Summit County readies for epic spring runoff into Dillon Reservoir, potential flooding in local waterways
As the days get warmer, the snowcaps in the High Country are about to shrink. An epic spring runoff is in the works after one of the best winters in recent years, and local water and emergency officials are preparing Summit County for the deluge.
Snowpack across the state is 654% of normal, according to the latest snow survey from the National Resources Conservation Service. That is 51 times larger than the state’s average snowpack at this time last year, with flooding a much bigger concern at this point than wildfire. The state of Colorado is drought-free for the first time in 20 years, according to the U.S. Drought Monitor.
To illustrate the change in fortunes, the county was on the verge of declaring Stage 1 fire restrictions at this time last year. Wednesday will mark one year since the Buffalo Mountain Fire nearly destroyed the Wildernest neighborhood near Silverthorne. That fire was borne out of extraordinarily dry and hot conditions after one of the worst winters in the state’s history.
This year, instead of supplying helicopters with water to dump on fires, Denver Water is draining water from Dillon Reservoir in anticipation of runoff, which is expected to really begin coming down in the next few weeks.
“This year being a high snowpack year, we know there’s going to be a lot of water getting into the reservoir,” Denver Water supply manager Nathan Elder said. “We’re trying to have enough space to catch that runoff while providing for safe outflows to the Blue River below the reservoir.”
At the moment, the reservoir — which is the main drinking water supply for 1.4 million people in the Denver metro area — is 75% full with 192,554 acre-feet of water. When full, the reservoir holds 257,304 acre-feet. An acre-foot of water would cover an area the size of an acre 1-foot deep. Given the current estimate for runoff volume, there will be more than enough water to fill it.
“The forecasting for the rest of June and July project a volume of anywhere from 169,000 acre-feet to 211,000 acre-feet coming into the reservoir,” Elder said. “That’ll fill it, but we’re probably not going to fill it until the Fourth of July to make sure we’re past that peak-inflow time.”
Elder said peak inflow to the reservoir is expected to start about a week later this year than usual, which also means Summit’s two marinas in Dillon and Frisco will have to wait before the reservoir is full enough for boating. However, boaters should have a lot more time for play this year compared with last, when boat ramps were retracted weeks before they normally would be due to low water.
“Typically, every year we target June 18 to be at 9,012-foot elevation needed for both marinas to be completely operational, but it’s going to be a little delayed this year,” Elder said. “But while the boating season might be shortened by a week on the front end, on the tail end, it should last quite a bit longer.”
The delay also means local emergency officials will be watching streamflows longer into the month, looking to spring into action if Tenmile Creek, Straight Creek or the Blue River approach the verge of flooding.
Current two-week projections show all three waterways approaching “action stage,” the threshold at which the towns and county are called to start flood mitigation preparations, by June 15.
Summit County’s director of emergency management Brian Bovaird said he closely has been watching the forecasts for flooding. That is opposed to last June when Bovaird, who recently had gotten the job as emergency director, was given a literal trial by fire.
“It’s like picking your poison,” Bovaird said. “Last year, it was wildfire. This year, it’s flooding. We’re expecting heavy runoff moisture, which is good for wildfire but makes us uneasy about the flooding risk.”
Bovaird said the county and towns have been on standby for weeks, and even if there is flooding, the county’s strict zoning requirements in 100-year floodplain areas mean homes are up to code in those locations and have flood insurance, minimizing the likelihood of significant damage or loss.
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