#ColoradoRiver District to release water for Grand Valley irrigators, Fryingpan and Roaring Fork will benefit

Colorado River Basin in Colorado via the Colorado Geological Survey

From The Grand Junction Daily Sentinel (Dennis Webb):

The Colorado River District has agreed to boost water levels to help fish in the Roaring Fork River watershed while also conserving water for use by local irrigators later in the season and improving the chances for boosting flows this fall for endangered fish.

The action also could help protect water quality in the case of anticipated ash in waterways due to expected flooding and debris flows resulting from the Lake Christine Fire near Basalt.

The river district is releasing water from Ruedi Reservoir above Basalt to boost flows in the Fryingpan River and Roaring Fork River to help reduce water temperatures to benefit trout. Low flows and warm temperatures in western Colorado have led to Colorado Parks and Wildlife urging anglers to avoid fishing later in the day on numerous western Colorado waterways due to the stress trout currently are facing.

The U.S. Bureau of Reclamation approved the river district releases last week. They are expected to range between 50 and 100 cubic feet per second.

River district spokesman Zane Kessler said the water to be released is owned and managed by the river district’s enterprise…

The water technically is being delivered downstream for Grand Valley irrigation needs but is creating environmental benefits on its way there. The water otherwise would have been delivered from Green Mountain Reservoir south of Kremmling.

Kessler said the Ruedi releases will allow for conserving a part of what’s called the historic users pool at Green Mountain Reservoir for use later in the season, which would benefit Grand Valley irrigators. The releases also increase the chances that, despite it being a dry year, that pool can be declared to have a surplus. That surplus could then be delivered in September and October to what’s known as the 15-Mile Reach, a stretch of the Colorado River in the Grand Valley where the flows would benefit endangered fish.

“This has never been done before,” Kessler said of the flow agreement. “But we’ve rarely seen river levels like this before either.”

The potential for easing the impacts of ash flow also could be felt in the Grand Valley. There is concern that ash flows could force the Clifton Water District to suspend use of Colorado River water. Area water providers have an agreement to help each other in meeting short-term water needs should that kind of emergency situation arise, but doing so this year would further deplete drought-stressed supplies.

Kessler said retaining some Green Mountain Reservoir water for release later in the year also could benefit recreational uses of the Upper Colorado River.

Meanwhile, the river district is taking another step aimed at helping ensure that benefiting fish in the Roaring Fork Valley doesn’t harm fish on the Colorado River upstream of the Roaring Fork confluence. The district is currently delivering what Kessler called “fish water” from Wolford Reservoir north of Kremmling into the upper Colorado River because it is having to lower the reservoir’s water level in preparation for doing some work on the dam there.

Heeding science in managing the #ColoradoRiver — The Mountain Town News #COriver

Eric Kuhn has retired as manager of the Colorado River Water Conservation District, but he believes he has an important message about the Colorado River. Photo credit: Allen Best/The Mountain Town News

From The Mountain Town News (Allen Best):

A time of big pivots for Colorado water — with yet another reckoning to come

Eric Kuhn is now retired as general manager of the Colorado River Water Conservation District, but he may be working on the most important project of his career, a book.

In that book, working with John Fleck of Albuquerque, he’s trying to make the case that science should not be ignored in figuring out how to manage the Colorado River during the 21st century—as it was when Congress approved the 1922 compact governing allocations among the seven states, Indian tribes, and, somewhat more fuzzily, Mexico.

Kuhn was honored recently in Glenwood Springs by his staff and others from around Colorado for his 37 years of work.

Trained as an electrical engineer, Kuhn had been a naval office on a nuclear-powered submarine before pursuing a career in nuclear power plants. But even in 1981, he could see that nuclear power wasn’t going in the right direction. When he noticed an advertisement in the Wall Street Journal for a position at the Glenwood Springs-based water district, he applied.

Obviously, he got the job, moving from energy to water, from California to Colorado.

It was sharp pivot in Kuhn’s life. And Colorado since 1981 has also pivoted hard in very fundamental ways in its conversations about water.

