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Snow falling in the mountains and valleys was a welcome sight in a state struggling with drought.
Heavy late-December snowstorms made that month the wettest it has been in at least two years, and snowfall from the more recent storms seems to be breaking La Niña’s dry winter curse. But experts caution the somewhat-promising start to winter is just that — a start.
It’s too soon to know whether the spate of precipitation will be fleeting or will multiply into more storms, building the snowpack needed for a healthy spring runoff to feed rivers and defying La Niña, a weather pattern that typically makes the Southwest drier than normal in the winter and spring.
“Fairly often, we get an early start to winter that looks really promising, and then it dries up,” said Rick Strait, state soil scientist.
Strait collects data for a monthly stream flow report issued by the U.S. Department of Agriculture’s Natural Resources Conservation Service.
March is usually when the biggest snowpack buildup occurs, so any forecasts before then must be considered preliminary, Strait said.
The storms so far have varied geographically, with snow falling heavily in some areas and barely touching others, which delivered an uneven benefit to New Mexico, he said.
Water managers said they’re grateful for any precipitation but will remain guarded until they get to spring without a long dry spell erasing the gains.
“It is better than it was,” said Carolyn Donnelly, a water operations supervisor at the U.S. Bureau of Reclamation. “But it’s very early, so it could go either direction.”
More snow needed
Late-December storms dumped almost 12 feet of snow on Wolf Creek Pass in southern Colorado, something few expected amid La Niña.
La Niña refers to a Pacific Ocean cooling pattern near the equator. It tends to push precipitation north, leading to more arid conditions in Southwestern states.
This is the second year in a row that the region is wrestling with this weather pattern. Last year, La Niña compounded the West’s prolonged drought that scientists say is resulting from climate change.
One water official said the December storms were a pleasant surprise during La Niña, but most of January turned out to be as dry as predicted.
The precipitation the region has received this winter could curb wildfire threats by dampening the flammable debris, but the snow that’s now on the ground will have to double by April to create a decent spring runoff, said Rolf Schmidt-Petersen, director of the Interstate Stream Commission.
“When it comes to the runoff, we need numerous additional storms over the next couple months,” Schmidt-Petersen said. “And it really needs to continue into April.”
January, February and March are the key months for snowpack accumulation, which becomes a barometer for the year’s surface water supply, he added.
Snowpacks, which have grown slimmer in recent winters, are vital in replenishing rivers that supply water for irrigation and household needs.
If not for the initial spurts of snow, the outlook for river flows would be bleak, Schmidt-Petersen said.
This seems to be part of a growing pattern of sporadic precipitation, making forecasting even more difficult.
“One thing that is notable to me this year is how long the dry periods are, with these short, punctuated wet periods,” he said. “So it’s this moving target you’re trying to keep up with.”
Donnelly noted La Niña doesn’t mean a year will be devoid of rain and snow. It’s just more likely to be drier than usual.
Nationally, the three-month forecasts in January said there was about a 50 percent chance of above-average temperatures and below-average precipitation, said Jason Casuga, acting CEO and chief engineer for the Middle Rio Grande Conservancy District.
For that reason, it’s too early for the district and the farmers in the middle valley to get their spirits up about the precipitation they’ve seen so far, he said, adding the March forecast will begin to paint a truer picture of the runoff.
“I caution my own self on getting too excited till those numbers hold up later into the season,” Casuga said.
Overcoming a deficit
Even if New Mexico has a banner year for precipitation and snowpack, it won’t be enough to mend the effects of a 22-year drought.
Two decades of drought — with historically dry conditions in the past two years — have parched the soil. Drier soil absorbs runoff like a sponge, keeping the water from flowing into rivers and, in turn, reducing downstream supply.
Strait said it will take at least two years in a row of healthy precipitation to restore the soils to their normal moisture levels. That is less likely to happen during La Niña, so it could take a while.
“We’re overcoming a deficit,” Strait said.
Precipitation, soil moisture and other data are compared to those in previous years between 1991 and 2020 in the federal streamflow report, he said.
Up until this year, the agency had used the period from 1981 to 2010, a wetter period that made the conditions of recent years fall further below the historic median.
“The new normal is drier,” Strait said.
Using the more recent and drier period as a baseline, soil moisture is 60 percent of normal in the eastern side of the Upper Rio Grande Basin and 80 percent to 100 percent normal on the west side, he added.
The difference is due to the area west of the Sangre de Cristo Mountains receiving much more snow this winter, he said. This suggests that drought recovery won’t occur evenly across the board.
Thanks in part to a fairly robust monsoon season last year, the U.S. Drought Monitor shows New Mexico in considerably better shape now than a year ago, when most of the state was mired in exceptional or extreme drought.
Still, the most current map shows most of the state ranging from severe to extreme drought, with a few areas that are moderate to abnormally dry.
Although the coming months are uncertain, Strait says he’s still glad to see a potentially positive trend.
“Things in general have improved since last year,” he said. “The improvement is appreciated.”
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