwhile, commercial and industrial users, which are not subjected to the same groundwater restrictions as residential customers, are allowed to build and pump without replenishment. The city has recently welcomed distribution centers from the retailers Five Below and Walmart. But Buckeye is not allowed to pump more groundwater to serve new outlying subdivisions. Instead, master planned communities like Teravalis that are located in an AMA are responsible for securing their own water and proving a 100-year renewable supply. This is called a certificate of assured water supply.
Until recently, local groundwater sufficed for these certificates. Howard Hughes will be using groundwater for Floreo, the 8,500-unit first phase of Teravalis that is now under construction. But at the moment water supply for the rest of the project and for other projects around it in the Hassayampa basin are in doubt because of a state determination in 2023 that local groundwater is insufficient and cannot be used for a certificate of assured water supply. The Home Builders Association of Central Arizona disputes the modeling that informed the decision, and filed a lawsuit on January 22 to reverse it.
In parallel, state lawmakers and water officials are attempting to promote workarounds that would appease homebuilders and cities like Buckeye and allow limited groundwater pumping in the short term, but also protect long-term groundwater sustainability in the AMAs.
One option, which has already been approved by the Gov. Katie Hobbs, provides places like Buckeye a way to become designated providers while still pumping groundwater in the interim. Buckeye leaders and representatives for the master planned communities initially objected to stipulations in the program that they felt required them to give up too much water for too little benefit. Nonetheless, Buckeye has now committed to applying for this ADAWS program.
The second consideration is a voluntary program to incentivize the conversion of farmland to housing. These discussions were initiated after Gov. Hobbs vetoed a bill on the topic last year because she felt the ideas needed more vetting. The intent is two-fold, said Tom Buschatzke of the Department of Water Resources: allow more housing to be built but also secure a long-term reduction in groundwater use by facilitating what has already been taking place in the state in the last century. The ag-to-urban concept would not help places like Teravalis, which is being built on desert land north of I-10, not former farmland. And there are still big unanswered questions about how much water could be given over to housing, how much would need to be replenished underground, which lands would qualify, and where the water could be used.
Billboards in Buckeye advertise new homes for sale. (Brett Walton/Circle of Blue)
Grady Gammage Jr., a lawyer at the Phoenix-based firm Gammage & Burnham who works at the intersection of real estate development and water supply, called the current groundwater situation a “logjam.” In his view, what’s needed is a compromise that allows for some groundwater use now with an assurance to build the expensive infrastructure to bring in an alternative water source down the road to fill the gap.
“One of the things that I think somebody needs to take the lead in thinking about is the big picture infrastructure solutions,” Gammage Jr. said.
Those discussions will take some time because state officials do not want to rush the process, said Patrick Adams, the governor’s water policy adviser. “We want there to be consensus, bipartisan work, and really rigorous analysis on these pretty impactful water policy program changes.”
Water-Efficient Designs
What gets built determines water use. New housing developments in Arizona require less water than their predecessors because of landscaping changes, said Spencer Kamps, vice president of legislative affairs for the Home Builders Association of Central Arizona. Xeriscaping – employing desert-native vegetation – is the norm, both through changes in code and changes in culture. To mimic a lawn aesthetic, some homes in new subdivisions have patches of artificial turf in front of the house. But turf grass is out.
Outdoor use is the biggest factor for a residential development’s water footprint. The dry desert air vacuums moisture from the ground and turf grass lawns are relatively thirsty embellishments. Terry Lowe, Buckeye water director, said that about 60% of the city’s residential water is used outdoors.
Many new developments in the state share a defining trait: they are built atop former farm fields. The replacement of crops with cul-de-sacs has helped moderate water use, which is less today than in the mid-1950s, when only a million people lived in the state.
Howard Hughes is pitching Teravalis as a continuation of this trend toward environmentally conscious development, though it is being built in the desert, not on formerly irrigated fields. A slide deck for investors notes the company’s intention to be “one of the leading sustainable MPCs in the nation with a strong focus on environmental awareness and innovative technology.” Its promotional materials advertise water-efficiency goals of 35% below the state average water use per person. There will be limits on pool size and covers required to reduce evaporation when not in use. Wastewater will be reclaimed and recycled for park irrigation. Howard Hughes representatives declined to be interviewed for this story or to respond to written questions about their water use and development plans.
Before sunrise in mid-October, roosters crow and nail guns can be heard in the distance. Construction workers are already at the job site on a day in which the temperature will exceed 100 Fahrenheit. (Brett Walton/Circle of Blue)
Achieving these goals requires help. Building decisions are a three-partner dance between developers, homebuilders, and municipalities. Developers like Howard Hughes are responsible for the big capital investments: buying land, acquiring water, and installing streets, sidewalks, and drainage. This is all the “horizontal” infrastructure.
Once these assets are in place, the “vertical” stage – homebuilding – can begin. Developers offer blocks of the platted land to established companies like Lennar, KB Home, Brightland, and Century Communities. These homebuilders follow local and state codes, as well as developer preferences, which can be stricter than code requires, Kamps said. In the case of Teravalis, Howard Hughes will set the water use goals and homebuilders will follow the lead.
That guidance from Howard Hughes is not yet available, according to one of the seven companies selected to build homes there. Jill Ebding of Courtland Communities said that Howard Hughes has not told them final water-efficiency design guidelines.
“We can submit a house plan with just four walls, a roof, and a foundation – here’s our floor plan,” Ebding said laughing. “But we haven’t set up anything with landscaping or anything additional like that.”
Will the designs in the Floreo phase of Teravalis be substantially different from what is already on the market? Ebding did not think so, at least not from Courtland Communities.
Road to Somewhere?
The road to Teravalis, at exit 109 from I-10, is named Sun Valley Parkway. Built by private investors in the late 1980s, the road was a lonely speculation that one day people would move here. Expected growth did not happen immediately. “It was like a road to nowhere that was great for biking, was great for truck driving schools going out and practicing and training,” Orsborn said about the parkway’s early years.
Teravalis, a project of Howard Hughes Holdings, a national real estate developer, envisions 100,000 homes in the desert north of Buckeye — if the company can find water for them. (Brett Walton/Circle of Blue)
Sun Valley is still, by and large, a lonely road. Tartesso is out this way, at the southern end, closest to central Buckeye. At the northern end, where the road loops east around the White Tank Mountains in the direction of Phoenix, is Sun City Festival. In the middle, miles from any habitation, is the blank slate of Teravalis and the outlines, in planning documents, of a half dozen other master planned communities. Gammage Jr. said that, due to the vagaries of real estate development, not all the housing units approved by the city will ultimately be built. But many will.
Such growth has been the history of Arizona since statehood: defying watershed limits while engineering solutions to fill the supply gap. Cities, meanwhile, have expanded farther into the desert and tapped increasingly distant water sources. New water sources will not be cheap water sources. Knowing this, Orsborn looks at future growth as a challenge to be met step by step.
“We don’t have to solve water for the entire 1 million people today,” Orsborn said. “We can do this incrementally and come up with the water needs for the next 10 to 20 years.”
If local groundwater is no longer available, the next chapter of growth in Buckeye will have to come from a creative alignment of finance, policy, technological innovation, and deal making – the New Arizona mix that sees a road in the desert and thinks it can lead somewhere.
Editor’s note: This article has been updated to reflect that Buckeye will apply for the state’s Alternative Designation of Assured Water Supply (ADAWS) program.
This story was produced by Circle of Blue, in partnership with The Water Desk at the University of Colorado Boulder’s Center for Environmental Journalism.
The Water Desk is excited to announce the participants for the Rio Grande Journalist Training and Workshop, taking place in Albuquerque, New Mexico, in January 2025.
This training program will bring together journalists dedicated to enhancing coverage of water issues along the Rio Grande, fostering collaboration among news outlets and deepening understanding of critical challenges facing the region.
The Rio Grande flows from the Rocky Mountains of Colorado, through New Mexico and Texas, while forming the U.S.-Mexico border. Like many Southwestern waterways, the river has been ravaged by a more than two-decade-long dry spell made worse by climate change. Coverage of the communities and ecosystems dependent on the Rio Grande is essential to understanding what’s at stake as the gap between water supply and demand widens.
The Water Desk selected 14 journalists to participate in the training, reflecting diversity in geography, race, ethnicity, gender and medium.
Participants:
Spenser Heaps, Indepdendent
Catherine Jaffee,Independent
Elizabeth Miller,Independent
Jeremy Miller,Independent, contributing writer, Sierra Magazine
Caitlin Ochs,Independent
Danielle Prokop,Source NM
Martha Pskowski, Inside Climate News
María Ramos Pacheco, The Dallas Morning News
Elliot Ross, Independent
Nadav Soroker, Searchlight New Mexico
Ishan Thakore, Colorado Public Radio
Caroline Tracey, Independent
Emery Veilleux, The Taos News
Christian von Preysing, KRGV-TV
As part of The Water Desk’s training program, participants will hear from legal experts, water users and tribal members along the Rio Grande to hear varying perspectives on how the river is a key part of the region’s cultural, political and geographic landscape.
The workshop will feature expert-led sessions on the complexities of water management and opportunities to network with peers and regional water experts. The Thornburg Foundation, a Santa Fe-based family foundation, is providing the financial support to make this training possible, while the program is the sole responsibility of The Water Desk.
The site where Ute Water plans to build Owens Creek Reservoir at 8,200 feet on the Grand Mesa was snow covered by mid-November. The Western Slope’s largest domestic water supplier has conditional water rights for the 7,000-acre-foot reservoir. Photo: William Woody
Just add waterThe site where Ute Water plans to build Owens Creek Reservoir at 8,200 feet on the Grand Mesa was snow covered by mid-November. The Western Slope’s largest domestic water supplier has conditional water rights for the 7,000-acre-foot reservoir. William Woody
Nearly two hours east of Grand Junction on a remote dirt road on the Grand Mesa is a nondescript, shallow, sage-brush-covered valley where two creeks meet.
The site, at 8,200 feet in elevation, is home to a wooden corral where ranchers with grazing permits gather their livestock and to the Owens Creek Trailhead where hikers set out for nearby Porter Mountain.
It’s also the spot where the largest domestic water provider on Colorado’s Western Slope plans to someday build a reservoir. The proposed Owens Creek Reservoir is modest in size, at about 7,000 acre-feet. It would help Ute Water Conservancy District satisfy the needs of its 90,000 customers into the future.
“Our job as a water provider is never done,” said Greg Williams, assistant manager at Ute Water. “You can develop one and you move onto your next project and go through that same process.”
Ute Water Assistant Manager Greg Williams, left, stands at the site of the proposed Owens Creek Reservoir on the Grand Mesa. Cities across the state have conditional water rights that save their place in line while they work to develop projects. William Woody
In most cases, water in Colorado must be put to beneficial use to keep a right to use it on the books. The cornerstone of Colorado water law is the system of prior appropriation, where the oldest water rights get first use of rivers. And hoarding water rights without using them amounts to speculation, which is illegal. But a Colorado water law feature known as a conditional water right allows water-rights holders to skirt this requirement and hold their place in line. The conditional water rights for the proposed Owens Reservoir date to 1972, although work to build this particular reservoir appears limited to preliminary studies and work on other related components of Ute Water’s system.
Ute Water, along with many other cities, conservancy districts and oil and gas companies across the Western Slope, are hanging on to water rights that are in some cases a half-century old without using them. Conditional water rights allow a would-be water user to reserve their priority date based on when they applied for the right, while they work toward eventually using the water. The result is millions of acre-feet worth of conditional water rights on paper that have been languishing for decades without being developed. Some of these rights are tied to large reservoir projects.
An analysis by Aspen Journalism found that across Colorado’s Western Slope, cities, conservancy districts, fossil fuel companies and private entities hold conditional water rights that would store about 2.6 million additional acre-feet from the Colorado River and its tributaries in not-yet-built reservoirs each bigger than 5,000 acre-feet. This is a staggering amount of water storage and more than the entire state of Colorado currently uses from the Colorado River basin, which is about 2.1 million acre-feet a year.
Most of this water would be stored in not-yet-built reservoirs, each bigger than 5,000 acre-feet. In some cases, the water would be stored in already-existing reservoirs, using conditional rights that would allow the reservoir to be refilled or enlarged.
Ute Water has plenty of company among the state’s conditional water rights holders. The Glenwood Springs-based Colorado River Water Conservancy District has rights from 1972 for the 66,000-acre-foot Wolcott Reservoir on Ute Creek in Eagle County; Mountain Coal Company says it wants to build the 75,000-acre-foot Snowshoe Reservoir on Anthracite Creek near Kebler Pass with rights from 1969; and Denver Water has plans for the 350,000-acre-foot Eagle-Colorado Reservoir on Alkali Creek in Eagle County using water rights from 2007. These are just a few examples of the 94 conditional water rights for new and existing reservoirs of 5,000 acre-feet or more planned for western Colorado identified by Aspen Journalism.
The 1922 Colorado River Compact promised 7.5 million acre-feet to the Upper Basin, which so far has never come close to using its half. The state of Colorado has the right to use 51.75% of the Upper Basin’s allocation.
In a way, this planned water development represents the hopes and dreams for the future growth of the Colorado River’s Upper Basin states — Colorado, Wyoming, Utah and New Mexico. The 1922 Colorado River Compact promised 7.5 million acre-feet to the Upper Basin, which so far has never come close to using its half. The state of Colorado has the right to use 51.75% of the Upper Basin’s allocation.
But some experts say these proposed reservoirs are unrealistic wishes of the past, a vestige of the mid-20thcentury frenzy of dam building across the West that is mismatched for 21st century conditions. They say if this scale of future development comes to pass, it would upend the system of water rights, as well as harm the environment. They say the water court system that keeps these phantom reservoirs alive is being abused and should be reformed. In the era of historic drought, climate change and crashing reservoir levels, where users already see shortages in dry years, some say this amount of water for new development simply does not exist.
The Colorado River flows past a golf course near Parachute. Cities, conservancy districts, energy companies and private entities have conditional water rights for 2.6 million acre-feet of water to be stored across the Western Slope. William Woody
The Upper Basin’s dreams of water development also highlight a central tension at the heart of the current disagreement between the Upper Basin and the Lower Basin states of California, Arizona and Nevada. The two sides have not been able to reach an agreement about how the river’s two largest storage buckets, Lake Powell and Lake Mead, should be operated in the future and how cuts should be shared in drought years. Negotiations are currently at an impasse.
“If all these water rights were developed, it would be a disaster. I think everybody understands that.”
Mark Squillace, a natural resources law professor at the University of Colorado Boulder
Over the past 100 years, the Lower Basin has fully developed its share of the river and then some. The Upper Basin has not, but it believes it is still entitled to, despite the contradictory nature of both committing to conservation while holding on to plans for new future uses.
“It’s especially a problem when we’re trying to find more water to reduce the amount of depletion on the Colorado River,” said Mark Squillace, a natural resources law professor at the University of Colorado Boulder. “If all these water rights were developed, it would be a disaster. I think everybody understands that.”
Holding on to conditional rights
The Colorado River meanders through the Grand Valley, where it turns peach orchards and alfalfa fields green. Ute Water, the largest domestic water provider on the Western Slope, plans to build additional reservoirs to serve its Grand Valley customers. William Woody
Entities can’t just hang on to conditional water rights in perpetuity. To maintain a conditional right, an applicant must every six years file what’s known as a diligence application with the state’s water court, proving that they still have a need for the water, that they have taken substantial steps toward putting the water to use and that they “can and will” eventually use the water. They must essentially prove they are not speculating and hoarding water rights they won’t soon use.
A cottage industry has sprung up around these diligence filings. Engineering firms produce studies that show a conditional water rights holder has worked to develop the water right. Attorneys file diligence applications with the water court and then see them through the sometimes yearslong process to get it renewed for another six years.
Aspen Journalism’s analysis looked at only the biggest proposed reservoirs on the Western Slope, but every year, hundreds of diligence applications are filed statewide for smaller amounts of water.
And the bar for proving diligence is low.
“It’s only limited by the imagination of the lawyer who’s filing the application about what you can claim for diligence,” said Aaron Clay, a longtime water attorney and water court referee in the Gunnison River basin, who teaches community courses about the basics of water law across the Western Slope.
The standard for reasonable diligence is much lower now than it was decades ago, Clay said, because state officials want at least some of these reservoirs to be built. The thinking is practical and political: Building more reservoirs makes it easier to control the timing and amount of water Colorado lets flow downstream.
Water court judges are hesitant to abandon these conditional water rights, even if they have been languishing without being used for decades partly because in Colorado water is treated as a fully vested property right, where the state may have to compensate water rights holders if they take it away from them. And owners of these rights believe they are valuable and are reluctant to let them go. The status quo is maintained because there’s no incentive for anyone to scrub these unused water rights from the books.
Water court judges are hesitant to abandon these conditional water rights, even if they have been languishing without being used for decades.
Some entities, such as Ute Water, have conditional water rights for several reservoirs, pipelines, pumping stations and other components of an integrated system. Applicants are not usually required to file separate diligence applications for each of the system’s components. For example, in Ute Water’s most recent diligence filing for Owens Reservoir, the conservancy district filed a combined application for 14 different components of an integrated system. The application, filed in August and still pending in Division 5 of water court, claims that work on one feature of the system constitutes reasonable diligence on all the features of the system.
