The route to the research site feels like a polar expedition. High in the mountains above Crested Butte, Colorado, a team of scientists trudges single file through the whiteout, following a chain of orange flags marking the route.
Each plod of their skis squishes down into the pillowy snow below, the kind that melts on contact and drenches jackets and gloves.
During some portions of the trek, the snowglobe conditions make it hard to tell where the sky ends and the ground starts. But after a few miles, a cluster of narrow gray columns starts to come into focus.
Eli Schwat, a member of the research team, stared up at the thin metal towers – each holding high-tech monitoring equipment – through a tightly-cinched jacket hood.
“What's the snow moon in Star Wars chapter five? It looks like Hoth,” said Schwat, a PhD student at the University of Washington. “It looks like the rebel base on Hoth.”
Schwat and his research partner, Danny Hogan, are neither arctic explorers nor stormtroopers. They’re more like detectives. The duo treks out to this site each day to help answer a mystery: How much snow evaporates into the air before it has a chance to melt?
Every winter, high-altitude snow melts and fills streams, rivers and reservoirs all around the Rocky Mountains. Some years, there’s a big gap between the amount of snow and the amount of water that ends up in the places where people measure and collect it. Scientists and water managers have limited data on why that happens. The disparity between snowpack and runoff has far-reaching implications for tens of millions of people who draw water from the Colorado River.
This hardy two-man crew plays an important role in helping people across the Southwest understand their water supply. The Colorado River watershed stretches from Wyoming to Mexico, supplying cities like Phoenix and Los Angeles and sprawling fields of crops that contribute to a multi-billion dollar agricultural economy. After two decades of drought and steady demand, the region’s dwindling supply is stretched thin, and accurate data on the amount of water entering the system this year is crucial for those who manage it.
Digging for answers
Sublimation is a natural phenomenon in which water evaporates into the air before it turns to liquid water, changing from a solid to a gas instantly. It isn’t often talked about, even among those who study Colorado River water supply, but the process of water turning straight to vapor is something many people have seen with their own eyes.
Jessica Lundquist, an engineering professor at the University of Washington and the head of the sublimation study, said it’s what causes dry ice to give off a spooky fog – the kind that you might see in a haunted house.
Snow sublimation is common in the arid West, since the region often has the right conditions – low humidity, high altitude, strong sunlight and dry winds. Those combine to create a perfect storm for the phenomenon.
In the case of dry ice, it’s carbon dioxide that’s turning into visible smoke-like vapor. Water, on the other hand, is much harder to see.
“This is a process that's extremely hard to measure,” Lundquist said. “You actually need to measure droplets of water that have turned into vapor that you cannot see. They're floating around the atmosphere, so you need really highly-specialized sensors that can look at that vapor moving around in the atmosphere.”
Those sensors are held up by the metal towers at the research site. Thin metal trusses – some reaching nearly 70 feet above the ground – contain more than a dozen pieces of monitoring equipment. They measure basic weather data such as wind speed, the amount of water vapor in the air, and temperature. Others use lasers and electric signals to get data on snow depth and soil moisture. Those sensors are posted at different intervals along the towers to gather data from various distances off the ground.
All of those measurements combine to help form an understanding of how much snow evaporates, and why. But another important data set comes from beneath the snow’s surface.
“Our advisor, Jessica Lundquist, always says that half of the job of being a snow scientist is digging,” Hogan said, shoulder deep in the snow. “So if you're good at digging, you'll probably be a good snow scientist.”
Lundquist, for her part, seems to be a fan of excavation. She said her favorite book is Holes by Louis Sachar, a young adult novel that follows a group of kids who are forced to spend all day digging holes in the middle of the desert.
Hogan and Schwat took turns with a packable aluminum shovel, tossing chunks of snow over their shoulders until only their eyes and baseball caps were visible above the hole.
“What makes a good pit?” Hogan said. “Wide enough for you to sit down in comfortably. Very straight, clean sides. You don't want a messy side. You want it to look really nice. The appearance is very important.”
Once the crew created a sufficiently pretty pit, they took measurements. One member of the duo crouched with a set of tools, reading the findings out to his above-ground partner, who jotted down numbers on a waterproof notepad. A pair of thermometers – one digital, one analog – are jabbed into the snow. A foldable ruler helps the researchers test the firmness of the snow at different distances from the surface, and a custom-built metal scoop called a “density cutter” lets them gather snow for weighing.
“The nice thing about all of these measurements is that there's probably one specialized tool,” Schwat said. “But everything else you could get at a hardware store.”
Another one of their tools is the “crystal card,” a small sheet of plastic covered in grid lines. Paired with a magnifying glass, it’s a useful backdrop for analyzing the size and shape of snowflakes. Hogan and Schwat climb out of the pit and study a few flakes against the bright blue card, which is about the size of a smartphone. Out of the 135 terms they could use to describe snowflakes, they choose about 10 to explain the appearances of these ones.
On a near-freezing day with wet snow, the researchers were in a hurry to look at each snowflake before it melted on the surface of the card. After inspecting a few in detail, the duo packed up their gear and began the trek back to their cabin.
A sky-high laboratory
Hogan and Schwat are far from the first scientists to spend a winter in this particular spot. Their winter homebase is the Rocky Mountain Biological Laboratory, or RMBL, pronounced “rumble” for short. The lab, a cluster of wooden cabins built on the footprint of a once-abandoned 1800s mining town, is hallowed ground for environmental researchers of all stripes.
Founded by a local biology professor in 1928, RMBL has hosted decades-long studies to determine how flora, fauna and other natural factors behave at high altitude.
