Early snowpack has runoff forecast up

crystal-6811

Crystal Dam on the Gunnison River spills during the 2011 runoff season. Dave Buchanan photo

 

Already several things stand out about this winter’s snowpack.

First, it was late arriving, with most areas reporting dry conditions up through late November.

Second, once it started, it came in a hurry, with snow levels going from barely there in early December to waist-deep a month later.

And third but certainly not the last we’ll hear from this winter, the runoff is forecast to be one of the highest in a decade.

“In early December, there was maybe 6 inches of snow at my house in Gunnison,” recalled Michael Dale during the Bureau of Reclamation’s quarterly Aspinall Unit Operations meeting earlier this month in Montrose. “Now, it’s this high,” holding his hand a bit above his waist. “We’re about to start digging tunnels.”

11717-blue-mesa-inflow

Courtesy Bureau of Reclamation

Levels have moderated a bit since then, but there still is enough snow and frigid temperatures that wildlife officials are putting out hay and pellets to lure deer and elk away from haystacks and cattle feeding grounds.

While skiers focus on snow depth, water managers focus on the amount of water in that snow, or snow water equivalent.

Remote precipitation-monitoring gauges across the Upper Colorado River Basin showed large jumps in late December and by the end of the month, the entire region (except for section along the Little Snake River on the Colorado-Wyoming border) was at least 129 percent of long-term average.

Local Bureau of Reclamation officials said nearly all the snow monitoring sites across the Upper Colorado River Basin saw 150-percent of their average precipitation during December.

“We thought December was a really good month and then we came into January,” said Erik Knight, hydrologist for the BOR West Region office in Grand Junction.

The Upper Gunnison Basin snowpack went from 69 percent of average on Dec. 1 to 119 percent on Dec. 31 and jumped to 171 percent of average by Jan 13.

“Most of the sites registered 200 percent of increase in the first 17 days of the month,” Knight said.

On Jan. 30, the Upper Colorado River Basin snowpack estimate was 161-percent of average.

That indicates a healthy runoff, and the Bureau of Reclamation’s Jan. 17 forecast for water year unregulated inflows to Lake Powell rose to more than 12 million acre feet (maf). That’s up from 9.5-maf forecast on Jan 4 and 7.83 maf forecast on Dec 1.

The inflow forecast for Lake Powell for just the April-July runoff season was 9 maf on Jan. 17, which is 126 percent above long-term average.

Knight showed a graph illustrating how many days it took five snow-monitoring sites across the upper Gunnison Basin to receive their monthly average snowfall in December and January. While most sites needed more than two weeks in December (and most of that coming in the last two weeks), none took more than 10 days (and one site took only six) to reach their January average.

And then they all doubled that amount in another 10 days or less.

The January runoff forecast says Blue Mesa may see 928,000 acre feet of inflow, about 136 percent of long-term average.

Despite the information available, risking a runoff forecast four months out always is thin ice.

Many factors – dry soils, warm and/or windy conditions, abrupt changes in weather pattern – can affect runoff.

“We have a long way to go,” Knight said. “The forecast is bound to change and it can go either way.”

But already dams across the state are expected to fill, he said.

“We are way ahead of schedule.”

 

 

 

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s