Municipal water providers such as Ute Water are given special deference under Colorado water law through something called the Great and Growing Cities Doctrine.
“The standard for diligence for a municipality is even lower,” Clay said. “We’re going to give them a little leniency with diligence by saying if you can still show us you’re going to need that water 30, 40, 50 years from now and you’re doing something toward it — studying it, working on the environmental issues or whatever — that’s going to be enough diligence to get you by for another six years.”
Owens Reservoir is just one of several Ute Water plans to develop. Williams said they are currently working to enlarge Monument Reservoir No. 1 and will then explore building Buzzard Creek Reservoir, Willow Creek Reservoir and Big Park Reservoir, all on the Grand Mesa.
“It remains to be seen the timing of when those reservoirs would be developed,” Williams said. “But our intent would be to continue developing each one of those sources.”
Squillace said that although he understands cities may need more leeway when it comes to long-term water planning, there is a lot of abuse of the conditional water rights system. The state water courts should be tougher on denying claims of diligence and stop granting extensions to water rights that haven’t been developed despite having had decades to do so, he said.
“You’re not supposed to sit on them for 20, 30, 40 years before you develop them,” he said. “It’s the failure of the state water courts to take diligence requirements seriously. They just apparently seem to give out these extensions of water rights without a whole lot of showing that there’s actually any kind of diligent work toward developing the water. I think it’s a huge problem.”
Uncertainty hangs over decades-old proposed reservoirs
Smaller proposed reservoir sites are scattered across Grand Mesa in western Colorado, and are underpinned by decades-old conditional water rights. William Woody
One way in which these conditional water rights could present a problem is the uncertainty they create for the state’s other water users, especially those who have put their water to use in the past 60 or so years.
Andrew Teegarden is a fellow at the Getches-Wilkinson Center for Natural Resources, Energy and the Environment at the University of Colorado School of Law. The University of Denver Water Law Review plans next fall to publish his paper “Uncertain Future: How Conditional Water Rights Have Created Unintended Consequences in Colorado.” When the owners of conditional water rights with older priority dates finally begin diverting water that they have not used for decades, they may cut off junior water users who began using water between the conditional right’s older date and the present day. Teegarden calls this “line-jumping,” and if all these proposed reservoirs were developed, it could upend the entire priority system.
If all these proposed reservoirs were developed, it could upend the entire priority system.
The solution, he said, is for Colorado to stop treating conditional rights as property rights. Lawmakers could also reform diligence standards and impose a strict time limit, such as 50 years, for applicants to put their water to beneficial use. Otherwise, these conditional rights should be abandoned.
“Clearly, the history and precedent surrounding conditional rights were well-intentioned on giving users within the system flexibility to implement large-scale projects and the security to hold their place in priority,” the paper reads. “These rights, though, come with unintended consequences and it is vital that reforms be implemented before people begin seeing their water rights curtailed or diminished.”
If these proposed dams are built, they could also have a negative impact on the environment. Western Resource Advocates and several other nonprofit and government organizations within Colorado work to improve riparian habitats and keep water flowing in rivers for the benefit of fish and ecosystems. Many of the groups’ projects try to mitigate the effects of cities and agriculture taking too much water out of rivers.
If these proposed dams are built, they could also have a negative impact on the environment.
John Cyran, senior attorney with WRA’s Healthy Rivers Program, said this 2.6 million acre-feet of proposed reservoirs is a time bomb.
“Given that so many streams are already in stressed positions, it’s a big problem for the environment,” Cyran said. “We’re trying to look at the river as it is now and figure out how we can make it healthier. If a bunch of new claims come on the river, that work will be for nothing.”
Cyran brings up another potential issue with conditional water rights: They are able to be bought, sold, changed and transferred to another owner, another location or another type of use. In October, the Middle Park Water Conservancy District transferred conditional rights for a 20,000 acre-foot reservoir on Troublesome Creek near Kremmling to a private ranch for just $10. Some worry that this Western Slope water could be sold to the Front Range. And WRA is opposing another instance in the White River basin where an oil and gas company wants to transfer its storage rights to a new location.
“We’re trying to look at the river as it is now and figure out how we can make it healthier. If a bunch of new claims come on the river, that work will be for nothing.”
John Cyran, senior attorney with WRA’s Healthy Rivers Program
“The idea is supposed to be a conditional right saves your place in line,” Cyran said. “There should be restrictions on water users trying to change those rights to some new purpose while retaining their senior priority. If you can’t use it for what you intended, it goes back to the river. You don’t get to use it for something else, and you don’t get to sell it to somebody to use for something else.”
Future water development tensions persist on Colorado River
But perhaps the biggest issue with 2.6 million acre-feet worth of new water storage may be the effect on, and implications for, the Colorado River basin as a whole. Water managers from each of the seven basin states are in the midst of hammering out a deal that would decide how Lake Powell and Lake Mead are operated and how cuts are shared among the seven states beyond 2026.
The Colorado River flows along I-70 in De Beque Canyon just east of the Grand Valley. Water users hold rights to store an additional 2.6 million acre-feet from the Colorado River and its tributaries in proposed reservoirs on the Western Slope. William Woody
Colorado officials have been rolling out new talking points, which include that the Upper Basin already uses about 30% less water in dry years because the water simply isn’t there, so the Lower Basin should take a corresponding proportionate cut of 30%.
At a time when water managers are debating how to share cuts in a hotter, drier future and where some water users are already suffering shortages, why is this large scope of water development in western Colorado still planned?
JB Hamby, chair of the Colorado River Board of California and the state’s lead negotiator in Colorado River talks, who also serves on the board of the Imperial Irrigation District, which is the biggest water user on the Colorado River, laughed when Aspen Journalism told him that Colorado has plans to develop 2.6 million acre-feet worth of new reservoirs on the Western Slope.
“That’s crazy,” he said.
At a time when water managers are debating how to share cuts in a hotter, drier future, why is this large scope of water development in western Colorado still planned?
Hamby said building 20th century-style infrastructure to develop more water in the Upper Basin does not make sense. He said all water users in the basin should be working together to find ways to collectively reduce their use. That includes navigating differing interpretations of the Colorado River Compact without involving the U.S. Supreme Court.
“That’s our best step forward, not pretending like it’s 1965, which it is not,” Hamby said.
Hamby was getting at something that is a major sticking point between the Upper and Lower basins: two different interpretations of an aspect of the 1922 Colorado River Compact.
The agreement assumed there was 16 million acre-feet of available water each year, with 7.5 million acre-feet each allocated to the Upper and Lower basins. The goal was to reserve an equal portion of the river’s flows for the Upper Basin to prevent rapidly growing California from taking all the water. Giving half to the Upper Basin ensured that the states could slowly grow into their full allocation.
A century later, the Upper Basin still has not done that and currently uses about 4.3 million acre-feet a year. Experts have pointed out that 16 million acre-feet was an overestimate of how much water was available to begin with, and after two decades of being wracked by drought and climate change, that amount of water surely no longer exists in the Colorado River basin system. The foundation of the Colorado River Compact was flawed.
Upper Basin water managers cling not only to what was promised to them 100 years ago but to the belief that as long as they don’t use more than the 7.5 million acre-feet allocated to them, they will not be in violation of the compact. However, some Lower Basin advocates believe that regardless of the Upper Basin’s use, the upstream states could be subject to a compact call if they don’t deliver 7.5 million acre-feet a year. Because river flows have diminished over the past 20-plus years, additional use in the Upper Basin could exacerbate shortages and trigger litigation from the Lower Basin in the form of a compact call, which could force cuts on the Upper Basin. Legal uncertainties about how a compact call could unfold complicates the dynamic and heightens animosity between the two basins.
Amy Ostdiek, chief of the interstate, federal and water information section of the Colorado Water Conservation Board, said an additional 2.6 million acre-feet of reservoir storage won’t increase the risk of a compact call.
“We have the right to the beneficial use of 7.5 million acre-feet a year and in the Upper Basin, Colorado gets 51.75% of the available supply,” she said. “I do not see these projects as putting us in danger of going over that number.”
Upper Basin water managers cling not only to what was promised to them 100 years ago but to the belief that as long as they don’t use more than the 7.5 million acre-feet allocated to them, they will not be in violation of the compact.
According to Jason Ullmann, Colorado’s head engineer at the Department of Water Resources, 2.6 million additional acre-feet of water exists in some years and could be developed, especially since most of that would be captured as spring runoff. The way reservoirs typically work is by storing snowmelt in the spring and releasing it as needed later in the year. But any new reservoir would be at the mercy of the particular and variable hydrologic conditions of any given year and may not always fill.
“Typically, storage buckets, the larger ones in particular, they may not accomplish a full fill every year,” Ullmann said. “It may not be a [2.6 million acre-foot] draw on the river every year. It’s just a water right for that amount of storage.”
Hamby said the Upper Basin point of view is one of the past and out of alignment with the hydrology of the river, which has been declining over the past two decades and is expected to continue to decline.
“The idea of developing new infrastructure to put more water to use does not make sense in this century,” he said. “And while there may be feelings of promises from 1922, this is 2024.”
What if it was all a dream?
One reason these proposed reservoirs don’t seem to worry many water managers is because nobody believes they will ever all be built. Although these projects represent the desires of the Upper Basin, this scale of development may be just a pipe dream.
Eric Kuhn, a Colorado River expert, author and former general manager of the Colorado River District, doubts that many of these reservoirs will be built, but not because the water isn’t there or because of the permitting hurdles, environmental impacts or expense of construction. Rather, Kuhn says there’s no longer a need for many of these storage buckets.
Some of these conditional rights, especially in the Yampa-White-Green River basin, are associated with oil shale development, which has become less economically feasible in recent years. There are no new large-scale federally subsidized irrigation projects on the horizon. And as more agricultural land is converted to residential developments across the West, water use goes down.
Oil and gas wells line the Colorado River along a rural stretch of western Colorado. Energy companies hold conditional water rights across the region, many linked to the potential future development of oil shale. William Woody
Cities such as Aurora and Las Vegas have implemented aggressive conservation programs and have proved they can grow without using a lot more water. As the Upper Basin continues to urbanize, it may never grow into its 7.5 million-acre-foot allocation. The only reservoirs that will realistically be built, Kuhn said, will be small (1,000 acre-feet or less) and on a creek where there’s municipal demand.
“Maybe you need additional storage for streams that don’t have enough storage today, but that’s a tiny, minute amount,” he said. “Conditional water rights are a product of 50, 60, 70, 80 years ago, when they had a purpose. I don’t even see that they have a purpose anymore. They also represent a whole bunch of projects that, if they had been economically feasible, would have been built a long time ago.”
“Conditional water rights are a product of 50, 60, 70, 80 years ago, when they had a purpose. I don’t even see that they have a purpose anymore.”
Eric Kuhn, former general manager of the Colorado River District
Although many entities continue to hang on to conditional water rights that they are unlikely to develop, some are starting to take a more clear-eyed approach, recognizing that some of these phantom reservoirs are dreams of the past and letting them go.
The River District has abandoned conditional reservoir rights on the Crystal River and other places; in January, a company with ties to oil shale development abandoned rights for a reservoir on Thompson Creek south of Carbondale; Colorado Springs recently gave up water rights for reservoirs in Summit County; and in October, the town of Breckenridge let go of water rights for two reservoirs on the Swan River but kept rights for a third: Swan River Reservoir No. 4.
James Phelps, director of public works for the town of Breckenridge, said they didn’t file the diligence claims this time for Swan River Reservoirs Nos. 1 and 2, which had water rights dating to 1981, because the town doesn’t need to develop that much reservoir capacity. Other factors in the town’s decision to not keep the reservoirs alive were the huge financial costs; the fact that housing developments encroached on the reservoir sites; and disturbance to the ecosystem in a place where residents place a high value on the environment.
“It was determined that if there was a need for the water in the future, whatever that need may be, we wouldn’t need to develop all three of those,” Phelps said. “We know that developing reservoirs is not an easy thing to do.”
Despite Colorado water courts’ tendency to rubber-stamp most diligence applications to keep alive decades-old unused water rights, there is at least one recent example of legal pushback on a reservoir enlargement project.
In October, a federal judge ruled that Denver Water’s Gross Reservoir expansion violated the Clean Water Act because it didn’t take into consideration the potential for a Colorado River Compact call and the declining hydrology of the basin. Although it’s unclear if this ruling would set a precedent for any other dam and reservoir project in Colorado, it signals a growing understanding of the risks that new water development could pose to the entire Colorado River system.
“The Colorado River Compact rests on a politically unpalatable truth — the Compact promised the basin states water that simply does not exist,” a footnote in the ruling reads. “The Court emphasizes this context for good reason: The cracked foundation of the Colorado River’s management system all but demands skepticism over any proposal that will affect the hydrology of the Colorado River basin.”
This story was produced by Aspen Journalism, in partnership with The Water Desk at the University of Colorado Center for Environmental Journalism.
How we produced this report
Aspen Journalism used publicly available data on conditional water rights from the Colorado Division of Water Resources to produce the interactive map of Western Slope reservoirs over 5,000 acre-feet. Information from this state database was confirmed for accuracy with state officials, who verified it was current as of September 2024. Information about who owns each water right was found in water court filings. We have mapped the reservoirs to the best of our knowledge by cross-checking publicly available information with water court filings, but inaccuracies may still exist.
This project looks at only the water rights for the largest 94 conditional reservoir water rights over 5,000 acre-feet on the Western Slope. Most of these would be stored in not-yet-built reservoirs. Some of this water would be stored in existing reservoirs using conditional rights that would allow the reservoir to be refilled or enlarged. There are more water rights for storage amounts smaller than 5,000 acre-feet, which Aspen Journalism did not attempt to quantify, meaning there is more than 2.6 million acre-feet of new reservoir storage planned for western Colorado.
Groundwater pours from an irrigation well in Buckeye, Arizona, an area of the state that has brackish groundwater both near the surface and deep underground. (J.Carl Ganter/ Circle of Blue)
The numbers are so vast, so enticing that they tantalize like a desert oasis.
Deep below the surface in Arizona – roughly a quarter mile underground – sit large volumes of water that are less salty than the ocean, but not easily used. At a depth of 1,200 to 1,500 feet, between 530 million and 700 million acre-feet fill this layer statewide.
If it were all pumped to the surface and purified, this brackish groundwater would supply Arizona’s water needs for a century or more. Problem is, it can’t all be pumped.
Though the numbers are legitimate – and detailed in an updated state assessment that was published in August – the reality for brackish groundwater, at this point, is more of a mirage. Exploiting this resource to satisfy the state’s demand for water in an arid climate is not as simple as drilling wells.
“This is not a new supply of water,” said Juliet McKenna, a hydrogeologist with Montgomery & Associates, the consulting firm that the state contracted for the brackish groundwater assessment. “This is physically groundwater and this is legally groundwater. And there are consequences and restrictions in both areas for trying to use this.”
McKenna, who managed the assessment, and other state water experts interviewed for this story explained that brackish groundwater has a slew of impediments – environmental, physical, financial, technical, regulatory, and legal – that limit its use, despite the efforts of enthusiastic backers in the Arizona Legislature who are looking for ways to counter the state’s declining Colorado River supplies.
“Brackish groundwater is still groundwater, right?” echoed Patrick Adams, water policy adviser to Gov. Katie Hobbs. “So its extraction impacts the aquifer as much as any other groundwater supply when it’s removed from storage. And really that needs to be considered – and its use needs to be considered –against that backdrop. Where’s the brackish groundwater located? What are the local groundwater conditions? What’s the health of the aquifer?”
Securing a reliable water supply is an existential question for high-growth Arizona and its desert economy. The Colorado River, a major source for central Arizona, has sputtered in the last two decades amid hotter, drier weather attributed to a warming climate. The state’s allocation from the river was whittled by at least 18% in each of the last three years. New operating rules that are under negotiation will likely extend or deepen those cuts past 2026, when current guidelines expire.
Water, as a result, is prominent in state policy debates.
Drilling into Arizona’s Brackish Supplies
A desire for more data on its water sources is why the Legislature inserted $50,000 for an updated brackish groundwater inventory in the 2023 budget. The Arizona Department of Water Resources then commissioned Montgomery & Associates to do the analysis.
Arizona is not alone in its quest to better understand its subsurface water. New Mexico is looking to expand its water supply by treating both brackish groundwater and the high-salinity, chemical-laden water that gushes out of oil and gas wells. To the east, the Texas Water Development Board has investigated and mapped the state’s brackish groundwater zones for the last 15 years. A $1 billion water fund approved by voters last year will include at least $250 million for marine and brackish water desalination.
The Arizona inventory identified 21 areas with brackish groundwater, four of which the state singled out for more detailed assessment. One focus area is the Little Colorado River Plateau, in the state’s northeast corner. About half of the assessed brackish groundwater is located there. (The assessment defined brackish groundwater as having total dissolved solids greater than 1,000 parts per million. Sea water, by comparison, is 35,000 parts per million.)
The other areas – Gila Bend, Ranegras Plain, and West Salt River Valley – are closer to the population centers in Maricopa County or to the Central Arizona Project canal that moves water across the state.
