Despite blizzard, #Colorado’s critical mountain #snowpack shrinks — @WaterEdCO #runoff

Snow covers cars in Denver’s Central Park neighborhood March 14, 2021. Credit: Jayla Poppleton via Water Education Colorado

From Water Education Colorado (Jerd Smith):

Despite the recent history-making blizzard on Colorado’s Front Range, statewide snowpack sits at 92 percent of average as of March 19, down from 105 percent of average at the end of February, according to the Natural Resources Conservation Service.

Just two river basins, the Arkansas and the Rio Grande, are registering above average at 101 percent and 106 percent respectively. Among the driest are the Gunnison Basin, at 86 percent of average, and the San Juan/Dolores, at 83 percent, both in the southwestern part of the state.

“The snowpack numbers are still below normal though they don’t look that bad,” said Peter Goble, a specialist with the Colorado Climate Center at Colorado State University. “But based on how dry soils were to start this accumulation season, we’re still pretty nervous about what water availability is going to look like.”

Those numbers are hard to believe for some, given that nearly 30 inches of snow fell in and around Denver the weekend of March 13, with some portions of the foothills and higher receiving more than three feet of snow. It is considered the fourth-largest storm in Denver’s history.

Colorado statewide snowpack basin-filled map March 25, 2021 via the NRCS.

According to the U.S. Drought Monitor, the entire state remains mired in drought, with nearly half classified as being extremely or exceptionally dry, the most dangerous categories.

Mountain snowpack is watched closely in Colorado and other Western states because as it melts, it fills rivers and reservoirs to supply the state’s cities, farms and industries with water for the coming year.

Thanks to 2020’s severe drought, in November, for only the second time in its history, the Colorado Water Conservation Board activated its municipal emergency drought response plan in an effort to help cities cope with the dry conditions.

As part of that effort some 14 metro area cities have agreed to coordinate how they inform community members of potential drought restrictions.

“The biggest thing is we don’t want to be counter-messaging anybody,” said Greg Baker, spokesperson for Aurora Water. Aurora is one of the members of the new drought coordination group. “Towns that have robust storage like Denver and Aurora may not need restrictions. But there are about 50 water utilities across the Front Range.”

Those that don’t have hefty storage systems might have to declare drought emergencies, as many did in 2012 and 2013, Baker said.

And when, for instance, major TV stations broadcast that there are no restrictions in Denver or Aurora, it makes it difficult for communities that have to impose limits to help customers understand the vast differences in drought response, he said.

How this year will play out isn’t clear yet, Baker said. Aurora’s reservoirs are at 63 percent of capacity, the low end of normal. Aurora draws its water from the mountains in the Arkansas, Colorado and South Platte river basins.

“A lot of customers forget that we may have had some good snow down here but that is not where we collect our water. It happens up in the mountains,” Baker said.

Even as mountain snows approach the average mark, soils remain dry and therefore capable of absorbing much of the snow that will melt in the spring.

“We’re getting reports that soil moisture is 10 inches below normal,” Baker said. “Will runoff be sucked up? We don’t know.”

Of particular concern to hydrologists and water watchers across Colorado is the forecast for the seven-state Colorado River Basin. The river begins high in Rocky Mountain National Park and, together with tributaries in Colorado like the Gunnison, Yampa, and Dolores rivers, it supplies all of the state’s Western Slope’s water as well as roughly half of the water for Front Range cities and tens of thousands of acres of farms in the Eastern Plains.

As it flows south and west, the river supplies not only Colorado but also Wyoming, Utah and New Mexico, a region known as the Upper Basin, and Nevada, Arizona and California, known as the Lower Basin. It also supplies Mexico.

The basin has two major storage reservoirs in the U.S. and they are filled almost entirely from the mountain snows generated in the Upper Basin. The forecast for the basin remains grim, with the U.S. Bureau of Reclamation estimating that Lake Powell will see inflows of just 47 percent of average as of March 3, the most recent data available.

According to Reclamation, the last half of 2020 was one of the driest periods on record in the Colorado River Basin, and closely resembles the deep droughts of 2002, 2012, 2013 and early 2018. These are, according to the March 3 report, four out of the five driest years on record.

Levels in Powell and Mead are likely to drop low enough this year to trigger additional cuts in water deliveries to Lower Basin states. The recent blizzard in Colorado, because it did not benefit Colorado’s Western Slope and the headwaters of the river as much as it did the Eastern Slope, aren’t likely to change that, according to Reclamation.

Jerd Smith is editor of Fresh Water News. She can be reached at 720-398-6474, via email at jerd@wateredco.org or @jerd_smith.

Westwide SNOTEL basin-filled map March 25, 2021 via the NRCS.

From The Glenwood Springs Post-Independent (John Stroud):

Unfortunately, recent snowstorms did very little to improve the mountain snowpack. And the near-term prediction for measurable precipitation isn’t promising.

That’s according to several sources of data and predictive models tracked by the USDA Natural Resource Conservation Service Colorado Snow Survey Program.

NRCS Hydrologist Karl Wetlaufer noted in his monthly snowpack report issued March 5 that, “While February snow accumulations did improve the snowpack in many parts of the state, snowpack still remains below normal levels in all major basins except the Rio Grande.”

At that time, the Colorado River Basin was at 84% of median snowpack, and just 71% of last year’s snowpack. Statewide, the median snowpack at that time was 85%, and only 77% of last year.

Then came the big one — sort of.

A major snowstorm the weekend of March 13 that mostly blanketed the the foothills and eastern Colorado with up to 2 feet of snow in places did have some impact on the high country snowpack. When it comes to Western Slope water, that’s where it mostly matters.

Just before that storm hit, on March 10, the Colorado River Basin was at 88% of median snowpack.

Likewise, one of the Colorado’s major drainages, the Roaring Fork River, with its headwaters on Independence Pass east of Aspen, was at 84% of median.

Afterwards, the area basin snowpack had improved to 91% and 90%, respectively.

As of Tuesday, with more localized snowfall in recent days, the Roaring Fork drainage had improved to 94% of median.

The summer and fall of 2020 was one of the driest periods on record in Colorado.

“This led to dry soil moisture conditions and the expectation is that snowmelt runoff will produce lower volumes than would commonly be observed with a similar snowpack,” Wetlaufer observed in his March 5 report.

Before winter even started, snow forecasters were saying Colorado would need multiple years of 150% to 200% of normal snowpack to improve the drought situation…

“There is currently a significant soil moisture drought that will consume a greater-than-average amount of snowmelt runoff, and leave less to streamflow runoff,” [Brian Domonkos] said. “To add to the complexity, low soil moisture means lower base flows in rivers and streams, which means more precipitation is needed to bring stream flows back to normal levels.”

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