Sacramento-San Joaquin River Delta

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The Sacramento-San Joaquin River Delta, or Delta California , is a large delta of the river and an extensive estuary in Northern California. The Delta is formed on the western edge of the Central Valley by meeting the Sacramento and San Joaquin rivers and lies in the east where the rivers enter Suisun Bay. Delta is recognized for protection by the California Bays and Estuaries Policy. The City of Stockton is located on the San Joaquin River on the eastern edge of the delta. The total area of â€‹â€‹the Delta, including land and water, is approximately 1,100 square miles (2,800 km ²).

Delta is formed by sea level rise after glaciation, leading to the accumulation of sediments of Sacramento and San Joaquin behind the Carquine Strait, the only outlet from Central Valley to San Pablo and San Francisco Bays and the Pacific Ocean. The narrowness of the Carquinez Strait coupled with tidal action has caused sediment to accumulate, forming large islands. Geologically, Delta has been around for about 10,000 years, since the end of the last Ice Age. In its natural state, the Delta is a large freshwater swamp, composed of many shallow and slough channels that surround islands of low peat and tulle.

Since the mid-19th century, most areas have been gradually claimed for agriculture. Erosion and wind oxidation have caused widespread declines in the Central Delta islands; most of the Delta region currently lies below sea level, behind a dike that produces the nickname "California's Holland". Most of the water supply to central and southern California also comes from here through a pump located at the southern end of the Delta, which provides water for irrigation in the San Joaquin Valley and municipal water supply to southern California.

Video Sacramento-San Joaquin River Delta

Geography Edit

The Delta consists of about 57 islands and reclaimed tracts, surrounded by 1,100 km (1,800 km) of dikes bordering 700 miles (1,100 km) from the waterways. The southwestern side of the Delta lies at the foot of the coastal hills of California, while in the northwest sits the lower Montezuma Hills. Most of the Delta is located in Contra Costa, Sacramento, San Joaquin, Solano and Yolo County. Delta's total population is 515,264 in 2000.

Overall, Delta covers 1,153 square miles (2,990 km ²), with 841 sq., mi (2,180 km ²), or nearly 73 percent, aimed at agriculture. About 100 mÃ‚Â² (260 km ²) of the Delta region is urban and 117 mÃ‚Â² (300 km ²) is undeveloped land. River, stream, slough and Delta waterways total about 95Ãƒ,Ã‚ sqÃƒ, mi (250Ãƒ, km ²) from the surface, although this is very fluctuating with the seasons and the ups and downs. Geologically, it is not regarded as a true river delta, but an inverted river delta, since it is formed inward (sediment accumulates progressively inland) rather than outward. The only other major river delta in the world located on this land is the Pearl River Delta in China.

The main river sources include the Sacramento River from the north, San Joaquin from the southeast, and the Calaveras River and Mokelumne from the east. The Calaveras and Mokelumne are both tributaries of the San Joaquin River. The Sacramento and San Joaquin rivers joins the western end of the Delta near Pittsburg, at the head of Suisun Bay, although they are connected upstream by Georgiana Slough, which was first used by steamers in the 19th century as a short cut between Sacramento and Stockton. The southwestern part of the Delta is also transitioned by the Central and Old Rivers, the former San Joaquin channel. These rivers carry over 30 million feet (37 km) of water through Delta each year - about 50% of all California runoff.

Nearby cities include Lodi and Stockton to the east, Tracy and Manteca in the south, Brentwood to the southwest, and Pittsburg and Antioch in the west. The state capital, Sacramento, lies to the north of the Delta.

The Sacramento River Water Funnel links Delta to the Port of Sacramento, with its terminal located near Rio Vista, on the northwest side of the Delta. The Stockton Ship Channel is a partially dredged and straightened part of the San Joaquin River that cuts directly through the Delta from Port of Stockton to the San Joaquin meeting with Sacramento near Antioch.

