Nature Area Hours: 1 Hour Before Sunrise to 1 Hour After Sunset

Union Reservoir is a 736 acre body of water providing many outdoor recreational activities. Originally called Calkins Lake, the reservoir was carved out during the last glacial age and is one of only a few natural lakes in Colorado. In 1903, the Union Ditch Company began drilling a tunnel to release water into the St. Vrain Creek. According to Colorado water law, that made Union a true reservoir.

The reservoir is located approximately 7 miles west of I-25.

Get the full scoop on activities – including wakeless boating, dog beach, swim beach and fishing – on the Union Reservoir webpage. There, you can also find information on hours and fees, as well as day-use shelter reservations.

Beginning in 2018, there will be no more overnight camping at Union Reservoir. Areas previously used for campsites will be reconfigured to provide additional day use opportunities and parking during peak periods. These changes will produce useful benefits for a larger number of patrons to enjoy. In the long-range future, design and construction of a modern campground with both tent and RV camping is planned. Learn more on the Union Reservoir Recreation and Trail Master Plan webpage. In the meantime, alternative local and regional camping opportunities can be found at reserveamerica.com.