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Climate change will reduce streamflow in the upper Colorado river basin as groundwater levels fall, study finds

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Climate change will reduce streamflow in the upper Colorado river basin as groundwater levels fall, study finds


The illustration shows historical atmospheric and environmental water loss and contributions. Credit: Caroll et al

The Colorado River makes life possible in many Western cities and supports agriculture that sustains people throughout the country. Most of the river’s water begins as snowmelt from the mountainous watersheds of Colorado, Utah, and Wyoming, and a warming climate will drastically reduce these streamflows, new research finds.

Researchers from Desert Research Institute (DRI), USGS, and Lawrence Berkeley National Laboratory teamed up for the new study, published May 23 in Nature Water.

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By applying warming to historical conditions for the East River in Colorado and using computer simulations to observe the impact on streamflow and groundwater levels, the scientists found that groundwater storage would fall to the lowest known levels after the first extremely dry year and fail to recover even after multiple wet periods. When groundwater levels fall, streamflows are drawn into the water table instead of contributing to Colorado River flows.

“We found that groundwater matters a lot,” says Rosemary Carroll, Ph.D., DRI research professor of hydrology and lead author of the study. “Even with historically observed wet periods in the model, the groundwater can’t come back from a single dry water year under end-of-century warming.”

The Colorado River has been in a drought state for decades, creating tensions around water rights throughout the Southwest. Scientists have been perplexed by falling river levels even in relatively wet years—in 2021, the Upper Colorado River Basin reached 80% normal snowpack but delivered only 30% of average streamflow to the river.

The study authors wanted to examine how warming in mountain basins may be contributing to this phenomenon. Increased temperatures alter the balance between snowfall and water availability in a number of ways, including more snow evaporation (known as sublimation), more precipitation falling as rain instead of snow, and more frequent melting throughout the winter.

Past research has largely overlooked the role of groundwater and how it may buffer, or intensify, streamflow loss from climate change.

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“I’m very interested in the relationship of groundwater contributions to streamflow—that has been a running theme in my research for a long time,” Carroll says. “A lot of studies indicate that in the short term, groundwater release to streamflow will help buffer drought impacts, but before this study, we didn’t have any knowledge on what that would mean over the long haul.”

Rising temperatures will significantly reduce streamflow in the upper Colorado river basin as groundwater levels fall, new research shows
The graphic illustrates how declining water tables under climate change would decrease streamflows. Credit: Jeremey Snyder, from Carroll et al.

The study authors used the East River as the focus for the research because it is representative of the headwaters of the Colorado River, as well as the significant weather and water monitoring infrastructure available. Ground observations and airborne mapping measure snowpack depth and density, streamflow, plant cover, and groundwater levels, among many other measurements throughout the watershed.

Historical data from 1987 to 2022 was used to create the computer model. The research team then applied 4 degrees Celsius of warming to this time period in two ways: for one simulation, warming was applied constantly across time, while in subsequent simulations, warming was applied to each season independently.

The approach allowed the scientists to examine the differing impacts of warming between seasons. Four degrees Celsius is representative of the projected climate at the end of the century based on observed warming of approximately 0.4 degrees Celsius per decade in the watershed. The simulation doesn’t account for likely changes in vegetation over the same timeframe.

The study showed that consistently warmer temperatures resulted in sharp declines in groundwater levels that were unable to recover to historical average levels during wet periods. Isolating the warming seasonally demonstrated the strong impact of warmer summers on water table declines, as the atmosphere increases evaporation rates, plants increase their water uptake, and soils dry out. The largest declines in water table elevations occur in the subalpine forests where conifer forests are most dense.

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“As the groundwater level drops, you lose more streamflow to the water table,” Carroll says. “When precipitation is low, the East River stops flowing for a portion of the summer. Of course, this would have dramatic effects on ecological health and agricultural irrigation.”