Maps Sacramento-San Joaquin River Delta

Geology, formation and natural conditions Edit

The Delta was once located on the large inland seabed in Central Valley, formed as a lifting of the California Mountains that blocked the waterways from the Sierra Nevada to the Pacific. About 560,000 years ago, water ran through the mountains, carving out the current Carquinez Strait and San Francisco Bay. Drainage of all water through this narrow gap forms congestion in Central Valley flow; this narrowing is crucial to provoke the slowing of river currents and the resulting sedimentary sediments that now form the Delta.

Delta in contemporary country (pre-1850s) began to form about 10,000 years ago at the end of the last Ice Age. During the global Ice Age the sea level was about 300Ãƒ, ft (91 m) lower than today, and the Delta region, as well as Suisun Bay, the Carquinez Strait and San Francisco Bay, is a river valley through which the continuation of Sacramento and the San Joaquin River flows into the Ocean Pacific. As sea levels rise again, sea water retreats through the Carquinez Straits to the Central Valley; the combination of narrow straits and tidal action pushed the interior dramatically to slow the flow of these rivers and force them to drop the sediment. Initial Delta consists of channel shifting, dunes, alluvial fans and floodplains that experience constant fluctuations due to the rapid rise of sea water - 1 inch (2.5 cm) per year. About 8,000 years ago, sea level rise was reduced, allowing wetland plants to survive in the Delta, trapping sediment; the growth and decay of these plants began to form the large peat deposits that make up the Delta islands. Delta reached a stable form similar to the mid-1800s state about 2,000-3000 years ago.

Immediately before large-scale human development, most Delta islands have cross-sections such as plates, with low natural embankments flanking the "marshy" bowl that sometimes floods with seasons and tides. The height of this natural embankment, formed from sedimentary sediments deposited by annual river floods, ranges from 1 foot (0.30 m) above the high tide average on Sherman Island on the Sacramento River, up to 7 to 8 feet (2.1 -2.4 m) in Andrus, Staten and Tyler Islands, which lies further east near the Mokelumne River. It is estimated that 60% Delta floods up to two hours each day at high tide; during tidal spring or river floods, it is not uncommon for the entire Delta to be underwater.

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History Edit

Humans have inhabited the Delta for up to 4,300 years. The original Delta estimates at the time of first contact with Europeans were about 3,000-15,000, mainly Miwok and Maidu, with some estimates ranging up to 20,000. Native Americans live in villages of 200-1,000 people on the eastern edge of the Delta, where the soil is taller and less susceptible to flooding. Their lives center around the reeds or the abundant tules that grow on the Delta islands, which they use to make houses, boats, and clothing. Staple foods include tulle roots and pollen, grains, wild fruits and grains, fish and games.

The Europeans first entered the Delta region in 1772, when Spanish explorer Don Pedro Fages and missionary Juan CrespÃƒÆ' observed Delta from the top of nearby Diablo Mountain. For decades, Delta was little used by the Spanish colonies. The expedition from 1806-1812 failed to find an appropriate mission location in the Delta region. However, military expeditions were often made to the Delta from 1813-1845 in response to hostilities between Native Americans and Spanish and then Mexicans; also some land grants were made around the Delta, including one for John Augustus Sutter, which started the first significant European settlement in the Central Valley in the northern Delta near present Sacramento.

The Spaniards forced a large number of Native Americans to work on missions; Many Native Americans flee far into the Delta to escape from their European masters. However, this does not protect them from illness. The malaria epidemic of 1833 destroyed the local native population; this may be exacerbated by the geography of the swamps in the area, which raise large numbers of mosquitoes.

The value of Delta agriculture was first recognized during the California Gold Rush, when farmers planted orchards on the Delta island to provide fresh fruit for the mining camps in the Sierra Nevada. Due to flat terrain coupled with the availability of fresh water throughout the year, irrigation here is cheaper and simpler than other California's fertile areas. As a result, Delta remained California's richest agricultural area (alongside Los Angeles County) until the 1940s, when large federal water projects eventually allowed full-scale irrigation from the central agency of Central Valley. Currently, Delta is still among the most productive agricultural areas in the state.

