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The weather in Colorado has seen its share of extremes over the past few years, from severe drought and late snows to mudslides and December wildfires. This spring, southwest Colorado is grappling with another threat: rapid, near-record-setting snowmelt in the San Juan Mountains.
Snowpack in the Delores, San Juan, Animas, and San Miguel basins, which extend from Telluride to Durango to Pagosa Springs, is just four percent of average as of May 30.
Roughly 50 miles to the east, snow at the headwaters of the Upper Rio Grande River in the San Luis Valley is also melting quickly, and was sitting at just nine percent of normal on May 30. “Snowpack acts as an extra reservoir of water storage in our mountains,” says Aldis Strautins, a hydrologist at the National Weather Service in Grand Junction. “Once we see the snowpack melt, it’s like losing an entire reservoir. The snowpack in southwest Colorado melted early and quickly.”
Becky Bolinger, the assistant state climatologist at the Colorado Climate Center, says that although the snowpack in the San Juans peaked at 94 percent of normal in April, it melted so fast that the benefits evaporated almost as quickly as the snow. The basin melts out on average on June 19 of each year, but it has melted as early as May 21 (in 2002 and 2018) and as late as July 21 (1995).
Bolinger and Strautins say the lack of spring snowstorms in the San Juans, above-normal temperatures, sublimation (snow lost to evaporation), and dust are all contributing factors. “It was a very windy spring, and that drew a lot of dust onto the snow,” Strautins says. Instead of reflecting light as snow does, dust is darker and absorbs more heat, which in turn melts the snow faster.
While not a one-to-one comparison, the region experienced similar melts in 2002 and 2018. Although 2002 and 2018 provided much less snow than this winter season, the snow this year melted out as if it were 2002 or 2018. Both of those years saw wildfires spark in June that grew to more than 50,000 acres.
Based on current water levels and historic data, here’s what to expect this summer in southwest Colorado.
An early, fast snowmelt means the soil doesn’t have time to soak in the water, which leads to runoff into streams and rivers. While most reservoir storage comes from snowmelt, replenishing the region’s soil with moisture is also important: The amount of water in the soil directly correlates to the drought a location is experiencing. Additionally, water temperatures play a crucial role in providing a healthy environment to fish and aquatic plants in Colorado—both of which could be impacted by the season’s early snowmelt. As the summer wears on, lower streamflows and warmer water temperatures in the region’s rivers and streams could lead to poor habitat for Colorado trout.
“If you want to recreate in the rivers of the San Juans, do it early [this summer],” Strautins says. With peak streamflows already realized in some rivers, the likelihood of kayaking or paddleboarding on the region’s rivers in July and August appears to be slim. Whitewater rafting will likely have a shortened season, and fishing could take a hit as well.
Although the snowpack in central and northern Colorado is higher than it is in the San Juans, Colorado is still in a drought. Existing snowpack can delay the beginning of wildfire season, but it won’t mitigate fire danger without the annual monsoon rains, which typically arrive in late summer. Additionally, reservoir storage has not returned to normal, which will impact area farmers and ranchers. Although water restrictions may not be widely imposed this summer, there is concern that more wide-ranging water restrictions may be needed in the coming years if storage levels aren’t replenished.
As we approach the hotter, drier months of summer, drought will inevitably lead to a higher risk of large wildfires. “The biggest concern with an early snowmelt is that you are lengthening the fire season for the mountains,” Bolinger says. The San Juans are particularly vulnerable. An early snowmelt means that soil and vegetation dry out more quickly—and the drier the landscape, the more fuel a potential wildfire has at its disposal. Heed Red Flag Warnings and follow any fire bans to minimize the potential damage that could be caused by wildfires this summer.
(Read more: A Megadrought Is Hurting Colorado Farmers)