Between Boulder And Longmont Is Colorado's Recreational Reservoir With A Big Swim Beach And Ethereal Mountain Views

While Colorado might be landlocked, there's no shortage of bodies of water to explore across its 104,000 square miles, including many natural lakes, reservoirs, and over 90,000 miles of rivers. In the Centennial State you'll find its largest body of water, Blue Mesa Reservoir, a picturesque lake with lounge-worthy beaches and endless water fun in the state's center. Carter Lake, one of its most unique adventure-packed lakes, sits just beneath the Front Range, located an hour from Boulder. About 26 miles to the south of Carter Lake, between Boulder and Longmont is another of Colorado's recreational reservoirs, Boulder Reservoir, where a large swimming beach awaits beneath stunning mountain views.

The Boulder Reservoir, known as "the Rez" to locals, is a 700 acre lake whose beginnings date to the 1950s as a water storage facility for the city, and provides around 20 percent of the city's drinking water currently. Boulder's resident mountains, The Flatirons, with five distinct sandstone peaks ranging from 6,900 feet to 7,630 feet high, rise above the reservoir, providing an ethereal landscape. Many of Boulder's approximately 104,000 full time residents, University of Colorado at Boulder students, and visitors know it also as a popular place for water and other outdoor recreation of all kinds, and the reservoir is open year round. You'll need to pay an entry fee from April 1 to October 31, the peak summer season, which ranges from $5 and up for individuals, and $10 and up for carloads, depending on the exact dates of your visit. Also, dogs are only permitted in the park from Labor Day through May 15th.

Locals consider the Rez their version of a beach, sans the crashing ocean waves, and is one of the largest swim beaches in the state. The family-friendly beach hours from May 23rd to September 1st are typically 10 am to 6 pm, with the beach closing at 5:30 on Thursdays. Visitors can swim only in the designated area, while a lifeguard is on duty, and adults must supervise children under 13 at all times. The reservoir's water temps tend to be on the cooler side, and temperatures must be at a minimum of 60 degrees Fahrenheit in the shallow area, and 64 degrees for the entire area to open. You can contact the Reservoir staff at 303-441-3461 to inquire about current temperatures, and visit the website for any other closure or pertinent information. Adverse weather conditions such as excessive wind and fog, thunder and lightning can lead to swim area closures.

You can still enjoy the water by boat, kayak, or paddleboard if you prefer not to take a dip in the water itself. For those with their own boat or other watercraft, an annual permit is required, which can be purchased online. You can also rent pontoon boats, paddleboards, kayaks, and canoes by the hour from Rocky Mountain Paddleboard inside the park, which also offers lessons from certified instructors. Pontoon boats hold up to 15 people and rentals start at $225, while personal watercraft rentals start at $30 and up depending on duration. If you want to fish the Reservoir, you'll find varieties such as bass, catfish, trout and walleye available, and you'll need to purchase an appropriate fishing license.

If you're visiting when the swim beach is closed or the water is just too chilly, there's still plenty of outdoor fun to be had at the Boulder Reservoir. The park is home to a multi-use trail, 13 picnic sites, a playground, and volleyball court. You'll also find a Visitor Services Center with restrooms, showers and locker room area for changing. For an easy beginner hike with incredible views of the lake and the surrounding mountains, head out on the 5.3 mile long Boulder Reservoir Loop Trail, which is used for running and cycling as well. You'll want to keep an eye out to spy potential wildlife in the park including geese, deer, multiple bird species, rabbits, and prairie dogs. During weekends, you can dine at Lakeside@Boulder, a cafe offering sandwiches, pizza, soft serve and beverages. You can find a comprehensive interactive online map of Boulder Reservoir on the city website.

The Rez also hosts a variety of sporting and athletic competitions, and community events on its premises. One of the more notable competitions is the Boulder Ironman 70.3 where the one lap swim portion is held on the Reservoir. During spring, the Reservoir hosts a series of Dash & Dine 5K events, where racers enjoy a dinner together following the run. During October leading up to Halloween, the city of Boulder hosts drive-in movie nights at the Reservoir. A famous movie festival, the iconic Sundance Film Festival moves to Boulder's idyllic setting in 2027 and the city is also considered one of America's prettiest cities and a dream come true for art lovers.