“We wanted it to be meaningful or useful,” said Ryan Mitchell, chief hydrologist for the state’s Department of Water Resources, about selecting the focus areas.
A kiosk in Bouse, Arizona, advertises “salt free” drinking water. The town is located in Ranegras Plain, one of the areas assessed in the state’s brackish groundwater inventory. (Brett Walton / Circle of Blue)
The discussions around brackish groundwater are as much about its limitations as its possibilities. McKenna pointed out several challenges. One, water in storage does not equal available water. The same physical drawbacks from pumping fresh groundwater also apply to brackish. As groundwater is pumped, the land above can crack and sink, damaging houses, roads, and other public infrastructure. The water table can drop and cause neighboring wells to go dry. Those outcomes can occur with relatively modest levels of pumping, let alone with a massive drawdown to access all the deep brackish groundwater assessed in the inventory. In an arid region, water at that depth is essentially non-renewable.
“If we dewatered those aquifers to 1,500 feet below ground surface, that’s an apocalyptic scenario,” McKenna said. “So we’re not pumping groundwater to those depths under any reasonable scenario. So the estimate of water that is there, in aggregate, does not translate to water that’s available for folks to use.”
Water is already used unsustainably in the study’s four focus areas. Each is currently operating at a groundwater deficit, McKenna said. More water is pumped out than is recharged.
Steep Challenges Remain in Using Brackish Water
Even if brackish groundwater is physically available, it is not necessarily desirable. Buckeye, one of the state’s fastest growing cities, sits within the Buckeye Waterlogged Area, located on the western outskirts of the Phoenix metro area. “Waterlogged” is a regulatory definition based on the area’s unique hydrogeology at the junction of three rivers: the Agua Fria, Gila, and Salt. Water pools here, and farmers have to pump it out so that their crops will grow. Due to salts in irrigation return flows, the water is brackish in places near the surface.
Buckeye, which pumps groundwater for its municipal supply, is surrounded by brackish groundwater, but Terry Lowe, the water resources director, says the city avoids it. For Buckeye, brackish groundwater is “not deployable,” as he puts it. Some of the Buckeye Waterlogged Area groundwater is between 3,000 and 4,000 parts per million of total dissolved solids, and the equipment and energy required to remove the salts is not cheap. “Treating that out is a waste of money,” he said.
What’s more, brackish groundwater has complications that involve waste disposal. Treating brackish groundwater produces a concentrated brine that must be handled delicately and expensively. Small quantities might be handled by a wastewater treatment plant. Large volumes are typically injected deep underground, but in Arizona that method is “effectively prohibited” without policy changes, a governor’s water council determined in 2022. The Arizona Department of Environmental Quality, the permitting agency for aquifer protection, said that no Class I deep injection wells operate in the state. Carollo, an engineering firm, concluded that cheaper brine disposal was essential for brackish groundwater to become an “economically viable water supply” in the state. Lowe also cited brine management as a reason his department shies away from brackish groundwater.
Then there are the legal and regulatory hurdles. The Legislature passed the Groundwater Management Act in 1980 in response to unsustainable use. It established Active Management Areas (AMA) to steward a finite resource. In practice, most users in the six AMAs need permission to pump and must replace a portion of their use. In the Phoenix AMA, which roughly corresponds with Maricopa County but also extends into neighboring Pinal, the goal is “safe yield” by 2025 – balancing groundwater extraction with recharge. It is not on track to meet that deadline. Incentivizing brackish groundwater use could put safe yield farther out of reach.
Farmers in the Buckeye Waterlogged Area must contend with elevated groundwater salinity. The area’s unique hydrogeology and irrigation legacy has resulted in salty groundwater near the surface. (Brett Walton / Circle of Blue)
And one more headwind: Arizona restricts the movement of groundwater within the state. Five groundwater basins are designated as “transport” basins. Water in these areas can be pumped and exported to an AMA. Most other groundwater must be used in its basin of origin. Without a change in legal status, brackish groundwater would be stranded in place, able to be used locally but not moved to the areas of highest demand.
“For us it’s still considered groundwater,” Mitchell said. “It’s still regulated the same, it’s still accounted for and tracked and all the authorities are still in place, whether it’s brackish or fresh, it’s still treated the same.”
The Search for Water
To state Rep. Alexander Kolodin, these hurdles – physical, financial, regulatory – are obstacles that can be overcome. Kolodin, a Republican who represents northeastern Maricopa County, is the most enthusiastic booster of brackish groundwater in the Legislature. He sees the big number in the updated inventory and grows excited.
“Arizona is sitting on an absolute ocean of brackish groundwater,” he said. With the state’s take from the Colorado River declining, Kolodin wants to consider other sources of water that could fill the gap. “I’m very interested in figuring out how we can tweak the law to utilize this resource’s maximum potential.”
Those tweaks at the state level, he said, would include reducing groundwater replenishment requirements in the AMAs for brackish water and relaxing the restrictions on moving groundwater out of its natural basin. “If you can’t transport it, you never really have much incentive to do it in rural areas because it’s still much more costly than our historical sources of water,” he said.
Kolodin advocated for $11 million in the state budget last year for a brackish groundwater pilot program. The Department of Water Resources published a request for information in October 2023. The pilot didn’t go much farther than that. Mitchell, who reviewed the submissions, said they read more like “qualifications packages” than a careful project plan. Due to a state budget shortfall this year, funding for the pilot was retracted.
Brackish groundwater boosters like Kolodin note the efforts in Texas, where the state government mapped its brackish reserves, estimated yields, required impacts analysis, and provided financing. El Paso has the country’s largest inland desalination facility, which has a production capacity of 27.5 million gallons a day. Mitchell, however, points out that the comparison is not one-to-one. Arizona has different hydrogeology, as well as more stringent legal and regulatory requirements.
The hunt for new water supplies is a longstanding feature of Arizona politics, extending back to the pursuit of the Central Arizona Project canal in the mid-20th century. In recent years, the prospectors have sought to turn salty water fresh.
A decade ago, under Gov. Jan Brewer, the state produced the Arizona’s Next Century report, which listed brackish groundwater as one of seven potential sources to augment the state’s supply.
Water augmentation was a major focus of Gov. Doug Ducey’s administration. In 2015, Ducey signed an executive order to establish the Governor’s Water Augmentation Council. In 2019, he signed another executive order that expanded the work to “investigate long-term water augmentation strategies for the state.” The Governor’s Water Augmentation, Innovation, and Conservation Council lasted until Gov. Hobbs was elected. In 2023, Hobbs formed the Governor’s Water Policy Council.
The Hobbs administration is less focused on brackish groundwater than her predecessors. The Governor’s Water Policy Council report, published earlier this year, does not mention it by name.
“Brackish groundwater development as a source for augmentation is not really at the forefront of where the Water Policy Council is focusing its efforts,” Adams, the governor’s water policy adviser, said.
For now, as more data is collected, brackish groundwater will remain just off center stage, with lingering questions about how and when it should be used.
“If it were to be utilized, it needs to be done so thoughtfully and mitigate impacts from pumping,” McKenna said. “It’ll be expensive, in terms of treating and permitting. But it is a supply that’s in our state, and like our other water supplies, I think we need to think about it and make thoughtful decisions about how to use it, if we want to use it.”
This story was produced by Circle of Blue, in partnership with The Water Desk at the University of Colorado Boulder’s Center for Environmental Journalism.
A directional boring machine sits outside a home in Edgewater, Colo., on Sept. 25, 2024. Crews are working on replacing lead pipes in homes built before the 1950s with copper pipes by drilling a new hole and abandoning the lead in place. (Emma VandenEinde / KUNC)
On an early morning, a quiet Denver neighborhood was temporarily transformed into a construction zone. A boring machine on the road outside someone’s home pointed a long, thin drill bit at a sharp angle toward a hole in the ground. It’s going to make a path for a new water service line.
All the commotion is for a singular purpose: to reduce the amount of lead flowing into Denver homes.
“Previously, the technology was pulling (the old line) or open trench excavation, which is not customer friendly,” said Denver Water’s Alexis Woodrow. “People do not like their entire yard dug up.”
A man grabbed a big coil of copper line and brought it into the home. Another contractor took out an electronic locator to help guide the boring machine operator.
Wesley Fischer with Five Star Energy Services brings a large coil of copper line from the truck into the nearby home. He will wait until the new hole is drilled and then connect the copper line to the drill bit, which will pull the new line through. (Emma VandenEinde / KUNC)
“They are essentially boring in a new line and then pulling out a copper (line) so they leave the lead abandoned in place,” said Woodrow, who manages the program. “That’s often because we can’t pull it out, or it’s just more efficient to put in a new line.”
This is just one of many work sites for the utility’s Lead Reduction Program – a nearly $670 million project designed to replace lead service lines with copper ones in the Denver area at no cost to the customer.
Lead is toxic. It can cause brain damage in children, as well as increase the risk of a miscarriage, according to the World Health Organization. Denver Water isn’t delivering lead-laden water to customers, Woodrow said, but old household plumbing and service lines can leech lead into that water and cause problems.
“There were homes in the Denver Water service area where lead levels were elevated and the corrosion treatment that we were doing was not sufficient enough to create that protection that they needed,” she said.
In 2012, Denver Water exceeded the lead action level of 15 parts per billion set by the Environmental Protection Agency, coming in at 17 parts per billion. Service lines are owned by the customer, but the utility felt the need to do something. The city researched effective treatment solutions and found that changing the pipe as well as increasing the pH of the water was their best bet.
Lead pipes contaminate the drinking and cooking water inside tens of thousands of Denver homes. They can impact peoples’ teeth, kidneys, blood, liver and more. (Emma VandenEinde / KUNC)
Denver Water has found nearly 65,000 lead lines in the city, primarily in homes built before the 1950s. That’s roughly 220 miles of pipe, according to Denver Water officials. The condition of about 17,000 lines is still unknown.
Since starting the Lead Reduction Program in 2020, the utility has replaced around half of the lines. They also sent Brita pitchers and filter replacements to homes that are still waiting to get their lines replaced.
“What we were giving to them through this program was a chance at health and safety,” Woodrow said. “(We’re saying), ‘You are likely to have a lead service line, so here’s what Denver Water is going to do to protect you.’”
These replacements come in the wake of the Flint Water Crisis in Michigan in 2014, when the city changed their water source from Lake Huron to the Flint River. Pipes corroded and there were no treatment methods in place. Lead levels were nearly double the lead action level set by the EPA in most of the homes, while others were in the hundreds or thousands for parts per billion.
It put the dangers of lead in drinking water in the national spotlight. So why weren’t Denver’s lines, and others, replaced sooner?
Siddhartha Roy is a professor at Rutgers University and has done research on the Flint Water Crisis. He said one reason could be that lead was the plumbing standard in the turn of the 20th century when many cities were growing rapidly.
“Cities had mandates that, ‘Hey, if you want public water, you have to use a lead pipe,’” he said. “There was an industry push. There was a lead lobby as hard as it is to believe that…it will poison you, but lead will last thousands of years.”
Woodrow with Denver Water said even as the dangers came to light, everything was still evolving and utilities were not sure what the best solution was at the time.
“I think there were a lot of questions within the industry, and also in public health, about how lead in drinking water kind of fits in the whole scale of lead exposure, and how serious it is,” she said.
Jason Stern grabs the extra part of the copper line that was pulled through the new hole in the ground. Even after the line is replaced, homeowners still are asked to use a water pitcher with a filter for a few months as the lead cycles out of the piping. (Emma VandenEinde / KUNC)
“You had steps like, ‘Oh, flush (the water) for a few minutes the night before you took a sample in the morning,’ and that lowers lead levels,” he said. “That made it appear that the problem was not as worse as we thought.”
This fall, the Biden Administration introduced a stricter policy, where cities have to remove all of their lead pipes by 2037. Cities will also have to comply with the new lead action level of 10 parts per billion.
Some local utilities have already gotten financial help from the EPA and the Biden administration to get started on this work. Denver Water received $76 million in funds from the Bipartisan Infrastructure Law to speed up this process. The utility was originally paying for its Lead Reduction program on its own with its water rates, bonds and hydropower sales.
Claire Thomas sits with her cat in her historic home that was built in 1890 in the Curtis Park Historic District in Denver, Colo., on Oct. 1, 2024. She got her lead pipe replaced at the end of August. (Emma VandenEinde / KUNC)
Roy said he’s cautiously optimistic.
“The question is financing,” he said. “The question is organizing this at grand levels, coordinating. There’s so much to be done…This is the single biggest policy jump on improving lead in water in more than 30 years.”
When lines do get replaced, it can be revolutionary. Claire Thomas lives in a historic home built in 1890 in the Curtis Park Historic District near the Five Points area of Denver. She got a water filter from the utility and never expected any sort of replacement.
“It was just, this is our way of life,” she said. “We drink from the Brita, and just kind of accepted that.”
Thomas and her partner cook a lot and have friends over often. They’d end up using more water than their small filter could handle.
“In reality, we’ve probably been drinking water that has lead in it because we’ve been overusing our filters,” Thomas said.
Thomas’ new copper pipe sits in her unfinished basement of her home. Contractors did a quick site visit of her home and told her what to expect before they scheduled a day for the replacement. Thomas was pleased by how quick the replacement was and the kindness of the contractors to sweep up the dust and be careful inside her home. (Emma VandenEinde / KUNC)
When she first heard from the utility that her lines were going to be replaced, she was elated.
“I’ve been in a lead water house for so long, I was so excited,” she said. “That same day we returned to the post office with our water samples.”
She got her line replaced at the end of August. She was shocked at how quick the process was and how kind the workers were, cleaning up the street within a week and being very careful within her home.
“(I) feel really lucky moving into this house and a year later being able to have normal water,” she said. “And as I say that, I realize that that’s a weird thing to have to be thankful for, but here we are.”
Denver Water has about 1,000 more replacements to finish before the end of the year. It plans to work in East Denver in 2025 to stay on track with the goal of finishing the whole project within 15 years.
To find out if you have a lead service line, you can enter your address on Denver Water’s Lead Service Line dashboard. Homeowners with questions can call the utility call center at 303-893-2444.
This story was produced by KUNC, in partnership with The Water Desk at the University of Colorado’s Center for Environmental Journalism.
The Rio Grande cuts through a mountain range on the border of the United States and Mexico. In the Forgotten Reach, upstream impoundments reduced water flow by more than 70 percent. (Omar Ornelas for Inside Climate News)
Reporting supported with a grant from The Water Desk at the University of Colorado Boulder’s Center for Environmental Journalism. Aerial photography support provided by LightHawk.
FAR WEST TEXAS—The year was 1897. Flood waters from the Rio Grande submerged entire blocks of downtown El Paso.
The New York Times described the crash of crumbling houses and the “cries of frightened women and children” on its May 26 front page. The raging river displaced hundreds of people and destroyed scores of adobe homes.
In Mexico, the Rio Grande is known as the Rio Bravo—the rough, or wild, river—signifying the force that caused several devastating floods in El Paso and neighboring Ciudad Juárez.
Today these historic floods are hard to imagine. The river channel in El Paso-Juárez now only fills during the irrigation season. Further downstream, the river is frequently dry in a 200-mile section known as the Forgotten Reach.
Inside Climate News documented this remote stretch of the river in July on a flight with the non-profit Light Hawk. Other than limited flows from springs and creeks, known locally as arroyos, this section of the Rio Grande barely has water.
That’s because reservoirs now harness the flows of snowmelt and monsoon rains that once defined the river and deliver that water to thirsty cities and sprawling farms. Making matters worse, climate change is increasing temperatures and aridification in the desert Southwest.
Competition over dwindling water is growing. All that leaves little water to support fish, birds and wetland ecosystems that once thrived along the Rio Grande.
But environmental scientists and local conservation advocates say there are opportunities to restore environmental flows—the currents of water needed to maintain a healthy river ecology—on the Rio Grande and its West Texas tributaries. Proponents of environmental flows are restoring tributaries and documenting little-known springs that feed the river. They are working with counterparts in Mexico to overcome institutional barriers.
Samuel Sandoval Solis, a professor of water resource management at the University of California Davis and an expert on the Rio Grande, compared this restoration model to a “string of pearls.”
“Ultimately, we start connecting these pearls,” he said. “And we start putting it back together.”
But to replicate and expand these local initiatives will require more funding and political support on the embattled binational waterway.
Water for Agriculture, but Not for Nature
For millions of years, the flow of the Rio Grande in present-day New Mexico and West Texas was dictated by two natural cycles. Spring snowmelt in Colorado sent water rushing downstream, triggering floods throughout the watershed. In the summer, the monsoon dumped rain on the desert and swelled the river.
These annual “pulses” of water sustained biodiverse ecosystems in the arid Chihuahuan Desert.
Karen Chapman, coordinator of the Rio Grande Joint Venture, a public-private migratory bird conservation partnership, said the Big Bend segment of the Rio Grande in West Texas is an “emblematic, important wetland for migratory birds in the middle of a big desert region.”
