Green Mountain Reservoir

A big, uncrowded reservoir north of Silverthorne with the Gore Range rising along its western skyline.

About Green Mountain Reservoir

Green Mountain Reservoir fills a long stretch of the Blue River valley at the northern end of Summit County, north of Silverthorne along CO-9. The tiny community of Heeney sits on the west shore, and the Green Mountain Reservoir Trail follows that western side.

The area offers boating, fishing for trout and kokanee, six Forest Service campgrounds at the reservoir and another along Cataract Creek next to the Eagles Nest Wilderness. It feels much quieter than Lake Dillon to the south, which makes it a good place to find open shoreline and wide views.

Water levels can drop significantly late in the season, exposing broad mudflats and sometimes closing the boat ramp.

Built to replace water sent from the Colorado River to the Front Range through the Big Thompson Project, this is a storage reservoir, so expect the water level to shift with seasonal demand. Worth checking conditions before planning a shot that depends on a full shoreline — a lower water level can actually expose interesting foreground rock and shoreline texture you won't see when it's full.

History

Green Mountain Dam was the first facility built for the Colorado-Big Thompson Project, the Bureau of Reclamation system that diverts Western Slope water to Northern Colorado's Front Range. Construction began in 1938 and finished in the early 1940s. The reservoir stores water to replace what the project takes from the Colorado River headwaters at Lake Granby, protecting downstream Western Slope users, and its power plant generates hydroelectricity. The earthfill dam stands 309 feet tall and the reservoir holds about 153,000 acre-feet at a full-pool elevation of 7,950 feet.

Photographing Green Mountain Reservoir

Best light: Sunrise is strongest, when first light hits the Gore Range peaks to the west across the water. Late September adds aspen color on the surrounding hills, and calm early mornings give the best reflections before afternoon winds.

Shots to look for

Gore Range alpenglow reflected across the reservoir from the east shore pullouts along CO-9 (24-70mm)
Exposed shoreline patterns and cracked mudflats at low water in late summer
Wide sunrise scenes from the Heeney side looking across the water
Telephoto compressions of the Gore Range's jagged ridgeline (100-400mm)

Photo tips

Use safe pullouts on CO-9; traffic moves fast
Low water late in the season changes the shoreline; scout before committing to a sunrise spot
This is bear country; food storage is required at campgrounds
Bring layers; wind can be strong across the open water
Boats must follow aquatic nuisance species inspection rules

Know before you go

The Heeney Marina boat ramp closed in July 2026 because of low water; check current USFS conditions
Hand-launching motorized vessels is prohibited due to invasive species risk
No potable water at many sites; bring your own
Food and garbage storage rules apply for bears

Frequently asked questions

Where is Green Mountain Reservoir?

In northern Summit County on the Blue River, along CO-9 north of Silverthorne, with the town of Heeney on its west shore.

Can you camp at Green Mountain Reservoir?

Yes. The Forest Service runs six campgrounds at the reservoir and another along Cataract Creek. Check Recreation.gov and the Dillon Ranger District for details.

Is the Green Mountain Reservoir boat ramp open?

It depends on water levels. The Heeney Marina ramp was closed for low water in July 2026, so check USFS alerts before you go.

Combine it with

Heeney · Silverthorne · Eagles Nest Wilderness · Lake Dillon

More Colorado spots

Emerald Lake · Old Dillon Reservoir Trail · Clear Creek Welch Ditch

Sources & further reading: en.wikipedia.org · fs.usda.gov. Conditions, fees and rules change; check with the managing agency before you go.