Union Reservoir Nature Area

Road Closure Notice

County Road 26 – just past the Union entrance going east to County Road 3.5 – will be closed through October 11 to replace the culvert at the Oligarchy ditch. Please enter Union from County Line Road. View the city’s road closure webpage.

Overview

461 County Road 26, Longmont, CO 80504
303-772-1265
union@longmontcolorado.gov

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.

Find Out More

• Activities
• Fees and Hours
• Future enhancement plans for Union Reservoir recreation & complementary trail
• Get real-time estimated entry wait times & water temperature
• Purchase Union Season Passes Online
• Special Events
• Union Reservoir as a water supply resource for Longmont
• Union Reservoir Map (PDF)