In 1850, Congress passed the Arkansas or Swampland Act, which allowed the transfer of rights to wetlands to private owners on condition that the land be reclaimed. In California, more than 2 million hectares (810,000 hectares) of wetlands are partitioned under the Swampland Act, of which 500,000 hectares (200,000 hectares) are in the Sacramento Delta-San Joaquin, roughly the same amount of land that has been developed. currently. Agricultural interest in the Delta is protected by embankment construction, the first major effort by Chinese workers from the 1850s to the 1870s. The Reclamation Council, established in 1861, collects the construction of embankments in the Delta by grouping the islands into a region known as the reclamation district. The early dikes are built from peat, and are particularly vulnerable to wind and water erosion. The Great Flood of 1862 wiped out many of the existing Delta infrastructure, forcing landowners to rebuild their dikes higher and stronger; more floods in 1878 and 1881 reinforce these ideas.

Although the ownership of land in the Delta was initially limited to 320 hectares (130 acres) per buyer, this limit was lifted in 1868, allowing large agricultural conglomerates to take the whole island and undertake a massive reclamation project. From 1868-1869, the entire island of Sherman, about 14,000 hectares (5,700 hectares), was dried and dried by embankment systems, smoke and sluice. In the 1890s, the original embankment system had largely been replaced with a stronger embankment consisting of clay dredged from the nearest river bed. By 1900, some 235,000 hectares (95,000 ha), or nearly half of the Delta's land area, had been reclaimed. Much of the farmland in the Delta was reclaimed in the 1920s.

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Economy and human use Edit

Agriculture Edit

Delta produces crops worth about $ 650 million annually (for the period 1998-2004), making it one of the most productive agricultural areas in the United States in terms of harvested value per unit area. Agriculture provides an additional benefit of more than $ 2 billion to the local economy. The main plants grown in the Delta include corn, wheat, straw, beet sugar, alfalfa, tomatoes, asparagus, and safflower; various fruits are also raised here, as well as some livestock. Plants in the Delta can not be irrigated using conventional methods because of the high absorption quality of peat soils and deviations caused by land subsidence. Irrigation is usually done periodically by pumping water into small "spud ditches", which spread the water to a large area and raise the local water table. High groundwater is then gradually being spent by the plants until irrigation is needed again.

Delta water channels are also major transportation corridors for agricultural products; Sacramento and Stockton ports, located on the Sacramento and San Joaquin rivers, respectively, are the most important inland port in California. The San Joaquin River in most of the Delta and Sacramento Rivers below under its connections to the Sacramento Inland Drains is routinely dredged to allow for the passage of large cargo ships. The Sacramento River corridor was maintained to a depth of 7 feet (2.1 m) early in 1899, and deepened to 30 feet (9.1 m) in 1955. Stockton Ship Channel has been dredged since 1913; However, the current depth of 37Ãƒ, ft (11 m) was achieved only in 1987.

Water supply Edit

Delta is often considered a nexus of water systems throughout the state of California. About half the total river flow in the state passes through this area, from which water is exported to San Joaquin Valley, Southern California and parts of the Gulf to supply 1.130,000 hectares (460,000 hectares) of agricultural land and 23 million people in the center and Southern California. Delta provides approximately 7 million acre feet (8.6 km ³) of water per year, of which about 100,000 acre feet (exported to the San Francisco Bay Area , 1.7 million feet (2.1 km ³) are used locally, and more than 5 million acres feet (6.2 km ³) are exported to San Joaquin Valley , the coast of Central and Southern California.

Brackish water intrusion into the Delta is a recurrent natural phenomenon; However, it became a serious problem after agricultural development in the Sacramento valley and San Joaquin over reducing inflows. The dual drought between 1910 and 1940 caused significant salinity intrusion in the Delta due to reduced freshwater flow. Delta's growing water quality problems provide an initial boost to build dams in the Central Valley river to encourage fresh-water flow in the dry season. This eventually became the Central Valley Project (CVP), a major California water system, mostly built between the 1930s and 1960s.

