Atmospheric rivers, commonly defined as long, narrow corridors in the atmosphere, much like rivers in the sky, transport moisture from the tropics. These “rivers” can produce large amounts of snow accumulation when they make landfall during the cold season. With over half of the streamflow in the Colorado River originating from water released by snow melt, it’s important to understand how atmospheric rivers can affect snowpack in the region.
In a new Geophysical Research Letter article, authors Mu Xiao, and Dennis P. Lettenmaier, identify the atmospheric rivers in the Upper Colorado River basin during a 65-year-long historical record and evaluate their contribution to mountain snowpack. It was found that almost one-third of the snowpack in the basin is attributed to atmospheric river induced snowfall. The primary origin of these atmospheric rivers are from the southwest, however, the pathways do not affect the amount of snow they yield.
“Given that over 70% of the Colorado River’s natural flow originates from snowmelt, it is of great importance to understand the characteristics of snow in the basin. In this study, we determine that on average atmospheric rivers contribute to nearly 30% of the basin’s total snow accumulation, which can yield over 20% of annual streamflow. We also find that atmospheric river related snow is highly important to the region during warm winters,” said author Mu Xiao.
This study was partially funded by the MAPP program.
Read the full paper here.
Here’s the release from Governor Gordon’s office:
Governor Mark Gordon’s Colorado River Working Group will hold its first meeting from 9 am to noon on Sept. 7 in Rock Springs. The group will discuss important Colorado River matters and monitor potential impacts to Wyoming. The kickoff meeting will be open to the public and led by the Wyoming State Engineer’s Office.
The formation of the Working Group comes in response to continuing drought conditions in the Colorado, Green and Little Snake River basins and associated issues concerning Colorado River Basin management. The Governor’s charge to the Working Group is to discuss and share Colorado River information with interested stakeholders in the Green and Little Snake River Basins. It is a continuation of a coordinated and proactive outreach effort that has been underway in Wyoming since 2019.
This group is made up of representatives of key water use sectors in the Green and Little Snake River Basins. Working Group members are:
Ben Bracken — Green River/Rock Springs/Sweetwater Joint Powers Board (retired) Brad Brooks — Cheyenne Board of Public Utilities
Senator Larry Hicks — Senate District 11 Representative Albert Sommers — House District 20
Jen Lamb — The Nature Conservancy
Aaron Reichel — Genesis-Alkali Ron Wild — PacifiCorp
The September 7th meeting will be held at Western Wyoming Community College in Business Office Room #3650 A&B in Rock Springs. More information, including background materials and future meeting agendas, will be posted on the Colorado River Working Group web page on the Wyoming State Engineer’s website: https://seo.wyo.gov/interstate-streams/wyoming-colorado-river-working-group.
From Water Education Colorado (Jerd Smith):
The federal agency that distributes electricity from hydropower plants in the Upper Colorado River Basin will ask its customers, including more than 50 here in Colorado, to help offset rising costs linked to Lake Powell’s inability to produce as much power due to drought.
The Western Area Power Administration (WAPA), which distributes Lake Powell’s electricity, is gathering public comments and asking its customers how best to cope with long-term drought conditions that have pushed Powell and other reservoirs to historically low levels.
As flows in the Colorado River have declined due to climate change and a 20-year megadrought, there is less water in its storage reservoirs and, therefore, less pressure to power the turbines, causing them to generate less electricity.
WAPA has had to nearly double the amount of extra power it has had to buy this year to ensure it can meet its contract obligations to its customers.
“It’s all bad news, but it isn’t necessarily unexpected,” said WAPA spokesperson Lisa Meiman.
WAPA power is among the most sought-after in Western states because it is sold at cost and because it is a renewable power resource, something highly valued in places such as Colorado, where utilities are working to reduce their reliance on fossil fuels.
WAPA often buys extra power if for some reason its customers’ electricity needs don’t match up with its hydropower production on a given day. It delivers power over a 17,000-mile transmission grid to six states and 5 million people.
But as flows in the Colorado River have shrunk, those purchases have become larger and more frequent.
Last year it bought an extra 413,000 megawatts of power. This year it has already purchased 833,000 megawatts of additional power, according to Meiman, and the agency expects that number to grow this year and likely again next year as the drought continues with no relief in sight.
This year, because of the power demands of the West’s growing population and the need for air conditioning to combat ultra-high temperatures, power costs are already soaring.
