Gross Reservoir
Gross Reservoir is a Denver Water lake in the foothills southwest of Boulder, open for fishing, non-motorized paddling, and hiking (no swimming), but a dam-raise project runs through 2027, so the south side is closed and you should check before you go.
Outdoor Boulder › Destinations › Gross Reservoir
Denver Water is raising Gross Dam by 131 feet, a five-year project. The south side of the reservoir is closed to the public, and fishing, boating, hiking, and picnicking have all moved to the free North Shore area. Blasting can close parts of the reservoir on short notice. Check Denver Water's Gross Reservoir recreation page and its MyMap before you drive up, and obey all posted signs and on-site staff.
Gross Reservoir quick facts
| Status / access | Open with major construction limits. Denver Water is raising Gross Dam through 2027. The south side of the reservoir is closed to the public, and recreation has moved to the free North Shore area. Blasting can close parts of the reservoir on short notice, so check Denver Water's recreation page and MyMap before you go. |
|---|---|
| Location | In the foothills southwest of Boulder, in Boulder County, reached by mountain roads. Denver Water owns and manages it. |
| Activities | Fishing, hand-launched non-motorized boating and paddling (canoes, kayaks, paddleboards), hiking, and picnicking, all from the North Shore area during construction. No swimming. No gas motors. |
| Fee / permit | Free. Denver Water lists no fees or reservations required to visit. Boats must be non-motorized car-top craft (no more than 18 feet); every person aboard needs a Coast Guard-approved life jacket, and kids under 13 must wear one. |
| Parking | In designated lots only. Denver Water expanded the free North Shore parking lot to make up for the closed south-side lots. No parking sunset to sunrise. |
| Dogs | Allowed on leash at all times. Pet waste must be picked up, and pets are not allowed in the water. |
| Best season | Late spring through early fall. Human-powered boating runs from the Friday of Memorial Day weekend through Sept. 30; kokanee snagging runs Oct. 1 to Dec. 1. |
Gross Reservoir at a glance
Gross Reservoir is a Denver Water reservoir tucked into the foothills southwest of Boulder, ringed by pine forest and steep canyon walls. It's quieter and wilder than the in-town Boulder Reservoir: a place for casting a line, paddling a kayak or canoe across cold mountain water, and walking the shoreline trails. It's owned and managed by Denver Water, not the City of Boulder, so the rules here are Denver Water's rules.
Is Gross Reservoir open? The dam project explained
Yes, it's open, but read this first. On April 1, 2022, Denver Water began a five-year project to raise Gross Dam by 131 feet, which will nearly triple the reservoir's water-storage capacity. Because of that construction, the south side of the reservoir is closed to the public through 2027, and recreation has shifted to the free North Shore area. The Osprey Point boat launch, the South Boulder Creek Inlet Trailhead, and the South Shore and Windy Point picnic and fishing areas are all closed while the work continues. On top of that, blasting operations can close parts of the reservoir with little notice. Check Denver Water's Gross Reservoir recreation page and its MyMap before you leave home, and once you're there, obey every posted sign and on-site worker.
Fishing at Gross Reservoir
Fishing is open from the North Shore area during construction, under Colorado Parks and Wildlife regulations and with a valid Colorado fishing license. Kokanee snagging has its own season here, running October 1 through December 1, after the summer boating season ends. Keep in mind the south-side fishing spots (South Shore and Windy Point) are closed for the duration of the dam work.
Boating, paddling, and the rules on the water
Gross Reservoir is a non-motorized, car-top boating reservoir: only boats you can lift onto a vehicle roof, no more than 18 feet long, are allowed, which covers canoes, kayaks, and paddleboards but rules out gas motors. The boating season runs from the Friday of Memorial Day weekend through September 30. By Colorado law, every person aboard must have a Coast Guard-approved life jacket, and children under 13 must wear one at all times. During construction, you launch from the North Shore; the south-side Osprey Point launch is closed.