Its most notable resident, the naturalist billy barr, has quietly become a cult hero to those interested in climate data. He has meticulously gathered data on plants, animals and snow around RMBL since the 1970s, building a deep understanding about how they’ve changed through the years. His remote, high-mountain home and scraggly beard have earned barr a reputation as a hermit, but the lab’s other winter residents say he is more social than he’s been made out to be in stories about his work.
barr, who prefers his name written in lowercase, is not part of the snow sublimation study, but said the lab’s high-mountain perch is perfect for gathering that kind of data.
“It will give an indication of what the natural world is doing without as much influence from humans,” he said. “Especially this time of year when not many people come out here. There's not many animals out here either because it's a rough environment to survive in, but it makes a good testing point.”
In some way or another, barr has been observing this pristine environment’s snow for decades. He said winters are noticeably shorter and snow is noticeably denser of late.
The site has recently lured another big snow research project. Researchers and tools associated with the Surface Atmosphere Integrated Field Laboratory (SAIL) campaign, funded by the U.S. Department of Energy, are also spending the winter in Gothic, Colorado. Shipping containers stuffed with more than four dozen instruments that measure precipitation, clouds, winds, and a host of other environmental factors, were brought to the Rocky Mountains after a previous stint in Antarctica. The SAIL team has been gathering data in Gothic since September 2021, with plans to wrap up in June 2023. Scientists hope the data will give them a more robust understanding of how water behaves at high altitude.
Every last drop
Researchers have zoomed in on the disappearing snow that never makes it into runoff mainly because they think there is a lot of it. In some recent winters, snowpack has reached as high as 90% of the yearly average. Yet, those same years saw as low as 50% of the annual average runoff, according to Colorado State University climate scientist Brad Udall.
Lundquist and her team are candid that snow sublimation is probably not the main driver of the disparity between snowpack and runoff levels. Scientists and water managers have become increasingly concerned with soil moisture in recent years. Recent summers and winters, warmer due to the effects of climate change, are baking the dirt and drying it out. When snow turns to water each spring, the dried-out soil soaks it up like a sponge and allows less water to make its way to the streams and rivers where people divert and collect it.
Scientists still don’t know how much of an impact recent reductions in soil moisture have on a shrinking Colorado River, and they know even less about the role that snow sublimation plays. That’s why Lundquist’s study offers the hope of a significant contribution to how the West understands its water.
“It's not just that the word is new or that no one's ever seen it,” she said. “It's the magnitude. I think this is one of the first studies to actually put so many instruments in one place to actually quantify the magnitude – and the physics that control the magnitude. People want to know the science to make management decisions on a very scarce resource.”
Although the snow sublimation study dives into a relatively niche subgenre of water science, the parched Colorado River basin needs all the data it can get.
“We know the Colorado River is oversubscribed,” Lundquist said. “Every drop of water is wanted by multiple people. So if you're off by the number of drops of water you're promising to somebody, they're not happy.”
Water managers across the Southwest have had to learn to live with less. Cities in the region have grown at a breakneck pace, forced to stretch finite water supplies across populations growing by hundreds of thousands of people over the span of a few decades.
“Our worst case scenario, from our perspective, is that we have to be in the habit of annually looking to the mountains to see, ‘What is the precipitation?” Cynthia Campbell, a water advisor with the city of Phoenix, told KUNC in January.
In an ideal world, Campbell said reservoirs function as a buffer against the fluctuation of dry years and wet years. But with those reserves shrinking to never-before-seen lows, cities that depend on the Colorado River can only plan one year at a time.
“That's just not enough time to make changes that you would have to make,” Campbell said. “But that is where we are. So, in some ways it might be our worst nightmare.”
It all comes back to climate change
These lean times have forced Colorado River water managers to keep an eye on increasingly granular water data, like snow sublimation and soil moisture. Earlier this spring, six states agreed on an unprecedented proposal to make significant new cuts to water use based on a plan that accounts for evaporation from Lake Mead, the nation’s largest reservoir.
The Colorado River crisis that has landed Southwestern water leaders in national headlines is a product of climate change. Environmental metrics show that warmer temperatures are driving major changes to where snow falls, how long it sticks around, and how likely it is to end up in reservoirs. Meanwhile, those who decide how the river is shared have been stuck in a standoff, arguing about who should feel the sting of painful cutbacks.
Supply has shrunk dramatically, and demand has stayed largely the same.
That thin-stretched water supply has gotten even harder to forecast in the past few years. Patterns that were previously accepted as concrete are now in question because of warmer temperatures – meaning reliable predictions about snowmelt are hard to come by.
“Being able to have a good number to look ahead for the season is really, really important in terms of making important management decisions in the river that affect all of the users,” said Edie Zagona, a hydrology and engineering professor at the University of Colorado Boulder. “Climate change is a major factor in all aspects of the problem with forecasting.”
Those forecasting problems apply to seasonal runoff predictions, but also long-term projections about how much water will be in the Colorado River and its reservoirs. While specific numbers are scarce, environmental scientists overwhelmingly agree that water is unlikely to return to the arid West in a significant capacity. Some assert that it no longer makes sense to describe the West’s current water shortage as a “drought,” preferring the term “aridification,” defined as a permanent reset of the baseline for how much water will be in snowpack, rivers and streams each year.
The difficulty in forecasting has driven up demand for new, robust data. It’s a demand that motivates the team studying snow sublimation. Jessica Lundquist, the head of the study, recalled some recent words of encouragement from a colleague.
“He said, ‘Jessica, the bar is low,’” Lundquist said. “‘Learn anything, and we'll know more than we knew a year ago. You can do this.’ So, it's both exciting and humbling.”
This story is part of ongoing coverage of the Colorado River, produced by KUNC, and supported by the Walton Family Foundation.
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