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Central California Valley

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NameColor on MapEPA Code‡
Northern Terraces7a
North Valley Alluvium7b
Butte Sink/Sutter and Colusa Basins7c
Southern Hardpan Terraces7d
Sacramento/Feather Riverine Alluvium7e
Sutter Buttes7f
Yolo Alluvial Fans7g
Yolo/American Basin7h
Lodi Alluvium7k
Stockton Basin7l
San Joaquin Basin7m
Manteca/Merced Alluvium7n
Westside Alluvial Fans and Terraces7o
Granitic Alluvial Fans and Terraces7p
Panoche and Cantua Fans and Basins7q
Tulare Basin/Fresno Slough7r
Kern Terraces7s
South Valley Alluvium7t
Antelope Plain7u
Southern Clayey Basins7v

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.


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About the Central California Valley

The Central California Valley is a relatively-flat region extending north-south in California, lying between the coastal mountain ranges as well as mountains inland.

The terrain is mostly flat, with some rolling hills.

The climate here is towards the driest end of Mediterranean California, with long, dry summers and mild winters with some rainfall. The climate is drier than the higher-elevation areas to the east and west, but wetter than deserts farther east and south. The low coastal mountains produce some rain shadow, but less than in areas with higher mountains. Precipitation here increases northward and at higher elevations. Proximity to the ocean moderates temperatures somewhat, but less than in coastal areas; hotter summer temperatures are more common here.

Much of the water in this area originates outside this region and enters by means of rivers and streams. There are both perennial and seasonal streams. The two large rivers, the San Joaquin and Sacramento rivers, are fed by moisture from the higher-elevation Sierra Nevadas to the east. Streams originating in the west are more likely to be seasonal.

Original vegetation cover here was mostly grassland with some savannahs, and woodlands in riparian areas. There were some wetlands. Little of the original cover remains, although there are relatively more of the bottomland woodlands and wetlands intact.

This area is heavily utilized for agriculture, which relies on extensive irrigation. Only about one-fourth of the cropland is not irrigated. Major crops include rice, almonds, apricots, olives, grapes, cotton, various citrus, and assorted vegetables. There is a small amount of dairy farming. Besides agriculture there is a small amount of oil and gas extraction. Although this region is less urbanized than the coastal areas in California, it still has some small to medium cities. The larger cities are Fresno and Sacramento, followed by Bakersfield, Stockton, Modesto, and the smaller cities of Redding and Chico.

Besides habitat loss due mostly to agriculture and to a lesser degree, urban development, this area faces major problems with increased soil salinity due to irrigation water evaporating in the semi-arid climate, and water contamination due to heavy agricultural chemical use.

This region is entirely surrounded by the California Coastal Sage, Chaparral, and Oak Woodlands. Although the rivers here drain into the ocean through the Bay Area, they flow through a narrow waterway surrounded by more rugged, higher-elevation areas that keeps this region more-or-less completely separated from the ocean.

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1. Wiken, E., Griffith, G. "North American Terrestrial Ecoregions - Level III", Commission for Environmental Cooperation, (2011) Web.