The Santa Maria Project, authorized in 1954, is located in California about 150 miles northwest of Los Angeles.
A joint water conservation and flood control project, it consists of the Twitchell Dam where construction began in July 1956 and was completed in October 1958.
The Reservoir was constructed by the Bureau of Reclamation, and a system of river levees was constructed by the Corps of Engineers.
The area was devoted to cattle ranching until the great droughts of 1862-1864 caused a decline in the industry.
In about 1867, settlers arrived and introduced new types of agriculture. Grain production soon developed into an important industry, and fruit and bean crops were started.
By 1900, fruit production began to decline, mostly from the unfavorable climate. Cattle raising continued to be prominent since a major part of the watershed was suitable for grazing.
Irrigation was introduced in 1897 when the Union Sugar Company of San Francisco began growing sugar beets near Betteravia. Development of artesian wells to irrigate the beets offered new opportunities, which led gradually to the establishment of intensive vegetable growing.
In 1898, a company was organized to take water from the Sisquoc River and transport it east by gravity canal to the city of Santa Maria and adjacent lands. Several years later a flood destroyed the dam and headgates, discouraging further efforts in this method of irrigation.
During the 1920s, the crop pattern shifted from beans and grain to vegetables and flower seeds. Irrigated agriculture is now attained by pumping from wells.
Construction of Twitchell Dam was started in July 1956 and completed in October 1958. During the construction period, the name of Vaquero Dam and Reservoir was changed to Twitchell Dam and Reservoir through the efforts of the Santa Maria Valley Water Conservation District and board of supervisors of Santa Barbara County, with the concurrence of the Board of Geographic Names and Reclamation.
As part of the project, the Corps constructed a series of levees and channel improvements along the Santa Maria River to protect the city of Santa Maria and the Santa Maria Valley.
Twitchell Reservoir impounds winter floodwaters for later release down the river channel at a predetermined rate for maximum percolation into the ground-water reservoir. Individual landholders pump water from this reservoir.
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Twitchell Dam is on the Cuyama River about 6 miles upstream from its junction with the Sisquoc River. The multiple-purpose Twitchell Reservoir has a total capacity of 224,300 acre-feet. It stores floodwaters of the Cuyama River, which are released as needed to recharge the ground-water basins to prevent salt water intrusion.
The objective of the project is to release regulated water from storage as quickly as it can be percolated into the Santa Maria Valley ground-water basin. Therefore, Twitchell Reservoir is empty much of the time, and recreation and fishing facilities are not included in the project.
Twitchell Dam is an earthfill structure, has a structural height of 241 feet, of which 216 feet are above streambed, a crest length of 1,804 feet, and contains approximately 5,833,000 cubic yards of material. The dam regulates flows along the lower reaches of the Cuyama River and impounds surplus flows for release in the dry months to help recharge the ground-water reservoir underlying the Santa Maria Valley, thus minimizing water waste.
After construction, Reclamation transferred operations to the Santa Barbara County Water Agency. The Santa Maria Valley Water Conservation District physically operates the reservoir.
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