The newly improved Frisco Bay Marina at Dillon Reservoir is now fully open for summer boating, kayaking, canoeing and generally enjoying some of Colorado's high-country recreation opportunities.

Improvements at the marina include a separate area for motorized boats and a bigger beach area for launching kayaks, canoes and paddleboards.

But while the project improves boating opportunities and safety on the reservoir, the Dillon Reservoir Recreation Committee's rules governing recreation remain the same.

Specifically, swimming is not allowed in Dillon Reservoir, or any Denver Water reservoir, because the water is too cold. Even in the summer months when the weather is warm and all the snow has melted, the average water temperature at Dillon Reservoir sits in the low 60s.

“The bottom line is that the water in our reservoirs is too cold for prolonged skin contact,” said Brandon Ransom, Denver Water's manager of recreation. “When you pair that with a lack of medical supervision, it’s just not a risk that makes sense to take.”

Dillon Reservoir’s primary function is to catch and hold water that will be used to supply drinking water to 1.4 million people in Denver and the surrounding suburbs. But the utility also tries to manage the reservoir to support recreation at the Frisco and Dillon marinas, which have an economic impact in Summit County.

The Town of Frisco's $4 million marina improvement project started in early March, when contractors began excavating the reservoir’s lakebed, accessible because of the reservoir’s low water level during the winter months. The excavation moved about 85,000 cubic yards of dirt, lowering the level of the lakebed around the marina up to 13 feet.

Some of the dirt from the excavation — dubbed Frisco’s “Big Dig” — was used to expand the beach and fishing areas near the marina. Some of it will become the foundation for three new acres of land that will be developed in the future.

Denver Water’s involvement in Frisco’s Big Dig stems from the groundbreaking Colorado River Cooperative Agreement, signed in 2013. The agreement settled decades of legal challenges over water rights and ushered in a new era of cooperation between Denver Water and West Slope stakeholders.

The agreement called for Denver Water to work with stakeholders to improve high-country rivers and included payments to local governments to benefit water supply and quality, the environment and recreation. In Frisco’s case, the money from Denver Water, about $700,000 since 2013 with an additional $450,000 pledged, helped pay for the Big Dig project.