Story at a glance
- Both Lake Powell and Lake Mead draw water from the Colorado River, which is fed by springtime snowmelt in the Colorado Rockies.
- Climate change means these snowpacks could melt earlier and evaporate faster as weather gets warmer.
- Warmer weather also means less snow may fall during storms.
A string of winter storms that brought heavier than average snow and rain across the west increased snowpack in the Western Rockies to 146 percent of average, a gain that holds the potential to boost reservoir levels in the coming months.
Despite the extra snowpack, experts say it’s too early to tell what things will look like in the spring, and that much more steady precipitation is needed to make any significant dents in the dwindling water supply of the Colorado River.
Over the past couple decades, a mega-drought in the Western United States has slowly dried up the region and significantly reduced the river’s levels, threatening the nation’s two largest reservoirs, Lake Powell and Lake Mead.
These reservoirs are fed by the Colorado River, which relies in large part on melting snowpack from the Colorado Rockies. Lake Powell captures water that falls in the Upper Colorado River Basin, while Lake Mead is fed by releases of Powell. Current snowpack in the Upper region is at 153 percent of average, while across Colorado, snowpack sits at 130 percent of its usual amount.
So, when it comes to winter storms “the more the merrier,” said Adrian Harpold, an associate professor of mountain ecohydrology at the University of Nevada, Reno.
“We need all the snowpack we can get,” Harpold said. “Snow is what, really, our whole water infrastructure in the Rocky Mountains is based on.”
Throughout the spring, the slow melting of mountain snowpack gradually fills up reservoirs and can seep into the ground. Essentially, the snowpacks serve as water banks for drier seasons.
However, climate change brings the threat of warmer weather and earlier springs, which could derail the benefits of more snowpack.
Warmer weather earlier means less snow could fall in the winter months, and snowpack could melt and evaporate faster. Snowpack in the region typically doesn’t reach its peak until April, leaving much unknown about what the pack will look like this spring.
With the Colorado River, “everything depends on the spring, how much snowfall we get, but also how warm it will be in the spring and how soon it gets warm,” explained Eric Balken, executive director of the Glen Canyon Institute.
“That's what's been the game changer in recent years. So, for the past several years, we've had roughly average snowpacks but we've had below average runoffs…getting a good snowpack no longer guarantees a good runoff.”
Lake Powell was formed by the construction of the Glen Canyon Dam in 1966. The institute advocates for draining Lake Powell to help replenish Lake Mead, restore the canyon, and reverse the decline of its ecosystem.
Since 2000, the average flow of the Colorado River has decreased by 20 percent.
Half of that decrease is attributable to rising temperatures. By 2050, additional temperature increases in the region are expected to reduce river flows by another 10 to 40 percent.
For most of the past two decades, the river system has been running a two- to three-million acre-foot deficit, and even a big runoff would “only buy the system another year or so,” Balken said.
As of January 23, Lake Powell sits at 24 percent of its current storage capacity, and Lake Mead at 28 percent.
To get Colorado River water levels back to where they once were, “it's going to take sustained, well above average precipitation down there. So that is [in] all the states of the Colorado River Basin stretching all the way to the crest of the Rocky Mountains,” said Nicholas Pinter, a professor and associate director of the University of California Davis Center for Watershed Sciences.
And despite the immediate, short-term benefits some of these weather anomalies may bring to isolated regions, the compounding effects of climate change will persist.
Along with faster snowmelt and less snowpack, warmer, drier conditions throughout the summer can evaporate more water from soils and reservoirs, explained Harpold. “That's the long-term thing that is very difficult to buffer without major global changes in our carbon emissions.”
Overall, one good weather season does not yield long-term solutions. Short-term weather events can buy time and give some relief, “but they will not buck the long-term trends of aridification,” Balken said.