Last year WAPA paid $25 per megawatt for its replacement power, Meiman said. This year it is paying $33 per megawatt, a 30% jump.
In Colorado, WAPA sells power to some of the state’s largest electric utilities, such as Tri-State Generation and Transmission, as well as cities, small towns and rural electric co-ops.
“We’re watching the situation closely,” said Natalie Eckhart, a spokesperson for Colorado Springs Utilities, which is a WAPA electric customer and which also draws a significant portion of its water from the Colorado River system.
“The bottom line is we care about this on all fronts,” Eckhart said.
Few expected power generation at Lake Powell to decline so quickly. The Colorado River Basin serves seven U.S. states and 30 Native American Tribes. For months, the U.S. Bureau of Reclamation and the Upper Colorado River Basin states of Colorado, New Mexico, Utah and Wyoming have been nervously watching what’s known as the minimum power pool level at Powell, the lowest elevation at which power can be produced, which is 3,490 feet. If the reservoir drops lower than that, all hydropower production will stop.
In July, as water levels at Powell continued to plummet, the U.S. Bureau of Reclamation, as part of the Upper Basin’s Drought Contingency Plan, began emergency releases of water from Utah’s Flaming Gorge, Colorado’s Blue Mesa, and New Mexico’s Navajo reservoirs to boost levels and protect Powell’s hydropower production.
And while those releases are expected to help keep the turbines functioning, the releases won’t be enough to restore them to full production, leaving WAPA little choice but to look at restructuring the way it sells power and to raise its prices.
WAPA is forecasting a 35% increase in its costs, but is working to minimize the impact on utilities that purchase its power and anticipates a 12% to 14% rate increase as early as December. Some utilities are preparing to buy power elsewhere, when possible, to reduce their costs.
Holy Cross Energy, a rural electric co-op based in Glenwood Springs that is also a WAPA customer, has spent years converting its power portfolio from fossil fuels to renewable energy sources including wind, solar and biomass, as well as hydropower.
While WAPA electricity comprises just 3% of its power portfolio, Holy Cross CEO Bryan Hannegan is worried that this renewable, low-cost power source is in jeopardy if flows from the Colorado River into Lake Powell continue to decline, as they are projected to do.
“It’s one of the cleanest and lowest-cost sources of power for a whole range of utilities,” Hannegan said. “It’s been a bedrock on which we built the West. For it not to be available … it’s a big deal.”
Jerd Smith is editor of Fresh Water News. She can be reached at 720-398-6474, via email at email@example.com or @jerd_smith.
From Circle of Blue (Brett Walton):
Every month the Bureau of Reclamation attempts to peer two years into the future of the Colorado River and its reservoirs.
Reclamation’s 24-month study is a staple forecasting product for the federal agency that manages a chain of dams in the watershed, including those that control lakes Mead and Powell, the country’s largest reservoirs — and currently two of its most consequential. The reservoirs are a key source of drinking water for about 40 million people, plus they store water that irrigates millions of acres of farmland and generates electricity for the Southwest. The reservoirs are also alarmingly dehydrated right now — about one-third full, the lowest since they were first filled. The entire basin is on alert.
The 24-month study, in the simplest terms, projects water levels for the next two years at 12 federal reservoirs in the Colorado River basin. Produced monthly, it’s one of several forecasting products that give water managers a sense of possible futures. It is also the foundation of essential water management decisions in the basin. Reclamation’s other forecasts, updated less frequently, look at mid-term (five years out) and long-term (multiple decades) scenarios.
Typically nested in wonkish obscurity, the 24-month study acquired newfound public prominence in recent weeks. The August results are the most important of all the months because they determine how much water will be released in the following year from Mead and Powell. Because Mead is so low, the August results triggered the first-ever Tier 1 shortage on the lower Colorado River, a declaration that means mandatory cuts in water deliveries in 2022 to Arizona, Nevada, and Mexico. Because Powell is so low, dam managers will release a comparative trickle of water next year, so little that Mead is likely to plunge even lower.
More eyes than usual on a technical product that was designed to guide reservoir operations means more potential for misinterpretation, especially by people unfamiliar with the study and its assumptions. Carly Jerla, Reclamation’s senior water resources program manager, said that the study has its defined uses but also its limits.
“It’s important to understand that we’re not saying that this is what we think is going to happen this year,” Jerla told Circle of Blue about the reservoir levels outlined in the 24-month study. “We’re not saying, ‘Plan for this and only this because we have crystal ball knowledge of what is going to happen.’”