Floods spread the seeds of cottonwoods and tornillos, a native mesquite shrub. Thriving wetlands attracted the southwestern willow flycatcher. Floodplains provided spawning habitat for the Rio Grande cutthroat trout and silvery minnow. Indigenous people harnessed the water for subsistence agriculture.
These cycles came to an end in the early twentieth century. In 1916, the Bureau of Reclamation completed Elephant Butte Dam outside Truth or Consequences, New Mexico. Its 301-foot retaining wall captured the crush of water coming out of the mountains. The dam released water on a precise schedule for farmers farther down the river. The three cities immediately downstream—El Paso, Las Cruces and Ciudad Juárez—continued to grow.
Agricultural fields line both sides of the Rio Grande between El Paso and Ciudad Juárez photographed in July 2024. The Rio Grande Compact determines how much water reaches Texas from the Rio Grande. (Omar Ornelas for Inside Climate News)
The Rio Grande Compact—signed in 1938 between Colorado, New Mexico and Texas—sealed the river’s fate. The compact ensured that farmers in all three states would get their share of water. But there was no obligation to guarantee water flowed beyond the last irrigation district south-east of El Paso, at a point called Fort Quitman. The once-mighty Rio Grande began to dry up downstream of that now abandoned ghost town.
When seasonal flooding ceased in the Forgotten Reach, salt cedars and arundo river cane invaded the floodplain and crowded out native cottonwoods and tornillos. With meager volumes of water in the river, sediment has built up and further hampered the flow. Wetlands shriveled and migratory birds lost stop-over points.
“The river transforms from a natural flashy system to a straight ditch,” explains Kevin Urbanczyk, director of the Rio Grande Research Center at Sul Ross State University in Alpine, Texas. “You lose the aquatic habitat when that happens.”
The Forgotten Reach ends where the Rio Conchos flows from Chihuahua into the Rio Grande at Presidio, Texas. Before the construction of Elephant Butte, over 500,000 acre feet of water reached Presidio each year. After the construction of the dam, the flow fell by 77 percent, according to the Army Corps of Engineers.
In West Texas, the Rio Grande Joint Venture works with landowners to restore grassland and riparian habitats near Rio Grande tributaries like the Terlingua Creek and Alamito Creek. These projects reduce the amount of sediment reaching the Rio Grande, a key intervention to improve flow on the river.
In recent years, flows have also declined downstream of Presidio. Mexico is obligated under the 1944 water treaty to send water from tributaries, including the Conchos, to the United States on a five-year cycle. But since the 1990s Mexico has consistently fallen behind, diminishing water levels in the Rio Grande downstream of Presidio.
The river ran dry through the iconic Santa Elena Canyon in Big Bend National Park in 2022. Rafting expeditions, a bedrock of the Big Bend tourism economy, rely on a river that is less and less dependable.
What water Mexico does deliver is stored at the Amistad and Falcon Reservoirs in South Texas. The Texas Commission on Environmental Quality (TCEQ) then distributes water from the reservoirs to irrigation districts and cities in South Texas and the Rio Grande Valley.
This section of the Rio Grande is considered “over appropriated,” which means there are more assigned water rights than there is water normally available. In other words, every drop of water already has an assigned end-user. There is no water left over for dedicated environmental flows in South Texas.
The problem was abundantly clear in 2001, when for the first time in decades the Rio Grande failed to reach the Gulf of Mexico.
Advocating for Environmental Flows Across Borders
Conservation advocates and scientists working on the Rio Grande face formidable challenges: a binational treaty dispute, climate change, an over-appropriated river. But UC Davis’ Sandoval Solis is convinced environmental flows are possible if water is managed differently.
Sandoval Solis would like to see Mexico release water from its Rio Conchos reservoirs to the Rio Grande to mimic the cycles of spring floods and the summer monsoon. He said better timing of releases can help native species without infringing on farmers’ water rights.
He acknowledged that environmental flows are not a priority in ongoing diplomatic talks as the U.S. works to compel Mexico to release any water. But he said “pulses” of water at opportune times could go a long way.
The idea has already been implemented on the Colorado River, another binational river governed by the 1944 water treaty. In 2014, water was released from the Morelos Dam to create a pulse flow that connected the Colorado River to the Gulf of California for the first time in 16 years. In 2017, the U.S. and Mexican governments agreed to ongoing water deliveries for restoration of the Colorado River delta in Mexico.
The Rio Grande winds through the Chihuahuan Desert in far west Texas. Diversions for agriculture and cities have reduced the flow by at least 70 percent compared to historical flow levels. (Omar Ornelas for Inside Climate News)
U.S. International Boundary and Water Commission spokesperson Frank Fisher said “nature-based solutions” have been part of the agency’s discussions with Mexican counterparts, but did not indicate whether there is interest in a pulse flow on the Rio Grande/Rio Conchos.
In February, the U.S. IBWC and its Mexican counterpart, known as CILA, created the Rio Grande Environment Work Group. The group has met several times this year to identify and implement binational environmental projects on the Rio Grande.
Karen Chapman of the Rio Grande Joint Venture advocated for the creation of the working group and is now a member. “There are folks on both sides of the river in both countries that are concerned about the health of the river and want to work towards some solutions,” she said.
There have been some successes in restoring flows to the Rio Grande. In a 2022 paper in Ecology & Society, Sandoval Solis and colleagues at UC Davis and the University of Oklahoma compiled examples of environmental flows throughout the Rio Grande/Rio Bravo watershed. They point to in-stream flows on Rio Grande tributaries in New Mexico and the first environmental water right in Mexico at the Cuatro Ciénegas wetlands as models to replicate.
A 2023 paper published in the Journal of Water Resources Planning and Management, by lead author Brian Richter of Sustainable Waters, with Sandoval Solis as a co-author, expanded on these ideas. The authors model how converting farmland to less water-intensive crops and leaving some acreage fallow could decrease consumption in agriculture, which currently uses 83 percent of the water rights in the watershed. This would make more water available for environmental flows, without reducing agricultural revenue.
Sandoval Solis said politics is getting in the way of expanding on these models to restore flows to the river.
“The problem of environmental flows on the Rio Grande is not about science,” he said. “We know that the river is drying and we know that it’s about willingness, political willingness.”
Protecting Groundwater that Feeds the Rio
Sul Ross’ Kevin Urbanczyk studies the Lower Canyons on the Rio Grande, downstream of Big Bend. At least once a year he loads up a canoe to reach the canyons, which are not accessible by road, where he measures the flow from aquifer-fed springs into the river.
Urbanczyk said that when Mexico does not send water from the Rio Conchos, all the water in this section of the Rio Grande comes from the springs. He said more research is needed to understand how groundwater contributes to the Rio Grande.
Texas has two separate systems to regulate surface water in a river and groundwater in aquifers. But Urbanczyk said regulations need to account for how these sources are interconnected. He worries that an increase in groundwater pumping near the river could deplete the springs’ contributions to the Rio Grande.
“We’re talking… as if they’re two different things,” he said. “But they’re not. It’s the same water, so the connection needs to be understood.”
The IBWC spokesperson said that historic water gauge data and field studies indicate that groundwater amounts to a discharge of approximately 200 cubic feet per second in the Big Bend region to the Amistad Reservoir.
“[IBWC] understands the importance of these groundwater contributions to providing reliable and predictable water supply to downstream users as well as sustaining environmental processes in the region,” said the spokesperson.
Environmental Flows Legislation in Texas
Largely absent from the discussion of environmental flows on the Rio Grande is the Texas legislation meant to achieve that very objective. In 2007, the Texas Legislature passed Senate Bill 3, which provides protections for environmental flows in Texas rivers and into bays and estuaries.
However, TCEQ excluded the Forgotten Reach from the environmental flows program for the Rio Grande from the outset. The Forgotten Reach would stay forgotten—there would be no environmental flow protections in this 200-mile long stretch of the river.
But in a 2008 study with the Army Corps of Engineers, TCEQ expressed interest in restoring the Forgotten Reach. The study explored restoration options and stated that “The ‘Forgotten’ Rio Grande might have great value as a laboratory for the art and science of rehabilitating perturbed rivers.”
The Rio Grande rises out of the agricultural valley and into the mountains of West Texas. This is the beginning of the Forgotten Reach, a 200-mile stretch of the river with little water flow. (Omar Ornelas for Inside Climate News)
The TCEQ declined a request for an interview about the environmental flows program. In an emailed statement, TCEQ spokesperson Victoria Cann did not respond to questions about why the agency excluded the Forgotten Reach from the program.
The TCEQ formed a scientific working group, including academics and civil society representatives, that recommended environmental flow regimes for the Rio Grande basin. TCEQ then formalized flow standards for the Rio Grande which were adopted into the state administrative code. However, a brief from the Texas Living Water Project points out that the standards TCEQ adopted were a far cry from what the scientific working group recommended.
Myron Hess, a water lawyer and consultant with the Texas Living Waters Project, authored a 2021 report on the “unrealized potential” of Senate Bill 3. The report states that efforts to revive environmental flows have “stalled” in most river basins. Hess said that the models to calculate environmental flow standards do not account for climate change, which is expected to diminish water resources in central and west Texas.
“As droughts get more severe there is going to be less and less water available to protect the environment,” he said. “It’s going to be a world of hurt.”
The TCEQ spokesperson did not respond to multiple requests for comment about the exclusion of climate change from the models. She said that the adopted standards can be revised if new information and data becomes available.
UC Davis’s Sandoval Solis characterized the Texas legislation as “a check box” for regulators to complete. He said the studies commissioned by the legislature have not been acted on.
“In the end you use those studies to do nothing,” he said. “You don’t have any teeth to enforce and to put some water in [the river].”
Despite the setbacks, Sandoval Solis still believes that flows can be restored to the drying Rio Grande. Human intervention over the past 130 years has dramatically transformed the river and stymied its natural flow. But even in the face of climate change he maintains that it’s not too late to reverse some of these changes.
“The river is very forgiving,” he said. “When we have seen the full river coming back to life… in a monsoon, in a hurricane… to me that’s been a very happy experience.”
The Rio Grande Gorge near Taos, New Mexico, on June 24, 2024. (Mitch Tobin /The Water Desk)
The Water Desk is excited to announce an in-person training and workshop for journalists interested in covering the Rio Grande watershed.
The Rio Grande faces significant challenges: climate change, aridification, pollution, development, population growth, invasive species and more. The river forms part of the U.S.-Mexico border and is a critical water supply for three U.S. states—Colorado, New Mexico and Texas. As supplies shrink and tensions ramp up, litigation among the river’s users continue to make headlines. Diplomatic relations between the U.S. and Mexico have the potential to affect the Rio Grande as well.
To equip journalists to better understand the river’s history, its current legal cases and future challenges, The Water Desk is hosting a training program for journalists in Albuquerque, New Mexico, on January 29-31, 2025. Participating journalists will hear from legal experts, tribal leaders, environmental advocates and other speakers who can shed light on the Rio Grande.
We will select up to 15 participants who represent diversity in geography, race, gender and journalistic medium. Travel, lodging, meals and other expenses will be covered for all attendees. Additional funding for story coverage after the training will be made available. The program will begin the evening of January 29 and conclude in the afternoon on January 31.
The Thornburg Foundation, a Santa Fe-based family foundation, is providing the financial support to make this training possible, while the program is the sole responsibility of The Water Desk.
The Colorado River Indian Tribes have the right to divert 662,402 acre-feet of water per year from the Colorado River for use on their lands in Arizona. Congress recently granted the tribes authority to lease some of this water to entities elsewhere in the state. (Brett Walton/Circle of Blue)
PARKER, Arizona – South of Headgate Rock Dam, beyond riverbanks lined with willow and mesquite, the broad floodplain of the Colorado River spreads across emerald fields and sun-bleached earth.
The Colorado River has nourished these lands in present-day western Arizona for millennia, from the ancestral Mohave people who cultivated corn, squash, beans, and melons, to the contemporary farmers of the Colorado River Indian Tribes, or CRIT, whose reservation extends for 56 miles along its namesake river.
CRIT has rights to divert a large volume of Colorado River water – nearly 720,000 acre-feet in Arizona and California combined, which is more than twice Nevada’s allocation from the river. To this point, the water has remained within the bounds of the CRIT reservation. But soon, the water might flow to lands far beyond CRIT’s borders.
Due to an act of Congress signed into law in January 2023, CRIT now has the authority to lease or exchange its water for use elsewhere in Arizona. (The authority does not apply to water rights held by CRIT on the California portion of its reservation.) Agreements signed in April with the Arizona Department of Water Resources and the federal Bureau of Reclamation to fulfill administrative requirements in the legislation brought the tribes another step closer to greater control over their water.
What remains is the work of negotiation, both within CRIT and with potential leaseholders. CRIT leadership must decide what it wants in leasing deals – how much water to part with, to whom, for what price, and for how many years. And they will have to find a partner who agrees to those terms.
CRIT’s leasing authority opens a new chapter, not only for the tribes but for other water users in the state who might covet CRIT’s high-value, high-priority Colorado River water. Leasing this water would represent a financial windfall for CRIT’s more than 4,600 enrolled members. CRIT leadership has framed it as an economic and civic development opportunity. For those on the other side of the deal – be they environmental groups, farm districts, mining companies, or fast-growing cities in the center of the state – it is a rare chance for a relatively secure source of water in an arid region where most supplies are already claimed or running out. Homebuilders west of Phoenix, for instance, have recently seen their access to local groundwater restricted by state regulators.
For CRIT leaders, the new powers come at an auspicious time. They see their duty as stewards of the river intersecting with the mounting challenges of maintaining Arizona’s desert empire amid merciless heat and a drying climate.
“With the climate crisis and the drought going on at the present time, there’s going to be a major shortage of water,” Dwight Lomayesva, CRIT Tribal Council vice chairman, said at a conference in March. “But we would like to be part of the solution to the problem.”
A valuable asset
CRIT is a union of sorts. Four tribes with distinct histories live on the 278,000-acre reservation that spans Arizona and California. The Mohave, known for farming and beadwork, and the Chemehuevi, masterful basket weavers, were original inhabitants of the land. The Hopi and Navajo came later. The federal Bureau of Indian Affairs relocated members of the two northeastern Arizona tribes to the area after World War Two.
Some 79,350 acres are farmed on the Arizona portion of CRIT’s reservation. More acres are dedicated to alfalfa than any other crop. (Brett Walton/Circle of Blue)
CRIT’s history and location translate into a strong water rights position. Like in most western states, water in Arizona is based on a priority system. “First in time, first in right,” as the saying goes. Junior users, who have a later priority date, are cut off first in times of shortage, while senior users like CRIT who have earlier claims can continue to divert.
CRIT’s reservation along the banks of the Colorado was established in 1865, making it one of the first in time in Arizona for water rights – and one of the last to lose access to water. Crucially, leased water retains its place in the priority system. That’s what makes it valuable, said Cynthia Campbell, the water resources management adviser for Phoenix. “That’s front of the line, basically.”
Not only does CRIT have secure water. The tribes also have a lot of it. Comparatively speaking, their water rights are massive. A display at the CRIT Museum makes the point visually. Tubes of foam insulation painted blue depict the volume of water held by tribes along the lower Colorado River. CRIT has the right to divert 662,402 acre-feet per year to its Arizona lands and 56,846 acre-feet to its much smaller landholdings across the river in California. The museum display reflects this bounty – the blue foam bar representing CRIT’s water towers over the others.
For now, CRIT is keeping its water leasing intentions close to the vest. Chairwoman Amelia Flores and Tribal Council members declined to be interviewed for this story.
John Bezdek, CRIT’s lawyer, said that Tribal Council had been focused on finalizing the state and federal agreements and is now turning its attention to how it might structure leases. “There’s a number of additional steps that need to be done in terms of developing a water code, developing provisions on how proposals will be evaluated, looking at those types of things,” Bezdek said. “And so that is all being done right now. We’re working on the next steps internally.”
Despite that public reticence, the contours of CRIT’s thinking have been previewed in other venues. Vice Chairman Dwight Lomayesva outlined his thoughts on the matter in a panel discussion earlier this year, when he participated in the Eccles Family Rural West Conference, held in Tempe, on March 27.
Lomayesva reiterated the cultural and spiritual significance of the Colorado River to his people. “We want to save the river,” he said. “We’re not just a benevolent nation trying to help other countries and tribes and water districts.”
Dwight Lomayesva, vice chairman of the Colorado River Indian Tribes, speaks at the Eccles Family Rural West Conference, held in Tempe, Arizona, on March 27, 2024. (Courtesy Bill Lane Center for the American West, Stanford University)
CRIT has a history of working with state and federal agencies to protect the Colorado River. The tribes participated in a pilot farmland fallowing program from 2016 to2019, in which they saved 45,373 acre-feet for storage in Lake Mead. That deal was the precursor to a larger commitment in 2020, when the tribes pledged to fallow 10,000 acres of farmland and store 50,000 acre-feet of water per year in the basin’s largest reservoir. For the three-year effort, the tribe earned $38 million, from the state and the Environmental Defense Fund.
CRIT’s capacity to lease water is directly related to the farming operations that take place on the reservation. About 79,350 acres are farmed on its Arizona lands, mostly for alfalfa. Some of the land is farmed by a tribal enterprise, but many of the acres are leased by non-tribal members. A majority of the fields are flood irrigated, an inefficient method in which only half of the water is taken up by the crop. The rest eventually flows back to the river or evaporates.
