What is Boulder Reservoir? A 700-acre park with a swimming beach, paddleboarding, kayaking, sailing, and fishing—all with Flatirons views. Entry is $7-10/vehicle. Open late May through September. The only place near Boulder where swimming is allowed. Arrive before 10am on summer weekends or you'll wait in line.
Overview
Location: 5565 N 51st St, Boulder
Size: 700 acres, 150-acre lake
Season: Late May - Labor Day (full operations)
Entry Fee: $7 weekdays, $10 weekends (Boulder residents); $10/$15 non-residents
Hours: Sunrise to sunset
Boulder Reservoir is the city's premier water recreation destination. Unlike most Front Range lakes that prohibit swimming, the Res (as locals call it) has a designated swim beach with lifeguards. The Flatirons loom to the southwest, creating a postcard backdrop for kayaking, paddleboarding, or lounging on the sand.
Activities
Swimming
The swim beach has lifeguards on duty during summer hours. Sandy beach area with gradual entry—good for kids. Water quality is tested regularly. No diving, no glass containers. The beach gets crowded by noon on hot weekends; morning visits are more pleasant.
Paddleboarding & Kayaking
Rentals available at the marina: SUPs ($20/hour), kayaks ($15-25/hour), canoes ($20/hour). Bring your own for free with park entry. The lake has enough space that it doesn't feel crowded even on busy days. Wind picks up in the afternoon—morning paddling is calmer.
Sailing & Windsurfing
Boulder Reservoir is a popular sailing spot with consistent afternoon winds. The Boulder Sailing Club operates here. Windsurfing and kiteboarding allowed in designated areas. Motorboats restricted to electric motors only—keeps it peaceful.
Fishing
Stocked with trout, bass, catfish, and walleye. Colorado fishing license required. Fish from shore or rent a boat. Early morning and evening are most productive. Ice fishing in winter when conditions allow.
Biking & Running
A 5.5-mile paved trail circles the reservoir—popular with cyclists and runners. Connects to the Boulder Creek Path network via the Diagonal Highway trail. Flat terrain makes it accessible for all fitness levels.
Facilities
- Sandy swim beach with lifeguards (summer)
- Boat rental marina
- Picnic areas with grills (first-come, first-served)
- Group picnic shelters (reservable)
- Restrooms and changing rooms
- Concession stand (summer weekends)
- Volleyball courts
- Large parking lot (fills by 11am on hot weekends)
Tips for Visiting
Arrive early: The parking lot fills by 10-11am on summer weekends. No overflow parking—once it's full, they close entry until people leave.
Bring everything: Concessions are limited. Pack food, drinks (no glass), sunscreen, and shade. There's little natural shade at the beach.
Check the wind: Afternoon winds make paddleboarding challenging but sailing excellent. Plan water activities accordingly.
Water shoes help: The beach is sandy but the lake bottom gets rocky in places.
Frequently Asked Questions
Can you swim at Boulder Reservoir?
Yes—it's one of the only lakes near Boulder where swimming is allowed. Lifeguards are on duty during summer season at the designated swim beach.
How much does it cost to enter Boulder Reservoir?
$7-10 per vehicle for Boulder residents, $10-15 for non-residents. Weekend rates are higher. Season passes available.
Can I bring my own kayak or paddleboard?
Yes. Park entry fee covers boat launching. All watercraft must be inspected for invasive species before launching.
Are dogs allowed at Boulder Reservoir?
Dogs are allowed in the park but not on the swim beach. Must be leashed. There's no designated dog swimming area.