Tom Alvey, who grows fruit and operates a packing shed in Hotchkiss, credited Kuhn with providing transparency and “getting the facts right” during his time as general manager of the Colorado River Water Conservation District, beginning in 1996.

Bill Trampe, who owns a ranch that sprawls between Crested Butte and Gunnison, lauded Kuhn for having “the foresight to see where we were headed and what we needed to do to be effective in protecting water for the Western Slope.”

Peter Fleming, the river district’s general counsel, testified to Kuhn’s “highly intellectual approach to negotiations.” As arguments and counterarguments were waged at one session, said Fleming, he observed Kuhn scribbling into a notepad. Peering over his boss’s shoulder, he said, he saw numbers. What did they represent? “He was calculating complex integers,” Fleming discovered. In that scribbling could be seen a larger lesson.

“He wasn’t disinterested in what was going on,” said Fleming. “He just knew that the timing wasn’t right for him to offer what would inevitably be a good solution.”

Denver Water’s Jim Lochhead was also at the gathering in Glenwood, just a few blocks from where he had for many years staffed the “Aspen office” of one of the state’s leading law firms. Lochhead drew attention to Kuhn’s influence beyond Colorado’s traditional Eastern Slope versus Western Slope schisms to the broader seven-state Colorado River Basin. There, Kuhn’s voice about preparing for a warming climate has become influential.

“He is collaborative. He is innovative. He thinks about different solutions. He listens. He tries to find the common ground,” said Lochhead, now chief executive of Denver Water, an agency that provides water to 25 percent of all Colorado residents.

A time of pivots

Nobody, however, spoke directly to the giant pivots in water politics, policies and problems in the 37 years since Kuhn arrived in Colorado.

One of the largest pivots had already begun in 1981. The federal government had spent most of the 20th century building the giant dams, canals and other hydraulic infrastructure in the West. In Colorado, the greatest ambition was evident in the gigantic transfer of water from the Colorado River headwaters near Grand Lake to the benefit of farmers in northeastern Colorado. It’s called the Colorado-Big Thompson Project.

The transfer—some would call it a heist — was opposed on the Western Slope, of course. One result of the compromise was a 1937 state law that created the river district and charged it with “conservation, use and development of water in the Colorado River and its principal tributaries in Colorado.” It covers 15 counties, including Pitkin, Garfield and Eagle. Southwestern Colorado has a similar district.

Another outcome was federal construction of Green Mountain Reservoir, on the Blue River north of Silverthorne. The dam had immediate benefits to the Western Slope, helping regulate flows to the benefit of farmers around Grand Junction. Much later, the regulated flows were crucial to providing water for endangered fish species in the Colorado River.

Green Mountain Reservoir, on the Blue River between Kremmling and and Silverthorne, was built for Western Slope interests. Photo/Northern Colorado Water Conservancy District via The Mountain Town News.

A later enterprise, the Fryingpan-Arkansas Project, hewed to the same template: It diverts water from the Roaring Fork drainage to farmers in southeast Colorado. For this, the Western Slope got Ruedi Reservoir. It was completed 50 years ago.

More projects were proposed, but in 1977 President Jimmy Carter announced they wouldn’t get funded. Westerners bristled and ridiculed Carter as a peanut-farmer in rain-drenched Georgia who didn’t understand the West. Ronald Reagan, arriving at the White House in 1981, was heralded as a Westerner who would right things. He only went half-way: Locals would have to come up with half the money for their dams and diversions. For most projects, it wasn’t nearly enough.

The Colorado River originates in Rocky Mountain Natonal Park and soon descends into the bucolic loveliness of Middle Park. Photo/Allen Best

Kuhn noted that during his time, two of the five projects on Carter’s hit list in Colorado were eventually built, if not to the sizes originally envisioned. One of them, Ridgway Reservoir (originally called Dallas Divide), provides hydroelectricity that is part of Aspen Electric’s 100 percent renewable portfolio.

Altogether, however, the river district during Kuhn’s time had a hand in building five smaller-size reservoirs. Wolford Mountain Reservoir near Kremmling, by far the largest, is two-thirds the size of Ruedi. It was built in co-operation with Denver Water.

