Dillon Reservoir’s water managers help extend the whitewater rafting season while meeting customer needs downstream.
By Jay Adams
Nothing says Fourth of July in Colorado like a day of rafting on a mountain river. Paddling through rapids is as much a tradition in our state as fireworks, hot dogs and apple pie.
Our nation’s birthday is one of the busiest days of the year for whitewater rafting. But there’s no rafting without rapids — and that’s where Dillon Reservoir comes in.
With a capacity of 257,304 acre feet, Dillon Reservoir in Summit County is Denver Water’s largest storage site, supplying 30 percent of Denver’s water. Water managers work to balance the demands of Denver customers while supporting the recreational economy on the Blue River and Dillon Reservoir.
“In the spring and early summer, Denver Water carefully manages outflows from Dillon Reservoir,” said Cindy Brady, water resource engineer at Denver Water. “We try to provide reliable and predictable rafting flows on the Blue River below Dillon Dam.”
In years with above-normal mountain snowpack, water planners gradually increase the outflow from Dillon to make room for the spring runoff that fills the reservoir. The approach minimizes high water through the town of Silverthorne and helps extend the rafting season.
“Instead of having a really high flow early on and then having it drop to an unraftable level, Denver Water manages the water so we have optimum flows as long as possible,” said Kevin Foley, president of Performance Tours Whitewater Rafting, sending rafters down class 3 whitewater trips on the Blue River for 30 years.
As Dillon Reservoir’s recreational role grew, Denver Water began working closely with Summit County and the rafting community to manage the river flows. “We work with the whitewater industry to understand their flow needs and communicate to them what to expect each year,” Brady said.
The best flows for rafting are when the river is running between 1,100 and 1,400 cubic feet per second, Foley said. “Knowing how much water is coming down is incredibly important when we plan our rafting season,” he said.
Outflows from Dillon Dam into the Blue River reached their highest level of the season at 1,490 cubic feet per second on June 15 and are expected to drop as the runoff slows and outdoor watering picks up in Denver.
“It’s a constant balancing act,” Brady said. “We always try to meet the interests of everyone to enhance the recreational experience.”