Mountain snowpack is in “good spot” before spring

Colorado’s mountain snow is measuring slightly higher than normal for this time of year, a vulnerable moment for cities and food growers ahead of spring, boosting confidence that water for crops, cattle and a growing population will be adequate.

Federal survey data showed the statewide snowpack at 106% of the norm between 1981 and 2010, but with significant variation between northern and southern mountains — a trend over the past decade.

And forecasters anticipated that dry soil from last year’s warm arid fall likely will reduce water in streams and rivers once snow melts. Much depends on snowfall this month, and March often brings heavy snow.

Southwestern Colorado faced drier conditions with snowpack between 86% and 94% of the norm, the U.S. Department of Agriculture’s

Colorado Snow Survey found. Snow in the South Platte River Basin (124%), Upper Colorado River Basin (114%) and Arkansas River Basin (109%) — the main water sources for Denver, Colorado Springs and northern Front Range cities — promised reasonably sufficient water.

Snow survey supervisor Brian Domonkos said Colorado was in “a good spot” overall, assuming more precipitation in the right places over the next few weeks.

The amount of water in rivers and streams “is going to be better in the northeast, and not as good in the southwest,” Domonkos said.

“In the southwestern corner of the state, we need more snow, above-average snow accumulation. In the northern part of the state, we’re above normal. We don’t need more. A little more would be good for the spring and summer runoff.”

Snowpack in Colorado’s high mountains serves as a natural reservoir, holding water until spring, when rising temperatures melt the snow. This sends water into streams and rivers.

Snow survey data between now and mid-April, when snowpack typically peaks, captivates water providers because Colorado snow feeds headwaters of major rivers. Strains on the Colorado River, in particular, rivet attention on anticipated runoff that soon will be diverted and stored in massive man-made reservoirs.

A growing population of more than 40 million across seven western states relies on the Colorado River, even as scientists warn that warming temperatures linked to climate change are decreasing flows.

At Denver Water, water supply manager Nathan Elder said he’s been checking snowpack data since October.

“We’re trending in a positive direction. The early indicators are that we’re headed for a normal or slightly above normal water year,” Elder said.

Substantial mountain snow doesn’t necessarily mean more water in streams and rivers. A relatively warm, dry fall led to dry soil, which can reduce streamflow.

“Even though we have abovenormal snowpack, we have really depleted soil moisture,” he said. “That roughly equates to normal runoff. The soil moisture is going to have to be refilled before you see a lot of flows in the streams.”

Denver’s reservoirs were 85% full, higher than the normal 80% at this time of year. Utility officials’ goal: Fill the reservoirs to 100% on July 1 to ensure water availability after snow on mountains melts and evaporates.

If spring temperatures climb too quickly, Denver Water cannot easily capture runoff because the city’s water rights are conditional for use after April 1. And while more snow is welcome, water managers said too much can cause flooding.

Denver planners have been working for years to expand Gross Reservoir, west of Boulder, to store more water from northern mountains. The idea is to become more resilient as snow becomes more variable.

Agriculture uses about 85% of Colorado’s water supplies. Among urban residents, people in Denver use around 80 gallons a day per person for all indoor and outdoor purposes. A utility push for efficiency includes a target of 40 gallons per person for indoor use.

“Climate change is going to increase the uncertainty of future precipitation and stream flows. We’re likely to see more extreme events, extreme droughts. That’s why we’re working on that northern Gross Reservoir expansion,” Elder said, “to cope with that future uncertainty by building more storage.”