Windy Gap Dam, located about four miles west of the town of Granby in Grand County, Colorado, impedes the natural flow of the Colorado River. When the dam was completed in 1985, Windy Gap Reservoir flooded a former elk pasture, creating a shallow body of water that has severely impacted a thirty-mile stretch of the Colorado River—from Windy Gap to the confluence with the Blue River. A bypass around Windy Gap Reservoir is needed to repair existing ecological damage and to mitigate the future impacts of diverting more water from the upper Colorado River.
Water projects already remove 65 percent of the upper Colorado River’s native flow. This water is diverted from the West Slope of Colorado across the Continental Divide to the farms and cities of the Front Range. The Windy Gap Firming Project proposed by the Municipal Subdistrict of Northern Colorado Water Conservancy District, combined with Denver Water’s proposed Moffat Project, would divert as much as 80 percent of the upper Colorado River’s native flow, further stressing a river system already dangerously close to collapse.
To analyze the potential impacts of the proposed Windy Gap Firming Project, a technical committee was formed. The committee was headed by Colorado Parks and Wildlife, with participation of the Municipal Subdistrict, Grand County, Colorado River Water Conservation District, Trout Unlimited, and an association of local ranchers and conservationists known as the Upper Colorado River Alliance (UCRA).
The technical committee determined that aquatic habitat downstream of Windy Gap is suboptimal. The Gold Medal trout fishery is in decline, with fish passage blocked by the dam and impeded in places by shallow riffles. During portions of the summer, water temperatures commonly exceed standards set by the Colorado Department of Public Health and Environment, and recent studies indicate that key bio-indicator species have been decimated immediately below Windy Gap.
After Windy Gap Dam was built, 38 percent of native aquatic insect species, including important mayfly and stonefly species, disappeared downstream. In the thirty-mile reach of the Colorado River below the dam, scientists found only a single specimen of sculpin, a native fish. Populations of sculpin and aquatic insects that have disappeared below the dam are healthy above Windy Gap and below the Colorado’s confluence with the Blue River—implicating Windy Gap Dam in the river’s demise.
Windy Gap Dam blocks the passage of gravels and cobbles that create healthy streambed habitat for trout and other aquatic life, but the dam allows the passage of fine sediment. This silt that passes the dam smothers cobbles and gravels, armoring the streambed with hardened layers of sediment. In addition, the shallow reservoir heats up quickly, sending warm, oxygen-poor water downstream of the dam. In the Colorado River below Windy Gap, algae and weeds thrive; trout and the creatures they feed on struggle to survive.
The first step in restoring the health of the upper Colorado River is constructing a bypass channel around Windy Gap Reservoir. The technical committee’s report concluded that a Windy Gap bypass will:
Water projects already remove 65 percent of the upper Colorado River’s native flow. This water is diverted from the West Slope of Colorado across the Continental Divide to the farms and cities of the Front Range. The Windy Gap Firming Project proposed by the Municipal Subdistrict of Northern Colorado Water Conservancy District, combined with Denver Water’s proposed Moffat Project, would divert as much as 80 percent of the upper Colorado River’s native flow, further stressing a river system already dangerously close to collapse.
To analyze the potential impacts of the proposed Windy Gap Firming Project, a technical committee was formed. The committee was headed by Colorado Parks and Wildlife, with participation of the Municipal Subdistrict, Grand County, Colorado River Water Conservation District, Trout Unlimited, and an association of local ranchers and conservationists known as the Upper Colorado River Alliance (UCRA).
The technical committee determined that aquatic habitat downstream of Windy Gap is suboptimal. The Gold Medal trout fishery is in decline, with fish passage blocked by the dam and impeded in places by shallow riffles. During portions of the summer, water temperatures commonly exceed standards set by the Colorado Department of Public Health and Environment, and recent studies indicate that key bio-indicator species have been decimated immediately below Windy Gap.
After Windy Gap Dam was built, 38 percent of native aquatic insect species, including important mayfly and stonefly species, disappeared downstream. In the thirty-mile reach of the Colorado River below the dam, scientists found only a single specimen of sculpin, a native fish. Populations of sculpin and aquatic insects that have disappeared below the dam are healthy above Windy Gap and below the Colorado’s confluence with the Blue River—implicating Windy Gap Dam in the river’s demise.
Windy Gap Dam blocks the passage of gravels and cobbles that create healthy streambed habitat for trout and other aquatic life, but the dam allows the passage of fine sediment. This silt that passes the dam smothers cobbles and gravels, armoring the streambed with hardened layers of sediment. In addition, the shallow reservoir heats up quickly, sending warm, oxygen-poor water downstream of the dam. In the Colorado River below Windy Gap, algae and weeds thrive; trout and the creatures they feed on struggle to survive.
The first step in restoring the health of the upper Colorado River is constructing a bypass channel around Windy Gap Reservoir. The technical committee’s report concluded that a Windy Gap bypass will:
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• Reconnect the river reach below Windy Gap Dam to the river and tributaries upstream, allowing trout and other species to move unimpeded through the free-flowing channel, and expanding habitat for fish and other aquatic life. • Reestablish coarse sediment transfer below the reservoir to scour the riverbed, restore gravel bars, and prevent streambed armoring. • Isolate the reservoir, decreasing water temperature problems and reducing harmful nutrient loads and invasive aquatic vegetation from the reservoir. |
Windy Gap Reservoir
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This bypass project will require two years to complete once final design and permitting is obtained. The project’s estimated cost is $9.6 million. Of this budgeted amount, $4 million has been committed by the Municipal Subdistrict and the Colorado Water Conservation Board, and an additional $385,000 has been raised by stakeholders. For the project to be successful, an additional $5.3 million is needed.
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Critical next steps include:
• Collect additional data and complete engineering studies. • Develop preliminary plans and calculate construction estimates. • Refine cost estimates and secure funding. • Consult with permitting agencies and prepare and submit permit applications. • Prepare final plans, construction drawings, and technical specifications. |
Colorado River Headwaters Byway
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After the Windy Gap bypass is successfully completed, UCRA will continue to advocate for additional river restoration. For example, narrowing the river channel below the dam will help recreate the optimal aquatic habitat that existed before the upper Colorado’s flow was diminished by water diversions.
The Upper Colorado River Alliance will not rest until the river has been restored to health.
The Upper Colorado River Alliance will not rest until the river has been restored to health.
Click here to download Colorado Parks and Wildlife -
2011 Colorado River Study.
Click here to download 2015 Windy Gap Reservoir Modification Study.
Click here to read UCRA's Letter to Legislators.
The map below shows the Upper Colorado River Watershed.
Decreased flow from Windy Gap to Kremmling due to diversions
Colorado River average daily flow at Hot Sulphur Springs (1904-1994)