This is important because CRIT can only lease water that it has put to consumptive use in at least three of the previous five years. The consumptive-use stipulation is part of the agreement signed with Arizona and Reclamation in April. CRIT diverts less Colorado River water than its allocation, so the agreement dictates that the tribes can’t part with unused water to which they have rights but bypasses their fields. In effect, it means that water conserved from farming is water that can be leased.
“That’s a very, very important component that we then have to factor into in terms of how we want to develop the program,” Bezdek said.
A huge impediment is CRIT’s obsolete means of moving water to its fields. The Bureau of Indian Affairs, a federal agency, owns and operates the Colorado River Irrigation Project, an irrigation system that is, by all accounts, deteriorating and badly needs repair. It was developed piecemeal starting in the 1870s and diverts water into the main line canal at Headrock Gate Dam. Two-thirds of the 232 miles of lateral canal are made of packed dirt, Lomayesva said. (All quotes from Lomayesva in this piece are from his comments at the March conference.)
Lomayesva said that one study pegged the cost of rehabilitating the system at $300 million – an amount of money that CRIT cannot afford. And even if it could, Lomayesva said that because the tribes do not own the water delivery infrastructure, they would hesitate to invest in it. But he said that leasing deals could provide the capital for farming on the reservation to become more efficient.
“We’re going to only market the water if we can use those funds to develop conservation systems – sprinklers instead of flood [irrigation], pipes instead of dirt ditches, recycle some of that water and reuse it again,” Lomayesva said. “That’s the only reason why we would market our water.”
Others have concluded that the outdated irrigation system is a hindrance. “The high cost to repair infrastructure, including lining canals, reconstructing gates and turnouts, and realigning reaches of the system, limit the Tribes’ ability to realize the full potential value of its water,” according to a 2018 Bureau of Reclamation study.
CRIT recently asked BIA to increase the amount it charges for irrigation water because the tribes believe that the system is underfunded and additional revenue could improve the irrigation infrastructure.
BIA did not respond to interview requests.
The Bureau of Indian Affairs, a federal agency, owns and operates the canal system that supplies the Colorado River Indian Tribes reservation with irrigation water. The system, which draws from the Colorado River, was developed piecemeal starting in the 1870s and needs repair. (Brett Walton/Circle of Blue)
Tribal members voted on an ordinance in 2019 that endorsed leasing and set certain boundaries for its implementation. The ordinance, which passed with 63 percent of the vote, was the result of an attempt a year earlier to recall all nine council members over some residents’ objections to leasing. Two council members, including former chairman Dennis Patch, lost their seats.
Under the ordinance, Tribal Council intends that the same number of acres will be farmed after water is leased. “We are farmers,” Lomayesva said. “We are farmers first, and we will probably always be farmers. And we want to continue farming. But the savings from conservation efforts, we could make some of that water available.”
The way for that to happen is for farming on the reservation to become more efficient – and that means applying less water to the fields. It could happen through conservation. But what tribal leaders like Lomayesva really want is a better irrigation system.
“Water could be made available for conservation or off-reservation leasing, exchange or storage in accordance with the requirements of the federal legislation and agreements if deferred maintenance was addressed along with improvements to the irrigation project,” according to a statement from the tribal government.
How much water might be available? In 2018, CRIT participated in a Bureau of Reclamation study to assess current and future tribal water use in the Colorado River basin. CRIT told Reclamation to assume that up to 150,000 acre-feet per year might be leased and moved off the reservation by 2060. CRIT used the same figure in a December 7, 2020, public meeting discussing the proposed legislation to authorize leasing. However, at the end of July the tribal government said in a statement, “No decisions have been made on a baseline amount of water to be available for leasing.”
What about the length of the leases? Many leases signed as part of a settlement extend for 99 or 100 years. CRIT’s authorizing legislation caps leases or exchange agreements at 100 years. But otherwise CRIT will be a free agent, able to negotiate its terms. Several water policy experts in Arizona interviewed for this story said they heard CRIT was considering a lease length of 25 years. The tribes, however, said in a statement that they have not decided any lease parameters.
Farming is a cultural legacy and economic driver for the Colorado River Indian Tribes. (Brett Walton/Circle of Blue)
The length is significant because of state water supply rules for municipalities. The Arizona Department of Water Resources requires proof of a 100-year supply. A shorter lease would not fully satisfy that requirement, but the water could be used in other ways, said Kathryn Sorensen, the former director of the Phoenix water department. It could be stored underground to offset groundwater pumping, or be paired with other water to fulfill the state’s 100-year directive. In the end, it will be a cost-benefit analysis for cities whether to lease CRIT water with a shorter term, she said.
“Each provider is going to have to weigh the length of the lease versus the priority and weigh the value,” said Sorensen, who is now with the Kyl Center for Water Policy at Arizona State University. “But, look, it’s the highest priority Colorado River water in the state. So it’s bound to be very valuable, even with a short [lease] term.”
Autonomy and flexibility
Though it has liquid riches, this form of tribal wealth has been stuck in place. Tribes elsewhere in Arizona determined their rights to the Colorado, Gila, Salt, Verde and other rivers through negotiated settlements.
In these agreements, tribes generally ceded a portion of their historical rights in exchange for state and federal funding to build the infrastructure that would deliver water to their lands. A settlement currently before Congress – the Northeastern Arizona Indian Water Rights Settlement – is the largest yet, a $5 billion proposal to determine water rights and build water supply and energy generation systems for the Navajo Nation, Hopi Tribe, and San Juan Southern Paiute.
Those settlements typically include leasing provisions. Twenty-four tribes in the West and eight in Arizona currently have leasing authority. The Fort McDowell Indian Community’s settlement, approved by Congress in 1990, for instance, sends 4,300 acre-feet a year to Phoenix. The lease extends for 99 years. Other central Arizona cities, including Gilbert, Glendale, Mesa, and Scottsdale, lease Colorado River water from the tribes, as do mining companies and a housing developer.
CRIT, however, is an entirely different case study. The tribes did not receive their water through a settlement. Their rights were part of the U.S. Supreme Court decree in 1964 that resolved a Colorado River quarrel between Arizona and California and set water allocations in the lower basin. The decree granted CRIT a significant volume of Colorado River water but it did not confer the right to lease. Instead, CRIT had to seek the blessings of Congress to gain leasing authority.
CRIT is now celebrating that authority. In April, three weeks before the state and federal agreements were signed, the tribes held a Water Rights Day, a community festival “honoring our continued commitment to the living river.”
This story was produced by Circle of Blue, in partnership with The Water Desk at the University of Colorado Boulder’s Center for Environmental Journalism.
The Colorado River is in the midst of one of the worst water crises in recorded history. Climate change and overuse are taking a significant toll. Leaders from seven U.S. states must compromise and reach a solution to prevent the river from collapsing.
LAist Correspondent Emily Guerin
To understand how negotiators from those states are thinking in this moment, Emily Guerin, a reporter for LA’s public radio station, LAist 89.3, took a deep dive into the river’s political landscape in her latest podcast series, “Imperfect Paradise: The Gen Z Water Dealmaker” from LAist Studios.
Emily brings a sharp eye to the river’s notoriously complex, multi-layered political landscape, and paints a compelling portrait of the most powerful people tasked with negotiating agreements to share the dwindling water supply.
In this recorded webinar, The Water Desk co-director Luke Runyon and Emily talk about narrative storytelling on the Colorado River, and what the story of the river basin’s most powerful decision-makers tells us about our ability to adapt to a changing climate.
Researchers prepare to take readings of the snowpack in Colorado’s San Juan Mountains to ground-truth a cosmic ray neutron sensor. Photos by Mitch Tobin.
Red Mountain Pass, Colorado –
Cosmic rays come from outer space.
These high-energy particles, which emanate from the sun but also from beyond our galaxy, travel across the universe, nearly at the speed of light, to reach Earth.
Our atmosphere and magnetic field shield us from cosmic rays, but secondary particles shower down and reach ground level. These particles are harmless to us, but some of them interact with water at the Earth’s surface and can provide important data on how wet or dry the local conditions are.
For years, cosmic rays have been employed to measure soil moisture. Now, high in the San Juan Mountains of southwest Colorado, scientists have been investigating how to use cosmic ray neutron sensors to calculate the water content of the snowpack, known as snow water equivalent (SWE).
SWE (pronounced “swee”) is of keen interest to water managers, irrigators, rafters and many others downstream from these high-country frozen reservoirs, which serve like mountain water towers but are vulnerable to warming temperatures due to human-caused climate change.
On a recent snowy morning, I tagged along with three researchers who were taking readings of cosmic ray neutrons with a mobile sensor known as a rover. They also ground-truthed the nearby snowpack by measuring its depth and density to calculate its water content.
Using cosmic rays has the potential to provide much more data on SWE than traditional approaches that measure the snowpack at a single point because this novel method gauges the water content over a far larger area.
The researchers gauge the water content of the snowpack by measuring its depth and density (click to enlarge photos)
In the prior 24 hours, nearby Silverton Mountain ski area had reported 14 inches of new snow. Up around Red Mountain Pass, there was at least that much, and the fresh layer made it tough to get around, even on snowshoes. The temperature on my dashboard read 10 degrees, and the snow sometimes blew sideways, sending the wind chill well below zero.
“Basically, the goal of our project is kind of to see how well this rover is at estimating SWE,” said Christina Chow, a graduate student at Colorado State University whose thesis is looking into the benefits and limitations of the rover for use in water resource management.
Nearby, the $70,000 cosmic ray neutron sensor sat in metal cabinets in the back of a hatchback, quietly doing its thing.
The cosmic ray neutron sensor fits in the back of a hatchback and provides data on the water content of the nearby snowpack.
The researchers drove the system along U.S. 550 at a steady 25 mph to take readings of the snow surrounding them. The scenic road, also known as the Million Dollar Highway, attracts tourists from around the world, especially during the warmer months when driving conditions on the serpentine path are less of a white-knuckle affair.
At a few points along the highway, the trio of researchers stopped to take measurements of the surrounding snowpack.
One of the crew’s tasks was using an app on their phones to measure the dimensions of the snowbank beside the highway so that it could be factored into the calculations derived from the sensor. In some places, snow plows and heavy machinery had concentrated the snow into towering masses that were downright challenging to climb.
The researchers had to navigate and map tall snowbanks along U.S. 550, also known as the Million Dollar Highway
The researchers also fanned out from the road to take readings of the snow depth and used a hollow tube to extract a core of the snowpack. That snow was then emptied into a plastic grocery bag and weighed in order to calculate its density and the SWE.
The tasks seemed challenging given the working conditions–my fingers were frozen even inside gloves–but the trio seemed in high spirits.
“It’s awesome to be out here,” Chow said. “We’ve had a couple cold days, so that’s been challenging, just to kind of warm up and everything, but, yeah, it’s been a blast.”
The rover takes a weighted average of the snowpack with a radius of about 200 meters (656 feet), so it provides data on a large area compared to traditional methods of measuring the snowpack at individual points, both by hand and with automated sensors known as SNOTEL stations.
“This is actually measuring SWE,” Chow said. “Not a lot of things can do this at this scale . . . it’s not at a point scale. It’s at this big, big footprint.”
SNOTEL stations remain the backbone of monitoring the mountain snowpack in the West and may have decades of data to analyze, but they’re fixed in space and don’t register how wind, shade and other factors may alter snow accumulation nearby.
While it’s convenient to drive with the rover on a highway, “the road has a signal that we have to account for,” Chow said.
Was the snowfall we were experiencing influencing the activity of the cosmic ray neutrons?
“We’ve been thinking about that a little bit. I’m not entirely sure,” Chow said. “Snow in the atmosphere will slow neutrons as well, so I’m sure it has some sort of signal.”
Another challenge? The complicated science behind cosmic rays.
“I’m still trying to get my head around all the nuclear physics,” Chow said.
From cosmic rays to soil moisture, by IAEA
So about those cosmic rays. They were first discovered in 1912 through experiments using a high-altitude balloon that earned physicist Victor Hess the 1936 Nobel Prize. The term “cosmic rays” was coined in 1925 by Nobel laureate and former University of Chicago faculty member Robert Millikan, according to this piece by the school, which notes:
“In the 20th century, cosmic rays helped scientists discover antimatter and the muon—the first evidence for subatomic particles beyond the proton, neutron and electron. Cosmic rays can also tell us about the chemical and physical makeup of the universe; about how the universe has changed over time; and what happens around supermassive black holes and in the hearts of exploding stars.”
The word “ray” is a misnomer because they’re actually high-energy particles. Here on Earth, the sun is considered the main source, but scientists have also documented them coming from galaxies beyond the Milky Way.
An artist’s rendering of a cosmic-ray air shower, developed in connection with a 2017 paper in Science. The paper argued that some cosmic rays come from beyond our galaxy. Source: EurekAlert!
The cosmic rays that hit our atmosphere produce fast, high-energy neutrons that are able to reach the snow and underlying soil. There, they interact with water molecules, in particular the hydrogen atoms, causing some of the neutrons to be slowed. If the sensor detects fewer fast neutrons, that means there’s more hydrogen–and water–in the area.
This year, the researchers are driving the rover along 45 miles of U.S. 550 and periodically stopping to take readings at 10 sites. Next year, they’ll shift to pulling the rover behind a snowmobile in the backcountry on unpaved roads, which will eliminate the effects of pavement and snowbanks. The year after that, they’ll use the technology in southwest Colorado’s Dolores River watershed, part of the larger Colorado River Basin.
“This study will be the first to extensively test a Cosmic Ray Neutron rover for SWE estimation,” according to the Center for Snow and Avalanche Studies.
Using cosmic rays to measure the snowpack could occupy the space between two technologies that are currently employed: fixed SNOTEL stations that provide data on a single point, and flights by Airborne Snow Observatories, which can measure snow depth and SWE over a whole watershed.
“This cosmic ray approach might be the middle guy where it’s not expensive, you can drive it at any time, you can get the data at any time,” said Jeff Derry, executive director of the Center for Snow and Avalanche Studies. “So if you had a wet spell or dry spell or whatever and you want to see changes over time, you can just go out and drive any old time you want.”
Next year, the rover will be towed behind a snowmobile on unpaved roads, eliminating the effects of the highway and snowbanks.
April 1, the midpoint in the water year, is an important milestone for scientists, water managers, and others who track the American West’s snowpack.
Each watershed has its own typical peak date for the snowpack, but in many places, April 1 has been a traditional moment for taking stock of how the spring snowpack is stacking up.
Accordingly, I’ve collected a variety of maps and charts below that illustrate the state of play on April 1.
Snowmelt accounts for the majority of the flow in many Western rivers, so the current status of the snowpack has major implications for the runoff that will supply downstream ecosystems, agriculture, and communities.
That said, the weather over the next couple of months will play a crucial role in the story of this year’s snowpack. There’s still plenty of time for more flakes to fall in the high country—snow is in the forecast for the next few days—while warm, sunny, and dry conditions could accelerate the meltout.
The map I shared at the top of this post shows a summary of conditions across the West, and it paints a variegated portrait. All of those green areas are close to the 30-year median, but there are also basins with less than 50% of normal (red) or more than 150% of the median (deep blue).
Last year around this time, I did a similar update on the April 1 snowpack and included the graphic below, showing conditions for the last three seasons:
The map below shows precipitation since October 1. As with the snowpack, the Southwest has suffered while portions of Northern California, Oregon, Nevada, and Montana have done well.
Overall, this season’s precipitation patterns “bore the telltale signs of a La Niña influence,” according to a recent post on NOAA’s ENSO blog:
“In particular, most of the southern U.S. and northern Mexico were predicted to be and turned out to be drier than average, with record-dry conditions in southern Arizona and parts of New Mexico. Wetter conditions were forecasted and did prevail over the northern part of the continent, particularly in Alaska and parts of the Pacific Northwest, as well as much farther south in Central America.”
Drilling down to the level of individual states, I looked through a slew of graphics and found a lot of places around average and not worth writing about. But below are a few different types of visualizations from the Natural Resources Conservation Service that caught my eye.
After a dreadful season, March storms were a blessing in Arizona, causing the black line in the chart below to spike upward, but the statewide snowpack was just 44% of the median (green line) on April 1.
In Colorado, which supplies water to 19 states downstream, conditions in the northern portion of the state are near normal, but in the south, it’s a different story: the Arkansas, Upper Rio Grande, Gunnison, San Miguel, Dolores, and San Juan basins are all struggling.
The skimpy snowpack in southern Colorado has pulled the statewide snowpack into below-normal territory. In the chart below, the dotted lines indicate possible trajectories for the rest of the season—a reminder that spring weather remains a wildcard.
In California, where the state runs its own system for tracking the snowpack, conditions are close to normal, but there’s still the same north-to-south gradient that we’ve seen all season. The statewide snowpack was at 96% of normal on April 1, but the northern region was at 118%, and the southern region was at 83%. This is the third year in a row with near- to above-average snowpack in California—something that hasn’t happened in 25 years.
If you’re curious about where there’s still snow on the ground, the two maps below from the University of Arizona’s SnowView interactive show the estimated snow water equivalent across the country and around the West.
