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Solano Project
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Solano Project History (67 KB) (pdf)
General Description| Plan| Development| Benefits
General Description

The Solano Project is mostly in Solano County, California, bordering the northeast extremity of San Francisco Bay. Lake Berryessa, the reservoir area behind Monticello Dam is in Napa County. Monticello Dam is the main project feature. Other important features are Putah Diversion Dam, Putah South Canal with a small terminal reservoir, and the necessary wasteways, laterals, and drainage works.

The project was designed to irrigate approximately 96,000 acres of land. In 1992 the total irrigated area was 71,445 acres. The project also furnishes municipal and industrial water to the principal cities of Solano County.

Putah Creek is the source of water for the Solano Project. The drainage basin, comprising 576 square miles above Monticello Dam, lies to the northwest of Solano County on the eastern slope of the Coast Range in Napa and Lake Counties. In late summer the stream has little or no flow; in winter the runoff occurs almost immediately after precipitation due to the absence of snow- pack and appreciable ground-water storage in the upper watershed.  

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Facility Descriptions

Monticello Dam and Lake Berryessa

  • Monticello Dam is located on Putah Creek where the stream crosses the eastern boundary of Napa County. It regulates flows along the lower reaches of Putah Creek and stores surplus water.
  • The dam is a concrete, medium-thick arch structure with a height of 304 feet above the foundation and a crest length of 1,023 feet.
  • Monticello Dam Powerplant was built in 1983. It is at the base of the Monticello Dam, and has 3 generators. The was built under a FERC license and is owned, operated and maintained by Solano Irrigation District.
  • Lake Berryessa has a storage capacity of 1,602,000 acre-feet.
Putah Diversion Dam

  • Putah Diversion Dam is located on Putah Creek approximately 6 miles below Monticello Dam. The principal function of the dam is to divert water into Putah South Canal.
  • The dam is a gated concrete weir structure with an earthfill embankment wing It is 29 feet high, and has a crest length of 910 feet.
  • The dam creates Lake Solano , which is about 1.5 miles long with a capacity of 750 acre-feet. The lake provides recreation in an area already popular for picnicking, boating, swimming, and fishing.
Putah South Canal

  • Putah South Canal starts at Putah Diversion Dam and runs easterly for about 3 miles, then turns southward to follow the edge of the foothills for about 30 miles, ending near Cordelia.
  • The irrigable lands are mainly below the canal and are served by gravity. Irrigable lands above the canal are served by pumping directly from the canal. In addition to providing irrigation water, the canal conveys municipal and industrial water for Vacaville, Fairfield, Suisun, and Vallejo, as well as neighboring military installations.
  • The canal is concrete lined, except for a 1 mile segment beginning at the Green Valley Siphon which is precast reinforced concrete pipe and designated as the Putah South Pipeline. The canal has a diversion capacity of 956 cubic feet per second with a terminal capacity of 116 cubic feet per second.
Terminal Dam

Terminal Dam is a compacted earthfill structure 24 feet high with a crest length of 870 feet. The 119-acre-foot reservoir is located at the end of Putah South Canal and serves as a terminal reservoir for the canal and a forebay from which water is delivered to Vallejo. This reservoir reregulates the terminal flows in the canal and provides a small carryover supply in case of an interruption in flow.

Green Valley Conduit

Green Valley Conduit, a high-pressure concrete pipeline ranging from 18 to 27 inches in diameter, extends 8,400 feet from the Putah South Canal into Green Valley. Leading from this main pipeline, 4,000 feet of subconduits, 12 to 18 inches in diameter, carry water across the valley to the farmlands.

