Boulder Reservoir Boulder Open Water Swimming

Boulder Reservoir spans 700 acres and serves as both a water storage facility and premier recreation destination for open water swimmers in Colorado. Access the reservoir via North 51st Street off of Highway 119, with parking available in designated lots for a daily fee. The facility includes changing rooms, showers, and restrooms located in the Visitor Services Center on the south side. The sandy swim beach features a designated swimming area staffed by American Red Cross certified lifeguards during operating hours from late May through early September. Swimming is only permitted when lifeguards are on duty and within the marked boundaries.

Connect with local swimmers through Boulder Aquatic Masters (BAM), which has been organizing open water swims at the reservoir since 1999. BAM hosts Tuesday and Thursday morning sessions from 6:15-7:40 AM throughout the summer season, welcoming swimmers of all abilities. The group also organizes the annual BAM Bare Bones Open Water Swim Series in August, featuring 1-mile, 2-mile, and 3-mile race options at this high-altitude venue situated at 5,300 feet elevation.

Weather conditions at Boulder Reservoir can change rapidly, and swimming may be suspended due to lightning, thunder, or high winds creating rough water. Arrive early during summer weekends as the 500-car capacity fills quickly. The reservoir maintains excellent water clarity, though temperatures remain cool even during peak summer months due to the elevation and mountain snowmelt source. Water quality monitoring is conducted by the City of Boulder(https://bouldercolorado.gov/services/drinking-water-quality), which maintains comprehensive testing programs for this municipal water supply. The protected location offers shelter from prevailing winds during morning hours, making early swims particularly pleasant before afternoon breezes pick up.