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San Juan-Chama Project
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San Juan-Chama Project History (68 KB) (pdf)
General Description| Plan| Development| Benefits


General Description

The San Juan-Chama Project consists of a system of diversion structures and tunnels for transmountain movement of water from the San Juan River Basin to the Rio Grande Basin. Authorized as a participating project of the Colorado River Storage Project, the San Juan-Chama Project provides an average annual diversion of about 110,000 acre-feet of water from the upper tributaries of the San Juan River.  Primary purposes of the San Juan-Chama Project are to furnish a water supply to the middle Rio Grande Valley for municipal, domestic, and industrial uses.  The project is also authorized to provide supplemental irrigation water and incidental recreation and fish and wildlife benefits.

Water is supplied for the following municipal, domestic, and industrial purposes: city of Albuquerque, 48,200 acre-feet; city and county of Santa Fe, 5,605 acre-feet; city of Los Alamos, 1,200 acre-feet; village of Los Lunas, 400 acre-feet; Twining Water and Sanitation District, 15 acre-feet; city of Espanola, 1,000 acre-feet; village of Taos, 400 acre-feet; town of Belen, 500 acre-feet; town of Benalillo, 400 acre-feet; and Jicarilla Apaches, 6,500 acre-feet. Supplemental water is provided for irrigation of 89,711 acres in the Middle Rio Grande Conservancy District, 20,900 acre-feet; and 2,768 acres in the Pojoaque Valley Irrigation District, 1,030 acre-feet. An annual allocation of about 5,000 acre-feet is available for the Corps of Engineer's Cochiti Reservoir for fish and wildlife and recreation purposes to maintain a minimum pool of 1,200 surface acres. There is an allocated but as yet uncontracted supply of 4,990 acre-feet.

Reclamation has focused its planning efforts in the San Juan River Unit by preparing a planning report/environmental assessment for the Hammond Project. A final report on the Hammond Salinity Control Project was published in December 1994.

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Collection System 

The project takes water from the Navajo, Little Navajo, and Blanco Rivers, which are upper tributaries of the San Juan River, for use in the Rio Grande basin.  Blanco Diversion Dam on the Rio Blanco diverts water to the Blanco Feeder Conduit, a closed conduit of 520 cubic feet per second capacity which conveys the water to Blanco Tunnel. Blanco Tunnel is a concrete-lined structure with 520 cubic feet per second capacity to carry water 8.64 miles fromthe Rio Blanco to a point near the Little Navajo River. Little Oso Siphon, a concrete siphon with a capacity of 520 cubic feet per second, carries water under Little Navajo River to Oso Tunnel. Little Oso Diversion Dam on the Little Navajo River upstream from the Little Oso Siphon diverts water from the Little Navajo River through the Little Oso Feeder Conduit, a closed conduit with a capacity of 150 cubic feet per second, to the Oso Tunnel.

The Oso Tunnel is a concrete-lined structure with a capacity of 650 cubic feet per second and a length of 5.05 miles. It carries water from Little Navajo River to a point near the Navajo River. The 650-cubic-foot-per-second Oso Siphon conveys water under the Navajo River where Oso Diversion Dam diverts water to the Oso Feeder Conduit. This conduit, with a capacity of 650 cubic feet per second, extends from Oso Diversion Dam to Azotea Tunnel.

The 12.8-mile-long concrete-lined Azotea Tunnel, with a capacity of 950 cubic feet per second, conveys water from Navajo River to Azotea Creek in the Rio Grande Basin. These imported waters flow down Azotea and Willow Creeks 11.78 river miles to Heron Reservoir.

Heron Dam

The regulating and storage reservoir is formed by Heron Dam on Willow Creek just above the point where Willow Creek enters the Rio Chama. The dam is an earthfill structure 269 feet high which forms a reservoir with a capacity of 401,320 acre-feet and a surface area of 5,950 acres. The spillway has a capacity of 660 cubic feet per second, and the outlet works has a capacity of 4,160 cubic feet per second  Storage from Heron Dam provides water for municipal, domestic, industrial, recreation, and fish and wildlife purposes and also provides supplemental water for irrigation.

Heron Reservoir is operated by Reclamation in compliance with applicable federal and state laws, including the San Juan-Chama Project authorization and the Rio Grande and Colorado compacts.  Under these laws, only imported San Juan-Chama Project water may be stored in Heron Reservoir; there are no provisions for storing native Rio Grande water.  Thus, all native Rio Grande water is released to the river below Heron Dam.

The outlet works for El Vado Dam, located 6 miles downstream of Heron Dam,  were enlarged in 1965-1966 so that San Juan-Chama Project releases from Heron Reservoir could be passed unimpeded through El Vado Reservoir. The capacity of the outlet works is 6,600 cubic feet per second.

Pojoaque Tributary Unit

The Pojoaque Tributary Unit, a component of the project authorized under PL 87-483, provides 1,030 acre-feet of supplemental water for approximately 2,800 acres of irrigated land.  Indian lands comprise about 34 percent of this total irrigated acreage.  Nambe Falls Dam and Reservoir provide storage for this unit.

