The Hwangho, the Yellow River, has its source in the northeast of the Tibetan Plateau. It flows in great turns towards the sea. On its way along the Gobi Desert and the Ordos Plateau, it flows through the so-called loess provinces of Gansu, Shaanxi and Shanxi. Here it absorbs a large number of sediment from flowing streams and rivers, which color its water yellow.
China has the largest loess area in the world. It stretches from the northwest between the Gobi desert and various mountain ranges to Beijing. The loess covers a total of around 500,000 km 2 , of which the loess plateau in the provinces of Gansu, Shaanxi and Shanxi accounts for around 275 600 km 2. The Loess Plateau lies between 34 ° and 41 ° north latitude and 103 ° and 113 ° east longitude. The loess soil was created by expulsion: the wind transported fine salt and rock dust from the Gobi desert, which was deposited in the grass steppes on the mountain edges. Geologists speak of an “aeolian origin” of the loess soil.
Loess formation began in the Pleistocene, around 1.2 million years ago. The bottom layer of the Chinese loess rests on red clay. Since then, layers of up to 200 m thick have built up in the Chinese loess regions. In the northwest the layers are on average between 50 and 100 m thick, in the loess plateau they reach the greatest heights. For comparison: The loess layer in the Magdeburg Börde, on the other hand, is only 2 m thick.
Due to its formation, loess soil has many vertical channels that quickly lead the surface water inwards. Therefore there is only little tree growth in the loess areas; only 13% of the area is forested. With reforestation programs, a “green wall” of around 5.3 million hectares is to be created in the northeast, north and northwest. In addition to containing the Gobi Desert, the Chinese government hopes that this will provide better protection of the soil from erosion and from the floods caused by the Hwangho. The slower the water from the loess areas reaches the river, the lower the annual floods.
Loess soil has been used for agriculture for over a thousand years. In order to supply the plants with the necessary moisture, complex irrigation systems had always been built. Because of its high mineral content, the soil is potentially very fertile and does not require additional fertilizer. Therefore, the loess areas are among the most productive agricultural areas. The fertility is limited on the one hand by the continental climate with hot summers and very cold winters and on the other hand by the relatively low rainfall of a maximum of 500 mm per year. The main crops are wheat, maize and millet, as well as cotton and soybeans.
Rivers: The rivers Amur , Hwangho , Jangtsekiang and Xi Jiang , which flow from west to east, are largely independent of the direction in which the mountains strike. With large arches and a direction that has changed many times, these rivers have sometimes created huge breakthrough valleys, e.g. B. the Yangtze gorges. The approximately 6,300 km long Yangtze is the third longest river on earth after the Nile and the Amazon. The Hwangho (4,845 km long) flows in deeply cut valleys through the loess areas of the north and when it enters the “Great Plain” carries a sludge load of almost 1 billion m 3 annually with itself, which results in a natural increase in the river bed and repeated dike breaks and sudden changes in the course of the river.
The Xi Jiang is the main river in southern China; it flows together with other rivers in a delta, the main branch of which is the Pearl River near Canton (Guangzhou). The rivers Indus , Brahmaputra , Salween and Mekong flowing to South and Southeast Asia follow the young folds of the Himalayas and its foothills. The distribution of surface water is extremely different from region to region and from season to season. The development of hydraulic engineering has therefore become a central task in the history of Chinese civilization.
Great Wall of China
Great Wall of China [ç-], Great Wall, Chinese in Latin letters Wan li Changcheng [-t ʃ a ŋ t ʃ ε ŋ; “Wall of 10 000 Li”], Mongolian Jagan Kerme [“white wall”], with a length of around 2,500 km that is still continuous today, it is the largest protective facility in the world (since 1987 a UNESCO World Heritage Site). Visit sunglasseswill for The Great Wall of China.
It was made under Emperor Qin Shi Huangdi (Ch’in Shih Huang-ti, 221-210 BC BC) and arose when older defenses in the five northern states of Qin, Zhao, Qi, Chu and Yan were connected and expanded. The Great Wall of China received its current shape in the 15th century (Ming Dynasty). It begins southwest of Jiayuguan in Gansu and, crossing the Hwangho twice and consisting of two arms in Hebei to protect Beijing, moves northeast to the Gulf of Liaodong. If all larger sections and branches are taken into account (which happens to different degrees and thus explains the various length specifications), the total length of the structure is around 6,700 km. More recent excavations (for example, in 2001 the discovery of the remains of a wall of a section from the Handy dynasty, about 500 km long, which extends west of Jiayuguan) and further research by Chinese archaeologists suggest that the wall was even longer at times. After a two-year survey project using the latest navigation technology, Chinese scientists even stated the total length of the wall to be around 8,800 km in April 2009. The building material in the west and south is mostly rammed earth (loess), in the north near Beijing stone. In the plain and in the passages it is around 16 m high, lower on steep peaks. The thickness is up to 7 m at the bottom and about 5 m at the top. Two-story towers are erected at intervals. After a two-year survey project using the latest navigation technology, Chinese scientists even stated the total length of the wall to be around 8,800 km in April 2009. The building material in the west and south is mostly rammed earth (loess), in the north near Beijing stone. In the plain and in the passages it is around 16 m high, lower on steep peaks. The thickness is up to 7 m at the bottom and about 5 m at the top. Two-story towers are erected at intervals. After a two-year survey project using the latest navigation technology, Chinese scientists even stated the total length of the wall to be around 8,800 km in April 2009. The building material in the west and south is mostly rammed earth (loess), in the north near Beijing stone. In the plain and in the passages it is around 16 m high, lower on steep peaks. The thickness is up to 7 m at the bottom and about 5 m at the top. Two-story towers are erected at intervals.
The watchtowers were connected to each other with flags, smoke and fire signals; they were manned by up to ten men. The gates are strongly fortified. The Great Wall of China, which was largely destroyed or dilapidated, has been restored in many places; v. a. It is open to tourism in several places north of Beijing.