Reclamation’s models, in fact, are not a crystal ball. Critics say that they are not pessimistic enough about the potential for extremely dry years. But as the Colorado River basin dries due to a warming planet, Jerla and others are actively considering how best to convey to the public and water managers alike the looming risks to water supplies and to prepare people, at least mentally, for the possibility that reality could turn out much worse than the forecast had projected…
Accurate mid-term weather forecasts, those that extend out a couple weeks and up to a year, are notoriously difficult to achieve, said Jeff Lukas, an independent climate researcher in Colorado who has worked in the basin for 20 years. It’s especially true in the mountainous terrain of Colorado and Wyoming, where the Colorado River and its main tributaries have their headwaters. Well-known seasonal patterns like the cyclical warming of the eastern Pacific during El Nino years can indicate wetter or drier, but without substantial precision.
Because the future is hazy, the models instead rely on the recent past as a guide, Lukas said. “We’re basically saying in the absence of real prognostic information, we’ll substitute history.”
Here’s how that works. The 24-month study process begins with the Colorado Basin River Forecast Center, a team of scientists operating within the National Oceanic and Atmospheric Administration. Their task is to assess what the rivers might do.
The River Forecast Center starts with current land and water conditions: soil moisture, snowpack, stream flow. From that baseline hydrologists feed their model, one by one, with historical weather observations from the years 1981 to 2015. In effect, it’s as if the temperature and precipitation from each year were repeated in today’s world. That produces 35 possible hydrological futures, each representing the past laid on top of the present.
The Bureau of Reclamation team takes those hydrological futures and uses them in its model of the Colorado River system. The aim of this system model, which includes water inflows and water uses, is to simulate reservoir levels as well as hydropower generation. Fed by the output from the hydrological model, the system model also produces future scenarios, called runs.
The middle result — the most probable — is the one that is presented in the main 24-month study report. It’s the result that determines how Mead and Powell will be operated. It’s called the most probable because it’s in the middle, if each of the runs was ordered from wettest to driest. It means that historically half the time it was wetter than the middle result and half the time it was drier.
There are drawbacks to this approach. The runs are not assessed as to how likely they are to occur, which means that a repetition of each of the past years is considered equally likely. The problem: there are more wet years in the 1981 to 2015 period than dry ones. (Runoff in 1983, for instance, was so extremely high that it almost broke Glen Canyon Dam.) Because of this imbalance, the middle result is arguably skewed toward wetter conditions, Lukas said.
Jerla said there is no scientifically valid way to privilege the likelihood of one outcome over another.
An update of the River Forecast Center’s data sets will soon help reduce the skew. Cody Moser, a senior hydrologist at the Center, told Circle of Blue that data from the years 2016 through 2020 will be added this fall. Instead of 35 historical hydrologies fed through the models, there will be 40. Adding the drier recent years will push the most probable outcome to a drier result, with reservoir projections in the 24-month study likely pushed downward at the same time…
The 24-month study is most associated with the most probable scenario. But recently Reclamation has expanded its offerings to include two other reservoir scenarios, now produced monthly: the minimum probable and the maximum probable. The minimum probable is the tenth percentile, meaning the third or fourth driest of those 35 historical hydrologies. The maximum probable is the ninetieth percentile, or the third or fourth wettest historical hydrology.
For the minimum probable, the tenth percentile of flows is used in the first year of the 24-month study, but the second year of the study is calculated with the twenty-fifth percentile, under the assumption that consecutive extremely bad years would not happen.
If you look only at the most probable result, you’re not seeing how bad things might plausibly get. Lake Mead today, when it is one-third full, sits at elevation 1,068 feet. The most probable elevation for July 2023 is 1,037 feet, when Mead would be 26 percent full. The minimum probable elevation for that date is 1,027 feet, when the gasping reservoir would be 23 percent full.
That’s a significant difference in elevation, and if the drier scenario came about it would change basin operations. But even the minimum probable has a flaw. It is not as pessimistic as it could — or maybe should — be.
“The minimum probable does not represent a worst-case scenario,” Jerla said. “If you wanted to be the ultimate pessimist, which I think probably makes sense given where the system is, things could be worse than what is provided in that minimum probable because it is only the tenth percentile.”
In other words, the minimum probable is not the minimum possible. There have been years in the last two decades with worse river flow conditions than what is represented by the minimum probable. Things could be drier still.