The River District under Kuhn also worked with Denver Water on other projects. But when Kuhn started work in Glenwood Springs, the relations were rocky. Denver wanted to build a giant dam in the foothills southwest of the city. Two-thirds of the water behind the Two Forks Dam was to have come from the Western Slope, primarily Summit County. Water was to go to Denver’s fast-growing suburbs.

Kuhn had been assigned to represent the river district on a task force appointed by then-Gov. Dick Lamm, to help sort through the controversy. The Western Slope task force aligned with the environmental community and together they conceded need for a small Two Forks as well as expanded diversions from Winter Park area for an enlarged Gross Reservoir west of Boulder. In exchange, the task force said, Denver needed to commit to greater water conservation. Denver Water’s leaders, confident of their rightness to the point of cockiness, refused.

The drama was cut short in 1991 when the administration of President George H.W. Bush vetoed the project, which was to be on federal land, based on environmental impacts.

Kuhn points out that the levels of conservation the Western Slope and environmentalists asked of Denver were much less than what has actually occurred. Denver Water now uses the same water for roughly double the number of people it did in 1990. The default expectation of ever-more water supplies has been shattered.

“You have this decoupling of municipal growth and water use, and we really didn’t see that coming in the early 1980s,” Kuhn said in an interview last week.

Denver, Aspen and other communities have been part of a national trend of declining per-capita use of water that may be far from over. It’s a simple matter of economics. Wringing the sponge of water conservation is cheaper. More expensive is buying water from farms on the Great Plains, but it’s still cheaper than developing new supplies.

The Colorado River wends its way through southern Utah and, at Glen Canyon, is impounded into Lake Powell. Photo/Allen Best

Still being debated is how much water Colorado has to develop out of its entitlement, under compacts governing the Colorado River. As with Two Forks, a notion that the solution to water shortages is to build more dams and divert more still lingers. It assumes water remains available. A state report issued several years ago concluded that Colorado had as much as 1.5 million acre-feet of water in the Colorado River to develop.

Kuhn scoffed at that estimate. He said then that no more than 150,000 acre-feet remained—and, quite possibly, not even that. Even allocations for existing water uses are questionable because of the dangling uncertainty of the warming climate.

After rummaging around climate change science beginning in about 2000, Kuhn became increasingly vocal through published papers and other work about the need to recognize the profound implications of a warming climate on water supplies in the Colorado River and the demands.

“I was just reading some of the work that was coming out in the early 2000s, and it’s largely proven to be generally correct,” he said last week. “I am surprised how quickly it has come on, because there is so much noise in the system,” he added, referring to the inherent variability of weather, both temperature and precipitation. “Even from one year to the next there can be a lot of noise.”

A cloudy crystal ball

What this means exactly for Colorado is still hard to say. There’s still too much uncertainty about impacts to justify significant infrastructure investments at this time, according to even Denver Water. Kuhn agrees.

“It will take a long time to see how that pattern (of change) sets up,” he said.

Climate modeling suggests—but with low confidence—less snow and precipitation for southern Colorado and more for northern Colorado. The Elk Range between Aspen and Crested butte can be seen as a divide between that wetter and drier future.

“If I were in the southwest, in Durango, I would be a heck of a lot more concerned than if I were in Steamboat Springs, based on what we know now—but it’s still a guess,” he said.

Just inside the Mexican border, at San Luis Rio Colorado, nothing remains of the Colorado River except for its sandy bed. Photo/Allen Best

For the broader Colorado River Basin, though, Kuhn expects less water in the Colorado River as it flows into the Grand Canyon past Lees Ferry. In this, last winter was a harbinger of the future. There are profound implications for how the seven states of the Colorado River Basin – plus Mexico—move forward.

And that is the big idea for the book now being written. In it, he and Fleck point to a report issued before the Colorado River Compact was formally adopted by Congress in 1928. The framers of the compact had assumed 16.4 million acre-feet average flows in allocating the waters among the seven basin states — with more yet due Mexico. In fact, flows during 20th century proved to be somewhat less, about 15 million acre-feet. The report provided accurate evidence of lesser flows beginning in 1875 and, more circumstantially, to 1850.