Today, the California Water Channel and the Delta-Mendota Canal, the two largest water transport facilities in the state, both draw water from the southern end of the Delta at Clifton Court Forebay. Built in the mid-twentieth century, the former supplies water to the Los Angeles Basin and California coastal centers through the Water Country Project; the latter, part of the CVP, provides an abundant supply of irrigation water in San Joaquin Valley. Although much of the water provided by these projects is used for agriculture and urban areas, some water is also provided for wildlife protection and habitat conservation work. Contra Costa Canal and North Bay Aqueduct also take on Delta water, which supplies the nearby San Francisco Bay Area. Locally, Delta provides water for cities in five districts and for more than 1,800 agricultural users.

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Effects of embankment systems and freshwater diversion Edit

The embankment system allows farmers to drain and reclaim almost 500,000 hectares (2,000 km ²) from Delta, then a tidal swamp. After the rivers are confined to the bottom of their rivers, peatlands from tidal swamps are exposed to oxygen. When the oxygen-rich peat soils decay and then releases carbon dioxide, a very large decline of soil is generated. Currently, most of the Delta is below sea level, with many western and central Deltas at least 15 feet (4.6 m) below sea level. Decreased soil has endangered the Delta embankment protection system, occasionally triggering the failure of the embankment and subsequent floods.

The decline of the soil also allows brackish water intrusion into the Delta, a problem exacerbated by the transfer of up to 25% of the fresh water flowing into the Delta. The declining volume of freshwater in the Delta has a profound effect on its ecology. In most years, large dams in Delta watershed completely withstand spring runoff; consequently Delta is most vulnerable to salinity intrusion between February and June. However, the regulations provided by the dam help to improve freshwater flow during the dry summer and autumn season, reducing the risk of salinity intrusion in these months.

The diversion located at the southern end of the Delta, however, has negated some of the benefits of the upstream dam. Strong pumps that supply water to the Central Valley Project and the Water Country Project cause the water in the Delta to flow from north to south instead of the natural direction from east to west. This has caused many environmental problems, such as the disturbance of fish migration and salinity accumulation in the eastern Delta, where salt can no longer be flushed into the sea by natural streams.

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Troubleshooting Edit

Since 1900, there have been more than 160 embankment failures in the Sacramento River Delta-San Joaquin. These figures include some failure of a single embankment structure. Failure cracks, also known as violations, can be caused by runoff or structural failure. One recent example of the failure of the embankment in the Sacramento River Delta-San Joaquin occurred in June 2004 when the breach of the embankment caused more than 150,000 acreÃƒ, Ã‚ Â· ft (190 million m3) of water to flood the entire island of Jones Tract. In January 2017 more dikes were violated.

However, significant improvements made to the Delta embankment system since 1982 have reduced the incidence of failure at this great failure in 30 years. The most up-to-date descriptions and discussions on the Delta embankment system can be found in the Delta Economic Protection Sustainability Plan. The study concludes that Delta dyke systems are now relatively strong but must be upgraded to effectively eliminate the risk of failure in extreme floods and earthquakes. It emphasizes the significant value of infrastructure that passes through the Delta, including water transport, in addition to life and property, and the value of Delta as a Place.

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Ecology Edit

About 500 species of plants and animals inhabit the Delta, which is one of the largest estuaries in western North America. Prior to the development of agriculture in the Delta region, many Delta islands were inhabited by Tule, bulrush, and numerous reeds that thrived in lowly clogged swampy areas. For thousands of years, the growth and decay of various swamps form a 50-foot peat layer (15 m) deep, the fertility of Delta soil is very high. Sedimentary sediments form a natural embankment around the border of the island, where larger trees, especially willows, are capable of rooting and forming large riparian forests. The riparian forest is most prominent along the Sacramento River and the lower Mokelumne River under its encounter with the Cosumnes River. Larger forests stand out on the outskirts of the Delta bordering the riparian zone. Consisting mainly of oak valleys, elderly squares and Oregon ash, these oak forests grow in bands stretching up to 3 miles (4.8 km) inland. Further from water sources, vegetation gives way to pasture. The Hyacinth has become one of the most destructive plants to the Delta waters. Within a year will spread and cover as much as 6500 sq ft of water space in one growing season. This has been a challenge for the agricultural community to be eliminated. Plants spread with shoots and spread the seeds, and the seeds fall to the bottom of the water, where they can stay alive in the dirt for years. The Hyacinth can form a doormat up to six feet thick, turn off light and become acid when they rot.

