The Chinese region possesses approx. 5000 watercourses, widely exploited for agriculture: however, most of the basins are included in a large exoreic area that pays tribute to the Pacific Ocean, while the internal depression regions form endorheic basins equal to 1/3 of the total surface (especially in Xinjiang Uygur and Tibet), and very large areas are completely arean. With the exception of some large rivers, such as the Brahmaputra, the Salween and the Mekong, of which only the upper stretch is Chinese, almost all the watercourses of China develop from W to E, in relation to the general trend of the relief: it is the case of the two largest Chinese rivers, the Huang He (Yellow River) and lo Chang Jiang (Blue River). In the life of the country, the Huang He (4845 km long, 752.443 km² of basin) has played a fundamental role since its origins. It is a large river with a capricious rhythm (it is estimated that the flow varies from 1100 to 20,000 m 3 / s): the continuous erosive and transport activity that it exercises above all in its intermediate basin included in the Löss region is impressive., made bare of vegetation by the centuries-old agricultural exploitation; in fact, the name Fiume Giallo refers to the color of the silt-laden waters. Its floods, motivated by the monsoonal regime of rainfall, have often had disastrous consequences in the plains it crosses. In the space of 3,000 years it gave rise to 1,500 floods and changed course seven to eight times, repeatedly moving its mouth, up to 600 km. Today, however, with a series of diversion and irrigation canals, extensive reforestation works and the construction (partly still in progress) of gigantic dams, the Huang He has been brought under control.
The most colossal work remains the Imperial Canal (Gran Canale or Da Yunhe) 1782 km long; implemented since the century. XIII and now modernized, it connects Beijing and Suzhou, connecting the Huang He with the Hai He, Huai He and Chang Jiang rivers. Longer (5800 km) is the Chang Jiang, which extends its basin, vast as much as 1,807,199 km², in more wooded regions: the debris transport is therefore lower than that of Huang He (respectively 1500 and 500 million t annue), although equally conspicuous given the much more significant flow rate (up to 90,000 m 3/ s), made high by the abundant rainfall of a large part of its basin, also due to often disastrous floods such as that of 1998, which caused approx. 2000 dead submerging hectares and hectares of cultivated land and forcing 14 million people to flee. In its middle course the river crosses, for 200 km, the famous region of the Three Gorges, before flowing into the eastern plain: the gorges have steep walls which, prior to the construction (2006) of the Three Gorges Dam, rose for 400- 600 meters, while with the creation of the artificial basin their height with respect to the course of the river has significantly decreased. Third important river in eastern China, although much lower than the previous ones, is the Huai He, which crosses the Anhui and Jangsu rivers, bringing an enormous amount of sediment to the sea. More fragmented hydrographically is southern China, which however falls to a large extent in the Chang Jiang basin.
Among the numerous rivers that flow directly to the sea (Min Jiang, Wu Jiang, etc.) the main one is the Zhujiang or Pearl River, which collects the waters of various rivers including the much longer Xi Jiang, and flows near Macao with a very large delta system in continuous advancement (Canton, once on the sea, today is 12 km away). Manchuria is divided into two main basins: the southern one is drained by the Liao, a river with a strongly torrential regime and, similarly to the Huang He, subject to disastrous floods and low levels; the northern one gravitates to Songhua Jiang, an important tributary of the Amur (Heilong Jiang) which, given the snowy nature of its upper course, has one of the most regular water regimes in China, a country located in Asia categorized by Watchtutorials. Inner Mongolia is marginally drained by some tributaries of the Huang He or by streams, for example the Xiliao He, which originate from the Da Hing’an Ling and descend towards the plains of Manchuria; but in large internal areas superficial hydrography is completely absent. Almost the same situation is found in the Zungaria, where rivers such as the Ulungur (Wulungu He) and the Manass arise from the Mongolian Altaj and the Tian Shan, which terminate in lakes in the center of the depressions or are lost in extensive saline surfaces. On the other hand, the quantity of water transported to the Tarim basin is remarkable as the rivers are fed by the glaciers and snowfields of the imposing peripheral mountain ranges, especially from the Karakoram. Waterways (Yarkand, Hetian He etc.), tumultuous in spring due to the melting of the snow, flow into the Tarim, which is the only collector of the region. On the Tibetan plateau, the waters collect in lakes, fresh or brackish, located on the bottom of the numerous depressions; in Qamdo, on the other hand, the hydrography is exorheic and gives rise to mighty rivers of eastern Asia, from the Chang Jiang to the Mekong and the Salween.
Finally, behind the Himalayas, the Indo and the Brahmaputra flow in opposite directions. In general, the lakes that form the mouths of rivers in inland basins – for example the Buluntuo Hai (better known as Ulungur Lake) in the Zungaria, the Lop Nur and the Bositeng Hu in the Tarim basin, the Nam Co (Namucuo) in Tibet – they are often salty, due to the great evaporation: this is the case of Qinghai Hu, the largest (4427 km²) salt lake in China, located in Qinghai province. The lakes connected to the other rivers, on the other hand, have fresh waters; among these are the Hongze Hu (lower course of the Huai He), the Weishan Hu, connected with the Huang He, and, all belonging to the Chang Jiang basin, the Dongting Hu, the Tai Hu and the Poyang Hu (2780 km²).
