Much to the enjoyment of skiers and the chagrin of commuters, Southwest Colorado has been pummeled by snowfall this winter. Across the region, the San Miguel, Dolores, Animas and San Juan river basins have recorded a snow-water equivalent that is 134% of the 30-year average.
Although the snowfall is likely to provide much-needed moisture to reservoirs and agricultural land, experts are warning against prematurely celebrating and overhyping the significance of the precipitation on long-term drought conditions in the West.
“One really good winter can actually go quite a long way. The water supplies that we ended up with in our rivers here in Colorado are very much driven by whether the snowpack is good or not in any given winter,” said Colorado State Climatologist and professor of atmospheric science Russ Schumacher. “But when you aggregate that all together into the water situation over the entire Southwest, where it's dependent on these huge reservoirs, 20-plus years of dryness are not going to be made up by one or two years of good snow.”
Despite the heaps of snow piled along city streets in Durango, the city is on track to receive only an average amount of snowfall in terms of inches of snow (as opposed to snow-water equivalent). As of Feb. 15, the city had received 45.2 inches of snow since the beginning of November, in line with an average accumulation of 45.4 inches.
The good news, however, is that only 48% of the Colorado River basin is experiencing “moderate drought” conditions or worse, according to the U.S. Drought Monitor. At this time last year, 82% of the basin was classified as experiencing “moderate drought.”
“It's been a fairly substantial, somewhat gradual improvement we've seen over the last seven to eight months,” said Curtis Riganti, a climatologist with the National Drought Mitigation Center.
However, the conditions are not necessarily indicative of an actual turnaround.
“The Drought Monitor generally does not take into account the really long-term time scales – the last 20-plus years – and the influences of that (the drought) on the reservoirs, on the water supply and everything else,” Schumacher said.
To accentuate the point, consider that Lake Powell, the second-largest reservoir in the nation responsible for generating hydropower for 6 million people, is at record-low levels and is in peril of drying up. While managers of reservoirs in the Four Corners are predicting they will have ample supply of water heading into the summer, Lake Powell contains just 41% of its 30-year median volume.
But even that number can be misleading.
The Colorado River Basin has experienced an ongoing drought for 20 years. So even 30-year median levels have been deflated by two decades of drought, notes General Manager of the Southwestern Water Conservation District Steve Wolff.
Wolff is also hesitant to celebrate just yet, in part because meeting the 100% benchmark of the 30-year median snow-water equivalent will not necessarily yield 100% runoff.
Low soil moisture in the region after years of dry weather means that more snow melt is absorbed into parched ground, reducing runoff yields. High winds and quickly warming temperatures can also have a negative impact on water availability.
Ken Curtis, the general manager of the Dolores Water Conservancy District, which manages McPhee Reservoir, said the above-average snowfall is likely to positively impact soil moisture and fire danger through July. After that, future weather will determine conditions going into the fall.
“If the monsoons don't make their appearance, that soil moisture is going to go back down and we could have fire risk and dry soils by next winter,” Curtis said.
High wind in the spring moves dust onto the snow, darkening the surface and causing it to absorb more sunlight and melt quickly. Although this could be good news for lower-basin reservoirs, snow melting faster and earlier than expected is a problem for upstream users.
“The users of the water depend on the water to be there at a certain time,” Schumacher said. “Especially when you get into the heat of the summer – that's when the water is usually really needed for irrigation. If all that flow is already gone by that point, then that can be a problem.”
Spring weather is likely to determine just how beneficial the impact of this La Niña winter is.
“You don’t know what kind of spring we’re going to get as far as runoff is concerned,” said Rep. Marc Catlin, who represents the 58th House District and is the vice president of the Colorado River Water Conservation District, at a panel on water conservation Feb. 8. “It’s not a drought-buster. We’ve been in a drought for nearly 20 years, so one season is not going to bust the drought for western Colorado. ... We need five or six years like we’re having right now.”
Despite limited downstream impacts, reservoirs in Southwest Colorado are in good shape heading into the summer.
“Right now we're well on-track for a full supply of water over on the west side,” said Curtis. “We obviously don't know what the next couple of months will do. They could chip away at that and hurt it.”
Curtis concurred with Catlin’s assessment that this winter does not indicate the end of the megadrought. Small-scale basins might be set up for success this year, but problems the size of Lake Powell demand solutions that one winter cannot deliver.
“We're small systems, we live by the snowpack. So a good snow year means a lot to us,” Curtis said. “... On the larger Colorado River Basin and West in general, that's where the larger problems are. One good year does not change the current multi-decade old drought in the West. The Meads and Powells of the world would take a decade of years like this to fill up.”
rschafir@durangoherald.com
