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General Description| Plan| Development| Benefits


General Description

The Collbran Project, in west-central Colorado, has developed, for multiple purposes, a major part of the unused water in Plateau Creek and its principal tributaries. Supplemental irrigation service is furnished to approximately 21,000 acres. Electrical energy is generated for use in west-central Colorado. Major project works include Vega Dam and Reservoir, two powerplants, two major diversion dams, about 37 miles of canal, and about 18 miles of pipeline and penstock. East Fork Diversion Dam and Feeder Canal, along with the Bonham-Cottonwood Collection System, carry water to Bonham Reservoir, which supplies water to operate the Molina powerplants. The project also rehabilitated and modified the operation of 17 small privately owned storage reservoirs on the Grand Mesa situated in the Cottonwood Creek and Big Creek watersheds. Two of the reservoirs, Blackman and Currier, were subsequently breached. Fifteen reservoirs now provide water for power generation through the exchange of storage water on Grand Mesa for irrigation water from Vega Reservoir.

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Vega Dam was constructed across the channel of Plateau Creek, forming a reservoir with a total capacity of 33,800 acre-feet and an active capacity 32,980 acre-feet. The reservoir store surplus flows of Plateau, Leon, and Park Creeks. The Leon and Park Creek flows are brought to the reservoir through the 2.7-mile-long Leon-Park Feeder Canal. The Southside Canal extends west from Vega Reservoir 32.8 miles to a terminal drop structure on Mesa Creek about 3.25 miles south of the town of Mesa, Colorado. The canal crosses several north-flowing tributaries of Plateau Creek to which releases are made but does not intercept their flow. Most project water from Plateau, Leon, and Park Creeks, including both storage and direct flow, is released from Vega Reservoir and delivered by the Southside Canal. Some water is released at Vega Reservoir into Plateau Creek for diversion by downstream ditches.

Water used for the generation of power is collected from the Big and Cottonwood Creek drainage areas at elevations of more than 9800 feet above sea level. These waters are stored by the 17 previously existing reservoirs on Grand Mesa or collected by the Bonham-Cotonwood pipeline and piped down the mesa slopes through two hydroelectric powerplants and released into Plateau Creek. The two powerplants have a combined capacity of 13,500 kilowatts.

Facility Descriptions

Vega Dam and Reservoir

Vega Dam is near the Grand Mesa in western Colorado, about 10 miles east of the town of Collbran. The dam is a zoned, rolled earth and rockfill structure with a maximum height above foundation of 162 feet, a crest length of 2,100 feet, and a volume of 981,825 cubic yards of material. The outlet works is near the left abutment and consists of an intake structure, 5-foot diameter concrete pressure conduit, concrete gate chamber for a 3.5-foot-square high-pressure emergency gate, 8-foot-diameter concrete horseshoe conduit containing a 51-inch-diameter steel pipe, control house containing two 2.25-foot-square high-pressure control gates, concrete stilling basin, and an outlet channel which discharges into the Southside Canal.

Vega Reservoir has a surface area of about 900 acres, with a capacity of 33,800 acre-feet, and a shoreline of approximately 7 miles.

Leon-Park Feeder Canal

The Leon-Park Feeder Canal conveys water from Leon and Park Creeks to Vega Reservoir. The canal begins at the Leon Creek Diversion Dam on Leon Creek and extends about 2 miles to a siphon under Park Creek. Water diverted from Park Creek by the Park Creek Diversion Dam, about 1,000 feet above the siphon outlet, then combines with the Leon Creek diversions, and flows about 0.7 mile to Vega Reservoir.

Southside Canal

The Southside Canal heads at the outlet works of Vega Reservoir and conveys irrigation water westward from the reservoir to project lands. The 32.8-mile-long canal has an initial capacity of 240 cubic feet per second and a terminal capacity of 50 cubic feet per second at Mesa Creek. Thirteen siphons carry the canal across major streams of the area, and seven concrete chutes are used to drop the canal in elevation. A 2,389-foot-long, 6.25-foot-diameter horseshoe tunnel carries the canal water through a ridge on the divide between Salt and Tea Creeks, eliminating canal construction through a badly eroded area.