In other words, it was wishful thinking to assume so much water — and based on what is known about global warming, it’s fair to assume even less water in the 21st century. Through the first 14 years of the century, according to the research of Brad Udall and Jonathan Overpeck, flows have declined 19 percent.

“It’s a story about ignoring inconvenient science,” Kuhn said of the book. “If you had accepted the science, it would have made the political job [of apportioning the waters] much more difficult.”

It’s a story from a century ago, he said — but one fully relevant going forward.

For more of Kuhn’s thinking about the future of the Colorado River, see brief white paper: “Tne Upper Basin is Watching.”

@USBR approves “coordinated” approach to increase #ColoradoRiver streamflow in the Grand Valley #COriver

Fryingpan River downstream of Ruedi Reservoir. Photo credit Greg Hobbs

From The Aspen Times:

The Colorado River District is working with state and federal water managers to increase flows in the Fryingpan River by as much as 100 cubic feet per second (cfs), helping trout in the watershed survive warm temperatures while supplying water for downstream irrigation needs in the Grand Valley.

Anticipated releases are expected to range between 50 cfs and 100 cfs and will be coordinated between the River District, the U.S. Bureau of Reclamation and the U.S. Fish and Wildlife Service to increase flows in the Fryingpan and Roaring Fork rivers downstream from Ruedi Reservoir.

“This should significantly benefit flows below Ruedi Reservoir,” said John Currier, chief engineer for the district. “We expect that the supplement flows may also help to mitigate water-quality problems anticipated from fire-related ash and debris flows stemming from the Lake Christine Fire on Basalt Mountain.”

Technically, the water will be delivered downstream for Grand Valley irrigation needs while creating environmental benefits as it flows downstream. Green Mountain Reservoir releases will be reduced by an equal amount in order to conserve storage for late-season releases, which in turn will be needed to help endangered fish near Grand Junction.

The coordinated approach was given final approval by the Bureau of Reclamation on Monday. In order to boost Fryingpan levels while the plan awaited approval, the U.S. Fish and Wildlife Service implemented a 50 cfs release from its dedicated endangered fish pool in Ruedi on Friday. Those flows were supplemented by 30 additional cfs Monday, bringing the flow in the Fryingpan to 200 cfs.

Both Ruedi and Green Mountain reservoirs contribute water to the Upper Colorado River Endangered Fish Recovery Program. In this case, the changed water release plan will benefit trout below Ruedi while endangered fish still receive water from upstream Colorado River reservoirs.

Increased flows of cold water out of Ruedi should also help to alleviate some stress on trout fisheries in the watershed brought on by higher-than-normal water temperatures. Colorado Parks and Wildlife announced voluntary fishing closures earlier this month on sections of the Colorado and Roaring Fork rivers.

#ColoradoRiver District: 2018 Annual Water Seminar “Risky Business On The Colorado River” @ColoradoWater #COriver

Beginnings. Photo: Brent Gardner-Smith/Aspen Journalism

Click here for all the inside skinny and to register. From the website:

The risk of draining a half-full Lake Powell is real. The risk one-third full Lake Mead going lower and triggering big water cutbacks is real. Uncle Sam has told the states to develop drought plans or else the U.S. will do it for them. Speakers and panels from the Southern Nevada Water Authority, the Upper Colorado River Commission, the Colorado River District and others will detail current conditions on the river and what the states plan to do about them. Whether you are a toothbrusher, ag producer, angler or rafter, there’s a lot to care about.

Cost is $30 and that includes lunch; $35 at the door. Students are free unless staying for lunch, which is $10

Registration Form

For information, call Meredith at 970-945-8522 or email mspyker@crwcd.org.

Speakers include:

John Entsminger, General Manager, Southern Nevada Water Authority
Amy Haas, the new Executive Director of the Upper Colorado River Commission (UCRC) (invited)
Eric Kuhn, retired Colorado River District General Manager, adviser to the UCRC
Andy Mueller, General Manager of the Colorado River District
Brenda Burman, Commissioner, U.S. Bureau of Reclamation (invited)

and more . . .

