The South Coast hydrologic region of California is one of the 10 major hydrologic regions of the state as identified by the California Department of Water Resources. The South Coast hydrologic region has a surface area of about , and includes all of Orange County, major portions of Los Angeles, Riverside, San Bernardino, San Diego, and Ventura counties, and a small portion of Santa Barbara County. The state-defined South Coast hydrologic region is roughly equivalent to the federally defined Southern California Coastal water resource subregion. The South Coast hydrologic region has 78 state-recognized alluvial groundwater basins and subbasins.
Significant geographic features include the Transverse Ranges and the Peninsular Ranges. Major rivers in the region include the Los Angeles River, San Gabriel River, San Diego River, San Luis Rey River, Santa Ana River, Santa Clara River, Santa Margarita River, and Ventura River.
The climate in the region ranges from Mediterranean to subtropical steppe. Annual precipitation in the region ranges from more than in the mountains to less than in some valleys, with an overall average of for the region.
Alluvial groundwater basins in the South Coast hydrologic region The South Coast hydrologic region overlies an aquifer with a number of identified alluvial groundwater basins and subbasins. An alluvial groundwater basin is essentially the top level of an aquifer, above less-permeable rocks below, such as limestone and shale. Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvial groundwater basin State basin code Basin priority Surface area (acres) Well yield (gpm) Maximum Well yield (gpm) Average Notes Upper Ojai Valley groundwater basin4-13,80020050Ojai Valley groundwater basin4-2Medium6,830600383Ventura River Valley groundwater Basin4-312,710Santa Clara River Valley groundwater basin4-4HighActon Valley groundwater basin4-58,2701,000140Pleasant Valley groundwater basin4-6Medium21,6001,000Arroyo Santa Rosa Valley groundwater basin4-7Medium3,7401,200950Las Posas Valley groundwater basin4-8Medium42,200750Simi Valley groundwater basin4-912,100394Conejo Valley groundwater basin4-1028,9001,000100Coastal Plain of Los Angeles groundwater basin4-11HighSan Fernando Valley groundwater basin4-12High145,0003,2401,220San Gabriel Valley groundwater basin4-13Medium154,0004,8501,000Tierra Rejada groundwater basin4-154,3901,200172Hidden Valley groundwater basin4-162,210Lockwood Valley groundwater basin4-1721,80035025Hungry Valley groundwater basin4-185,31028Thousand Oaks Area groundwater basin4-193,11039Russell Valley groundwater basin4-203,10025Malibu Valley groundwater basin4-226131,0601,030Raymond groundwater basin4-23High26,2003,6201,880Coastal Plain of Orange County groundwater basin8-2High224,0004,5002,500Upper Santa Ana River valley 8-3Elsinore groundwater basin8-425,7005,400San Jacinto groundwater basin8-5High188,000Hemet Lake Valley groundwater basin8-616,700820196Big Meadows Valley groundwater basin8-714,20012034Seven Oaks Valley groundwater basin8-84,080Bear Valley groundwater basin8-9Medium19,6001,00500San Juan Valley groundwater basin9-1Medium16,7001,000San Mateo Valley groundwater basin9-22,990San Onofre Valley groundwater basin9-31,250Santa Margarita Valley groundwater basin9-4Medium6261,980Temecula Valley groundwater basin9-5High87,8001,750Cahuilla Valley groundwater basin9-6Medium18,200500San Luis Rey groundwater basin9-7Medium37,0002,000500Warner Valley groundwater basin9-824,0001,800800Escondido Valley groundwater basin9-92,89019050San Pasqual Valley groundwater basin9-10Medium4,5401,7001,000Santa Maria Valley groundwater basin 9-1112,30050036San Dieguito Creek groundwater basin9-123,5601,800700Poway Valley groundwater basin9-132,470200100Mission Valley groundwater basin9-147,3501,000San Diego River Valley groundwater basin9-15Medium9,8902,000El Cajon Valley groundwater basin9-167,16030050Sweetwater Valley groundwater basin9-175,2901,500300Otay Valley groundwater basin9-186,8301,000185Tijuana groundwater basin9-197,4102,000350Batiquitos Lagoon Valley groundwater basin9-22741Batiquitos LagoonSan Elijo Valley groundwater basin9-238831,800Pamo Valley groundwater basin9-241,500Ranchita Town Area groundwater basin9-253,13012522Cottonwood Valley groundwater basin9-263,850Campo Valley groundwater basin9-273,550<40Potrero Valley groundwater basin9-282,020San Marcos Area groundwater basin9-322,13060
See also Southern California Coastal water resource subregion
References
External links California groundwater basis lookup