Snowpack for Colorado River ends season 11% above normal

Greg Haas
·4 min read
2

LAS VEGAS (KLAS) — Water for a thirsty Las Vegas has been building up over the past month and a half and snowpack levels are 11% above normal on April 1 — the date that snow normally peaks as warmer weather begins to set in.

The above-average “snow water equivalent” (SWE) is a measure of how much water is stored in the snow in the Upper Colorado River Basin — a vast 17,800-square-mile region that feeds the river and its tributaries in five states. More than 40 million people rely on the river for water.

That extra 11% is a surprise after last year, when SWE came in at 160% of normal on April 1, 2023. Rosemary Carrol, a research professor of hydrology for the Desert Research Institute (DRI), said in mid-March that researchers have noticed a “whiplash” effect that often brings a very dry year after a wet winter.

But it hasn’t happened this year. And snow won’t stop for a while yet.

As April begins, the graph is tracking higher with more snow expected at the end of the week in the mountains at Rocky Mountain National Park, which falls into a subregion known as “Colorado Headwaters.” At lower elevations, a mix of rain and snow is expected.

Carroll noted that most of the SNOTEL (Snow Telemetry) stations where snow is monitored are at lower altitudes. The snow that matters most is generally at the highest altitudes, but retrieving data at those levels would be extremely difficult.

“Snowpack in the Upper Colorado is looking good right now,” according to Dan McEvoy, regional climatologist with the Western Regional Climate Center.

“Using the basin average, which consists of 130 SNOTEL stations that measure snow water equivalent (SWE), the current conditions as of April 1 is 114% of median SWE for the date and 104% of median peak. The median peak date is April 6 so it is good to see that the basin has already surpassed the peak about a week early. Storms over the last week have been helpful for continuing to build snowpack.”

McEvoy, who is based in Reno, said, “This is all good news for drought and water supply but it is still important to monitor conditions during the snow melt season which tends to be about mid-April through June.” And a lot can still happen.

“Despite a good snowpack now if we have persistent warm and dry conditions during the snow melt season the snow can melt faster than normal which can increase the likelihood of drought in the summer,” he said.

A graph maintained by water-data.com shows SWE at 111% of the median level (over the past 30 years) on April 1.

“The water year started off looking pretty weak but a strong February and March have been great for the snowpack (SWE or Snow Water Equivalent),” according to David Fordham of water-data.com. “And storms continue to line up from the Pacific so I am hopeful we can get to 110%+ (maybe 115%) of the 30 year average (WYs 1991-2020) before the longer days and warming temps send SWE going the other way.”

Two consecutive years above normal snowpack levels is bucking the trend reported in a July 2023 study that showed runoff has declined 10.3% over the past 140 years because of increasing hotter temperatures. “Without this warming, the Colorado Basin would have had significantly larger amounts of water available, equal to the size of Lake Mead, over the duration of the 2000–2021 megadrought.”

Last year’s wet winter helped refill Lake Mead and Lake Powell, the nation’s two largest reservoirs. But they are still low. Lake Mead is currently at 37% of capacity, and Lake Powell is at 33%.

The map maintained by the U.S. Bureau of Reclamation was not updated on Monday. The map below is from Friday. Precipitation for the region is at 106% of normal and SWE is at 111% — see the blue box in the center of the map below. This information will be updated if Reclamation updates its map on Monday.

A look at changes over the past two weeks for all the subregions within the Upper Colorado River Basin:

  • Upper Green: From 98% on March 16 to 97% on March 29

  • Lower Green: From 123% on March 16 to 125% on March 29

  • White-Yampa: From 113% on March 16 to 110% on March 29

  • Colorado Headwaters: From 108% on March 16 to 106% on March 29

  • Gunnison: From 103% on March 16 to 105% on March 29

  • Dirty Devil: From 131% on March 16 to 150% on March 29

  • Lower San Juan: From 150% on March 16 to 262% on March 29

  • Dolores: From 106% on March 16 to 115% on March 29

  • Upper San Juan: From 100% on March 16 to 108% on March 29

Higher snowpack levels in the upper Colorado Rockies are more important to the river, but all the water matters. The San Juan River in northern New Mexico could see a big boost this year with the region at 262% of normal snow levels.

McEvoy also noted that the Bureau of Reclamation is still forecasting below-normal April-July runoff.

“Currently the forecast is for 85% of normal April-July runoff,” he said.

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