Click here to view the Twitter fest from last year (#crdseminar).

Western Slope to keep studying water without state funds, Front Range support — @AspenJournalism

Lake Powell April 12, 2017. Photo credit Patti Weeks via Earth Science picture of the day.

From Aspen Journalism (Brent Gardner-Smith) via The Aspen Times:

Two Western Slope water conservation districts are moving forward with the third phase of a “risk study” exploring at how much water might be available to bolster water levels in Lake Powell, and they are doing so without state funding to avoid Front Range opposition to the study.

Lake Powell today is half-full and dropping and water managers say several more years like 2018 could drain the reservoir, which today contains 12.3 million acre-feet of water. And the looming water shortage is revealing lingering east-west tensions among Colorado’s water interests.

Officials at the Colorado River Water Conservation District and the Southwestern Water Conservation District, whose boundaries include the Yampa, Colorado, Gunnison, and San Juan river basins on the Western Slope, are eager to answer some forward-looking questions.

How much water in a hotter and drier world might still be available from Western Slope rivers to divert and put to beneficial use, for example.

And how much water might be made available from current water users to send downriver from each of the major Western Slope river basins to help fill Lake Powell?

Those are sensitive questions in Colorado, on both sides of the Continental Divide.

And powerful Front Range water interests think the state should be answering them, not the two Western Slope conservation districts.

A state agency, the Colorado Water Conservation Board, approved a $32,000 grant in March 2015 to help pay for the first phase for the Western Slope’s “risk study.”

Then the CWCB kicked in $40,000 in March 2017 for the second phase of the Western Slope’s risk study.

But that second grant-review process brought opposition from the Front Range Water Council, which unsuccessfully sought to block the requested funding from the Western Slope.

“The opposition to Phase II of the risk study was focused on concerns related to the direction and management of the study coming solely from the West Slope without East Slope involvement, and being funded by the state,” said Jim Lochhead, the president of the Front Range Water Council and the CEO of Denver Water, in a statement released July 20. “Risks on the Colorado River are of statewide concern and any such studies are better conducted by the state, through its Colorado Water Conservation Board.”

The Front Range Water Council is an ad-hoc group that includes Denver Water, Northern Water, Aurora Water, the Pueblo Board of Water Works, Colorado Springs Utilities, the Southeastern Colorado Water Conservancy District, and the Twin Lakes Reservoir and Canal Company.

The first two phases of the Western Slope’s risk study showed that 1 million to 2 million acre-feet of water from current water users may be needed to bolster levels in Lake Powell, especially if more water is also diverted to the Front Range.

Today, irrigators on the Western Slope use about 1.3 million acre-feet of water a year, while the Front Range uses about 541,000 acre-feet from the Western Slope to meet municipal and agricultural demand.

As such, officials at the Western Slope conservation districts are now asking if, say, 10 percent of that water use was cut back over time, in a voluntary and compensated demand management program, and the saved water was banked somewhere — ideally Lake Powell itself — would that be enough to keep the big reservoir full enough to still produce power at Glen Canyon Dam and deliver enough water downstream to the meet the terms of the Colorado River Compact?

And if it was enough, how much should come from each Western Slope basin?

On Monday in Glenwood Springs, Andy Mueller, the general manager of the Colorado River Water Conservation District, acknowledged that the 2017 funding request from the Western Slope “ran into a lot of political opposition from the Front Range, basically saying, ‘You guys are asking questions that may harm our state.’ And the questions that were posed in Phase II were essentially dumbed down in order to comply with that request so that we could get the [state funding]. So our board and the Southwestern board voted unanimously to proceed to fund [Phase III of the study] on their own.”

Mueller was addressing the members of the Colorado Basin Roundtable when he described the 2017 process. The roundtable, which reviews grants for the CWCB, had twice voted to fund the risk study, along with three other Western Slope roundtables.

And even without state funding, it’s still important to the two Western Slope conservation districts that the four Western Slope basin roundtables now conceptually support the third phase of the risk study.

