The Western Slope snowpack has piled up to its normal peak weeks ahead of usual, and with more snow in the forecast, the healthy supply promises some relief to receding Colorado reservoirs, experts say.
Rivers in western Colorado help feed the Colorado River Basin, which provides water to 40 million people across the West. The basin is experiencing its worst drought in 1,200 years — by some estimates, it would take three average snow years with zero consumption to get reservoirs in the basin back to normal. This year, the snow is deep in the mountains that serve as headwaters for the Colorado River with some areas even reporting historically high snowpack levels.
“To me, the most impressive thing about this year’s snowpack is that, typically, in a normal year we reach our normal peak around April 1. We’ve already reached that peak snow value in early March, and we’re still trending upward,” said Paul Miller, service coordination hydrologist with the Colorado Basin River Forecast Center. “So we’re well ahead of schedule, so to speak, and we still have some time to add to the snowpack.”
As of Monday, Colorado’s statewide snowpack was 127% of median from 1991 to 2020, according to SNOTEL data compiled by the Natural Resources Conservation Service.
The numbers were looking even better on the Western Slope. The snow-water equivalent — the amount of liquid water in snow — was at 147% of the historical average in the Gunnison Basin, and 136% of the average in the Yampa and White basins as of Monday. The snow-water equivalent in the San Miguel, Dolores, Animas and San Juan basins in southwestern Colorado was 149% of average, the highest statewide.
From above, satellites are also tracking the total snow-covered area in Colorado, said Adrienne Marshall, a computational hydrologist at the Colorado School of Mines.
“That’s essentially as high as it’s ever been in the last 20 years, which is when we have the satellite record for, for this time of year,” said Marshall, who specializes in using different data modeling techniques to understand how climate change is altering water resources.
However, in eastern Colorado the Arkansas Basin’s snow-water equivalent was 78% of the historical average, and the South Platte Basin was at 106% as of Monday.
“We’re looking at a lower-than-average peak snowpack for all of those mountains that will ultimately feed into the Arkansas River, so that’s one concern,” said Becky Bolinger, Colorado’s assistant state climatologist. “That means you’ll have less runoff, less available for irrigation, water supply. Rivers might be lower this summer.”
For the Colorado River Basin, how snowpack levels ultimately translate into spring water supply depends on factors like remaining snowfall and soil moisture.
Unusually wet weather patterns in the forecast for the rest of March could continue to boost numbers in the basin and across the state, Miller and Bolinger said. Over the next couple of weeks, the Colorado Basin River Forecast Center is projecting about 1 to 2.5 inches of snow at higher mountain elevations. Lower elevations can expect between 0.5 and 1 inches of rain and/or snow.
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“I really don’t see anything right now that would flip that situation and take us into a drought,” Bolinger said.
However, the basin has seen some of the driest soil on record in recent years, Miller said. As spring runoff occurs, parched soil sucks up moisture, leaving less to travel downstream and replenish reservoirs in need. Although soil moisture conditions looked slightly better in November compared to 2020 and 2021, large chunks of the state are still reporting conditions that are drier than usual, based on historical data.
Even considering drier soil, hydrologists still expect to see flows that are well above average throughout the basin, Miller said.
While helpful, the healthy snowpack is not going to lead to recovery on the huge downstream reservoirs, Lake Powell and Lake Mead, Bolinger said.
“They’re too big,” she said. “They’re too massive. This is just one year.”
These massive water savings accounts have been dwindling during the ongoing drought, now in its 23rd year, prompting a state of emergency for water users across the West. In 2021, Blue Mesa Reservoir in Gunnison County conducted emergency releases to help bolster water levels in the drought-depleted Lake Powell. The move dropped Blue Mesa’s water level and kneecapped the local summer economy.
This year, Lake Powell will likely end the 2023 water year, which closes Sept. 30, at an elevation of about 3,555 feet, or about 32% of its capacity, according to Bureau of Reclamation forecasts in February. That’s about 35 feet higher than its elevation on Monday.
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Glen Canyon Dam can no longer generate hydroelectricity when Lake Powell’s elevation reaches 3,490 feet, its minimum power pool elevation. Dead pool, when water can’t flow through the dam, is 3,370 feet.
By some estimates, the Colorado River Basin would need three years of normal snowpack and absolutely no water use to refill all the reservoirs, Miller said.
With current levels of water use, “we’d probably need to have this kind of year consecutively for, oh gosh, probably six or seven years,” he said.
In Colorado, the snowpack is promising some good recovery for reservoirs around the state, Bolinger said. But water district managers and water users are still keeping a cautious eye on incoming precipitation.
Greg Peterson, executive director of the Colorado Ag Water Alliance, said the snowpack looks good now, but the next few months hold no guarantees. For the Arkansas River Basin, “it’s a feast or famine watershed,” he said.
“At least who I talk to, nobody is taking this that the drought is over,” Peterson said. “It’s all just, ‘This is a gift. We got a year. It buys us some time to figure out all of our other problems.’”
Ken Curtis, the general manager of the Dolores Water Conservancy District, said people in his southwestern Colorado district see the promising snowpack but are reluctant to be too hopeful.
“So far it’s been positive, but everybody’s probably a little shell-shocked still. Like, a ‘I’ll believe it when I see it’ kind of thing,” he said.
In southwestern Colorado, which has seen some of the driest soil moisture levels in the state in recent years, drought has been “hitting on all cylinders,” Curtis said. In 2021, McPhee Reservoir in Curtis’ district was forecasting 27% of its historical 35-year average runoff. At one point, irrigators were forecast to receive just 1 inch per acre of irrigation water, or 4.5% of the 22 inches per acre provided when the reservoir fills completely.
This year, a good snowpack would mean more carryover water supply for the next year and extra security if next winter is dry.
“It looks like we’ve got a good chance of a full supply for the first time since 2019, so that’s great,” he said.