Why snowfall in the Colorado Rockies probably won’t ease drought – The Hill

history at a glance

  • Both Lake Powell and Lake Mead draw water from the Colorado River, which is fed by spring snowmelt in the Colorado Rockies.

  • Climate change means that these snowpacks could melt sooner and evaporate faster as the weather gets warmer.

  • Warmer weather also means less snow can fall during storms.

A series of winter storms that brought above-average snow and rain to the West increased snowpack in the Western Rockies to 146 percent of average, an increase that has the potential to increase reservoir levels in the coming months.

Despite the additional snowpack, experts say it’s too early to tell how things will look in the spring and that much more consistent rainfall will be needed to significantly impact the Colorado River’s dwindling water supply.

In recent decades, a mega-drought in the western United States has slowly drained the region and significantly lowered the river’s level, threatening the country’s two largest reservoirs, Lake Powell and Lake Mead.

These reservoirs are fed by the Colorado River, which depends in large part on the melting snowpack of the Colorado Rockies. Lake Powell catches water falling into the Upper Colorado River Basin while Lake Mead is fed by Powell releases. Current snow cover in the upper region is 153 percent of average, while snow cover throughout Colorado is 130 percent of its usual amount.

So when it comes to winter storms, “the more the merrier,” said Adrian Harpold, associate professor of mountain ecohydrology at the University of Nevada, Reno.

“We need all the snow cover we can get,” Harpold said. “Snow is the foundation of all of our water infrastructure in the Rocky Mountains.”

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Throughout spring, the slow melting of the snowpack in the mountains gradually fills the reservoirs and can seep into the ground. Essentially, the snowpacks serve as water banks for drier seasons.

However, climate change brings with it the risk of warmer weather and earlier springs, which could negate the benefits of higher snow cover.

Earlier warmer weather means less snow could fall in the winter months and the snowpack could melt and evaporate faster. Snowpack in the region does not typically peak until April, leaving much unclear as to what the pack will be like this spring.

With the Colorado River, “It all depends on the spring, how much snow we get, but also how warm it will be in the spring and how quickly it will warm up,” explained Eric Balken, executive director of the Glen Canyon Institute.

“That has changed the rules of the game in recent years. So in recent years we’ve had about average snowpack, but we’ve had below-average runoff. Good snowpack no longer guarantees good drainage.”

Lake Powell was created by the construction of Glen Canyon Dam in 1966. The institute is committed to draining Lake Powell to replenish Lake Mead, restore the canyon, and reverse the decline of its ecosystem.

Since 2000, the Colorado River’s average flow has decreased by 20 percent.

Half of this decrease is due to rising temperatures. By 2050, additional temperature increases in the region are expected to reduce flows by an additional 10 to 40 percent.

For most of the past two decades, the river system has had a deficit of two to three million acre-feet, and even a large runoff would “just buy the system another year or so,” Balken said.

As of January 23, Lake Powell is at 24 percent of its current storage capacity and Lake Mead is at 28 percent.

Bringing the Colorado River water levels back to where they were before “requires sustained, well-above-average rainfall down there. So that’s it [in] all states of the Colorado River Basin extending to the crest of the Rocky Mountains,” said Nicholas Pinter, professor and associate director of the University of California Davis Center for Watershed Sciences.

And despite the immediate, short-term benefits that some of these weather anomalies can bring to isolated regions, the amplifying effects of climate change will continue.

Warmer, drier conditions during the summer, along with faster snowmelt and less snowpack, can allow more water to evaporate from soils and reservoirs, Harpold explained. “That’s the long-term thing that’s very hard to buffer without big global shifts in our carbon emissions.”

Overall, a nice weather season does not bring any long-term solutions. Short-term weather events can buy time and bring relief, “but they won’t buck the long-term trend of drying out,” said Balken.


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