Delta was formerly populated by herds of deer and deer; their path was so wide that early Spanish explorers thought the area was inhabited by livestock. A significant number of California grizzly bears can also be found in the Delta. Extensive wetlands of the Delta support large-scale bird populations, even today, half of migratory waterfowl in California still passes through Delta. A survey in 2012 records a spring duck population of 48.6 million, the highest number since its inception in 1955. Major mammals in the Delta have not fared either; with most of its habitat being converted to agriculture, the remaining populations are particularly vulnerable to human impacts and natural disasters. The Grizzlies were hunted to extinction, while the 1878 flood swept away the last herd of deer in the Delta.

Delta is home to about 22 species of fish, including some Pacific salmon species, striped bass, steelhead trout, American shark and sturgeon. About two-thirds of California's salmon pass through the Delta on their way upstream to lay their eggs. The small Delta smell is a key indicator species for the health of the Delta ecosystem. Delta fish populations have been significantly reduced due to swamp reclamation and freshwater diversion. In 2004, Delta Smelt was found to be on the brink of extinction. The survival of Delta Smelt has been one of the largest environmental controversies in California, because environmental measures imposed to protect its inhabitants often reduce the amount of water available to federal water projects that depend on pumped water from the Sacramento-San Joaquin Delta.

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Conservation efforts Edit

After several rounds of mitigation after Smelt Biological Opinion (BiOp) 2005 which pumps restrictions from the State and Federal projects of the Delta, a number of potential solutions to the Delta problem have been proposed. It follows the CALFED process that has offered several step-by-step solutions. The first set of alternatives will retain Delta in its current state and configuration. The second will restore parts of the Delta closer to its natural state but includes the construction of additional Perifer Canals to maintain the water supply currently supplied by Delta.

The Department of Public Works of Contra Costa County works with the Coastal Commission of California and Boating and Waterways Departments to protect the quality of drinking water, prevent pollution, and promote the health of the Delta environment.

In April 2009, the Sacramento River in the Delta was declared a state water system most threatened by the American Rivers environmental group, due to water shortages caused by Delta environmental problems, declining fish populations and aging dikes, among other problems.

Since the 1940s, various groups have lobbied for the construction of the Peripheral Canal to divert the flow of water from the Sacramento and San Joaquin rivers directly into federal waterways that take water from the southern end of the Delta. Currently, fresh water entering the Delta must flow through the maze of river channels and sloughs before entering Clifton Court Forebay north of Tracy, where water is pumped into the California Waterways and Delta-Mendota Canoes. In addition, a large number of other smelly and endangered Delta species are killed by pumping plants that provide water for the waterways.

The current proposal, known as the Delta Bay Conservation Plan, requires the construction of a twin tunnel under the delta and is closely linked to Governor Jerry Brown. However, the proposal of the Edge Canal has been criticized for reducing the amount of fresh water flowing through the Delta. Farmers in the Delta are among the most opposed to the project because it will reduce the amount of water available to them for irrigation.

All solutions, however, are aimed at generating Delta that simultaneously supports a living ecosystem and continue to supply fresh water to the Central Valley Project, the Water Country Project and the Bay Area.

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References Edit

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Works cited Edit

Pierce, Patricia (June 1988). "Geoarchaeological Analysis of Sacramento-San Joaquin Delta Prehistory, California" (PDF) . Calfed Bay-Delta Program . Retrieved 2013-08-20 .
Reisner, Marc (2004). Dangerous Places: A Disgraceful California Destiny . Penguin Books. ISBN 0-679-42011-8.
Thompson, John (2006). "Initial Reclamation and Neglect Central Sacramento-San Joaquin Delta" (PDF) . Sacramento History Journal . University of California Berkeley . Retrieved 2013-08-15 .

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Sacramento-San Joaquin River Delta

Jumat, 15 Juni 2018