The Mystery of the Colorado River’s Missing Water
As the West continues to dry up, water managers are under increasing pressure to accurately predict how much of the valuable resource will enter the system each spring. One of the biggest challenges facing state water managers — including officials from the Bureau of Reclamation, the gatekeeper of Lake Powell and Lake Mead — is deciding how much water to release from the reservoirs to meet the needs of downstream users.
While transpiration and soil moisture could be among the other culprits of water loss, one of the biggest unknowns is sublimation, said Ian Billick, managing director of RMBL.
“We need to eliminate this uncertainty in the water balance,” Billick said.
get it right
The East River’s tributaries eventually flow into the Colorado River, which supplies water to nearly 40 million people in seven western states and Mexico. This watershed has become a place where more than a hundred years of biological observations converge. Many of these studies have focused on understanding the life cycle of water.
Lundquist’s project is one of the most recent. Due to the complexity of the intersecting processes driving sublimation, the team placed more than 100 instruments in an alpine meadow south of Gothic known as Kettle Ponds.
“Nobody’s ever done it right before,” Lundquist said. “And so we’re trying our best to measure absolutely everything.”
Throughout the winter, the multitude of devices quietly recorded data every second of the day – measurements that would give the team an overview of the snow’s history. A device called a sonic anemometer measured wind speed, while others recorded temperature and humidity at different altitudes. Instruments known as snow pillows measured moisture levels, and a laser imaging system called lidar created a detailed map of the snow’s surface.
From January through March, the three coldest months of the year, Daniel Hogan and Eli Schwat, graduate students working at Lundquist at the University of Washington, drove from their snow-covered cabin in Gothic to Kettle Ponds to monitor the ever-changing snowpack.
Their skis featured skins, a special fabric that sticks to the skis to help them grip the snow better. The two men crunched the ground as they made the almost daily trip to the site, sleds full of gear in tow. It was a chilly March day, but the scorching reflections of the snow made it feel warmer than it actually was. When Hogan and Schwat arrived, they dug a pit in the snow surface just in front of the canopy of humming instruments.
The pair carefully recorded the temperature and density of the snow inside. A special magnifying glass revealed the structure of individual snowflakes, some from recent storms and others found deeper in the pit, weeks or even months earlier. All of these factors can contribute to how susceptible snowpack is to sublimation.
This would be just one of many pits dug as snow continued to blanket the valley. If all the measurements the team takes over the course of a winter are like a book, a snow pit is just a single page, Hogan said.
“Together that’s the whole winter story,” he said while standing in one of the pits he was studying. Only the top of his head protruded from the snow pit as he examined the strata.
Lundquist’s team began analyzing the collected data long before the snow began to melt.
They hope it will one day give water managers a better understanding of how severely sublimation is eroding the region’s water balance — and help them make more accurate predictions for what is likely to be an even hotter and drier future.