On Monday, the members of the Colorado roundtable unanimously passed a resolution to that effect.

Mueller assured the roundtable members that the two districts will work to make the mechanics, and the results, of the evolving water-modeling tool available.

“We really want to make sure that what we’re doing is an open and transparent modeling process,” Mueller said. “Because we think that data that everybody can agree on is data that can then elevate the conversation with respect to the risk in the Colorado River.”

Mueller also told the roundtable that interest from the Front Range is welcomed during the third phase of the study, up to a point.

“We have reached out to the Front Range,” he said. “I went over to their joint roundtable in May and explained to them what we were doing and welcomed their participation, input, their views. Didn’t welcome their censorship, but welcomed their thoughts.”

Heather Sackett of Aspen Journalism contributed to this story. Aspen Journalism is reporting on water and rivers in the Roaring Fork and Colorado river basins in collaboration with The Aspen Times and other news organizations.

A look back at Eric Kuhn’s career at the #ColoradoRiver District @ColoradoWater #COriver

From The Aspen Daily News (Allen Best):

Trained as an electrical engineer, Kuhn was pursuing a career in nuclear power plants when he happened to notice a job advertisement in the Wall Street Journal for a position in Glenwood Springs. That was in 1981. Obviously, he got the job, moving from energy to water, from California to Colorado.

It was sharp pivot in Kuhn’s life. And Colorado since 1981 has also pivoted hard in very fundamental ways in its conversations about water.

Tom Alvey, who grows fruit and operates a packing shed in Hotchkiss, credited Kuhn with providing transparency and “getting the facts right” during his time as general manager of the Colorado River Water Conservation District, beginning in 1996.

Bill Trampe, who owns a ranch that sprawls between Crested Butte and Gunnison, lauded Kuhn for having “the foresight to see where we were headed and what we needed to do to be effective in protecting water for the Western Slope.”

Peter Fleming, the river district’s general counsel, testified to Kuhn’s “highly intellectual approach to negotiations.” As arguments and counterarguments were waged at one session, said Fleming, he observed Kuhn scribbling into a notepad. Peering over his boss’s shoulder, he said, he saw numbers. What did they represent? “He was calculating complex integers,” Fleming discovered. In that scribbling could be seen a larger lesson.

“He wasn’t disinterested in what was going on,” said Fleming. “He just knew that the timing wasn’t right for him to offer what would inevitably be a good solution.”

Denver Water’s Jim Lochhead was also at the gathering in Glenwood, just a few blocks from where he had for many years staffed the “Aspen office” of one of the state’s leading law firms. Lochhead drew attention to Kuhn’s influence beyond Colorado’s traditional Eastern Slope versus Western Slope schisms to the broader seven-state Colorado River Basin. There, Kuhn’s voice about preparing for a warming climate has become influential.

“He is collaborative. He is innovative. He thinks about different solutions. He listens. He tries to find the common ground,” said Lochhead, now chief executive of Denver Water, an agency that provides water to 25 percent of all Colorado residents.

Nobody, however, spoke directly to the giant pivots in water politics, policies and problems in the 37 years since Kuhn arrived in Colorado.

One of the largest pivots had already begun in 1981. The federal government had spent most of the 20th century building the giant dams, canals and other hydraulic infrastructure in the West. In Colorado, the greatest ambition was evident in the gigantic transfer of water from the Colorado River headwaters near Grand Lake to the benefit of farmers in northeastern Colorado. It’s called the Colorado-Big Thompson Project.

The transfer — some would call it a heist — was opposed on the Western Slope, of course. One result of the compromise was a 1937 state law that created the river district and charged it with “conservation, use and development of water in the Colorado River and its principal tributaries in Colorado.” It covers 15 counties, including Pitkin, Garfield and Eagle. Southwestern Colorado has a similar district.

Another outcome was federal construction of Green Mountain Reservoir, on the Blue River north of Silverthorne. The dam had immediate benefits to the Western Slope, helping regulate flows to the benefit of farmers around Grand Junction. Much later, the regulated flows were crucial to providing water for endangered fish species in the Colorado River.