Distribution Systems

Local irrigation districts have the option of building their own distribution systems. Solano Irrigation District, pursuant to Public Law 130, has completed a $15-million distribution drainage system

Operating Agencies

  • Monticello Dam and Lake Berryessa, Putah Diversion Dam, and Putah South Canal headworks are operated and maintained by the Bureau of Reclamation. The Putah South Canal (except headworks) and Green Valley Conduit are operated by the Solano Irrigation District under contract with the Solano County Flood Control and Water Conservation District.  Lake Berryessa website

  • In February 1999, Reclamation and the Solano County Water Agency renewed the contract for the operation and maintenance of Solano Project facilities. The 25 year contract will allow Solano County Water Agency to continue to manage Monticello Dam, Putah Diversion Dam, Lake Solano, and the Putah South Canal. The contract provides for a maximum of 207,350 acre-feet of water annually.

  • In February 1999, Reclamation and the Napa County Flood Control and Water Conservation District renewed a 25-year contract for the delivery of 1,500 acre-feet of Solano Project water for urban use

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After gold was discovered in California, people poured through Solano County as it was on a direct route between San Francisco Bay and the goldfields. Communities grew rapidly, and agriculture expanded. An army post established at Benicia in 1849 was later turned into a major arsenal. In 1856, the U.S. Navy completed a shipbuilding and ship repair base at Mare Island opposite the city of Vallejo.

Following the severe drought in the 1860`s, large-scale grain raising began, followed by a more diversified agriculture based on irrigation and dryland crops. Sheep and cattle raising continued to hold an important place in the economy of the area. Specialty crops came into prominence as demand for agricultural products in the San Francisco Bay area increased and water well capability was developed. With the increased irrigation and the municipal and industrial development of the county, the demand for water resulted in the utilization of all of the more readily available sources of supply.    More...


The problem of obtaining additional water to maintain the existing development became more and more critical. About 1940, the Solano County Board of Supervisors organized the Solano County Water Council to study the areas in greatest need of additional water and to promote general water development in the county.

The Solano Irrigation District was formed February 26, 1948, under the sponsorship of the council to obtain irrigation water from the proposed multiple-purpose Solano Project. To further the general water development, the Solano County Flood Control and Water Conservation District was authorized in 1951 by the State legislature and was activated on November 28, 1951, by the Solano County Board of Supervisors.

The Solano Project was included in the Bureau of Reclamation`s comprehensive plan for development of water resources of the Central Valley Basin, California, as a part of the Yolo-Solano Project which is included in the plan under the West Side Sacramento Valley Area (Senate Document 113, 81st Congress, lst session.

A preliminary draft of the proposed report was prepared early in 1947 outlining the details for a combined Cache and Putah Creek development in accordance with the general Yolo-Solano Project plan referred to in the Central Valley Basin comprehensive report. A project planning report (House Document 65, 81st Cong., 1st sess., March 15, 1948) which outlined the plan of development of only Putah Creek resulted in the authorization of the present project.


The Solano Project was authorized by the Secretary of the Interior on November 11, 1948, under the terms of the Reclamation Project Act of 1939.


Construction of the project began in 1953. Monticello Dam and Putah Diversion Dam were completed in 1957 and Putah South Canal early in 1959.

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Principal crops are corn, wheat, sugar beets, tomatoes, fruits, nuts, and irrigated pasture.

Municipal and Industrial

The project supplies about 32,000 acre-feet annually to the cities of Vallejo, Vacaville, Fairfield, Benicia, and Suisun. Water is furnished through the city systems to Travis Air Force Base, Mare Island Naval Shipyard, and Benicia Arsenal.


Reclamation administers the Lake Berryessa Recreation Area. This has seven developed concession resorts which offer boating, swimming, water skiing, fishing, camping, and picnicking. A two-lane public boat launch ramp and a day-use area are being constructed to augment the facilities offered by the concessionaires. Lake Solano Recreation Area, administered by the Solano County Parks Department, offers camping, picnicking, swimming, boating, and fishing.

Flood Control

It is estimated that flood damages amounting to $5.015 million were prevented by project facilities during 1957-1995.

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Last updated: May 17, 2011