The Mysterious Loss Of Water In The Colorado River

High winds ripped at Gothic Mountain, watching over the cottages tucked in Gothic, Colorado, an isolated outpost accessible only by skis during the valley’s severe alpine winters. The plumes of snow that rose from the peak briefly formed a cloud before dissipating.

Many people would miss the snow that seemed to vanish into thin air. However, in a location where water supplies is gradually dwindling, every snowflake counts. Every year, an unknown amount of the snowfall in the Rocky Mountain West evaporates into the atmosphere, as it was doing on Gothic Mountain, just outside the ski resort town of Crested Butte.

A group of researchers from Gothic’s Rocky Mountain Biological Laboratory (RMBL) are attempting to unravel the enigma in the East River watershed, located at the highest portions of the Colorado River Basin, by focusing on a process known as sublimation. Snow in the mountains can sometimes skip the liquid phase entirely, transitioning directly from a solid to a vapor. The phenomena is responsible for ranging from 10% to 90% of snow loss. This margin of error is a significant source of uncertainty for water managers attempting to forecast how much water will enter the system once the snow melts.

Although scientists can monitor how much snow falls to the ground and how rapidly it melts, there is no perfect way to determine how much is lost to the atmosphere, according to Jessica Lundquist, a researcher who focuses on snow and weather patterns in the Alps. Lundquist led the Sublimation of Snow study in Gothic with support from the National Science Foundation during the 2022-’23 winter season, attempting to investigate how much snow disappears and what environmental circumstances cause it to evaporate.

“It’s one of those nasty, wicked problems that no one wants to touch,” explained Lundquist. “You can’t see it, and only a few tools can measure it.” Then there’s the question of what will happen with climate change. Will there be less water for the rivers? Is there more of it in the atmosphere or not? And we simply don’t know.”

The snowmelt from Gothic will eventually replenish the streams and rivers that feed the Colorado River. When runoff is lower than projected, it pressures a system that is already stressed because to persistent drought, climate change, and rising demand. Snowpack levels near the region’s headwaters, for example, were not far below the historical norm in 2021—not bad for a winter in the West these days. However, snowmelt in the Colorado River’s tributaries was just 30% of usual.

“You measure the snowpack and assume that the snow is just going to melt and show up in the stream,” said Julie Vano, a research director at the Aspen Global Change Institute and a project collaborator. Her work aims to assist water managers in deciphering the science behind these processes. “It simply wasn’t there.” “What happened to the water?”

As the West continues to dry out, water managers are under growing pressure to forecast how much of the valuable resource will enter the system each spring. One of the most difficult decisions for federal water managers, especially officials at the Bureau of Reclamation, the gatekeeper of Lake Powell and Lake Mead, is determining how much water to release from reservoirs to meet the needs of downstream customers.

While transpiration and soil moisture levels are two potential causes of water loss, one of the biggest unknowns is sublimation, according to Ian Billick, executive director of RMBL.

“We need to close that uncertainty in the water budget,” Billick added.

Getting It Right
The East River’s tributaries eventually flow into the Colorado River, which serves roughly 40 million people in seven western states and Mexico. More than a century of biological observations have collided in this watershed, with many of these research focusing on understanding the water’s life cycle.

One of the most recent is Lundquist’s project. Because of the complexities of the intersecting mechanisms that produce sublimation, the team set up over 100 devices in Kettle Ponds, an alpine meadow just south of Gothic.

“No one’s ever done it right before,” stated Lundquist. “As a result, we’re doing our best to measure everything.”

Throughout the winter, the collection of equipment discreetly captured data every second of the day, providing the researchers with a snapshot of the snow’s history. A sonic anemometer detected wind speed, while others measured temperature and humidity at different elevations. Snow pillows detected moisture content, and lidar, a laser imaging technology, made a comprehensive map of the snow’s surface.

Daniel Hogan and Eli Schwat, doctoral students at the University of Washington who work under Lundquist, skied from their snow-covered cabin in Gothic to Kettle Ponds to observe the ever-changing snowfall from January to March.

Their skis were outfitted with skins, a unique fabric that adheres to skis to improve their grip on the snow. The two men crunched against the ground on their near-daily excursion out to the site, sleds full of equipment in tow. It was a cold March day, but the stinging reflection of the snow made it feel warmer. When Hogan and Schwat arrived, they dug a hole in the snow just beyond the canopy of buzzing equipment.

The temperature and density of the snow within were meticulously recorded. A powerful magnifying glass revealed the structure of individual snowflakes, some from recent storms and others from weeks or even months ago, found deeper in the crater. All of these variables can influence how susceptible the snowpack is to sublimation.

As snow continued to fall in the valley, this would be only one of several pits dug. If all of the measures the team takes during the winter are like a book, a snow pit is simply one page, according to Hogan.

“Together, that gives you the whole winter story,” he stated as he stood inside one of the pits he was investigating. As he inspected the layers of snow, only the top of his head poked through.

Long before the snow started melting, Lundquist’s team began evaluating the data they collected.

They believe that it will one day provide water managers with a greater grasp of how much sublimation consumes the region’s water budget, allowing them to make more accurate projections for an even hotter and drier future.

The Mysterious Loss Of Water In The Colorado River

High winds ripped at Gothic Mountain, watching over the cottages tucked in Gothic, Colorado, an isolated outpost accessible only by skis during the valley’s severe alpine winters. The plumes of snow that rose from the peak briefly formed a cloud before dissipating.

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