Twitchell Dam on the Cuyama River
|Origin||Confluence of Alamo Creek and Dry Canyon Creek|
|Mouth||Santa Maria River|
|Basin countries||United States|
|Length||118 mi (190 km)|
|Source elevation||3,790 ft (1,160 m)|
|Mouth elevation||354 ft (108 m)|
|Avg. discharge||54.3 cu ft/s (1.54 m3/s)|
|Basin area||1,132 sq mi (2,930 km2)|
|Left tributaries||Santa Barbara Creek, Cottonwood Creek, Mustang Creek, Pine Creek|
|Right tributaries||Quatal Creek, Huasna River|
The Cuyama River (// kwee-YAH-mə, // koo-YAH-mə, or // kwee-YAM-ə) is a 118-mile-long (190 km) river in southern San Luis Obispo County, northern Santa Barbara County, and northern Ventura County, in the U.S. state of California. It joins the Sisquoc River forming the Santa Maria River. The river's name comes from an Indian village named for the Chumash word kuyam, meaning "clam" or "freshwater mollusk".
The Cuyama River's source is in the Chumash Wilderness area of the Los Padres National Forest at an altitude above 8,000 feet (2,400 m). The river's upper reaches are in Ventura County, where several tributaries join before the mainstem river exits Los Padres National Forest. After leaving the national forest the river enters Santa Barbara County and flows through the 45-mile-long (72 km) Cuyama Valley, which lies between the Caliente Range and the Sierra Madre Mountains. The river flows past the towns of Cuyama and New Cuyama. Through most of the Cuyama Valley and downriver to its confluence with the Sisquoc River the Cuyama River forms the approximate boundary between Santa Barbara County and San Luis Obispo County.
Downstream from the Cuyama Valley the river enters Twitchell Reservoir, after which it flows another 6 miles (9.7 km) to its confluence with the Sisquoc River. The joined streams are called the Santa Maria River, which flows about 20 miles (32 km) to the Pacific Ocean.
The river's course has been altered over its history by fault displacement.
About 66 miles (106 km) from its source the river reaches Twitchell Reservoir, formed by Twitchell Dam. The dam provides flood control and allows water to be released gradually, so that as much of it as possible will seep into the soil and recharge the groundwater aquifer. The water is released as quickly as possible while still allowing it percolate into the ground, so the reservoir is often empty. The river and the reservoir are usually dry during the summer, when there is little or no rain. However, large flows can occur following winter storms.
- Bright, William; Erwin G. Gudde (1998). 1500 California Place Names: Their Origin and Meaning. University of California Press. p. 46. ISBN 0-520-21271-1.
- U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map, accessed March 15, 2011
- Santa Maria River Tributaries: Cuyama River and Sisquoc River, The Trust for Public Land
- U.S. Geological Survey Geographic Names Information System: Cuyama River
- Floods in Cuyama Valley, California, February 1998 , United States Geological Survey
- Cuyama Valley Photos, United States Geological Survey