Central Valley (California)

As of 2010 some 7.2 million people lived in the Central Valley; it was the fastest growing region in California.[7] It includes 12 Metropolitan Statistical Areas (MSA) and 1 Micropolitan Statistical Area (μSA). Below, they are listed by MSA and μSA population. The largest city is Fresno followed by the state capital Sacramento. The following metropolitan and micropolitan statistical areas listed from largest to smallest:

After English and Spanish, Hmong is the third most commonly spoken language in the Central Valley.[8]

The dominant grass of the valley was Nassella pulchra mixed with other species, but today only 1% of the grassland in the valley is intact. Grassland flowers include California poppy (Eschscholzia californica), lupins, and purple owl's clover (Castilleja exserta), which can still be seen, especially in Antelope Valley in the Tehachapi Mountains. Riverside trees include willows, western sycamore (Platanus racemosa), box elder (Acer negundo), Fremont cottonwood (Populus fremontii), and the endemic valley oak (Quercus lobata).

The Central Valley was once home to large populations of pronghorn antelope (Antilocapra americana), elk including the endemic tule elk subspecies (Cervus elaphus nannodes), mule deer (Odocoileus hemionus), California ground squirrels, gophers, mice, hare, rabbits and kangaroo rats, along with their predators including the San Joaquin kit fox (an endangered subspecies surviving on the San Joaquin Valley's hillsides). The valley's wetlands were an important habitat for wintering waterbirds and migrating birds of other kinds. Reptiles and amphibians of the valley include the endemic San Joaquin coachwhip snake (Masticophis flagellum ruddocki), blunt-nosed leopard lizard (Gambelia sila), Gilbert's skink (Eumeces gilberti) and the western aquatic garter snake (Thamnophis couchii). Endemic invertebrates are present. The Central Valley is home to endemic fish species, including the Sacramento Pikeminnow, Sacramento Perch, Sacramento Blackfish, and Sacramento Splittail.

The Great Valley Grasslands State Park preserves an example of the valley's native grass habitat, while oak savanna habitats survive near Visalia. Areas of wetland and riverside woodland are found in the north especially by the Sacramento River system, including the Nature Conservancy's Cosumnes River Preserve just south of Sacramento, Gray Lodge Wildlife Area, Butte Sink Wildlife Management Area, and other patches in the delta area. Remaining vernal pools include Pixley National Wildlife Refuge between Tulare, California, and Bakersfield and Jepson Prairie Preserve in the delta. Large blocks of desert scrubland exist in the southern San Joaquin Valley and in the Carrizo Plain, just outside the valley, but offering a similar landscape.

The wetlands have been the target of rescue operations to restore areas replaced by agriculture.[12]

These patches of natural habitat are disconnected, which is particularly damaging for wildlife that is used to migrating along the rivers. Agriculture, grazing land, and the draining of lakes and rivers have radically altered the valley habitats. Most of the grassland has been overtaken by new species; most vernal pools have been destroyed, leaving only those on the higher slopes; the marshland has been drained; and the riverbank woodlands have nearly all been affected.

The valley gives its name to Valley fever, which is primarily a disease of the lungs that is common in the southwestern United States and northwestern Mexico. It is caused by the fungus Coccidioides immitis, which grows in soils in areas of low rainfall, high summer temperatures, and moderate winter temperatures. These fungal spores become airborne when the soil is disturbed by winds, construction, or farming. This illness frequently takes weeks or months to resolve. Occasionally Valley Fever is life-threatening or even fatal.

Due to the agricultural industry's large presence in the Valley, pesticide drift and leaching have become concerns. Residents risk contamination when living in proximity of application sites.

Tule fog /ˈtuːliː/ is a thick ground fog that settles along the valley's length. Tule fog forms during the late fall and winter (California's rainy season), after the first significant rainfall. The official season is from November 1 to March 31. This phenomenon is named after the valley's tule grass wetlands (tulares). Auto collisions caused by the tule fog are the leading cause of weather-related casualties in California.

Sierra Nevada runoff provides one of California's largest water resources. The Sacramento River is the second largest river to empty into the Pacific from the contiguous United States, behind only the Columbia River and greater than the Colorado River.[30] Combined with the fertile and expansive area of the Central Valley's floor, the Central Valley is ideal for agriculture.[31]

The Central Valley is one of the United States's most productive growing regions. This is made possible by engineering the watercourses to prevent flooding during the spring snowmelt and drying up in the summer and autumn.[32] Many dams, including Shasta Dam, Oroville Dam, Folsom Dam, New Melones Dam, Don Pedro Dam, Hetch Hetchy Dam, Friant Dam, Pine Flat Dam and Isabella Dam, were constructed on the rivers, with many of them being part of the Central Valley Project.[32] These dams impact physical, economic, cultural, and ecological resources: for example, enabling development of its vast agricultural resources but leading to the loss of the Chinook salmon.[33]

Post-World War II demand for urban development, most notably the San Francisco Bay Area and the Los Angeles/Inland Empire/San Diego, required water resources. Moreover, agriculture in the southern Central Valley required far more water than available locally. The Feather River in the Sacramento Valley was looked to as a water source, leading to the California State Water Project. This transports water to the southern San Joaquin Valley and urban areas south of the Tehachapi Mountains.[34]

Runoff from the Sacramento and San Joaquin Rivers is intercepted in the delta through a series of pumps that divert water into the California Aqueduct, which runs south along the length of the San Joaquin Valley.[35] In parallel, pumps divert water into the Delta–Mendota Canal. The flow of the Sacramento River is further supplemented by a tunnel from the Trinity River (a tributary of the Klamath River, northwest of the Sacramento Valley) near Redding.[36] Cities of the San Francisco Bay Area, also needing water, built aqueducts from the Mokelumne River and Tuolumne River that run east to west across the middle part of the Central Valley.[37][38]

Most valley lowlands are prone to flooding, especially in the old Tulare Lake, Buena Vista Lake, and Kern Lake rivers. The Kings, Kaweah, Tule and Kern rivers originally flowed into these seasonal lakes, which would expand each spring to flood large parts of the southern San Joaquin Valley. Farms, towns and infrastructure in these lakebeds are protected with levee systems, while the risk of floods damaging properties increased greatly.

