Gross Reservoir

click for larger image

Description (courtesy of Rick Lewis, Denver Water Recreation Site Coordinator)

This hidden Gem lies in the foothills above Boulder, Colorado on the South Boulder Creek Drainage as it cuts its way through fantastic Granite rock outcroppings sculpted by Glaciers. Completed in 1954 as a water storage facility by Denver Water, the reservoir was off limits to paddlers, but the recent approval for a hydroelectric generating license by the Federal Government has opened the water to boating.

Cartop boats, including kayaks, canoes and rowboats, multi-chamber inflatables that can be carried to the water will be allowed. Not permitted will be sailing craft, sailboards, gas or electric motors, belly boats or trailered craft. The paddling season will extend from Memorial Day through September 30.

The setting here at Gross Reservoir is fantastic, dominated by the snow-covered peaks of the Continental Divide, pine-covered slopes are accented by polished Granite outcroppings. With over fourteen miles of shoreline and several long arms the scenery is splendid. At over three hundred feet in depth and an altitude of 7500 feet, Gross is a cold water lake providing excellent trout fishing.

Paddling here can prove challenging, especially when strong winds race downslope off the Divide or thunderstorms form quickly. The glassy surface can be transformed to whitecaps and gusts of wind exceeding 60 miles per hour within minutes. That combined with the very cold water poses risks for the unprepared, always wear your life vest and keep an eye on the weather.

As Recreation Manager I will be on site providing land and water patrols to aid the public and provide information and safety. The Reservoir is open from sunrise to sunset. Gross Reservoir is in a remote location with limited facilities, so come prepared with adequate supplies and clothing to meet the extremes in weather which can range from 85 degree heat to an icy hailstorm.

We here at Denver Water are excited and proud to provide an excellent paddling opportunity and to maintain high safety standards.

Statistics:

Accommodations:

Fees:

Operating Hours:

Directions:

From Denver, take Hwy. 93 north from Golden to Hwy. 72 West, Coal Creek Canyon, climb 7 miles to Crescent Park Rd. on right then 1 mile to Gross Dam Rd. to right, follow signs to Osprey Boat Launch Site.

Contact:

Phone: (303)634-3641

E-Mail: richard.lewis@denverwater.org

Mail: Denver Water 1600 W. 12th Ave. Denver Co. 80204-3412 Mail Code 731

Other phone numbers:
Colorado Division of Wildlife: 303-291-7227
USFS Boulder District: 303-444-6600
Boulder Sheriff: 303-441-3624

Conditions (excerpted from the Gross Reservoir Recreation Management Plan)

Summertime monsoons often bring short mid-afternoon thunder or hailstorms accompanied with high winds. It's not uncommon to have northwest winds reaching 80 mph during the summer. Chinook winds strike between November and March, with gusts exceeding 100 mph. In general, the northern and western aspects adjacent to the reservoir are prone to higher winds.

Summer temperatures are generally mild - days above 95 degrees are rare, humidity is low. Winter temperatures are usually quite cold. The skies are clear about 115 days out of the year and partly cloudy another 130 days. Annual precipitation averages between 20 and 25 inches. Over half of the precipitation falls during the months of April and May. January and February are the driest months. Warm, sunny winter days generally melt snow quickly, although snow can linger in some areas throughout the winter.

The depth of the reservoir results in cool water temperatures throughout the year. Summer water temperatures only reach 18 degrees Celsius (64 F) on the surface. Temperatures cool 2 degrees C (3.6 F) per foot below the surface, down to 6 feet. Below 6 feet, water temperatures are generally in the 6 (42 F) to 8 (46 F) degree C range. According to the U.S. Coast Guard, survival times for victims in water of this temperatures range from 1 to 3 hours depending upon environmental factors and the person's physical condition.

The water levels at Gross Reservoir fluctuate greatly depending upon the time of year and user demand. Rarely does the reservoir maintain a consistent level for any length of time. Water levels can fluctuate as much as 100 feet throughout the year. Typically a low water elevation of 7,180 feet occurs in early May prior to spring run-off. By mid June the reservoir usually reaches its capacity at 7,280 feet. Due to high water demands, Denver Water attempts to keep the reservoir fairly full through June, July and August. However, by July or August customer demands are usually greater than the water supply, so the water level begins to drop. During the winter there is very little fluctuation in water level.

Boating Regulations (excerpted from the Gross Reservoir Recreation Management Plan)

• Non-motorized car-top craft (compiled from the Colorado State Statutes and U.S. Code of Federal Regulations): A recreational vessel of no more than 18 feet in length (excepting tandem, sea/ocean going or touring kayaks up to 24 feet in length), hand propelled, open, monohull, multi-compartment (chamber) inflatable craft; or non-inflatable craft, non-sailboard, subject to U.S. Coast Guard and Colorado safety standards, non-commercial, non-racing that can be lifted onto and taken from the top of a passenger vehicle.

• Gross Reservoir will be open to non-motorized, car-top craft from sunrise to sunset, from Memorial Day weekend through September 30. The reservoir will be opened to kayak take-out (South Boulder Creek to Haul Road) from May 1 to September 30. Emergency closures will be enacted when conditions (ice, water levels, fire, etc.) or Denver Water operations warrant.

• Areas within 100 feet of the reservoir dam and spillway.
• Resource protection areas along Forsythe Canyon and Winiger Gulch Inlet or other locations identified as important resource protection areas.

Maps

Web Resources