This area is open seasonally. Before visiting, please call or check for current information on road openings and closures on the Road Status Table.
Winiger Ridge is the dominant landscape feature on Gross Reservoir's western shores. A network of seasonal four-wheel-drive roads and non-motorized trails offers opportunities to explore the area during summer months. The Forsythe Canyon Trailhead provides parking for year-round access.
Gross Reservoir is managed by Denver Water. Please visit their website for regulations and additional information. The free Boulder Ranger District Motor Vehicle Use Map displays National Forest System (NFS) routes open to motorized travel and is available online and at the Boulder Ranger District offfice.
Camping along NFSR 359 is permitted at designated campsites only (see map).
At a Glance
All vehicles must be either street-legal or registered annually through Colorado State Parks' OHV Registration Program. All motorized vehicles are restricted to open routes designated for their use. Contact your local District Office for a copy of the local Motor Vehicle Use Map.
Gross Reservoir; treat water for drinking.
Vault Toilet at Forsythe Canyon Trailhead
U.S. Forest Service and Denver Water Board
Boulder Ranger District, 2140 Yarmouth Ave, Boulder, CO 80301, Phone 303-541-2500, Fax 303-541-2515; Contact Us
Directions: From Boulder, head west on Canyon Boulevard (Colorado Highway 119) to Magnolia Road (about 4.5 miles up from the mouth of the canyon). Turn south on Magnolia and follow it for 6.6 miles. Turn south on Boulder County Road 68 and follow it two miles to National Forest System Road (NFSR) 359. Turn south on NFSR 359
Forsythe Canyon Trail heads east down a narrow gulch, starting about 300 yards south of the beginning of NFSR 359. It follows Forsthe Canyon for about a mile to the shore of Gross Reservoir.
The Osprey Trail runs above the southern shoreline of Gross Reservoir, below the Union Pacific Railroad grade. Beginning at Denver Water Board's Osprey Point Trailhead, it ends at the South Boulder Creek inlet.
Easy to Intermediate
OHV Riding & Camping
OHV Road Riding
All motor vehicles are required to stay on legal routes designated for motorized use. Motor Vehicle Use Maps have been created for every ranger district of the Arapaho and Roosevelt National Forests and Pawnee National Grassland. They are updated annually and are free of charge. Contact your local office for the latest version.