Country United States Type of dam Concrete arch Length 600 ft (180 m) Catchment area 559.4 km² Impound Santa Ynez River | Opening date 1920 Impounds Santa Ynez River Height 59 m Surface area 100 ha | |
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Location Santa Barbara County, California Similar Bradbury Dam, Little Pine Mountain, Twitchell Reservoir, Cold Spring Trail, San Marcos Pass | ||
Gibraltar dam
Gibraltar Dam is located on the Santa Ynez River, in Santa Barbara County, California, in the United States. Forming Gibraltar Reservoir, the dam is owned by the city of Santa Barbara and its primary purpose is municipal water supply. The dam and reservoir provide about 4,600 acre feet (5,700,000 m3) to Santa Barbara each year, supplying 29.4% of the city's water.
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Map of Gibraltar Dam, California, USA
Completed in 1920 just above Devils Canyon, about 5 miles (8.0 km) north of Santa Barbara across the Santa Ynez Mountains, the dam was originally a concrete arch structure about 170 feet (52 m) high, impounding a reservoir with a capacity of 14,500 acre feet (17,900,000 m3). Gibraltar was the first major dam built on the Santa Ynez River. Diversions from the dam greatly supplemented the flow of water through the Mission Tunnel, which was excavated in 1912 to intercept groundwater flow under the Santa Ynez Mountains and channel it south to Santa Barbara. It was not until 1922 when Gibraltar Reservoir first reached capacity.
The reservoir has suffered from heavy sedimentation, and by 1948 was left with just 7,800 acre feet (9,600,000 m3) – 53.8% of the original capacity. To address this problem the dam was raised to a height of 194.5 feet (59.3 m) and a new buttressed spillway section added, again increasing storage capacity to 14,500 acre feet (17,900,000 m3). By the early 21st century, the reservoir's capacity had been reduced to 7,264 acre feet (8,960,000 m3). Attempts have been made to slow the rate of silting, including the construction of the Mono and Agua Caliente debris dams that together have prevented 1,089 acre feet (1,343,000 m3) of sediment from reaching Gibraltar, but the reservoir continues to accumulate sediment at a rate of 150 acre feet (190,000 m3) per year.