The map below displays snowfall accumulation since the start of the water year on October 1. What stood out for me was the unusual swath of snow that fell across the Southeast in January, including a major winter storm in New Orleans.
Snowfall accumulation so far during the 2024-2025 water year. Source: Pivotal Weather.
The map for the U.S. Drought Monitor shows that dry conditions prevail over a large portion of the lower 48 states, with some areas in the West now recording “extreme” and “exceptional” drought.
The graphic below shows how the U.S. Drought Monitor has changed over the past six months. All that yellow, orange, and brown in the Southwest indicates that conditions have degraded so far this water year.
Teton Range and Snake River near Jackson, Wyoming, in March 2018. Photo by Mitch Tobin.
I can’t vouch for its shelf life in the Trump administration, but the U.S. Environmental Protection Agency continues to publish a revealing set of indicators of climate change impacts, including 14 connected to snow and ice.
These data sets, many of them visualized with simple maps and time-series charts, show the unmistakable effects of warming and cover a wide range of subjects, including public health, ecosystems and oceans.
Below I share and describe nine graphics that focus on snowfall, snow cover and the American West’s snowpack. All of these measures document concerning trends about this corner of the cryosphere—the frozen portion of the Earth’s surface.
The downward trajectory for snow carries serious consequences, including reduced water supplies, increased wildfire activity, imperilment of species and harm to outdoor recreation.
I’ve been meaning to write about these indicators for a while, but the task took on added urgency when I started to read about scientists and others scrambling to download data and other resources from federal websites before the information was removed by the Trump administration (see stories here and here for more).
On February 26, Trump said during a cabinet meeting that he planned to slash EPA’s staff by 65%, with aides later clarifying that this number referred to budget cuts.
Curious about whether these indicators will continue to be published, let alone updated, I emailed EPA’s press office, but the agency declined to comment for this story.
These climate change indicators have gone through layers of scientific peer review and involve partnerships with more than 50 data contributors, including government agencies, academic institutions and other organizations (see this FAQ on the EPA website for more). I’ve listed sources at the bottom of the post.
“EPA’s indicators are designed to help readers understand observed long-term trends related to the causes and effects of climate change. In other words, they provide important evidence of ‘what climate change looks like,’” EPA says. “Together, these indicators present compelling evidence that climate change is happening now in the United States and globally.”
Snowfall
This indicator looks at snow in the contiguous 48 states using two measures: the total amount of snowfall and the fraction of precipitation that falls as snow rather than rain.
EPA notes the many ways in which snowfall is critical, both economically and ecologically: snowmelt provides the bulk of the water supply in many Western communities, snowfall underlies winter recreation activities and snow keeps some species alive. Snowfall is the major driver of the two indicators discussed below: snow cover and the snowpack.
Overall, warming leads to increased evaporation of moisture into the sky and more resulting precipitation, but higher temperatures are causing more of this precipitation to fall as rain, rather than as snow. “Some places, however, could see more snowfall if temperatures rise but still remain below the freezing point, or if storm tracks change,” according to EPA. “Areas near large lakes might also experience more snowfall as lakes remain unfrozen for longer periods, allowing more water to evaporate. In contrast, other areas might experience less snowfall as a result of wintertime droughts.”
As shown in the map below, snowfall from October to May decreased in many parts of the contiguous 48 states from 1930 to 2007, with 57% of stations declining. More than 400 stations are included in the data set, and their average change was a decrease of 0.19% per year. EPA says the stations were selected for their high-quality, long-term data, but it’s not clear why the data ends in 2007; it would be interesting to see updated figures.
The graphic below shows a pronounced shift in the rain/snow mix for precipitation: more than 80% of the stations saw a decrease in the percentage of precipitation falling as snow from 1949 to 2024. This data set runs from November through March, but in some regions, that time period doesn’t capture the entire snow season.
EPA highlights some regional differences in the snowfall trends. In the Pacific Northwest, there has been a decline in both total snowfall and the fraction of precipitation falling as snow. Some areas in the Midwest have seen a decrease primarily due to changes in the snow-to-precipitation ratio, but other locations, such as those near the Great Lakes, have received more snow than in the past.
The process of measuring snow depth is familiar to anyone who has used a yardstick in their backyard, but EPA notes that precisely measuring snowfall is challenging because it’s subject to human error, and snowfall can vary dramatically across short distances due to wind, trees and other factors. Snow gauges may catch less snow than rain because of the wind, and many of the stations in mountainous regions are in lower-elevation valley towns that may not reflect conditions higher up.
Snow cover
One important measure of snow’s prevalence is the amount of land it covers. With this indicator, the depth or water content of the snow doesn’t matter: this metric only concerns whether there is snow or not. Thanks to satellite imagery, scientists can look back many decades to study trends in snow cover; in this case, the time series extends back to 1972.
Changes in both precipitation and temperature affect snow cover. Dry times mean less snow on the ground, but even with normal precipitation levels, the snow cover may be reduced if it’s too warm to snow, causing rain to fall instead.
Climate change is influencing snow cover around the world, and the reverse is also true: the fraction of land covered by snow affects the Earth’s climate because snow is so much more reflective than bare ground or open water. Snow’s high “albedo” means that it exerts a cooling effect, but if snow cover is reduced, the planet’s surface absorbs more energy from the sun.
“On a more local scale, snow cover is important for many plants and animals. For example, some plants and animals rely on a protective blanket of snow to insulate them from sub-freezing winter temperatures,” according to EPA. “Snow cover also keeps the soil moist, so if the snow melts away earlier in the spring, the soil may dry out sooner, which can stress plants and increase the risk of wildfire.”
The chart below shows the average area in North America (minus Greenland) that was covered by snow each year, based on an analysis of weekly maps.
Although the line in the graphic above looks flat, snow cover decreased slightly at a rate of about 2,083 square miles per year.
In the most recent decade (2014-2023), the annual average area covered by snow was 3.25 million square miles, which was about 3% less than during the first 10 years of the time series (1972-1981). That’s nearly 93,000 square miles less, or an area slightly smaller than Michigan, according to EPA.
The graphic below shows how snow cover has changed during each of the four seasons. “Decreases in snow cover have largely occurred in spring and summer, whereas winter snow cover has remained fairly steady over the time period studied and fall snow cover has increased,” according to EPA. “Spring and summer snow cover can have a particularly important influence on water supplies.”
EPA’s final indicator for snow cover concerns the length of the season, as shown in the chart below. This measure ends in 2013 and only covers the contiguous 48 states and Alaska, rather than all of North America.
“Between 1972 and 2013, the U.S. snow cover season became shorter by nearly two weeks, on average,” EPA says. “By far the largest change has taken place in the spring, with the last day of snow shifting earlier by 19 days since 1972. In contrast, the first date of snow cover in the fall has remained relatively unchanged.”
Snowpack
The snowpack—the seasonal accumulation of snowfall—plays a critical role in the West’s water supply and ecosystems. The annual melting of the West’s snowpack fills rivers, reservoirs and irrigation canals, providing vital water to crops, residents and wildlife while also generating hydropower at dams. “In most western river basins, snowpack is a larger component of water storage than human-constructed reservoirs,” EPA notes.
This indicator is based on snow water equivalent (SWE), the key measure of the snowpack’s water content. The SWE at a location is equivalent to the depth of water you’d get by melting a column of snow.
Some trees rely on the snowpack for insulation from freezing temperatures, and EPA says that “fish spawning could be disrupted if changes in snowpack or snowmelt alter the timing and abundance of streamflows” (see EPA’s streamflow indicator for more on this issue). A diminished snowpack can also “accelerate the start of the wildfire season and promote more wildfire activity in the western United States and Alaska,” according to EPA.
The map below shows trends in the American West’s snowpack from 1955 to 2023: red circles indicate declines, blue circles show increases and the circles are sized according to the magnitude of the change. Overall, April SWE declined at 81% of the sites, with an average decrease of about 18%. “Large and consistent decreases in April snowpack have been observed throughout the western United States,” according to EPA. “Decreases have been especially prominent in Washington, Oregon, northern California, and the northern Rockies.”
Although SWE increased at some stations, the overall trend was downward in all 12 states included in the indicator. In the Pacific Northwest region (Idaho, Oregon and Washington), all but four stations saw decreases in the snowpack.
The map above is based on nearly 700 measuring sites, but the graphics below are based on a smaller subset of 340 stations that have daily data stretching back to 1982.
One metric examines changes in the timing of the West’s peak snowpack from 1982 to 2023, as shown in the map below. Red triangles indicate earlier peaks, blue triangles show later peaks and the triangles are sized according to the size of the change.
“Almost 80 percent of sites have experienced a shift toward earlier peak snowpack,” according to EPA. “This earlier trend is especially pronounced in southwestern states like Colorado, New Mexico, and Utah.”
EPA also reports the date at which the West’s snowpack peaked from 1982 to 2023, as illustrated in the chart below. There is considerable year-to-year variability in this measure, but based on the long-term average rate of change, peak snowpack has come earlier by an average of nearly seven days since 1982.
Finally, EPA reports how the snowpack season’s length has changed from 1982 to 2023, as shown in the map below. At about 80% of the sites, the snowpack season decreased (red circles), with an average decline of about 15 days.
Telluride and the San Juan Mountains in southwest Colorado in January 2025. About one mile of relief separates the town and the highest mountaintops. Photo by Mitch Tobin.
Sometimes snow falls when the air temperature is warmer than water’s freezing point of 32° Fahrenheit.
Figuring out the dividing line between rain and snow has long flummoxed forecasters, especially in places like the high country of the American West, where complex topography and dramatic elevation differences shape the weather.
The fuzziness of the boundary can have life-or-death implications.
If rain falls on top of snow, that can cause disastrous flooding.
“We saw that in Yellowstone in 2022,” said Meghan Collins, associate research scientist at the nonprofit Desert Research Institute. “There was a really large snowpack in the Northern Rockies, forecasters called for snow, and it came as rain and it washed out roads, it washed out bridges and it washed out houses.”
Meteorologists and transportation officials want to know if roads are being coated with rain or snow so they can alert the public and deploy snowplows.
Avalanche experts care about the type of precipitation because that can be a pivotal factor in predicting the risks facing people recreating in the backcountry.
As climate change shifts snowflakes to raindrops, a better understanding of the dividing line between rain and snow is also of interest to water managers, ecologists and others who monitor streams and rivers that support both ecosystems and economies.
To gain a clearer picture of the rain-snow transition and its impact on the water cycle, scientists have been using a free phone app and data from thousands of volunteer observers who provide real-time reports of what precipitation type they’re seeing.
The observations from the NASA-funded citizen science project—known as Mountain Rain or Snow—have highlighted the shortcomings of existing approaches to differentiating the phases of precipitation, according to a study published in Geophysical Research Letters in December.
“It’s very hard for weather monitoring technologies to estimate rain versus snow without ground-based observations, and so this project is seeking to fill a gap that has connections to multiple fields,” said Collins, a co-author of the study who works on the crowdsourcing project.
So why might it be snowing when the temperature is several degrees above 32?
“This is not a change to the law of physics, but it does point to the complexity of our atmosphere,” Collins said. “Snow forms in layers of the atmosphere that are colder than where we live, work, and play.”
On the way to the ground, the snowflakes may persist while passing through warmer layers. Humidity levels play a key role in determining the rain-snow threshold. In relatively dry, continental conditions, such as in the Rocky Mountains, there are fewer water vapor molecules in the atmosphere, so the melting of snowflakes is slower, preserving them longer.
Crowdsourcing precipitation data
The project, which began in the Sierra Nevada in January 2020, relies on nearly 2,000 observers who have submitted more than 85,000 observations of precipitation as of December 2024 (see bottom of post for how to sign up).
Volunteers are asked to use an app to record whether they’re seeing snow, rain or mixed precipitation. The app records the time and location, using the device’s Global Positioning System, then transmits the data for processing.
A screenshot of the web-based reporting app.
There’s no need for observers to record the temperature. That information comes from the nation’s extensive network of weather sensors, plus some complex modeling that fills in the intervening areas with temperature data.
“We ask observers to send us observations whenever they see precipitation start or change type,” Collins said. “It’s those transitions between rain, snow and that wintry mix that we’re really interested in, especially around the freezing point.”
NASA’s interest in the project stems from its Global Precipitation Measurement Mission, a constellation of satellites that tracks weather via remote sensing and uses algorithms to determine if it’s raining or snowing.
The project helps NASA understand “where the satellite mission does well in estimating precipitation phase and where it struggles,” Collins said.
The December research paper used 39,680 observations from volunteers from January 2020 to July 2023 to assess three forecast products that distinguish between rain and snow.
“All products performed poorly in detecting subfreezing rainfall and snowfall above 2°C,” according to the study. “Crowdsourced data could help enhance methods used to determine precipitation phases and improve real-time weather forecasts.”
The study noted that previous research has revealed difficulties in determining what type of precipitation is falling from about 0°C to 4° Celsius (32° to 39.2° Fahrenheit).
“Unlike commonly used methods for determining precipitation phases, crowdsourcing visual observations of precipitation phases provides an effective and accurate way to monitor rain and snow patterns,” the paper concluded.
A flow chart helps volunteer observers decide how to submit an observation.
Informing forecasts
Raindrops and snowflakes are both made of water, but whether one or the other falls makes a big difference to water managers. A snowflake might remain up in the snowpack for months, while a raindrop might quickly run toward a river. A better understanding of the rain-snow threshold can inform the accounting of water planning efforts that hinge on the annual runoff season.
“If we know that there’s going to be more snow coming down, then we know better how much water we have in our snowpack, which is good for water balances and water budgets for the next water year,” said Nayoung Hur, another co-author of the study and a water resources engineer at Lynker, a science, engineering, and technology company. “How much streamflow are we going to have? What’s the peak runoff going to be? Are we going to have enough groundwater recharge for areas that rely on groundwater for their drinking water source or just water source?”
Another potential benefit of the project is informing avalanche forecasts.
“To the extent that what they’re doing improves the weather forecast, it’s massively helpful to us,” said David Reichel, executive director of the Sierra Avalanche Center, which provides forecasts for the greater Lake Tahoe area. “Precipitation is a major driver of avalanches, and so understanding if you’re going to get a foot of snow or an inch of rain or six inches of snow and then a half inch of rain—this part of the weather forecast is really influential on the avalanche forecast and what avalanche problems we’re likely to expect.”
One challenge is that the avalanche center publishes its forecasts early in the morning, but very few people are submitting real-time observations in the wee hours when it’s still dark out.
Rain-on-snow events can increase the avalanche danger by adding weight and infiltrating into the snowpack.
“Water in the form of rain is heavy, and even a little bit on a winter snowpack will significantly increase the avalanche danger,” Reichel said.
The Mountain Rain or Snow project is helpful to a variety of users, but it confronts a number of obstacles due to the complexity of mountain weather. For example, while computer models can provide high-resolution estimates of the temperatures where observations are recorded, those figures are not without errors since there are only so many weather stations out there.
Another challenge, Hur said, is that “a lot of people end up submitting their observations where it’s most comfortable,” such as from home, so there’s a comparative lack of data from places like the backcountry and mountaintops.
Even so, the extensive network of observers provides useful data and the scientists involved in the project say they’re impressed by the volunteers’ dedication. When the project ran a photo contest, it received 177 submissions from the field.
“Our observers are amazing,” Collins said. “There’s just a lot of talent and motivation in the community.”
Sign up to receive storm alerts via text: using the table below, find your region’s keyword and text it to 855-909-0798. You’ll receive a link to the web-based app.
A USGS hydrologist uses a velocity rod to estimate streamflow as part of a project to develop methods for monitoring streamflow in remote headwater streams. (USGS)
Wyoming’s water chief wants emergency funds for hydrologists to measure flows in the state’s portion of the troubled Colorado River Basin, documentation he said is vital to preserving irrigation and other uses.
State Engineer Brandon Gebhart asked for $167,210 in supplemental budget funds, a piddling amount in the world of western water finances, but a critical sum necessary to launch the work this spring. He called parts of the proposed allocation an “emergency,” a designation that would enable disbursements to begin this fiscal year.
Among other things, the money would employ three full-time hydrographers to measure flows in the Green and Little Snake river drainages. The total figure covers money specifically directed toward Colorado River issues as Wyoming girds to protect irrigators and other water users.
Climate change and drought have upset basin flows and could upend allotments agreed to in the seven-state 1922 Colorado River Compact. That, in turn, could threaten Wyoming’s water rights.
“What we’re seeing is an increase [in] demand and a decrease in supply,” Gebhart told members of the Legislature’s Joint Appropriations Committee in December. “This likely means that our downstream states will have a greater interest in our water. Being a headwater state, it’s somewhat concerning.”
Upper basin states — Wyoming, Colorado, Utah and New Mexico — don’t agree with lower-basin users in Arizona, California and Nevada on how or whether to reapportion dwindling runoff that supports some 40 million people. Lower basin states want equal “one-for-one” cuts shared between the two divisions, Gebhart told irrigators last summer.
“Mandatory reductions are pretty much a hard ‘no’ for me,” a position shared across the upper division, Gebhart said.