Nambe Falls Dam

Pojoaque Irrigation Unit, made up of Nambe Falls Dam and storage reservoir, provides supplemental irrigation water for about 2,800 acres in the Pojoaque Valley.  It serves the Pojoaque Valley Irrigation District and Indian pueblos of San Ildefonso, Nambe, and Pojoaque. The dam is a concrete and earth embankment structure 150 feet high which forms a reservoir with a capacity of 2,023 acre-feet.

Diversion Dams

Blanco Diversion Dam
Little Oso Diversion Dam
Oso Diversion Dam

Operating agencies

Reclamation operates Heron Dam as described above in the Heron Dam section.  Operation and maintenance of Nambe Falls Dam and Reservoir is performed by the Pojoaque Valley Irrigation District, but Reclamation maintains oversight responsibilities.

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Through prehistoric Indian activity at Sandia Cave northeast of Albuquerque, pueblo communities established before 600 A.D., Spanish settlement in 1598, and the homesteading development in the late 1840's, the Rio Grande Valley has accommodated and nurtured man. The waters provided by the San Juan-Chama Project flow to the descendants of these cultures, helping to continue the varied lifestyles represented.

Along the upper San Juan River drainage, the project's water source, a similar settlement pattern, with variations, developed. A desert culture base underlay the Anasazi development, but climatic conditions and the influx of the ancestors of the modern Navajo and Ute Indians limited pueblo development. Spanish exploration in the area is known as early as the search for gold in 1765, with settlement later in the century. Reports by trappers in the 1820's brought prospectors and miners, and eventually permanent settlers.


Studies of the possibility of diverting San Juan River Basin waters into the Rio Chama, a tributary of the Rio Grande, began immediately following the first World War, but surveys of the features involved began in 1933, with the Bunger Survey. This survey was resumed in 1936, as a part of the Rio Grande Joint Investigations, to determine the need for the project.

The investigations established the basis for recognizing, in the Rio Grande Compact, the possibility of a transmountain diversion to bring water from the San Juan River into the Rio Grande Basin. The Colorado River Basin report, issued by the Bureau of Reclamation in 1946, established the quantity of water that was considered for the transmountain diversion during the negotiation of the Upper Colorado River Basin Compact.

In 1950, in the interest of coordination, the Secretary of the Interior appointed a committee known as the San Juan River Technical Committee. A summary report was prepared in May 1950, and the committee presented progress reports in 1951 and 1952.

Field work on the San Juan-Chama Project was resumed at the beginning of 1951, and interim reports were prepared by the Bureau of Reclamation through 1955, when a feasibility study was prepared. This study was supplemented in 1957 and was followed by authorization of the project. Volume I of the definite plan report, covering the diversion and regulation elements of this project, was approved on August 10, 1964.


The San Juan-Chama Project was authorized by Congress in 1962 through PL 87-483, which amended the Colorado River Storage Act of 1956 (PL 84-485) to allow diversion of Colorado River basin water into the Rio Grande basin of New Mexico.  The original planning projections were for an ultimate diversion of 235,000 acre-feet per year, with an initial phase development for an average annual diversion of up to 110,000 acre-feet.  Only the initial phase was authorized and subsequently constructed by Reclamation.


Construction of Azotea Tunnel began on April 22, 1964, and was completed on November 11, 1970. Other construction included Blanco Diversion Dam and Tunnel, awarded on May 11, 1965, and completed May 22, 1969; Little Oso and Oso Diversion Dams and Oso Tunnel awarded on February 1, 1966, and completed on November 11, 1970; Azotea Creek Channelization, awarded on August 14, 1967, and completed on December 6, 1968; Willow Creek Channelization, awarded on March 20, 1969, and completed on August 2, 1970; Heron Dam and relocation of State Highway 95, awarded August 8, 1967, and completed June 9, 1971.

Construction also included the enlargement of the outlet of existing El Vado Dam so Heron Reservoir releases could be bypassed through El Vado Reservoir. The contract was awarded on July 22, 1965, and completed December 29, 1966.

Construction of Nambe Falls Dam, part of the Pojoaque tributary irrigation unit, was awarded on June 13, 1974, and completed June 28, 1976.

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Municipal, Domestic and Industrial Supplies Acre-feet Provided
City of Albuquerque 48,200
Jicarilla Apache 6,500
City and County of Santa Fe 5,605
County of Los Alamos 1,200
City of Espanola 1,000
Town of Belen 500
Village of Los Lunas 400
Village of Taos 400
Town of Bernalillo 400
Town of Red River 60
Twining Water & Sanitation District 15
Irrigation Supplies 
Middle Rio Grande Conservancy District 20,900
Pojoaque Valley Irrigation District 1,030
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Fish and Wildlife and Recreation

The project provides a supplemental water supply for various communities, supplemental supply for irrigation, and substantial fish and wildlife and recreation benefits have been created at El Vado Reservoir, Heron Reservoir, Nambe Falls Reservoir, and Elephant Butte Reservoir and at Cochiti Reservoir an associated Corps of Engineers facility.

Last updated: May 17, 2011