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Floatin’ on the 4th: Making waves on the Blue River

Dillon Reservoir’s water managers help whitewater rafters while meeting customer needs downstream.  

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 plays an important role.

With a capacity of 257,304 acre feet, Dillon Reservoir in Summit County is Denver Water’s largest storage site, holding about 40 percent of the stored water supply for the Denver metro area. 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.”

Dillon Reservoir opened in 1963 and its primary role is to store water for the Front Range. Denver Water also manages the reservoir to provide secondary benefits which include helping out the rafting community. “We work with the whitewater industry to understand their flow needs and communicate to them what to expect throughout the rafting season,” Brady said.

Whitewater rafting through the spectacular alpine scenery beneath The Eagles Nest Wilderness area on the Blue River. Photo courtesy of Performance Tours Whitewater Rafting.

In years with above-normal mountain snowpack, water planners gradually increase the outflow from Dillon to make room for the mountain snow runoff that fills the reservoir. The approach minimizes high water through the town of Silverthorne and can help extend the rafting season.

"Instead of having a really high flow early on and then having it drop to an unraftable level later on, we like to have optimum flows as long as possible,” said Kevin Foley of Performance Tours Whitewater Rafting. “Knowing how much water is coming out of the dam is incredibly important when we plan our rafting season,” he said.

Outflows from Dillon Dam into the Blue River typically peak around the first week of July and start to drop as the mountain snow runoff subsides and Denver Water begins to send water from Dillon to customers in the metro area when outdoor watering picks up.

“It’s a constant balancing act,” Brady said. “We always try to meet the interests of everyone to enhance the recreational experience.”