Central Valley (California)
The California Central Valley (English: California Central Valley) is about 600 km long and up to 80 kilometers wide valley in Central California. It is bounded on all sides by mountain ranges: the California Coast Mountains to the west, the Sierra Nevada to the east, the Klamath Mountains to the north and the Tehachapi Mountains in the south. The valley is drained by the rivers Sacramento River in the north and San Joaquin River in the south. After these rivers is called the northern part of the valley and Sacramento Valley, the southern San Joaquin Valley. Both rivers join just to the north of the center of the valley and flow west through the only natural opening of the valley to the bay of San Francisco from. The Central Valley is very strong earthquakes by numerous faults.
The California Central Valley is in the range of subtropical winter rainfall climate; the entire rainfall pours almost exclusively from December to April. In summer, however predominates arid climate. In the north there is more rain ( moderate rainfall) than in the low-rainfall south. The Pacific high, which in summer is located west of the coastal mountains in southwest California can bring no precipitation in the southern part of the valley, because access is denied through the mountains. Originally almost the entire valley was covered with grasslands, remains of which are preserved only in the Carrizo Plain National Monument since the valley today is characterized by intensive agriculture.
The valley lies west of the agronomic dry boundary, whereby the rainfed agriculture is no longer possible. By underground water reserves in the south, an artificial irrigation is possible, but poses risks such as salinisation and soil fertility decline in itself. The temperatures in the Central Valley fall and winter rarely drop below 8 ° C, which is a year-round cultivation possible. The typical vegetation form the Longitudinal of the California white oak ( Quercus lobata ), California holm oak (Q. agrifolia ) embossed Californian oak savanna, which is used by endemic species such as the Yellow -billed Magpie ( Pica nuttalli ).
The valley is often referred to as the fruit garden of America. From here, all of the U.S. will be supplied, and also products are being exported to other countries. The crops are especially popular in the U.S. because they are very rare. The can dates, almonds, rare fruits and vegetables or wine to be. In total more than 50,000 square kilometer area about 250 different agricultural products are grown, accounting for a turnover of 17 billion U.S. dollars ( 2009) is obtained.
To protect the products, you have come up with special methods. These include furnaces, which are set up in the winter and the cold air will stir up as frequent cold katabatic winds could cause freezing of the fruit otherwise. Alternatively, the fruit and vegetables is injected with water. When the water freezes, heat is released ( heat of crystallization ), so that the temperature of the fruit for a long time can be kept at the freezing point - their juice freezes because of the solute only at lower temperatures.
However, a major problem is the watering. Since there are differences in height of up to 600 meters, water has to be pumped uphill frequently. These farmers have installed 174 electric pumps up to now, but very much energy and are very expensive due to the high maintenance and cost. Furthermore, there are also channels, but in which a large evaporation danger as they run unprotected over the terrain and the sun has free access. Remedy underground water tunnels, most of which are in the mountains and from there take the water. Another option is to dams. They begin each year on the water of melting snow and here it is also stored. This water is in turn used to produce energy, which can then drive the pumps.
The fruit garden is one of the largest energy consumers in the United States and groundwater, which is a problem especially in water-scarce south of the State of California.
The situation between the two parallel mountain chains perpendicular to the main wind direction leads to frequent temperature inversions. Due to the population growth since the mid-20th century, this act by frequent smog conditions. The Central Valley falls Even when the particulate matter because of these climatic conditions by bad values : half of all cities in the United States, exceeding the WHO guideline value, are located in the Central Valley, California.