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.
Low Water Levels Delay Swim Beach Opening
Water levels at Union Reservoir are lower than normal for this time of year and are affecting access.
Swim Beach Opening Delayed for Safety
After a safety review with Recreation staff, Park Rangers, and Risk Management, the City has decided to delay opening the Union Reservoir Swim Beach, which was planned for Memorial Day weekend.
Why the Delay?
Low water levels have exposed parts of the old lakebed that still contain glass, fishing gear, and other debris from the reservoir’s past. Rangers have cleared the visible shoreline, but we can’t confirm that submerged areas are safe.
Next Steps
We’ll wait until the water rises enough to cover the cleaned lakebed and sandy beach. Once it’s safe, we’ll open a smaller swim area and expand it as water levels increase.
When Will It Open?
We’re not sure yet. The Union Reservoir Ditch Company says it could be anywhere from mid-June to August, depending on water flow and system needs. Thank you for your patience—we’ll open the Swim Beach as soon as it’s safe to do so.
Impacts on boating access and fishing piers:
• Extended walking from shore to the waterline is required: foot protection is recommended
• Boat docks and the paved ramp do not extend into the waterline
• Shallow water depth conditions exist
• Fishing piers are not near the waterline
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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