No swimming
Body contact with the water is not permitted at Gross Reservoir. Swimming, wading, and cliff jumping are all prohibited, and pets aren't allowed in the water either. This is a fishing and paddling reservoir at high elevation, not a swim spot. If it's a swim day you're after, Boulder Reservoir has a designated, lifeguarded swim beach in season.
Parking, dogs, and hours
Public access runs sunrise to sunset, and there are no fees or reservations to visit. Park only in the designated lots: Denver Water expanded the free North Shore lot to replace the closed south-side parking, but don't leave a vehicle parked overnight, sunset to sunrise. Dogs are welcome on leash at all times, you pack out pet waste, and pets stay out of the water. Trails here are for foot travel only.
How to get there and best time to go
Gross Reservoir sits in the mountains southwest of Boulder and is reached by winding foothill roads. Because the dam project has closed the south side and routed everyone to the North Shore, the exact way in can change during construction, so lean on Denver Water's recreation page and MyMap for the current route rather than an old set of directions. For paddling and open-water fishing, come between late May and the end of September; for kokanee snagging, October into early December. Give yourself extra time on the narrow mountain roads either way.
Nearby trails and guides
- Boulder Reservoir: the in-town reservoir with a swim beach, if swimming is what you want.
- Nederland: the mountain town up the canyon, a good base for a foothills day.
- All hikes in Boulder: the full hiking hub, sorted by difficulty.
Recommended nearby
A few local spots we'd point a Gross Reservoir day toward.
[CLIENT SLOT: featured paddle or gear rental for a Gross Reservoir day]
[One honest line: where to rent a kayak, canoe, or board before heading up.]
[CLIENT SLOT: featured cafe on the way up from Boulder or Nederland]
[One honest line: coffee or a bite before the mountain drive.]
[CLIENT SLOT: featured restaurant in a foothills gateway town]
[One honest line: a meal after a day on the water.]
Gross Reservoir FAQ
Is Gross Reservoir open right now, and what's happening with the dam?
It's open for recreation, but with real limits from construction. Denver Water is raising Gross Dam by 131 feet to nearly triple the reservoir's storage, a five-year project running through 2027. The south side of the reservoir is closed to the public, so fishing, boating, hiking, and picnicking have all shifted to the free North Shore area. Blasting operations can close parts of the reservoir on short notice. Always check Denver Water's Gross Reservoir recreation page and its MyMap before you drive up.
Can you fish at Gross Reservoir?
Yes. Fishing is open from the North Shore area during the construction project, under Colorado Parks and Wildlife rules and a valid Colorado fishing license. Kokanee snagging has its own season, October 1 through December 1. The south-side fishing spots (South Shore and Windy Point) are closed while the dam work continues.
What are the boating and paddling rules at Gross Reservoir?
Only non-motorized car-top boats are allowed, meaning craft you can lift onto a vehicle roof, no more than 18 feet long, so canoes, kayaks, and paddleboards are in and gas motors are out. The season runs from the Friday of Memorial Day weekend through September 30. Everyone aboard must have a Coast Guard-approved life jacket, and children under 13 have to wear one at all times. Launching happens from the North Shore during construction; the Osprey Point boat launch on the south side is closed.
Can you swim at Gross Reservoir?
No. Body contact with the water is not permitted at Gross Reservoir: swimming, wading, and cliff jumping are all prohibited, and pets aren't allowed in the water either. It's a paddling and fishing reservoir, not a swim beach. If you want to swim near Boulder, Boulder Reservoir has a designated swim beach in season.
How do you get to Gross Reservoir?
Gross Reservoir sits in the foothills southwest of Boulder and is reached by winding mountain roads. Because the dam project has closed the south side and rerouted access to the North Shore, the exact approach can change during construction. Use Denver Water's Gross Reservoir recreation page and its MyMap for the current route in, and give yourself extra time on narrow mountain roads.
Sources
Facts on this page are drawn from these authoritative sources: