Water managers say slight reprieve from April storms not expected to last
April showers and cooler temperatures brought sighs of relief to drought-stressed water managers, but don’t expect laughter to follow.
Water supplies across the Gunnison Basin remain in the drought level, and short-term weather predictions call for higher temperatures and less precipitation, several speakers said Thursday during the quarterly Aspinall Unit Operations meeting in Grand Junction.
The meetings bring together local, state and federal water managers to discuss water management in the upper Gunnison Basin and operation plans for the three Aspinall Unit dams: Blue Mesa, Morrow Point and Crystal.
The 2013 water year, October 2012 through September 2103, began with a deficit, said Erik Knight, hydrologist with the Bureau of Reclamation Western Colorado office in Grand Junction.
“October and November were very dry across Colorado and got us in an early hole, which is very difficult to escape,” he said. “January was looking good, we got good precipitation, but it fell at lower elevations” where it melts sooner.
February and March continued drier than normal, but April brought a jump in precipitation, reaching 150 to 200 percent of average in parts of the Gunnison Basin.
Knight said along with the increased precipitation, April temperatures were 4 to 6 degrees below long-term average, similar to April 2012 temperatures.
Ambient temperatures make a big difference in terms of when runoff hits the streams, he said.
“Cooler temperatures keep the snow on the ground longer and keep it in the mountains,” Knight said.
Much of the runoff forecast begins with soil moisture, and soil moisture in western Colorado at the end of 2012 “was a pretty sad-looking situation,” said Greg Smith, senior hydrologist with the Colorado River Basin Forecast Center.
Figures from December 2012 show soil moisture across the Gunnison Basin averaging no better than 70 percent of normal, and in some places it was less than 50 percent.
Dry soils mean runoff doesn’t run off. Instead, it soaks into the ground, never reaching streams and rivers running to storage reservoirs.
The cycle broke a bit in April, with increased moisture showing a “definite turnaround,” Smith said.
He added, “The new snow situation totally turned around” with a “remarkable difference in snowpack.”
Still, it’s well below average, Smith said.
Runoff forecasts can be unreliable and may change rapidly, though not for lack of trying.
Weather — past, present and future — plays a major role in what reaches downstream farms and faucets.
Unseasonably warm winds can steal snow faster than it melts, yet those same winds can bring water-laden spring snows to augment the snowpack.
As Knight said, cooler weather delays snowmelt, and so far that’s kept high-country snows on the ground.
However, Aldis Strautins of the National Weather Service in Grand Junction said the next week or so should bring higher temperatures and lower precipitation to western Colorado.
The April 15 runoff forecast for Blue Mesa Reservoir calls for 340,000 acre-feet, an improvement on the 315,000 acre-feet in the April 1 forecast but still only 50 percent of the 30-year average of 680,000 acre-feet.
Last year, Blue Mesa received only 206,000 acre-feet of runoff.
“We’re well into the dry category” in terms of reservoir management, Knight said.
One result of the wetter-than-expected April is the cancelation by Denver Water of its plan to drain Antero Reservoir.
Accordingly, Colorado Parks and Wildlife canceled the emergency fishing regulations and restored the two-trout bag limit at Antero.
The drawdown would have moved water from Antero through the South Platte River and store it in Cheesman and Eleven Mile reservoirs.
According to Denver Water, Antero Reservoir has the highest evaporation rate of any of the water utility’s reservoirs. Storing the water in Cheesman and Eleven Mile reservoirs would save about 4,000 acre-feet of water.
A similar drawdown was done in 2002.