By including declining water table levels in the analysis, the study found that streamflow reductions nearly double when compared to simulations that examined the impacts of climate change in the region without accounting for groundwater declines. This is because of the multiple impacts occurring simultaneously: less water flows to streams from the aquifers, while more stream water drains into the soil.

The research demonstrates the need to jointly manage forest and groundwater in the Upper Colorado River Basin, as well as account for the exchange of surface and groundwater in mountain basins, to minimize streamflow declines under climate change, Carroll says.

“I think of groundwater as your savings account,” she adds. “Snowpack is like your checking account; it changes from year to year. Groundwater is a longer-term investment—it can smooth out the really wet and dry years. But if you start consistently reducing that groundwater year after year, then you can no longer modulate those extremes.”

More information:
Declining Groundwater Storage Expected to Amplify Mountain Streamflow Reductions in a Warmer World, Nature Water (2024). www.nature.com/articles/s44221-024-00239-0

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Climate change will reduce streamflow in the upper Colorado river basin as groundwater levels fall, study finds (2024, May 23)
retrieved 23 May 2024
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Colorado needs a sane, viable opposition party

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Colorado needs a sane, viable opposition party


If you are upset with the increasing regulatory burden in Colorado, the exodus of too many large employers, accelerating property taxes, the condition of the roads and all of the funding for transit schemes with low demand, of course you can lay the blame on Democrats who control all levers of state government.  The same holds if your misgiving centers on annual […]



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Coworking firm Industrious takes former WeWork space in Denver

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Coworking firm Industrious takes former WeWork space in Denver


Industrious, a national coworking brand, is opening a new location in LoHi.

The company has snapped up 25,000 square feet at The Lab building at 2420 17th St., just off Platte Street. Industrious has an existing LoHi location just up the road at 2128 W. 32nd Ave.

“They are going to draw from different populations. … No doubt they’re close to each other, but [this is a] different product type, just in terms of build-out,” said Peri Demestihas, an Industrious executive.

Demestihas said the current LoHi location has been full for two years, which indicates demand for more space. That existing spot is more for established businesses with a greater emphasis on private offices. The new location will be geared more toward smaller companies and the solo entrepreneur.

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In total, there will be 379 dedicated “office seats” and 18 “access seats,” which can be used by anyone.

Industrious has a conservative mindset when it comes to growth, Demestihas said. The company also operates in Upper Downtown and by I-25 and Colorado Blvd.

“These are the submarkets we like and if we can find the right building and we can get the right structure, … without those things, we’re not going to go to those submarkets. It’s got to suit our members.”



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Contamination, climate change and political drama stall clean water for Colorado’s Arkansas Valley – High Country News

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Contamination, climate change and political drama stall clean water for Colorado’s Arkansas Valley – High Country News


The western stretch of the Arkansas River, which flows from its headwaters in the Rocky Mountains across the plains of southeastern Colorado, is in trouble. That trouble is compounded by uncertainty about what, exactly, is polluting and drying the river, and how such problems can be fixed. 

Overshadowed by the ongoing political brawl over the Colorado River, the Arkansas River Valley rarely appears in national news. But since Dec. 30, when President Donald Trump vetoed a bipartisan bill that would have secured favorable terms for funding to complete a $1.39 billion, 130-mile water pipeline, the region has become the stage for yet more drama about water in the Western U.S.

The Arkansas Valley Conduit is part of a decades-long effort to replace the dwindling, contaminated water in this stretch of the Arkansas Valley with clean water from Colorado’s Western Slope and the Pueblo Reservoir. If completed, it will supply water to roughly 50,000 valley residents, many of whom can no longer count on municipal supplies for safe drinking water.

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Pundits portrayed Trump’s veto as retaliation against Colorado politicians: Republican Rep. Lauren Boebert, who helped force the November vote for the release of the Epstein files, and Democratic Gov. Jared Polis, who has resisted pressure to pardon Tina Peters, a county clerk in western Colorado convicted of tampering with voting machines during the 2020 election. Sens. Michael Bennet and John Hickenlooper, both Democrats, condemned the administration for “putting personal and political grievances ahead of Americans.” The Salida-based Ark Valley Voice declared a “Reign of Retribution Punishing Deep Red Southeastern Colorado.” The New York Times, emphasizing the same irony, observed that “A Trump Veto Leaves Republicans in Colorado Parched and Bewildered.” 

