Union Reservoir Nature Area, located in Longmont, Colorado, is a 736-acre body of water offering a diverse range of outdoor activities. Originally known as Calkins Lake, it was formed during the last glacial age and is one of the few natural lakes in Colorado. The area provides opportunities for boating, fishing, swimming, and picnicking, making it a popular destination for both locals and visitors. The reservoir's natural beauty and tranquil atmosphere create a unique experience for those looking to enjoy nature and recreational activities.
Union Reservoir is situated approximately 7 miles west of I-25 and about 3 miles from downtown Longmont, making it easily accessible for day trips. The area is managed by the City of Longmont, which has implemented plans to enhance its recreational and environmental features. Despite its natural charm, the reservoir has limited amenities, so visitors should plan accordingly.
The reservoir's history dates back to 1903 when it became a true reservoir with the drilling of a tunnel to release water into St. Vrain Creek, primarily for irrigation purposes. Today, it serves as a significant water supply resource for Longmont and surrounding areas.