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The reason you aren’t allowed to swim in Dillon Reservoir may surprise you

It doesn't have to do with water quality. And it's the same reason you can't swim in other Denver Water reservoirs.

Coves of the Dillon Reservoir are pictured near Dillon on July 30, 2021. (Andy Colwell, Special to The Colorado Sun)

By Lindsey Toomer, The Summit Daily

Water-contact sports, such as swimming, scuba diving, water skiing and wakeboarding, are all prohibited in Dillon Reservoir — but why?

Basically, because the water is too cold, making it dangerous for recreationists.

The reservoir is owned and managed by Denver Water, which means all decisions relating to the body of water are the organization’s jurisdiction. Swimming is prohibited in all Denver Water reservoirs for similar safety reasons.

Brandon Ransom, Denver Water’s recreation manager, said the combination of low water temperatures and thin air makes it dangerous for folks to swim. He also said search and rescue efforts would be difficult since it is such a large body of water.

“We get a lot of folks from all over the country, all over the world really, that may not be accustomed to that elevation,” Ransom said. “And you can combine the elevation with the thin air and cold water, and you can have a real situation if you really get into that.”

Olympic pool temperatures are required to be between 77 and 82 degrees Fahrenheit depending on the sport. Once water temperature gets below 77 degrees, breathing ability can be affected while swimming. At its warmest, Ransom said Dillon Reservoir will reach maybe 65 degrees between mid-August and September, though surface temperatures can be warmer.

Ransom added that the Dillon Reservoir Recreation Committee is in the process of modifying its rules and regulations. The proposed new rules and regulations would allow folks to wade around the edges of the water, but outright swimming would still be prohibited, Ransom said.

If approved, that would mean splashing around in the water would officially be permitted at the Frisco Marina beach, which Denver Water says is for launching kayaks, canoes and paddleboards.

He said any rules and regulations the committee proposes have to go through the Summit Board of County Commissioners, and any new rules would go to a public hearing for adoption at the commission’s Aug. 10 meeting.

Other water contact sports like water skiing and wakeboarding are also prohibited on the reservoir. Ransom said this is due to the same safety concerns but also because of the atmosphere Denver Water wants to see at Dillon Reservoir.

“Dillon has kind of a quiet, Alpine environment atmosphere,” Ransom said. “And personal watercrafts like jet skis and wakeboarding and things of that nature, it’s just been something that we’ve kind of steered away from. We want to respect that quieter atmosphere that Dillon provides.”

While swimming is prohibited in Dillon Reservoir, it is allowed at Green Mountain Reservoir, which is about 25 miles north of Dillon. Ransom said rules vary from place to place but that places at lower elevations around the Front Range typically will allow swimming.

Ransom also added that, to his knowledge, swimming has never been permitted in Dillon Reservoir, or at least not since the formation of the Dillon Reservoir Recreation Committee in 1990.


Updated at 11:40 a.m. on Aug. 10, 2021, to correct the author’s byline.


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