A later enterprise, the Fryingpan-Arkansas Project, hewed to the same template: It diverts water from the Roaring Fork drainage to farmers in southeast Colorado. For this, the Western Slope got Ruedi Reservoir. It was completed 50 years ago.

More projects were proposed, but in 1977 President Jimmy Carter announced they wouldn’t get funded. Westerners bristled and ridiculed Carter as a peanut-farmer in rain-drenched Georgia who didn’t understand the West. Ronald Reagan, arriving at the White House in 1981, was heralded as a Westerner who would right things. He only went half-way: Locals would have to come up with half the money for their dams and diversions. For most projects, it wasn’t nearly enough.

Kuhn noted that during his time, two of the five projects on Carter’s hit list in Colorado were eventually built, if not to the sizes originally envisioned. One of them, Ridgway Reservoir (originally called Dallas Divide), provides hydroelectricity that is part of Aspen Electric’s 100 percent renewable portfolio.

Altogether, however, the river district during Kuhn’s time had a hand in building five smaller-size reservoirs. Wolford Mountain Reservoir near Kremmling, by far the largest, is two-thirds the size of Ruedi. It was built in co-operation with Denver Water.

The River District under Kuhn also worked with Denver Water on other projects. But when Kuhn started work in Glenwood Springs, the relations were rocky. Denver wanted to build a giant dam in the foothills southwest of the city. Two-thirds of the water behind the Two Forks Dam was to have come from the Western Slope, primarily Summit County. Water was to go to Denver’s fast-growing suburbs.

Kuhn had been assigned to represent the river district on a task force appointed by then-Gov. Dick Lamm, to help sort through the controversy. The Western Slope task force aligned with the environmental community and together they conceded need for a small Two Forks as well as expanded diversions from Winter Park area for an enlarged Gross Reservoir west of Boulder. In exchange, the task force said, Denver needed to commit to greater water conservation. Denver Water’s leaders, confident of their rightness to the point of cockiness, refused.

The drama was cut short in 1991 when the administration of President George H.W. Bush vetoed the project, which was to be on federal land, based on environmental impacts.

Kuhn points out that the levels of conservation the Western Slope and environmentalists asked of Denver were much less than what has actually occurred. Denver Water now uses the same water for roughly double the number of people it did in 1990. The default expectation of ever-more water supplies has been shattered.

“You have this decoupling of municipal growth and water use, and we really didn’t see that coming in the early 1980s,” Kuhn said in an interview last week.

Neither did Aspen, for that matter. Both Denver and Aspen have been part of a national trend of declining per-capita use of water that may be far from over. It’s a simple matter of economics. Wringing the sponge of water conservation is cheaper. More expensive is buying water from farms on the Great Plains, but it’s still cheaper than developing new supplies.

Still being debated is how much water Colorado has to develop out of its entitlement, under compacts governing the Colorado River. As with Two Forks, a notion that the solution to water shortages is to build more dams and divert more still lingers. It assumes water remains available. A state report issued several years ago concluded that Colorado had as much as 1.5 million acre-feet of water in the Colorado River to develop.

Kuhn scoffed at that estimate. He said then that no more than 150,000 acre-feet remained — and, quite possibly, not even that. Even allocations for existing water uses are questionable because of the dangling uncertainty of the warming climate.

In retirement, Kuhn may be working on the most important project of his career. Working with John Fleck of New Mexico, he’s writing a book about the Colorado River in a time of global warming.

After rummaging around climate change science beginning in about 2000, Kuhn became increasingly vocal through published papers and other work about the need to recognize the profound implications of a warming climate on water supplies in the Colorado River and the demands.

“I was just reading some of the work that was coming out in the early 2000s, and it’s largely proven to be generally correct,” he said last week. “I am surprised how quickly it has come on, because there is so much noise in the system,” he added, referring to the inherent variability of weather, both temperature and precipitation. “Even from one year to the next there can be a lot of noise.”

What this means exactly for Colorado is still hard to say. There’s still too much uncertainty about impacts to justify significant infrastructure investments at this time, according to even Denver Water. Kuhn agrees.

