Warm March temperatures eating into Aspen’s once amazing snowpack | PostIndependent.com

Warm March temperatures eating into Aspen’s once amazing snowpack

Scott Condon
The Aspen Times
The green line in this graph shows the snowpack at the headwaters of the Roaring Fork River east of Aspen was climbing quicker than in the average year before dropping off this month. Without a change in weather, snowpack might not reach the median level.
U.S. Natural Resources Conservation Service |

SHRINKING SNOWPACK

The Natural Resources Conservation Service maintains an automated snow telemetry station near Grizzly Reservoir, east of Aspen. Readings from the site show how the snowpack is disappearing.

Date Snowpack % of median

Jan. 20 142%

Feb. 17 135%

March 10 120%

March 22 105%

Unseasonably high temperatures over the past week have eaten up an Aspen-area snowpack that once was ridiculously high.

The snowpack remains above average at most automated snow telemetry stations in the Roaring Fork watershed, though it has been losing ground by the day recently.

If the current weather pattern holds with unseasonably warm temperatures, it could have implications ranging from poor spring skiing conditions, a quick peak runoff on rivers and stress on aquatic species, experts said Wednesday. An early loss of snow cover also could lead to the landscape drying out sooner and becoming susceptible to wildfires.

However, winter could return just as quickly as it disappeared, said Liza Mitchell, education and outreach coordinator for the Basalt-based Roaring Fork Conservancy.

“It just sort of comes down to what the weather is,” she said. “If we get a couple of big storms, we could see our snow-water equivalent go back up.”

Snow-water equivalent is the amount of water the snowpack would produce if melted.

The Roaring Fork watershed as a whole — which spans the Crystal and Fryingpan valleys — was at 131 percent of median for snowpack Wednesday, Mitchell said. But an exam of the individual snow telemetry sites in the watershed gives a better picture of what’s happening.

The snowpack at the headwaters of the Roaring Fork River east of Aspen slipped from 142 percent of median on Jan. 20 to 124 percent on Feb. 24, then dropped to 105 percent of median as of Tuesday, according to data provided by the U.S. Natural Resources Conservation Service.

The snowpack is free-falling at the summit of McClure Pass. It plummeted from 145 percent of median on Jan. 20 to 89 percent Tuesday.

“McClure is the first one to fall below 100 percent,” Mitchell said.

The loss hasn’t been as pronounced at the highest elevations of the Crystal River and Fryingpan River drainages. Schofield Pass has the highest snowpack ever recorded on a March 21 date in the 32 years since the snow telemetry site was installed, according to the NRCS. It was at 172 percent of median.

At Ivanhoe in the Fryingpan Valley, the snowpack was at 159 percent of median Tuesday.

The snowpack usually builds on Independence Pass until the second week of April, but instead it’s in decline this March, at least so far. The daytime high temperatures were above freezing for all but three of the first 21 days of March at an elevation of 10,600 feet. There’s also only been snow two days so far this month.

It’s advantageous to have the high country covered with snow for a variety of reasons, according to Karl Wetlaufer, a hydrologist and assistant snow survey supervisor for the NRCS in Denver.

“When everything is snow covered then you’re going to have a much higher albedo, which is the amount of energy bounced back to space,” he said. Bare ground absorbs solar energy.

When soil is wet, it tends to move water from snowmelt more efficiently and more water will make it to rivers and streams, Wetlaufer said. Bare, dry ground soaks up more water.

Maintaining the snowpack longer also creates higher streamflows for a longer period before they return to base levels, Wetlaufer said.

Mitchell said it is fortunate that a bunch of dust hasn’t blown in from the Colorado Plateau and coated the mountain snowpack like in some recent years.

“If there is dust on the snow surface, or once bare ground is exposed, the darker color absorbs radiation and that increases the rate of snowmelt,” she said.

Warming spring temperatures increase the temperature of the snowpack. “Once it’s the same temperature, all the energy goes into melting the snow,” Mitchell said.

The snowpack levels and runoff projections make it likely that reservoirs will fill, regardless of whether winter returns. However, an early runoff would still have negative implications for streams. There could be a lower water yield overall because of increased evaporation, if reservoirs fill early, Mitchell said. And if landscapes dry early, there will be greater transpiration — absorption of water by plants.

“If the rivers peak and those higher flows subside earlier in the season, we may see low water for a longer period of time,” Mitchell said. “With low water, we often see higher water temperatures, which can be quite stressful on the aquatic life we have here, from macroinvertabrates to rout and sculpin.

“This temperature stress can negatively impact these cold water species, especially over extended periods of time,” she continued.

scondon@aspentimes.com


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