Enhanced storage
“You’re not going to hear me in the press,” Gebhart told irrigators in Baggs last summer, but he’s outlined Wyoming and upper basin states’ position in several public meetings.
“We have less water than was ever anticipated when the compact originated,” Gebhart said. “The last 22 to 24 years are the driest, the least flow in that basin in over 1,000 years.”
The 1922 Colorado River Compact requires upper division states to allow 75 million acre-feet to flow past Lees Ferry, a gauging station just below Lake Powell’s Glen Canyon Dam, during a rolling 10-year span. Wyoming’s responsible for about 14% of that and, conversely, can use a similar percentage of what doesn’t run past the gauge.
Wyoming believes it hasn’t fully tapped its 1922 share and is pursuing three significant water storage projects to fulfill its rights. Those are at New Fork Lake, Fontenelle Reservoir and a proposed reservoir on the West Fork of Battle Creek above the Little Snake River.
Those plans would primarily increase water available to Wyoming irrigators and other users. Enhanced storage could also help fulfill Lees Ferry flow obligations, but Gebhart has made clear Wyoming is unwilling to contribute “more than what we’re already under obligation for in the compact,” unless that comes from conservation, including paid-for voluntary conservation.
Unlike the lower basin states that rely on Lake Mead, “we don’t have a large reservoir to supply our releases,” Gebhart said. Instead, Wyoming’s Colorado River Basin reservoirs provide only late-season irrigation, not years of backup.
“We’re dependent on whatever Mother Nature gives us [in] the run of the river,” Gebhart said. But, “the hydrology is drying out. We have less.
“We already suffer what they refer to as shortages,” he said. “Every year we go out, we regulate off users because there’s not enough water.”
The Fontenelle Reservoir stores water from the Green River in southwestern Wyoming, above the Flaming Gorge reservoir. (Ted Wood/The Water Desk)
Enhanced measurements
For Wyoming to protect its share, it needs to know how much water diverted from rivers makes it to agricultural fields. Without documentation that can withstand legal challenges, others might say Wyoming is consuming more water than it puts to beneficial use.
Beyond what water makes it to the alfalfa field, hydrologists could also document how much leaks from irrigation canals and flows back to the main waterway, thereby remaining in the system.
They can also measure how much of the water applied to fields eventually seeps back to a river or stream and down toward the lower basin. Rules of thumb that previously served water managers may not stand up in court.
For example, Wyoming has long operated its dam, reservoir and irrigation systems, assuming that half of the water applied to a field eventually rejoins the river as return flows. The state also acknowledges that up to 80% of the water running through a canal, depending on its construction and underlying geologic composition, can leak before arriving at its destination.
The amount of seepage and phreatophytic losses — canal-side, plant-used water — is an “area of agriculture data collection that need[s] to be updated and verified,” the U.S. Bureau of Reclamation said in 2022. Toward that end, Wyoming recently directed a study on canal loss from long and porous irrigation aqueducts.
More hydrographers and scientific measures would buttress Wyoming’s claims.
“We recognize that it is very tough for us to conserve a large amount of water,” Gebhart told irrigators last summer. A paid-for voluntary conservation program would allow the state to put water savings on a ledger. In Gebhart’s words, Wyoming would “stash it away in a federal facility with our name on it until it’s needed,” to satisfy 1922 compact requirements at Lees Ferry.
Although upper and lower basin states are at odds, Gebhart said it’s not too late to reach a consensus on how to operate the complex system before the federal government steps in and forces a compromise. Those negotiations, if they happen, are not going to be done in public, he said.
Despite his reluctance to make direct statements to the press, that “doesn’t mean that we’re not here,” Gebhart said.
This story was produced by WyoFile, in partnership with The Water Desk at the University of Colorado Boulder’s Center for Environmental Journalism.
Aerial view of the Sawatch Range in central Colorado on February 2, 2023. Photo by Mitch Tobin, The Water Desk.
I’ve been a generalist most of my career, sometimes even working as a “general assignment reporter,” so I frequently find myself trying to learn about new subjects and bodies of research.
After many self-imposed crash courses, I know that one of the most helpful steps is to understand the terminology used in an issue or field.
Snow science has been no exception, so as I’ve tried to educate myself about the West’s snowpack, I’ve encountered plenty of unfamiliar words and concepts—and realized that my understanding of some things was primitive or outright wrong.
To help me—and you—better understand snow, I’ve compiled a glossary below with definitions of key terms and explanations of important concepts. I begin with an overview of snow and the hydrologic cycle, then explain words and terms in alphabetical order.
I’ve drawn on several other existing glossaries and resources that I’ve listed at the bottom of this post.
It all begins with snowflakes, which are formed in the atmosphere when water vapor in the air condenses into ice crystals around a particle, such as dust. As they fall, snowflakes may grow complex patterns that are determined by temperature and humidity.
Snow is one of several types of frozen precipitation, and there’s a difference between snowflakes and snow crystals. As Ken Libbrecht, a CalTech physics professor and one of the world’s leading experts on snowflakes, explains:
“When people say snowflake, they often mean snow crystal. The latter is a single crystal of ice, within which the water molecules are all lined up in a precise hexagonal array. Snow crystals display that characteristic six-fold symmetry we are all familiar with . . . A snowflake, on the other hand, is a more general term. It can mean an individual snow crystal, but it can also mean just about anything that falls from the winter clouds. Often hundreds or even thousands of snow crystals collide and stick together in mid-air as they fall, forming flimsy puff-balls we call snowflakes. Calling a snow crystal a snowflake is fine, like calling a tulip a flower.”
A freezing cloud laden with moisture is a prerequisite for snowflakes, but so are the tiny particles, known as nuclei, upon which the water will freeze. The gist of cloud seeding, a technology meant to boost snowfall, involves creating more nuclei in clouds by shooting chemicals, such as silver iodide and dry ice, into the atmosphere.
Once a snow crystal is born, it grows as more water vapor condenses through two main processes: faceting and branching.
Not every storm will produce a menagerie of iconic crystals on your ski pants with those dendritic, radiating formations worthy of a holiday card. In fact, scientists like Libbrecht have come up with dozens of categories to describe the diversity of shapes. The graphic below, from Libbrecht’s SnowCrystals.com, shows his classification scheme.
The different shapes are due to varying conditions in the atmosphere when the flake forms and grows, which is summarized in Libbrecht’s diagram below.
Snow crystal morphology diagram. Source: Ken Libbrecht, SnowCrystals.com.
The horizontal axis at the bottom shows the temperature, while the vertical axis on the left is a measure of humidity known as supersaturation. These two factors—temperature and humidity—are different in every weather system and can change dramatically on a snowflake’s tumble through the sky.
The science behind the graphic above, known as a snow crystal morphology diagram, was “discovered in the 1930s by Japanese physicist Ukichiro Nakaya and his collaborators,” according to Libbrecht. The diagram below is a classification by Nakaya, who is credited with creating the first artificial snowflake.
Ukichiro Nakaya’s categorization of snowflakes. Source: SnowCrystals.com.
“Nakaya used to say that snowflakes are like hieroglyphs from the clouds,” Libbrecht writes, “because you can infer the conditions in the clouds by examining the shapes of the falling snow crystals.”
Freezing rain, sleet and graupel
A precious, unique snow crystal high in the atmosphere may not survive in that state on its way to terra firma. As the flake falls, it may encounter warmer conditions that cause it to melt and turn into rain. Or the precipitation may be classified as the dreaded freezing rain if the drops turn to ice on cold surfaces at ground level. Another possibility is for the snow to melt on its way down, but then freeze again before reaching the ground, which is sleet. The graphic below from the National Weather Service summarizes how these types of precipitation differ.
There’s one more type of precipitation connected to snow worth mentioning. Graupel, which is also known as “soft hail” and “snow pellets,” begins as snow, but the flakes pick up an extra layer of moisture known as rime on their way to the ground as supercooled droplets adhere to the crystals.
Snow flurries. Light snow falling for short durations. No accumulation or light dusting is all that is expected.
Snow showers. Snow falling at varying intensities for brief periods of time. Some accumulation is possible.
Snow squalls. Brief, intense snow showers accompanied by strong, gusty winds. Accumulation may be significant. Snow squalls are best known in the Great Lakes Region.
Blowing snow. Wind-driven snow that reduces visibility and causes significant drifting. Blowing snow may be snow that is falling and/or loose snow on the ground picked up by the wind.
Blizzards. Winds over 35 mph with snow and blowing snow, reducing visibility to one-quarter mile or less for at least three hours.
For blowing snow and blizzards, it doesn’t need to be actually snowing: the mobilization of snow on the ground can create treacherous conditions of low visibility.
Hydrologic cycle: precipitation, evaporation, transpiration, sublimation, runoff, and more!
After precipitation falls, where does it go? Let’s take a quick tour around the hydrologic cycle, also known as the water cycle. Evaporation, the process by which a liquid becomes a gas, is an important factor in snowpack dynamics, with higher temperatures due to climate change increasing the conversion of liquid water to water vapor.
Transpiration occurs when water is absorbed by plants and released as water vapor through pores in leaves. This key component of the hydrologic cycle, combined with evaporation, equals evapotranspiration. In the context of the snowpack and climate change, if areas are snow-free and expose plants for a longer period due to warming, that would increase the volume of water that plants transpire and potentially decrease the amount of water reaching streams and rivers.
Sublimation occurs when snow and ice transition directly from the solid to the vapor phase without going through the intermediate liquid phase. Hard to measure, sublimation can be a significant player in the snowpack’s dynamics. It’s influenced by temperature, humidity, winds and other factors.
Surface runoff refers to the portion of precipitation that flows over land, while runoff more broadly includes the water that infiltrates into the soil and discharges into streams and rivers.
Infiltration is how water on the surface becomes soil moisture below ground. This process is affected by soil type, land cover, topography and other factors. Existing levels of soil moisture determine how much water can be absorbed and how much will run off. Some water percolates down and recharges groundwateraquifers.
The “efficiency” of runoff is the fraction of annual precipitation that becomes runoff, rather than being lost through evapotranspiration and sublimation. Many factors impact runoff efficiency, including soil moisture, land cover and weather conditions.
Below are three graphics illustrating the water cycle, all from the U.S. Geological Survey.
Source: U.S. Geological Survey.
Glossary of snow-related terms
Accumulation and ablation
Accumulation is the process by which snow and ice are added to the snowpack or a glacier. Snowfall is obviously the most important form of accumulation for the snowpack, but there is also frost deposited from surrounding air, plus some other rarer forms of frozen precipitation, such as graupel, that may be occasionally thrown into the mix.
Ablation describes the loss of snow and ice from an area due to melting, evaporation, sublimation, wind and other factors. The ambient temperature, the amount of incoming solar radiation and the reflectivity (albedo) of the snowpack play major roles in determining ablation, which can be thought of as the opposite of accumulation. The ebb and flow of ablation and accumulation is what determines the status of the snowpack and the size of glaciers.
Albedo
Albedo is a measure of the fraction of solar energy that is reflected from a surface. It ranges from 0 to 1. Surfaces with very high albedo, such as snow and ice, reflect a large fraction of incoming sunlight, while those with low albedo, such as bare ground or open water, absorb most of the energy. Albedo is derived from the Latin word for white, albus.
The Earth’s overall albedo is 0.3, but fresh snow can be around 0.9, which is why you can get a nasty sunburn on the slopes in winter. The albedo values of various other materials are in the graphic below that I created using data from MOSAiC: Multidisciplinary Drifting Observatory for the Study of Arctic Climate.
Dust-on-snow events can dramatically decrease the albedo of the snowpack and hasten its melting. On a global scale, albedo plays an important role in climate regulation. The less ice there is on the planet, the more solar radiation is absorbed, leading to further warming. Conversely, an increasingly frosty planet reflects more and more sunlight, cooling the planet further, freezing more ice, and so on, which is what happened to the planet when it turned into “Snowball Earth” many hundreds of millions of years ago.
Atmospheric river
An atmospheric river (AR) is “a long, narrow, and transient corridor of strong horizontal water vapor transport that is typically associated with a low-level jet stream ahead of the cold front of an extratropical cyclone,” according to the American Meteorological Society’s Glossary of Meteorology. These plumes of moisture are sometimes likened to “rivers in the sky” because they transport so much water vapor from the tropics toward higher latitudes. ARs can be beneficial and bust droughts, but they can also be hazardous by causing deadly flooding and extreme winter storms.
When ARs are forced upward by mountains or other forces, the water vapor cools, condenses and precipitates, as shown in the graphic below. This NOAA figure says the amount of water vapor in a strong AR “is roughly equivalent to 7.5-15 times the average flow of water at the mouth of the Mississippi River.”
The AR Scale is based on two factors: the duration of the event and its “maximum vertically integrated water vapor transport,” a measure of its water content and the speed at which it’s moving. As shown in the graphic below, there are five categories, with the bottom two described as primarily beneficial.
These three terms all refer to an area of land where precipitation collects and drains off into a common outlet, such as a river or bay. These terms are often used interchangeably, but basin is the formal geographic unit that’s used to report snowpack figures. In the American West, some water projects use massive pumps, tunnels and canals to move significant volumes of water from one basin to another to supply water for farms and cities. These are known as transbasin diversions.
Bomb cyclone and bombogenesis
A bomb cyclone is a rapidly strengthening extratropical cyclone that has experienced a drop in atmospheric pressure of at least 24 millibars in 24 hours. These storms can cause very severe weather, including intense snowfall, high winds and flooding.“When a cyclone ‘bombs,’ or undergoes bombogenesis, this tells us that it has access to the optimal ingredients for strengthening, such as high amounts of heat, moisture and rising air,” writes Esther Mullens, Assistant Professor of Geography at the University of Florida. “Most cyclones don’t intensify rapidly in this way. Bomb cyclones put forecasters on high alert, because they can produce significant harmful impacts.”
The term was coined in 1980 by MIT meteorologists Frederick Sanders and John R. Gyakum. In 2018, Gyakum told The Washington Post the name “isn’t an exaggeration — these storms develop explosively and quickly.”
We often hear about bomb cyclones hitting the Eastern Seaboard, where they can draw on the relatively warm waters of the Gulf Stream. The January 4, 2017, satellite image below shows a classic bomb cyclone. This event was also described as a Nor’easter, a storm along the East Coast characterized by strong northeast winds and heavy precipitation, but not all nor’easters are bomb cyclones.
Source: NASA.
Bombogenesis can also occur in the middle of the country or along the West Coast, as shown by the satellite image below from January 1, 2023.
Satellite image of a bomb cyclone approaching the West Coast on January 4, 2023. Source: NASA
See this excellent video below from The New York Times for a visual explainer of bomb cyclones.
Cloud seeding
Cloud seeding is an artificial process of boosting precipitation by adding particles, typically silver iodide, to clouds in order to provide nuclei around which water droplets and snowflakes can form. The technology is used by a number of water providers and ski resorts in the West. A 2020 study in the Proceedings of the National Academy of Sciences that used radar and precipitation gauges found that “cloud seeding can boost snowfall across a wide area if the atmospheric conditions are favorable,” according to the National Science Foundation, which funded the research. Learn more about cloud seeding in this story from Water Desk grantee Jeremy Miller.
A National Science Foundation “Doppler on Wheels” at Packer John Mountain in Idaho. Photo by Josh Aikens
Cryosphere
The cryosphere encompasses all the frozen parts of the Earth’s surface: snow cover, glaciers, permafrost, sea ice, ice sheets, ice shelves, icebergs and river/lake ice. The cryosphere stores freshwater for more than 1 billion people and helps regulate the planet’s climate by reflecting sunlight (see albedo). The term derivesfrom the Greek word kryos, meaning “cold” or “frost.” The illustration below shows the cryosphere’s components.
Virtually all of the cryosphere is located near the poles, with the extra-polar regions containing only 0.5% of ice and snow by volume.
Nearly all of the snow-covered areas are located in the Northern Hemisphere, ranging from 47 million square kilometers in winter to just 7 million square kilometers in summer, as shown in the graphic below. At its maximum in winter, snow covers about one-half of the Northern Hemisphere’s land mass. “The areal extent of snow varies more rapidly and more dramatically than that of any other widely distributed material on Earth,” write Olav Slaymaker and Richard E.J. Kelly inThe Cryosphere and Global Environmental Change.
Nearly all of the snow-covered areas are located in the Northern Hemisphere, ranging from 47 million square kilometers in winter to just 7 million square kilometers in summer, as shown in the graphic below. At its maximum in winter, snow covers about one-half of the Northern Hemisphere’s land mass. “The areal extent of snow varies more rapidly and more dramatically than that of any other widely distributed material on Earth,” write Olav Slaymaker and Richard E.J. Kelly in The Cryosphere and Global Environmental Change.
The chart below breaks down the cryosphere’s components into four categories: snow cover, sea ice, permafrost and ice. This graphic includes components that appear during different seasons. While snow cover in the Northern Hemisphere blankets around 47 million square kilometers in January, snow cover in the Southern Hemisphere only amounts to about 4 million square kilometers in late July.