For those managing the project, the veto is a setback but not a showstopper. The first dozen miles of the conduit have already been completed, and enough capital is on hand for at least three more years of construction. “Some (coverage) has been saying it’s the end of the project, which is totally false,” said Chris Woodka, senior policy and issues manager of the Southeastern Colorado Water Conservancy District. “It’s still being built; the veto was not for any reason that had anything to do with the project, and we’re working in every way we can to make this affordable.” 

For valley residents, the issue is personal. This rural region is more culturally aligned with western Kansas than with Front Range cities. Like people throughout the Great Plains, the local residents are grappling with eroding social services and the rising cost of living. The scarcity of safe water magnifies uncertainty. “If you don’t have clean water,” said Jack Goble, general manager of the Lower Arkansas Valley Water Conservancy District and a sixth-generation rancher, “you really don’t have anything.”

A resident prepares to fill jugs with purified water at the Rocky Ford Food Market in Rocky Ford, Colorado. The town’s water supply is contaminated with unsafe levels of radium and uranium. Credit: Michael Ciaglo
Lawrence Armijo, maintenance operator for the town of Manzanola’s water treatment plant. While the plant filters out most toxins, it is not equipped to remove radium and uranium from the groundwater.
Lawrence Armijo, maintenance operator for the town of Manzanola’s water treatment plant. While the plant filters out most toxins, it is not equipped to remove radium and uranium from the groundwater. Credit: Michael Ciaglo

“HOW EASY IT IS,” wrote William Mills in his 1988 book The Arkansas, “to take a river for granted.” 

The Arkansas Valley of Colorado is the ancestral homelands of the Plains Apache, Comanche, Kiowa, Cheyenne and Arapaho peoples. A geographical corridor across the Southern Plains, it was a route for incursions and ethnic cleansing by non-Native fur trappers, traders, military expeditions, hide hunters, railroad developers and settlers. Those settlers include my ancestors; I grew up in southwest Kansas, where generations of my family farmed and ranched along the dry Cimarron River. The Arkansas Valley, with its dwindling water and flatlands, feels like home.

By 1900, settlers had diverted the Arkansas into a maze of ditches. Irrigation and migrant labor supported sugar beet factories, vegetable cultivation and Rocky Ford’s famous melons. Such practices remade the riverbed, increased salinity, and reduced flow. As with the Colorado River, water rights were assigned partly on wishful thinking. Today, the Arkansas Valley is one of the region’s most over-appropriated basins, and the river’s annual flow has dramatically declined. A short distance past the Kansas line, the river is entirely dry.

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The Arkansas is being drained in new ways. Climate change and a record-breaking snow drought are intensifying the scarcity. Over the last half-century, growing Front Range cities have purchased water rights from farmers in the valley. Exchange agreements allow cities to swap these rights for ones farther upstream, leaving the downstream flow diminished and dirtier. Between 1978 and 2022, nearly 44% of the irrigated farmland in the Lower Arkansas Valley Water Conservancy District was taken out of production.

Critics call it “buy-and-dry.” They say the removal of water has disastrous consequences for an agricultural region. “If you take all of that water out of an economy that completely depends on it,” Goble said, “it just breaks a community.” Faced with the prospect of litigation from local water districts, cities like Aurora claim to be developing more sustainable arrangements.

“If you don’t have clean water, you really don’t have anything.”

THE ARKANSAS’ WATER is changing, too. The river is diverted into dozens of canals and fields. What doesn’t evaporate or get absorbed returns as runoff or sinks through the alluvial gravels that connect to the riverbed. Each time a drop of water returns, it carries more dissolved minerals. As the river’s volume lessens, the concentration increases in what is left. By the time the river reaches the Kansas border, the water regularly contains 4,000 milligrams or more per liter — making it about eight times saltier than a typical sports drink and unsuitable for growing many crops.

