Central Valley (California)
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The Central Valley is a large, flat valley that dominates the central portion of the U.S. state of California, United States. It is home to many of California's most productive agricultural efforts. The valley stretches nearly 400 miles (600 km) from north to south. Its northern half is referred to as the Sacramento Valley, and its southern half as the San Joaquin Valley. The two halves are joined by the shared delta of the Sacramento and San Joaquin Rivers, a large expanse of interconnected canals, streambeds, sloughs, marshes and peat islands.
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[edit] Boundaries and population
Bounded by the Cascade Range to the north, the Sierra Nevada to the east, the Tehachapi Mountains to the south, and the Coast Ranges and San Francisco Bay to the west, the valley is a vast agricultural region drained by the Sacramento and San Joaquin rivers.
These counties are commonly associated with the Central Valley:
- North San Joaquin (San Joaquin, Stanislaus, Merced)
About 6.5 million people live in the Central Valley today and it is the fastest growing region in California. There are 10 Metropolitan Statistical Areas (MSA) in the central valley. Below, they are listed by (MSA) population.
- Sacramento Metropolitan Area (2,042,283)
- Fresno Metropolitan Area (1,002,284)
- Bakersfield Metropolitan Area (756,825)
- Stockton Metropolitan Area (664,116)
- Modesto Metropolitan (505,505)
- Visalia Metropolitan Area (410,874)
- Merced Metropolitan Area (241,706)
- Chico Metropolitan Area (214,185)
- Redding Metropolitan Area (179,904)
- Yuba City Metropolitan Area (165,080)
[edit] Geology
The flatness of the valley floor contrasts with the rugged hills or gentle mountains that are typical of most of California's terrain. The valley is thought to have originated below sea level as an offshore area depressed by subduction of the Farallon Plate into a trench further offshore. The San Joaquin Fault is a notable seismic feature of the Central Valley.
It was later enclosed by the uplift of the Coast Ranges, with its original outlet into Monterey Bay. Faulting moved the Coast Ranges, and a new outlet developed near what is now San Francisco Bay. Over the millennia, the valley was filled by the sediments of these same ranges, as well as the rising Sierra Nevada to the east; that filling eventually created an extraordinary flatness just barely above sea level; before California's massive flood control and aqueduct system was built, the annual snow melt turned much of the valley into an inland lake.
The one notable exception to the flat valley floor is Sutter Buttes, the remnants of an extinct volcano just to the northwest of Yuba City which is 44 miles north of Sacramento.
Another significant geologic feature of the Central Valley lies hidden beneath the delta. The Stockton Arch is an upwarping of the crust beneath the valley sediments which extends southwest to northeast across the valley.
Physiographically, the Central Valley lies within the California Trough physiographic section, which is part of the larger Pacific Border province, which in turn is part of the Pacific Mountain System.[1][2]
[edit] Climate
The northern Central Valley has a hot Mediterranean climate (Koppen climate classification Csa); the more southerly parts in rainshadow zones are dry enough to be Mediterranean steppe (BShs, as around Fresno) or even low-latitude desert (BWh, as in Bakersfield). It is hot and dry during the summer and cool and damp in winter, when frequent ground fog known regionally as "tule fog" can be impenetrable. Summer temperatures reach into the mid to upper 90s°F (30s°C), and occasional heat waves might bring temperatures well over 100°F (38°C), with some locations topping out at around 115°F (46°C). Winter and spring comprise the rainy season — although during the late summer, southeasterly winds aloft can bring thunderstorms of tropical origin, mainly in the southern half of the San Joaquin Valley. The northern half of the Central Valley (the Sacramento Valley) has more precipitation than the dryer southern San Joaquin Valley.
[edit] Rivers and delta
The Sacramento and San Joaquin Rivers flow through the northern and southern halves of the valley, respectively. The two rivers join to form the San Joaquin-Sacramento River Delta, an unusual inverted river delta, behind the Carquinez Strait. Streams in the southern third of the San Joaquin Valley terminate in Tulare Lake and Buena Vista Lake. By the mid twentieth century, however, nearly all of the water in these streams wa diverted for agriculture and these lakes are usually dry except during exceptionally large snowmelt floods. Major tributaries include:
[edit] Sacramento Valley
[edit] San Joaquin Valley
- San Joaquin River
- Cosumnes River
- Mokelumne River
- Calaveras River
- Stanislaus River
- Tuolumne River
- Merced River
- Chowchilla River
- Fresno River
These rivers are not tributary to the San Joaquin River:
- Kings River
- Kaweah River
- Kern River
[edit] Flooding
Most lowlands of the Central Valley are prone to flooding. Major public works projects beginning in the 1930s sought to reduce the amount of snowmelt flooding by the building of large dams. In 2003 it was determined that Sacramento had both the least protection against and nearly the highest risk of flooding. Congress then granted a $220 million for upgrades in Sacramento County. [1] Other counties in the valley that face flooding often are Yuba, Stanislaus, and San Joaquin.
[edit] Economy
Agriculture remains the primary industry in the Central Valley. The Central Valley is one of the most productive agricultural regions in the world. It is commonly referred to as the "fruit basket of the world." A notable exception has been the Sacramento region, where the large and stable workforce of government employees helped steer the economy away from agriculture. Despite state hiring cutbacks and the closure of several military bases, the Sacramento economy has continued to expand and diversify and now more closely resembles that of the nearby San Francisco Bay Area. Primary sources of population growth are people migrating from the San Francisco Bay Area seeking lower housing costs, as well as immigration from Asia, Central America, Mexico, Ukraine and the rest of the former Soviet Union.
[edit] Agriculture
Virtually all non-tropical crops are grown in the Central Valley, which is the primary source for a number of food products throughout the United States, including tomatoes, almonds[3], grapes, cotton, apricots, and asparagus. Four of the top five counties in agricultural sales in the U.S. are in the Central Valley (2002 Data). They are Fresno County (#1 with $2.759 billion in sales), Tulare County (#2 with $2.338 billion), Kern County (#4 with $2.058), and Merced County (#5 with $2.058 billion). [4]
