Warm temps mean average snowpack leads to lower rivers
If it were just about snowpack, this would be a great water year.
But due to drought conditions for the Roaring Fork Valley and most of the state late last year, streamflow forecasts are expected to be below average.
Statewide, the snowpack for 2020 was just above average, according to the National Resources Conservation Service survey for the month of March.
But because of the marginally higher temperatures in the summer months, that snow runoff will likely lead to lower stream flows than normal.
“Many factors contribute to this but a large portion of that is due to drier than usual soils which will absorb future snowmelt and precipitation on its way to stream channels,” the NRCS said in its report.
“There’s a cycle. Of course, the soil dries out in the summer,” said Don Meyer of the Colorado River District in Glenwood Springs.
Rising temperatures, even small increases, have an impact on the soil, Meyer said, which could be an issue in years to come.
“They’re modest increases, but they do affect, I think, the antecedent moisture. Going forward, as the climate warms, I think that’s going to be more of a factor,” Meyer said.
The dry soil affected runoff in 2019, which was one of the best years for snowpack in recent memory, Meyer said.
For many of the high places around Colorado, the streams will be full and reservoirs should stay at normal storage.
But downstream, it’s a different story. The River District projects that stream flows of the Roaring Fork River when it reaches the Colorado River will be below average.
The problems are exacerbated the further down the basin one goes.
Given the regional conditions, streamflow into Lake Powell is only expected to be 77 percent of the 30-year average.
As of April 1, the snowpack for the upper Colorado River watershed was tracking just above average. The date of peak snowpack is typically the second week of April, which gives forecasters some confidence in what to expect as far as water supply for the rest of the year.
The Roaring Fork watershed was at 112 percent of normal as of April 1, despite low precipitation in March.
The streamflow forecast for the Roaring Fork River at the confluence with the Colorado River is expected to be just 85 percent of normal.
One of the major concerns about water in Colorado is fulfilling interstate compacts to keep reservoirs at Lake Meade and Lake Powell full.
It’s not looking likely that this year will help fill those lakes at all, Meyer said. It could take multiple years like 2019 to actually replenish those reserves.
But recent agreements between states have helped reduce the risk of a call being placed on the upper part of the rivers.
“Right now, there’s a bandaid on the system with the agreements that were signed in early 2019,” Meyer said.
Long-range forecasts for this year predict higher than normal temperatures and about average precipitation through the summer.
“Climate change is more about variability than anything else, and that’s what we’ve seen,” Meyer said.
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