Minerals are not the only problem. The river basin and alluvial gravels are also contaminated with radium and uranium. Last year, a study by the Colorado Geological Survey found that the levels of radioactivity in more than 60% of the private wells sampled in the valley exceeded federal standards. 

The radionuclides are called “naturally occurring.” But natural uranium usually stays locked in rock. In the valley, irrigated agriculture sets it into motion. Uranium is mobilized by complex interactions between oxygen, sediments, water, microbes and nitrate. Nitrate is a common fertilizer. One study found that valley farmers had over-applied it for decades. This pulls out radionuclides, turns them loose, and flushes them into the river’s shallow aquifer. Levels rise as the river moves east through agricultural lands.

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Contamination is not news in the valley. People have worked on cooperative solutions for decades. To meet safe water standards while the conduit is under construction, the towns of La Junta and Las Animas installed filtration systems. But cleaning the water creates hyper-contaminated wastewater, which is currently diluted and poured back into the river.  “The only true solution,” said Bill Long, president of the Southeastern Colorado Water Conservancy District board, “is a new source.”

Orlando Rodriguez, Pate Construction foreman, climbs out of a hole where sections of the Arkansas Valley Conduit will be connected.
Orlando Rodriguez, Pate Construction foreman, climbs out of a hole where sections of the Arkansas Valley Conduit will be connected. Credit: Michael Ciaglo

THE CONDUIT WOULD PROVIDE safe water to a region too often disregarded. But the project also raises questions about what can truly be bypassed and what cannot, and about the fate of the river itself.

Near Cañon City, upstream from the conduit, the Lincoln Park/Cotter Superfund site contains a former uranium mill, millions of tons of radioactive waste, coal mineworks and tailing ponds. The site sits less than two miles from the Arkansas River. It is known to be contaminated with the same compounds — radionuclides, selenium, sulfates — that affect communities downstream.  

Local residents have worked for decades to raise awareness and hold a revolving cast of agencies, regulators and owners accountable for the pollution. “It has taken us a lifetime,” said Jeri Fry, co-chair of Colorado Citizens Against Toxic Waste. “As the years have gone by, we have been the ones holding the memory.” 

“The only true solution is a new source.”

Without memory, they say, contamination is normalized as background, treated as an isolated issue, or denied. “We’ve been stonewalled on many of our legitimate concerns,” said Carol Dunn, vice-chairperson of the Lincoln Park/Cotter Community Advisory Group. She believes state regulators avoid testing for fear of uncovering inconvenient facts.

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The most inconvenient would suggest connections between contamination in the valley and industrial pollution upstream, which affects not only Cañon City but the communities of Leadville, Pueblo and Fountain Creek. For Fry, all of the known and unknown pressures on the river point to the same fundamental problem. “We are not treating our water as though it is a sacred thing,” she said. “And it is. It’s got to be.” 

Russell Van Dyk, owner of Lloyd’s Ice and Water in Rocky Ford, Colorado, closes up his store at the end of the day. The residents of Rocky Ford and surrounding towns rely on purified drinking water because the area’s groundwater has been contaminated by uranium and radium.
Russell Van Dyk, owner of Lloyd’s Ice and Water in Rocky Ford, Colorado, closes up his store at the end of the day. The residents of Rocky Ford and surrounding towns rely on purified drinking water because the area’s groundwater has been contaminated by uranium and radium. Credit: Michael Ciaglo

We welcome reader letters. Email High Country News at editor@hcn.org or submit a letter to the editor. See our letters to the editor policy.

This article appeared in the May 2026 print edition of the magazine with the headline “The absence of clean water.”   

This story is part of High Country News’ Conservation Beyond Boundaries project, which is supported by the BAND Foundation and the Mighty Arrow Family Foundation.

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