As Jerla puts it regarding the minimum and maximum probable: “There is an area above and below those that have futures that folks should be aware of.”
Reclamation already runs its five-year projections with what it calls “stress test” hydrology. This scenario is a replication of the years 1988 to 2019, and represents hotter and drier conditions that have settled over the basin. Udall and others argue that Reclamation should consider running its models with an even more stressful test: the years 2000 to 2004, the last time that Lake Powell almost crashed.
“That five-year period is really unique,” Udall explained. Annual runoff averaged 9.4 million acre-feet, a fraction of what coursed through the river throughout the last century. The average annual runoff in the years for the stress test hydrology is about 13.3 million acre-feet. That makes the first years of this century unique, Udall said. And frightening. “There’s nothing like it in the 20th century. It’s stunning how bad a period it is, and we could be in the middle of that right now.”
The next update of the five-year projections will come out in early September. Five years is a tricky time frame to analyze, Jerla said. It’s far enough in the future that current conditions lose their predictive power. But it’s close enough to be relevant for farmers, city utilities, and marina operators — all of whom need to plan for near-term water supply. Jerla and her colleagues are trying to thread that needle, thinking hard about how to “provide the public with a good understanding of future outcomes and future risks without confusing the heck out of them.”
In an effort to prop up water levels at the declining Lake Powell, federal water managers are negatively impacting recreation on Colorado’s biggest man-made lake.
That’s the message from Colorado water managers and marina operators at Blue Mesa Reservoir in Gunnison County. On Aug. 1, the Bureau of Reclamation, which operates the reservoir, began emergency releases. By the time the releases are finished the first week of October, Blue Mesa is projected to fall to its second-lowest level ever, just 215,000 acre-feet, or 22.8% of its 941,000-acre-foot capacity.
As of Sept. 1, the reservoir was 37% full, which is about 68 feet down from a full reservoir, and a ring of muddy shoreline was growing. Parking lots and boat slips sat empty, and Pappy’s Restaurant was closed for the season. The dwindling water levels are first impacting Iola, the easternmost of Blue Mesa’s three basins. Iola is where the Gunnison River now cuts through a field of mud.
Eric Loken, who operates the reservoir’s two marinas (Elk Creek and Lake Fork), said he was given only nine days’ notice to empty Elk Creek Marina’s 180 slips. The dock system’s anchors, which are not built for low water, had to be moved deeper. He said about 25 people lost their jobs six weeks earlier than normal and the marinas lost about 25% of its revenue for the year.
“There are tons of people who would like to be out here boating and are very disappointed,” Loken said. “Normally on Labor Day weekend, you can barely find a place to park. So it’s definitely been a big hit to us as a business for sure.”
The Elk Creek Marina and restaurant are closed for the season, although the boat ramp is still open and is expected to be accessible through the end of the month. The Lake Fork Marina is open through Labor Day, but the boat ramp has closed for the season. The Iola boat ramp is restricted to small boats only and is scheduled to close after Labor Day.
“We are just trying to make it through the holiday weekend and then we will be shutting up this marina too,” Loken said.
The Bureau announced July 16 that it would begin emergency releases through early October from three Upper Basin reservoirs: 20,000 acre-feet from Navajo, on the San Juan River; 125,000 acre-feet from Flaming Gorge, on the Green River; and 36,000 acre-feet from Blue Mesa, on the Gunnison River. The goal of the releases is to prop up water levels at Lake Powell to preserve the ability to make hydropower at Glen Canyon Dam. The 181,000 acre-feet from the three upstream reservoirs is expected to boost levels at Powell by about 3 feet.
The three reservoirs are part of the Colorado River Storage Project, and their primary purpose is to control the flows of the Colorado River; flatwater recreation has always been incidental. But the releases at Blue Mesa illustrate the risks of building an outdoor-recreation economy around a highly engineered river system that is now beginning to falter amid a climate change-fueled drought.
Although the secretary of the Interior can authorize emergency releases without coordination from the states or local entities, Loken, along with some Colorado water managers, is not happy about the timing or the lack of notice from the bureau. Under normal drought-response operations, the federal government would consult with state and local water managers before making releases.
“We had very little time to handle this decision that was made that none of us have any power over,” Loken said.
John McClow, general counsel for the Upper Gunnison Water Conservancy District, said Colorado should make noise and complain about what he called a clumsy execution of the releases. McClow has also served on the Colorado Water Conservation Board and is an alternate commissioner on the Upper Colorado River Commission.