Bonham Dam and Reservoir

Bonham Dam is located on Grand Mesa, 12 miles south of Collbran. The dam consists of two embankments separated by a knoll. Reclamation rehabilitation in 1962 added earth and rockfill material to the crest and downhill face of the dam, raising the crest 2 feet. This allows a 4-foot freeboard above the normal reservoir water surface. The completed structure is 1,360 feet in length, has a 25-foot-wide crest, and is 38 feet high. The spillway was rehabilitated and now has a capacity of 1,830 cubic feet per second.

Bonham Reservoir, in operation for more than 70 years, has a total capacity of 1,220 acre-feet. The Bonham power water outlet works consists of a 750-foot inlet channel, intake structure to a 36-inch-inside-diameter, steel-lined conduit, and a gate structure with a 36-inch cast-iron slide gate. The 36-inch steel-lined conduit is reduced to a 33-inch-inside-diameter, steel-lined pipe where it becomes the Bonham pipeline at a manhole structure about 100 feet downstream from the gate structure.

East Fork Diversion Dam and Feeder Canal

The East Fork Diversion Dam and Feeder Canal divert the natural flow of the East Fork of Big Creek and releases from Atkinson and Lambert Reservoirs to Bonham Reservoir. The East Fork Diversion Dam is a concrete ogee, gravity-type structure with overflow section and wingwalls of concrete and embankments of compacted earth at each end of the dam. The concrete headworks are controlled by one 3-foot-square slide gate, feeding the canal. The sluiceway is controlled by a 6-foot-square radial gate.

The East Fork Feeder Canal, with a capacity of 35 cubic feet per second, has a length of 1.3 miles. The first mile conveys water from East Fork to Atkinson Creek; the water is then carried by the stream channel for approximately 600 feet, where it is redirected into the feeder canal. The water is then carried by the feeder canal to its terminal drop structure, located at the east end of Bonham Dam, for storage in Bonham Reservoir.

Bonham-Cottonwood Pipeline

The Bonham-Cottonwood pipeline collects water from small streams and reservoirs in the watersheds of Big and Cottonwood Creeks and delivers it to the Upper Molina penstock. The pipeline, consisting of two main branches and several smaller feeder lines, delivers a maximum of 50 cubic feet per second to the Upper Molina penstock.

The Bonham section, 5.4 miles long, extends from Bonham Reservoir to the Upper Molina penstock. It consists of a 36-inch pretensioned concrete pipe with a maximum capacity of 50 cubic feet per second. A feeder line delivers water into this section from an unnamed stream inlet west of Bonham Reservoir.

Extending about 4 miles from Cottonwood Reservoir No. 1 to the Upper Molina penstock is the Cottonwood section of the pipeline. It receives water directly from Cottonwood No. 1, DeCamp, and Big Meadows Reservoirs, as well as from three uncontrolled stream inlets which also take releases from six other reservoirs. This section has a maximum capacity of 28.3 cubic feet per second. The pipe ranges from a minimum of 18-inch inside diameter to a 36-inch maximum.

Grand Mesa Collection System Features

Atkinson Dam
Big Creek Dam
Big Meadows Dam
Bonham Dam
Cottonwood No. 1 Dam
Cottonwood No. 2 Dam
Cottonwood No. 4 Dam
Cottonwood No. 5 Dam
DeCamp Dam
Forty Acre Lake Dam
Kitson Dam
Lambert Dam
Little Meadows Dam
Neversweat Dam
Silver Lake Dam 

Diversion Facilities

East Fork Diversion Dam
Leon Creek Divsersion Dam
Park Creek Diversion Dam

Power Sources

The Upper Molina penstock extends from the junction of the Bonham and Cottonwood pipelines, then continues approximately 2.4 miles down the north slope of Grand Mesa, and terminates at the Upper Molina Powerplant. The penstock consists of welded steel pipe with a capacity of 50 cubic feet per second, ranging in diameter from 36 inches at the junction with the Bonham-Cottonwood collection system to 33 inches in the lower section.

