Union Reservoir Nature Area
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.
Reservoir Access
Union Reservoir is open for:
- Boating
- Fishing
- Kayaking
- Paddleboarding
- Picnicking
- Dog beach use
Questions? Email Union@longmontcolorado.gov.
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)
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