“There’s no reason they couldn’t have waited another couple weeks or another month to release that water from Blue Mesa to get it to Lake Powell,” McClow said. “It goes back to consultation and timing. Had they even asked, it would have been easy to say, ‘Hey, can you wait so you don’t kill our business?’”
Last month at Colorado Water Congress’ summer conference — a gathering of water managers, researchers and legislators in Steamboat Springs — Rebecca Mitchell, CWCB’s executive director and the state’s representative to the UCRC, told the audience that the impacts of ending the boating season early at Blue Mesa trickle down to all Coloradoans.
“That means dollars in Colorado. That is who we are in Colorado,” she said. “It’s definitely had an impact in that local community when we talk about the recreation. That is heavy.”
Mitchell said water managers in the Upper Basin states (Colorado, Utah, New Mexico and Utah) will be carefully monitoring the impacts of the reservoir releases and figuring out how to quantify those impacts, which she called devastating. The states will work with the bureau to develop a plan for how to send water to Lake Powell in future years, taking into consideration the timing, magnitude and duration of the releases, she said.
“Where can the states and the bureau make the best decisions to lessen the impacts?” she said.
The National Park Service operates the Curecanti National Recreation area, including the campsites, picnic areas, visitors centers and boat ramps that run the 20-mile length of the reservoir. According to numbers provided by the Park Service, Curecanti gets nearly a million visitors a year. The reservoir is popular among anglers for its trout and Kokanee salmon fishing. Blue Mesa is one of three reservoirs — along with the much smaller Morrow Point and Crystal reservoirs — on the Gunnison River, collectively known as the Aspinall Unit.
Gunnison Country Chamber of Commerce Director Celeste Helminski said her organization is planning an event later this month: the world’s largest snow dance. A big winter would help refill Blue Mesa.
“The water definitely has me concerned for the future,” she said. “We see a lot of summer recreationists who come and spend the whole summer at several of the campgrounds. It’s just going to take a lot to replace that water. It’s going to take awhile to get back to levels of what recreationists come for.”
Bureau spokesperson Justyn Liff could not provide any insight into how the timing decision for the releases was made, but pointed out that although lake recreation was impacted, downstream rafting and fishing in the canyon are getting a boost from the roughly 300 cubic-feet-per-second extra water that the releases provide. The Gunnison River below the Gunnison Tunnel diversion, which takes a large portion of the river’s outflow from the Aspinall Unit for delivery to downstream irrigators, was running around 600 cfs the first few days of September, according to USGS stream gauge data. This is a critical data point for boaters running the Black Canyon or Gunnison Gorge sections of the river, which are below the stream gauge. At 600 cfs, the river is flowing 11% above the median for this time of year.
“If we had waited six weeks, that would have been six weeks less of commercial rafting/guided fishing on the Gunnison River downstream from Aspinall,” Liff said.
Although the local impacts to recreation are acute, the impacts of not being able to make hydropower at Lake Powell would probably be much worse. The dams of the CRSP are known as “cash register” dams. The power they produce is used to repay the costs of building the project, maintain operations and provide power to millions of people.
The Western Area Power Administration distributes Lake Powell’s electricity, including to some power providers in Colorado. According to Water Education Colorado, electric costs will surge as Glen Canyon Dam struggles to produce hydropower because of declining water levels.
The bureau’s target elevation for Lake Powell is 3,525 feet, in order to provide a buffer that protects hydropower generation; if levels fall below 3,490, all power production would stop. Lake Powell is currently about 31% full, at 3,549 feet, which is the lowest surface level since the reservoir began filling in the 1960s and ‘70s. According to projections released by the bureau in July, Lake Powell has a 79% chance of falling below the 3,525 threshold in the next year. The emergency releases are intended to address this.
“A loss of power generation is a pretty significant issue compared to a few months of boating on Blue Mesa,” McClow said. “Locally, yes, it hurts, but in the big picture, I don’t know if you can make a fair comparison.”
As water levels at Blue Mesa continue to fall, Loken worries that this may be just the beginning of an era of empty reservoirs.
“(The releases) don’t solve the long-term problem,” Loken said. “We are just going to end up with an empty Lake Powell and a bunch of empty reservoirs upstream. I think the powers that be really need to put pencil to paper and figure this out.”
Aspen Journalism covers water and rivers in collaboration with The Aspen Times. For more, go to http://www.aspenjournalism.org.