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Colorado: More water woes ahead?

State water task force gets a gloomy winter outlook, with odds climbing for dry conditions through March

Exposed shoreline terraces along Dillon Reservoir in Summit County, Colorado.

Statewide snowpack conditions as of Nov. 20.

By Bob Berwyn

FRISCO — Colorado could be in for another dry winter, but at this point, the state’s water providers have not revealed any specific plans to respond to continued drought.

Even after hearing a gloomy outlook on winter precipitation, big municipal utilities said they’re in a wait-and-see mode — and hoping for snow.

But there’s no reason to expect a particularly snowy pattern. In fact, all indications are that precipitation may end up below average once again, barring an some anomalous storm event this winter.

“Don’t shoot the messenger,” said meteorologist Klaus Wolter, with NOAA’s Earth Systems Research Laboratory in Boulder. “Most of the information I have is dry. I hope I’m wrong,” Wolter said, offering a seasonal outlook for a state water availability task force.

Wolter said that, based on current atmospheric and ocean patterns, he’s fairly confident of his dry winter outlook, with history suggesting a “pretty high” forecast skill for the January to March period.

With El Niño no longer in the picture, the key ingredients in Wolter’s outlook are colder than average water in the North Pacific (negative PDO) and warmer than average water in the northeastern Atlantic. In the past, that combination has spelled trouble for Colorado, Wolter said.

Relief could come from an anomalous storm — a wet river of air from the Pacific that sometimes works its way inland to Colorado, Wolter said, adding that the lack of early season snow is particularly worrisome from a water supply standpoint.

Snow in the late fall and early winter sets up a solid base to the snowpack that melts slowly in the spring and contributes disproportionately to spring runoff.

“Late fall moisture is critical to runoff in Colorado River … Unless we see a big turnaround in December, we could be looking at another below average runoff year,” he said.

That outlook should be worrisome for the state’s major water providers, who implemented only modest conservation measures last summer, banking on a rebound in snowfall after last winter’s drought. As a result, statewide water storage is well below average for this time of year, with reservoirs so far down that many would be unlikely to fill even with average precipitation this winter.

Denver Water’s system storage is about 71 percent of capacity, compared to the historic average of about 85 percent, according to Bob Steger a raw water supply manager with the utility. Other major Front Range water providers reported similar figures.

“It all depends what happens during the next six months … If we had normal carryover storage we can fill on a less than average year,” Steger said.

A burst of above average precipitation from monsoon-fueled rainfall in July may have lulled some water managers into a false sense of security, but overall, the past year has been very dry. During the past seven months, precipitation in the Colorado River Basin above Lake Powell was just 54 percent of average. Inflows into Lake Powell the last two months were the lowest on record, triggering renewed concerns about the future allocation of water between the Upper and Lower Basin states.

As of mid-November, statewide snowpack was at 50 percent of average, with the Colorado River Basin snowpack trending as one of the lowest years on record for the water year to-date.

Temperatures the last couple of months have been near average, which means Colorado might not quite break the all-time average high annual temperature, set in the Dust Bowl year of 1934.

But average temperatures have again been edging upward in November, said state climatologist Nolan Doesken, adding that 2012 will almost certainly end up as one of the three warmest years on record.

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