Climate change is already taking a toll on the cryosphere, and even more drastic reductions are projected in the decades ahead as the planet warms. Glaciers, sea ice, ice sheets, permafrost, river/lake ice and snow cover in the Northern Hemisphere are all in trouble. For a solid overview of the global impacts, see the Intergovernmental Panel on Climate Change’s “Special Report on the Ocean and Cryosphere in a Changing Climate.”
Dust-on-snow
Dust-on-snow is exactly what it sounds like: deposition of airborne dust on the snowpack. More generally, scientists talk about light-absorbing particles that alter the reflectivity of the snowpack. In places like Colorado, dust-on-snow events are a big deal because the darker material reduces the snow’s albedo and causes it to absorb more heat, accelerating melting. While some airborne dust is natural, research has found that dust levels have soared since the West was settled due to agriculture, roads, development and other factors. See the Colorado Dust-on-Snow Program from the Center for Snow and Avalanche Studies for more on the issue.
The West’s increasing dryness threatens to reinforce snow loss by increasing the amount of dust that lands on the snowpack, thereby accelerating its melting. As a result, the most recent National Climate Assessment (NCA5) cautions that “under increasing aridity, agricultural practices such as fallowing and grazing on rangelands will need careful management to avoid increased wind erosion and dust production from exposed soils.” Adding insult to injury, NCA5 warns that those soils will be more susceptible to blowing around because hotter summers will “degrade protective desert soil crusts formed by communities of algae, bacteria, lichens, fungi, or mosses.”
Dust covers the snowpack of the San Juan Mountains near Telluride, Colorado, in May 2023. Photo: Mitch Tobin/The Water Desk with aerial support by LightHawk.
Glaciers and glacial landforms
A glacier is a large, perennial mass of ice and snow that moves slowly downhill under the influence of gravity. A glacier will form if the accumulation of snow and ice exceeds their loss through ablation (via melting, evaporation, sublimation and other forces).
Glaciers around the globe are threatened by warming and are used as a barometer of climate change effects. The graphic below, from the U.S. Environmental Protection Agency, shows a precipitous decline in reference glaciers around the globe from 1956 to 2023.
The photographs below show how Alaska’s McCall Glacier changed from 1958 to 2023.
Past Ice Ages covered many of the West’s mountains in ice, and the current landscape still reflects these past glaciations, which both erode and deposit material. (At the height of the Last Glacial Maximum, around 20,000 years ago, about one-quarter of the Earth’s land area was covered by glaciers.)
The diagrams below show some common glacial landforms, followed by definitions of terms most relevant to the American West.
Source: National Park Service. The photo on the right shows Mount Conness in Yosemite National Park.Source: National Park Service. Diagram A shows common glacial landforms; B is a photo of McCarty Glacier in Alaska, C is Yalik Glacier in Alaska, and D shows common types of glacial deposits.
Glossary of glacier-related terms
Arête: sharp, narrow ridge formed between two cirques or glacial valleys
Cirque: bowl-shaped depression carved by a glacier at the head of a valley
Col: saddle-shaped pass between peaks formed by two glaciers on either side of a ridge
Comb: jagged ridge caused by glacial erosion
Crevasse: deep crack in a glacier’s surface caused by stresses from the ice’s movement
Drumlin: elongated hill of glacial sediment shaped by the flow of ice
Esker: long ridge of stratified sediment deposited by meltwater streams flowing beneath a glacier
Firn: snow that has been compacted and crystallized but not yet converted to glacial ice
Glacial erratic: rock or boulder transported by a glacier far from its origin
Glacial step: step-like formation caused by differential erosion in glacial valley
Hanging valley: a tributary valley at a higher elevation due to glacial erosion of the main valley that often includes a waterfall
Horn: pyramid-shaped peak formed by the erosion of at least three cirques
Kettle lake: depression formed by the melting of a block of ice in glacial outwash
Mass balance: the difference between the amount of snow/ice gained through accumulation and the volume of snow/ice lost through ablation (via melting and sublimation); glaciers grow due to a positive balance and shrink due to a negative balance
Moraines: deposits of glacial sediment, including terminal (at the toe of a glacier), lateral (along the sides of a glacier) and medial (when lateral moraines join at the intersection of glaciers)
Nunatak: a peak that protrudes above the surrounding glacier or ice sheet and is not covered by ice
Outwash plain/delta/fan: formation created by the deposition of sediment as meltwater flows out of a glacier and deposits sand/gravel in a spreading formation
Tarn: small mountain lake in a cirque
U-shaped Valley: a valley with a wide, relatively flat floor and steep sides, formed by the carving of a glacier (in contrast to a V-shaped valley caused by river erosion)
Where are glaciers in the West?
According to the Glaciers of the American West, an online resource by Portland State University researchers, there are 8,348 glaciers in eight Western states, not including Alaska, with the most by far in Washington. These glaciers and permanent icefields range from “rivers of ice on Mount Rainier that are over 8 km (5 mi.) long to tiny patches of ice in the Rocky Mountains not much larger than a city block,” according to the site.
The diagram below shows the general locations where glaciers are found in the American West (not all of the purple areas are perennially frozen!).
These are the two main ways that scientists study and monitor the snowpack (plus many other natural phenomena). In-situ measurement involves the direct collection of data at a location using instruments in the field. In the context of snow, in-situ data may be collected by hand or via the automated sensors of a SNOTEL station, such as snow pillows. In-situ data tends to be very detailed and high quality, but for manual measurements, data collection may be time/labor intensive, and with fixed SNOTEL stations, data is limited to a single point in a complex landscape.
Remote sensing refers to data collected from a distance through devices such as satellites, aircraft and drones. These platforms use radar, lidar and other technologies to detect electromagnetic radiation at various wavelengths to provide data on snow cover, snow water equivalent, albedo, temperature, snow grain size, vegetation health and other measures. Owing to their remote vantage, these technologies can scan vast areas to collect data, including places that would be difficult to access, but they tend to have much lower spatial resolution and accuracy compared to measurements taken on the ground by people and sensors.
The table below shows how different bands in the electromagnetic spectrum respond to various snowpack properties.
Lake effect snow
Lake effect snow occurs when cold air moves over relatively warm water in an unfrozen lake, causing heavy, localized snowfall downwind from the water body.
Satellite imagery from November 18, 2014, showing lake effect snow around the Great Lakes. Source: NASA Earth Observatory.
The phenomenon is best known for its effects around the Great Lakes, but a similar process also plays out in Utah around the Great Salt Lake (the Wasatch Mountains also enhance snow production due to the orographic effect).
As shown in the National Weather Service graphic below, warmer, moist air from an unfrozen lake rises into the colder air passing above and then condenses to produce bands of heavy snow on the leeward side of the lake. “Lake effect snow usually occurs during the late fall and winter months and is capable of producing as much as 2-3 inches of snow an hour with event totals ranging from 60-100 inches,” according to NASA. The process is known as bay effect snow and sea effect snow when the cold air passes over those types of water bodies.
“Megadroughts are persistent, multi-year drought events that stand out as especially extreme in terms of severity, duration, or spatial extent when compared to other droughts of the last two thousand years,” according to NOAA’s National Integrated Drought Information System. There is no consensus on the exact definition of a megadrought, but they have been recorded throughout history on all continents except Antarctica. Scientists say the American Southwest has been in a megadrought since 2000 (sometimes referred to as the “millennial drought”).
The graphic below, from a 2022 review paper, shows where and when megadroughts have occurred in the Common Era.
This paper suggested the following definition for a megadrought: “persistent, multi-year drought events that are exceptional in terms of severity, duration, or spatial extent when compared to other regional droughts during the instrumental period or the Common Era.”
Megadroughts can be caused by natural climate variability, but researchers also believe that human-caused climate change can exacerbate the problem by altering precipitation patterns and increasing evaporative demand.
The severity, duration and geographic extent of megadroughts can have profound impacts on the natural environment and human societies, with the collapse of several civilizations linked to these exceedingly dry times.
Some scientists also use the term aridificationto refer to the long-term drying of an area and argue that the process is now transpiring in the American West. “This shift in the hydrologic paradigm is most clear in the American Southwest, where declining flows in the region’s two most important rivers, the Colorado and Rio Grande, have been attributed in part to increasing temperatures caused by human activities, most notably the burning of fossil fuels,” according to a 2020 study.
Orographic lift and the rain shadow
Orographic lift occurs when an air mass ascends a mountain range or other elevated terrain. As the air rises, it cools (due to the dry adiabatic lapse rate of 5.5°F per 1,000 feet of elevation gain). If conditions are right, water vapor will condense and precipitate as the higher terrain “wrings out” the moisture. This is why the windward sides of mountains are wetter than the leeward sides, where a drier rain shadow may occur. The American West has many classic examples of the orographic effect, such as the Sierra Nevada and Cascade Mountains receiving copious precipitation as storms move in from the Pacific Ocean while areas to the east of the mountains are very dry. Even hundreds of miles inland, precipitation generally increases with altitude and the direction of the wind hitting mountain ranges plays a major role in determining snowfall amounts. Some ski areas, for example, do better with a southwest wind while others may be favored when weather comes in from the northwest. The graphics below from the National Weather Service illustrate how orographic lift around Washington’s Olympic Mountains creates a rain shadow to the east.
You may also hear the term upslope snow to describe the orographic effect, as shown in the graphic below. Along Colorado’s Front Range, an upslope storm refers to a system that pumps moisture from the plains westward toward the mountains, which receive copious snowfall due to the Rockies forcing the moisture-laden air upward.
Permafrost is a layer of soil or rock that remains permanently frozen for at least two years. Found in polar regions and high-elevation locations, permafrost is a carbon sink that releases heat-trapping greenhouse gases when it thaws. The melting of permafrost can also cause infrastructure problems and lead to rockfall in mountainous areas. “Seasonally frozen ground is near-surface soil that freezes for more than 15 days per year,” according to the National Snow and Ice Data Center. “Intermittently frozen ground is near-surface soil that freezes from one to 15 days per year.”
Polar vortex
The polar vortex is a large area of low pressure and cold air surrounding the Earth’s poles. The vortex always exists, but it gets stronger in winter and can sometimes influence the weather at lower latitudes. As shown in the graphic below, the polar vortex features a strong band of winds high in the stratosphere, around 10 to 30 miles above the Earth’s surface and far higher than the jet stream.
A strong and stable polar vortex contains cold air near the poles, but when the vortex weakens it can force cold air southward into the mid-latitudes while drawing warm air toward the North Pole.
The animation below shows what happened in January 2019, when the polar vortex caused frigid air to descend on the continental United States.
When rain falls on an existing snowpack it can lead to rapid snowmelt and flooding. A 2018 study found that rain-on-snow events are projected to become less frequent at lower elevations because of snowpack declines, especially in warmer areas like the maritime region along the Pacific Coast. At higher elevations, however, these events are expected to become more common. The greatest increase in flooding risk is projected in the Sierra Nevada, Colorado River headwaters and Canadian Rockies.
SNOTEL and snow pillows
SNOTEL (as in snow telemetry) is a network of around 900 sites that automatically measure the depth and water content of the snowpack while also providing data on temperature, precipitation and other climatic conditions. The stations use a snow pillow filled with liquid antifreeze to measure the weight of the snow above and calculate snow water equivalent (SWE), the key measure of the snow’s water content. While some stations use cellular and satellite communications, most use “meteor burst” technology to transmit their data by bouncing a radio signal off a band of ionized meteorites 50 to 80 miles above the Earth.
Using skis, snowshoes, snowmobiles or even helicopters, surveyors periodically travel to snow courses and use a metal tube known as a snow sampler to collect data at a series of points along the snow course, which is typically 1,000 feet long. By pushing the aluminum tube into the snowpack until it touches the ground, surveyors can extract a snow core that is weighed to calculate snow water equivalent (see this page from the California Department of Water Resources for lots of photos and info about how these surveys are done).
Employees of the California Department of Water Resources measure the snowpack in the Sierra Nevada on April 3, 2023. Photo: Kenneth James, California Department of Water Resources.
“Historically, snow course measurements were the first form of snowpack data collection, starting in 1906 when Dr. James Church from the University of Nevada measured a course he laid out on Mt. Rose near Reno,” according to the Natural Resources Conservation Service (NRCS). Before the advent of SNOTEL in the 1970s, snow courses were the main way the snowpack was measured, so the data for snow courses often go back much further in time.
Aerial markers are another method for measuring the snowpack in very remote locations that are tough to access. These tall metal pipes have horizontal cross members that can be seen from an aircraft, allowing surveyors to measure the snow depth. With an estimate of the snow’s density, surveyors can calculate the snow water equivalent. In recent years, NRCS has outfitted some aerial markers with sensors, as shown in the photo below.
A snow deluge is a relatively new term applied to the biggest snowpack seasons. Researchers define it as a year in which April 1 snow water equivalent is at least a 1-in-20-year event. California’s epic 2023 winter qualified as a snow deluge (and was a 1-in-54-year event, according to the scientists). Like atmospheric rivers, snow deluges can be both beneficial and hazardous. See this story for more on snow deluges and a Q&A with one of the researchers who defined the term.
Snow drought
A snow drought is a “period of abnormally little snowpack for the time of year,” according to the federal National Integrated Drought Information System, which reports that the American West “has emerged as a global snow drought ‘hotspot,’ where snow droughts became more prevalent, intensified, and lengthened in the second half of the period 1980 to 2018.”
A “dry” snow drought results from below-normal cold season precipitation, while a “warm” snow drought occurs when there is near-normal precipitation, but it falls as rain rather than snow due to warmer temperatures. Unusually early snowmelt can also cause a warm snow drought.
Snowpack, snow cover and snow line
The snowpack is the accumulation of snow on the ground, especially in mountainous areas. This natural reservoir stores water in the winter and releases it during warmer months, making it a key component of the hydrologic cycle. While the depth of the snowpack is of interest to skiers and snowboarders, water managers and researchers are particularly attuned to the snowpack’s water content, typically expressed as snow water equivalent, or how much water you’d get if you melted a column of the snowpack.
Snow cover refers to how much land is covered by snow at a specific time. While the simple presence/absence of snow does not provide information on the snowpack’s depth or water content, snow cover is still an important dimension of an area’s hydrology and geology. Compared to snow water equivalent, snow cover is easier to measure with a remote sensing technology such as satellite imagery. Snow cover acts as an insulator, protecting the ground, vegetation and animals while also increasing albedo by reflecting solar radiation. In the Northern Hemisphere, about half the land surface is covered in snow at the winter maximum.
A dataset from the National Snow and Ice Data Centerclassifies snow cover according to five classes:1) no snow, 2) ephemeral snow, 3) transitional snow, 4) seasonal snow and 5) perennial snow. The maps below show the classification for the world and the Western Hemisphere.
The snow line is the altitude that separates snow-covered from snow-free areas. The term may be applied in the short term to individual storms (e.g., a forecaster may predict at what elevation rain will turn to snow). At higher latitudes, the permanent snow line is the altitude above which snow remains on the ground year-round. In general, the higher the latitude, the lower the snow line. Rising temperatures due to climate change are leading to rising snow lines, which has major implications for the water supply, snow sports and alpine ecosystems. One study predicts that California’s snowline will be 1,600 feet higher by the end of the 21st century, causing lower-elevation ski areas to lose more than 70% of their natural snow.
Snow water equivalent (SWE)
Snow water equivalent, or SWE (pronounced as “swee”), is a critical measure of the snowpack’s water content. It reports how much water you’d get if you melted a column of snow. SWE is primarily captured by automated SNOTEL stations and manual measurements in snow courses, though it can also be calculated using aircraft and other technologies. This metric is of particular interest to water managers who need to know how much potential snowmelt lies above their reservoirs, dams, canals and distribution systems as they try to navigate between droughts and floods while meeting the needs of their customers.
Streamflow and hydrographs
The snowpack can be hard to measure, and our observations only go back so far, but scientists have a better handle on the current and historic flow of water in streams and rivers thanks to an extensive network of gauges. Streamflow is typically measured in cubic feet per second—1 cfs is equivalent to 7.48 gallons per second and will produce about 449 gallons per minute, nearly 27,000 gallons per hour, more than 646,272 gallons per day, and almost 236 million gallons per year.
A hydrograph is a data visualization that shows the streamflow rate (also referred to as discharge) at a specific point over time. Hydrographs may also show various flood stages and include both historic data and future projections. The image below shows an example of the hydrographs produced by NOAA. See this page from the National Weather Service for definitions of terms related to hydrographs.
National Avalanche Center Encyclopedia. The National Avalanche Center provides an excellent glossary and encyclopedia on avalanche terminology. Created by Doug Abromeit, Bruce Tremper and many other avalanche professionals, this resource provides definitions of 74 terms along with many helpful graphics, photos and diagrams.
Snowpack Monitoring in the Rocky Mountain West: A User Guide. This 2020 report from the Western Water Assessment at the University of Colorado Boulder is an excellent guide to the region’s snowpack, how it’s monitored and how you can access data from a variety of sources.
Colorado River Basin Climate and Hydrology: State of the Science. This 2020 report is another helpful publication from the Western Water Assessment. It discusses the basin’s weather, climate and hydrology, plus how climate change is affecting the river’s flow.
SnowSlang is a personal passion project of mine that includes a master glossary and individual posts on key terms related to snow, skiing, snowboarding and the alpine environment.