“It will take a long time to see how that pattern (of change) sets up,” he said.

Climate modeling suggests — but with low confidence — less snow and precipitation for southern Colorado and more for northern Colorado. The Elk Range can be seen as a divide between that wetter and drier future.

“If I were in the southwest, in Durango, I would be a heck of a lot more concerned than if I were in Steamboat Springs, based on what we know now—but it’s still a guess,” he said.

For the broader Colorado River Basin, though, Kuhn expects less water in the Colorado River as it flows into the Grand Canyon past Lees Ferry. That, he thinks, should have profound implications for how the seven states of the Colorado River Basin – plus Mexico—move forward.

And that is the big idea for the book now being written. In it, he and Fleck point to a report issued before the Colorado River Compact was formally adopted by Congress in 1928. The framers of the compact had assumed 16.4 million acre-feet average flows in allocating the waters among the seven basin states — with more yet due Mexico. In fact, flows during 20th century proved to be somewhat less, about 15 million acre-feet. The report provided accurate evidence of lesser flows beginning in 1875 and, more circumstantially, to 1850.

In other words, it was wishful thinking to assume so much water — and based on what is known about global warming, it’s fair to assume even less water in the 21st century. Through the first 14 years of the century, according to the research of Brad Udall and Jonathan Overpeck, flows have declined 19 percent.

“It’s a story about ignoring inconvenient science,” Kuhn said of the book. “If you had accepted the science, it would have made the political job [of apportioning the waters] much more difficult.”

It’s a story from a century ago, he said — but one fully relevant going forward.

New @USBR modeling suggests a bigger risk of #ColoradoRiver shortage than y’all might think — @JFleck #COriver

From InkStain (John Fleck):

The conventional calculation of Colorado River shortage risk, which people like me frequently report, shows a 51 percent chance of Lake Mead dropping into “shortage”, below the magic trip line of elevation 1,075 at which mandatory cutbacks kick in, in 2020. But a new approach to modeling risk, which lots of folks (*cough* me *cough*) think more accurately represents the changing climate, shows a significant risk of a much quicker drop in Lake Mead’s levels, blowing quickly past 1,075, with a greater than 50 percent chance of dropping below 1,050 sometime in 2020. Absent actions to reduce water use, Lake Powell has a greater than one in four chance of dropping near power pool (the level at which it could no longer generate electricity) by the mid-2020s.

It is to the Bureau of Reclamation’s credit that they’re not only running the new modeling methodology in parallel with the more traditional approach, but that they’re doing this in a very public way, presenting both last week at the Basin States principals meeting in Santa Fe as part of the federal effort to get negotiations over water use cutbacks back on track.

Here’s the Mead graph showing the traditional modeling approach (the blue) and the newer “stress test” (shown in red):

I like this graph (kudos to Carly Jerla and the other wizards at the Bureau for coming up with such a clear visualization) because of how intuitively it shows how different the answers are when you use the two different approaches. Especially visually striking is the probability “cloud” showing the statistical range of possibilities. The old blue approach shows a decent chance of wetness refilling reservoirs. The newer red approach not only offers no such blue bits of optimism, but shows some statistically credible chances of Lake Mead seriously tanking very soon.

The difference between the two modeling approaches gets to the heart of the importance of the “period of record” you use to analyze river flows in support of decision-making.

The traditional (blue) approach uses historic river flows from 1906 to 2015 as the basis for a statistical simulation of the range of possible futures given current reservoir levels. This is classic “stationarity” – assume the future will be like the past. The specific model then uses what’s called the “index-sequential method” (ISM), which is a bog standard way of modeling the statistics of river flows.

The new approach (red), which has come to be known as the “stress test”, is based on the view of some water managers and scientists that the old full-record approach is understating risk, because the past climate – especially in the case of the Colorado River that exceptionally wet first quarter century of the record – is putting more water in the river in your simulations than we can realistically expect any more because of a warming climate. The stress test still uses the ISM, but instead of the full record, it uses 1988-2015, which seems more like a modern climate than the full thing back to 1906.