Central Valley (California)

This article is about California's Central Valley. For other uses, see Central Valley.

The Central Valley of California

Part of the Valley as seen from the air

Central California in the summer

The Central Valley is a large, flat valley that dominates the central portion of the U.S. state of California. It is home to many of California's most productive agricultural efforts. The valley stretches approximately 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 Sacramento valley gets about 20 inches of rain annually, but the San Joaquin is very dry, even desert in places. The two halves meet at the shared delta of the Sacramento and San Joaquin Rivers, a large expanse of interconnected canals, streambeds, sloughs, marshes and peat islands. The Central Valley is around 42,000 square miles, making it roughly the same size as the state of Tennessee.

1 Boundaries and population
2 Geology
3 Climate
4 Rivers and delta
5 Economy
6 Agriculture
- 6.1 National Farmworkers Association (NFWA)
7 Social issues
- 7.1 San Joaquin Valley Congestion
8 Highways and infrastructure
9 References
10 External links

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.

Counties commonly associated:

North Sacramento Valley (Shasta, Tehama, Glenn, Butte, Colusa)
Sacramento Metro (Sacramento, El Dorado, Sutter, Yuba, Yolo, Placer)
North San Joaquin (San Joaquin, Stanislaus, Merced)
South San Joaquin (Madera, Fresno, Kings, Tulare, Kern)

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. The largest city is Fresno, followed by the state capital Sacramento.

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)

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.

An example of the extreme differences between the geology of the valley floor and that of the rugged hills of the Coast Ranges (Between Tracy and Patterson, CA:Interstate 5)

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]

Climate

Tule fog in Stanislaus County in December

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 obscure vision. Summer daytime temperatures reach 90 °F (32 °C), and occasional heat waves might bring temperatures exceeding 104 °F (40 °C). Mid Autumn to spring comprises 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 but occasionally to the Sacramento Valley. The northern half of the Central Valley receives greater precipitation than the semidesert southern half.

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 was diverted for agriculture and these lakes are usually dry except during exceptionally large snowmelt floods. Major tributaries include:

Sacramento Valley

San Joaquin Valley

View of the Tuolumne River near Waterford.

These rivers are not tributary to the San Joaquin River:

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. ^[3] Other counties in the valley that face flooding often are Yuba, Stanislaus, and San Joaquin.

Economy

A typical Central Valley scene at ground level

Agriculture remains the primary industry in most of the Central Valley. A notable exception to the predominance of agriculture has been the Sacramento area, 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, Sacramento's 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.

Agriculture

The Central Valley is one of the world's most productive agricultural regions. On less than 1 percent of the total farmland in the United States, the Central Valley produces 8 percent of the nation’s agricultural output by value: 17 billion USD in 2002. Its agricultural productivity relies on irrigation from both surface water diversions and groundwater pumping from wells. About one-sixth of the irrigated land in the U.S. is in the Central Valley.^[4]

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^[5]^[6], 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). 2002 Data Sets

Early farming was concentrated close to the Sacramento-San Joaquin Delta, where the water table was high year round and water transport more readily available, but subsequent irrigation projects have brought many more parts of the valley into productive use. For example, the Central Valley Project was formed in 1935 to redistribute and store water for agricultural and municipal purposes with dams and canals.

National Farmworkers Association (NFWA)

It was in the Central Valley, especially in and around Delano, that farm labor leader Cesar Chavez organized Mexican American grape pickers into a union in the 1960s, the National Farmworkers Association (NFWA), in order to improve their working conditions.

Social issues

San Joaquin Valley Congestion

Since the 1980s, Bakersfield, Fresno, Visalia, Tracy and Modesto have exploded in both area and population, as housing values along the coast increased. Many people from Los Angeles and the San Francisco Bay Area relocated to growing San Joaquin Valley suburbs in search of more affordable housing while retaining employment outside the Valley. This has led to traffic congestion between their Valley residences and their Bay Area employment with accompanying air pollution. Air pollution has become a principal environmental and health concern as long ago as the 1960s, and resulted in the establishment of the California Air Resources Board in 1967. The San Joaquin Valley now has the worst air quality in California, along with the highest asthma rates.

Highways and infrastructure

The valley in late August.

Highways Interstate 5 and State Route 99 run, roughly parallel, north-south through the valley, meeting at its north and south ends. Interstate 80 crosses it northeast-southwest from Rocklin to Vacaville.

In addition to highways, the California Aqueduct follows I-5 from Tracy on southwards to Southern California across the Transverse Ranges and the federal Central Valley Project includes numerous facilities between Shasta Dam and the Grapevine. PG&E's and Western Area Power Administration's system of three 500 kV wires (Path 15 and Path 66) run through the valley. Path 26 also runs in the southernmost part of the San Joaquin Valley.

BNSF (Burlington Northern Santa Fe Railway) and Union Pacific Railroad both have railway lines in the Central Valley. The BNSF Bakersfield Subdivision runs from Bakersfield to Calwa, four miles south of Fresno. From Calwa the BNSF Stockton Subdivision continues to Port Chicago, west of Antioch. The Union Pacific Railroad Martinez Subdivision runs from Port Chicago through Martinez, Richmond and Emeryville to Oakland. The UP's Fresno Subdivision runs from Stockton to Sacramento. Amtrak operates six daily San Joaquins trains over these lines.

References

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