The Great Flood of 1862 was the valley's worst flood in recorded history, flooding most of the valley and putting some places as much as 20 feet under water.

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 loan for upgrades in Sacramento County.[39] Other counties in the valley that often face flooding are Yuba, Stanislaus, and San Joaquin.

California is a state that has experienced consistent on and off drought for many years. In 2012, there was a major drop in precipitation levels in the Central Valley which has caused an almost constant drought and low-level precipitation levels throughout the Northern California region. As of 2014, the highest levels of precipitation occur during the months of December and January, and because of the climate of the Central Valley, rainfall is the most common form of precipitation.

Although rainfall is very necessary and welcomed in places like California because of its climate and history of drought, the landscape causes rainfall to be harmful as well. There is a very strong positive correlation between rainfall and slow-moving landslides in Northern California, especially in the Central Valley region. Changes in climate and precipitation levels have shown that consistent average rainfall has increased the amount and intensity of landslides within the past 5–6 years. This information was shown in a study that focused on the behavior of these slow-moving landslides and how their nature changed with years of extreme average rainfall versus minimal average rainfall. In 2016, the average annual precipitation levels were lower because of a drought that was coming to an end at that time. The minimal rainfall in that year showed that 119 landslides had been moving. Comparatively, in 2017, there were very extreme levels of precipitation in the Central Valley, which cause 312 landslides to move that year.[40] Slow-moving landslides are impacted even if the intensity of the rainfall is not as severe.

Consistent, moderately intense rainfall increases the saturation of water in the ground. This over saturation is what causes the movement of a slow-moving landslide, rather than the more quick moving and rigorous landslides that also occur in this region of California. Quick-moving landslides are caused by very intense rain, or sometimes earthquakes, that make a greater difference in the land in a shorter amount of time. According to a survey paper written in 1988 about a storm that occurred in 1982 in the Central Valley region, rainstorms that can cause that type of landslide happen about every 5 years. Landslides to higher degrees, such as ones that happened due to the 1982 storm, only occur every 20 to 100+ years. This intense storm in the San Francisco Bay area caused a lot of damage as a result of moving debris and landslides. They caused damage to the land and put people living in these areas that are susceptible to these disasters in great harm. The aftermath of this storm was a costly one, and involved millions of dollars in retributions to restore the land and surrounding areas. It also led people to make greater efforts into planning around the danger of these landslides, as in how to manipulate the land to accommodate the consequences.

That is just one example of the great impact landslides have on the Central Valley region of California. Although these harmful natural disasters are now handled with more knowledge and have been extensively researched, they still often cause harm to many communities.

Out of the past twenty two years California has experienced significant drought conditions for thirteen years. From 2000 to 2018 was the second driest period that California has ever experienced. The driest three-year period ever in California was from 2012 to 2014. Three quarters of the state of California is experiencing extreme drought conditions. There are also multiple types of droughts such as agricultural droughts, meteorological droughts, snow droughts, and hydrological droughts. All of these droughts affect California in different ways. Droughts can damage forests and can cause wildfires. Droughts cause forest to become dry which causes trees to die. Dead trees result in wildfires. The U.S. drought monitor is released every Thursday, showing which parts of the U.S. are in a drought. It started in 2000, and since then the longest duration of a drought in California lasted a total of 376 weeks. It started on December 11, 2011, and ended on March 5, 2019. The most intense period captured on the drought monitor was on the week of July 29, 2014. It showed that 58.41% of California's land was affected by a drought. In 2014–2015, farm-related losses in California totalled $5 billion and 20,000 farmers also lost their jobs.

The Central Valley is one of the world's most productive agricultural regions.[42][5] More than 230 crops are grown there.[5] 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: US$43.5 billion in 2013.[43] California's farms and ranches earned almost $50 billion in 2018.[44] The valley's productivity relies on irrigation from surface water and badly depleted underground aquifers.[45] About one-sixth of the US' irrigated land is in the Central Valley.[46]

Virtually all non-tropical crops are grown in the Central Valley, which is the primary source for produce throughout the United States, including tomatoes, grapes, cotton, apricots, and asparagus.[47] Six thousand almond growers produced more than 600 million pounds (270×10^⁶ kg) in 2000, about 70 percent of the world's supply and nearly 100 percent of domestic production.[48][49]

The US' top four counties in agricultural sales are in the Central Valley (2007 Data).[6][50]

Early farming was concentrated close to the Sacramento-San Joaquin Delta, where the water table was high year round and water transport readily available. Subsequent irrigation projects brought many more parts of the valley into productive use.[51] The even larger California State Water Project was formed in the 1950s and construction continued over the following decades.

In the 1960s, farm labor leaders Cesar Chavez and Dolores Huerta organized Mexican American grape pickers into a union, the National Farmworkers Association (NFWA), in order to improve their working conditions. This organizing took place primarily in the Central Valley because of the extensive agriculture, especially in and around Delano.[52]