Perhaps the best-kept secret in Boulder County is the Gross Reservoir built back in 1954 to capture the water from the South Boulder Creek drainage. The 440-acre lake is 7,500 feet above sea level with the peaks of the Colorado Rockies looking down from the west.
The water stored there is managed by Denver Water on the east side and the Roosevelt National Forest Boulder District on the west. The reservoir was named for former Denver Water chief engineer Dwight Gross and continues to supply water for Denver while regulating the runoff from the mountains to the west.
Just a short drive from Boulder, Gross Reservoir offers tremendous, but primitive outdoor experiences. The east side of the reservoir is open year-round, and open to boating from May to September, but the west side is closed during the winter.
Boating: Boating is permitted, but motors are not. Neither is swimming nor wading, so your only option is to stay on top of the nearly 3/4 square mile of water.
Camping: Camping is allowed, but there are no established campsites and no amenities along the dozen or so miles of meandering lakeshore. High-clearance vehicle recommended. There is dispersed camping permitted in designated sites along Forest Road 359 on the west side of the reservoir.
There is no fee for camping and use is heavy. There are no amenities, but you can find a vault toilet at the Forsyth Canyon Trailhead nearby.
Fishing: If you’re a fisherman, the lake abounds in many game species, some fairly rare in Colorado water. Rainbow, brown, and lake trout are stocked by the Colorado Division of Wildlife along with splake and Kokanee salmon. These cold-water species thrive in the frigid waters of this high-altitude lake.
Another species, favored by anglers for its tenacity and by the challenge of actually hooking one, is the tiger muskie. Tiger muskie is a ferocious-looking predatory fish with rows of razor-sharp teeth. It is the apex predator in many freshwater environments.
Hiking: Hiking is a featured activity at Gross Reservoir. One of the most popular hikes is a two-mile trek up the Forsyth Canyon Trail as it follows a stream to a small waterfall.
The water is frigid all year, even in the summer months, and the weather is unpredictable due to the lake being so close to the continental divide. Wind can come up quickly and unannounced. With the only amenities a restroom and picnic tables there isn’t much help if an emergency arrives.
Rock Climbing: Intrepid climbers can find huge boulders to conquer near the east shore of the lake. Bouldering has become a new pastime for many outdoor sportspeople.
Winter Recreation: Rugged fishermen sometimes set their tip-ups on the thick ice and fish through the winter. A few hardy ice skaters take to the lake at the same time.
From Boulder – Take Boulder Canyon Drive west to the 9th Street intersection then turn south. Stay on 9th until you reach Chautauqua Park, then take the hard right turn west. The Chautauqua Park changes to Baseline Road before becoming Flagstaff Road. Remain on Flagstaff Road until you reach the Gross Reservoir parking lot and you’re there.
Address: Forest Service Rd 359, Nederland, CO 80466
Season: Eastside (open year-round) | Westside (closed in winter)
Boating: May-September | No motors permitted