Bonham Reservoir acts as a forebay for the Upper Molina Powerplant, which controls releases up to a maximum capacity of 50 cubic feet per second from the reservoir. Upper Molina Powerplant consists of a single 8,640-kilowatt generating unit constructed on the east bank of Cottonwood Creek, operating at a design head of 2,490 feet with power tailwater discharges up to 50 cubic feet per second into the Molina Equalizing Reservoir.

The Lower Molina penstock extends 4.7 miles from the Molina Equalizing Reservoir to the Lower Molina Powerplant. The penstock consists of steel pipe ranging in diameter from 36 inches at its upper end to 30 inches at the lower section. It has a maximum capacity of 50 cubic feet per second.

The single-unit Lower Molina Powerplant is located on the south bank of Plateau Creek near Molina, Colorado. It has an installed capacity of 4,860 kilowatts at a design head of 1,400 feet and a maximum water discharge of 50 cubic feet per second. Both plants are operated in conjunction with Colorado River Storage Project power operations.

Power generated at the powerplants is transformed to a transmission voltage of 115 kilovolts at two substations constructed adjacent to the plants. A 5.5-mile transmission line leads from the substation at the Upper Molina Powerplant, delivers energy produced at the plant to the substation at Lower Molina Powerplant, and then connects to the Tri-State Generation and Transmission system for distribution.

Operating Agencies

The Bureau of Reclamation operates the 15 small Grand Mesa reservoirs, Bonham-Cottonwood pipeline, and the Molina Powerplants and penstocks. Since January 1, 1963, the Collbran Conservancy District has operated Vega Dam and Reservoir, the Leon-Park Diversion Dams and Feeder Canal, and the Southside Canal.

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Numerous small private reservoirs were constructed on Grand Mesa to regulate the runoff of Big, Cottonwood, Mesa, and Bull Creeks. These reservoirs are filled with water during the spring runoff, and the stored water is released on demand of the irrigators in Plateau Valley to supplement the low natural streamflows of late summer. Individual water users or small cooperative associations built most of the reservoirs in basins formed by glacial action.

Privately constructed canals and ditches are also operated intermittently throughout the winter months to supply the communities of Collbran and Mesa and the rural area with domestic and stock water.


Investigations were initiated in 1937 to study the needs of the area for proper development of its abundant resources. Included in the plans for developing the necessary supplemental irrigation water for arable lands was the plan to generate additional power for industrial and domestic use.


Authorized July 3, 1952, by act of Congress (Public Law 445, 82nd Congress, 2nd Session). Primary purposes of the project include agricultural, municipal and industrial, and recreation.


The contract for construction of Vega Dam was awarded in 1957 and the dam was completed in 1960. Other construction and rehabilitation contracts were awarded beginning in 1959. All work was completed in 1962.

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Vega Dam and the Southside Canal provide water for the supplemental irrigation service to 22,210 acres of project lands. Principal crops are alfalfa, hay, small grains, and pasture. These crops are used primarily to support beef cattle and sheep production.

Recreation, Fish & Wildlife

Construction and operation of the reservoirs have improved lake fisheries and wildlife values. Some minor damage to stream fisheries and wildlife values resulted from the reduction of flows downstream from storage or diversion structures and from inundation of stream habitat in the Vega Reservoir area. However, the net effect is an increase in fish and wildlife. The Vega State Recreation Area is administered by the Colorado Division of Parks and Outdoor Recreation. Fishing, camping, boating, picnicking, and sightseeing are the principal activities. In 1996, visitation totaled 91,235. The State of Colorado and Reclamation are upgrading the facilities at the Vega State Recreation Area to include accessible features for peole with disabilities. Completion of these upgrades is planned for the summer of 2000.

Hydroelectric Power

Two hydroelectric powerplants are in operation, with a combined installed capacity of 13,500 kilowatts.

Flood Control

Although there is no specific reservoir capacity assigned for flood control, the Collbran Project has provided an accumulated $63,000 in flood control benefits from 1950 to 1999.

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Last updated: Apr 18, 2011