Below average snowpack has translated to stream flows that are half of normal levels |

Below average snowpack has translated to stream flows that are half of normal levels

Buffalo Mountain and surrounding peaks in the Gore Range are reflected off Dillon Reservoir on April 27, 2020. During spring runoff this year, area stream flows are about half of what is typical.
Photo by Jason Connolly / Summit Daily archives

Summit County’s snowpack is below average, but local streams are what are really suffering with significantly low flows.

Treste Huse, a senior hydrologist for the National Weather Service in Boulder, said stream flows in Summit County are looking “not so great” with a number of streams and rivers showing below normal levels.

Huse explained that the Blue River, Tenmile Creek and Keystone Gulch are experiencing below normal stream flows. Straight Creek and Snake River are faring better, reporting near normal to normal flows.

Summit County Water Commissioner Troy Wineland explained that precipitation from October through April was between 70% and 80% of average.

“Out of gate, we were below average as far as precipitation up on the mountains,” Wineland said.

Wineland said soil moisture content also plays a role in stream flow. Because the past two summer and fall seasons were also lacking in precipitation, soil moisture locally is well below average. Because the soil is dry, runoff will soak into the ground before making its way down streams and into reservoirs.

The Blue River Basin snowpack — which is calculated by averaging basin snow telemetry sites in the drainage — peaked at 85% of average this year, Wineland said. Given the soil dryness, a snowpack that is 85% of average will translate into about 50% to 60% of average stream flow at best.

“What you’re seeing now as far as current conditions, (stream flows) are below average primarily because we don’t have much snow on the mountains, and what little snow we do have, a lot of it is filling that deficit in the soils before making it to the creeks,” Wineland said.

As for overall water supply, Huse said it looks low for streams heading into local reservoirs, which unsurprisingly could contribute to low reservoir storage this year.

“The Blue River at (Dillon Reservoir) is only forecast to be 53% of normal stream flow volumes for May through July. … Downstream at Green Mountain Reservoir, same thing: 53% of normal,” Huse said.

Huse said stream flow peaked around April 2 compared with a more typical peak in mid-April. When asked just how bad 53% of normal is for reservoir forecasts, Huse said it’s “pretty bad” and added that precipitation forecasts for spring don’t look promising. The two-week forecast shows below-normal precipitation.

As for long-term forecasts, Huse said June shows conditions that are warmer and drier than normal across north central and northeast Colorado. July and August are also forecast to be warmer and drier than normal.

“Between the below-normal precipitation forecast and the stream flow outlooks showing only half normal stream flow this summer and then the snowpack being far less than normal … it’s not looking real good,” Huse said.

Currently, Dillon Reservoir is sitting at 95% of average.

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