Yang-zi'-xiang (Tibetan: འབྲི་ཆུ, Dričhu; , Chinese Pinyin Yángzǐ Jiāng, characters 扬子江), or The Blue River is a river in the central PRC (Qinghai, Tibet Autonomous Region, Sichuan, Yunnan, Chongqing, Hubei, Hunan, Jiangxi, Anhui, Jiangsu, Shanghai ). The name Yangziang, by which the river is known in some languages, including Czech, is the original local name for the lower course of the river, under which European missionaries first recognized it. In China, it is usually called Changjiang (, Chinese pinyin Cháng Jiāng, simplified characters 长江, traditional 長江; Czech "Long River"). With a length of 6,300 km, it is the longest river on the entire Eurasian continent. On a global scale, it is the third longest (behind the Amazon and the Nile) and the longest river in the territory of one country. The river basin has an area of 1,800,000 km² and represents a fifth of the territory of the PRC and home to a third of its population.
It springs from glaciers at an altitude of 6,621 m on the northern side of the Tangla and Ku-ku-sh'-ln mountains in the central part of the Tibetan Plateau in the extreme southwest of Qinghai Province. Under the name Ulan-Muren, it flows through a wide swampy valley. It is successively named Tchuo-tchuo (Chinese pinyin Tuotuo, characters 沱沱) and Tchung-tchien (Chinese Pinyin Tongtian, characters 通天, Heavenly River). It leaves the Tibetan Plateau and crosses the East Tibetan Mountains. Under the name Jinsha Jiang (Chinese Pinyin Jinsha Jiāng, characters 金沙江, River of Golden Sands), it flows through narrow and deep gorges, overcoming many rapids. In its middle course, it flows through the southern edge of the Sichuan Basin, in which it has a calm flow and reaches a width of 300 to 500 m. It crosses the eastern mountain border of the basin and creates three gorges with a total length of approximately 100 km. At the beginning of the 21st century, the Three Gorges dam was built in these places. Before its completion, the river here narrowed to 120 to 200 m, and the depth reached up to 100 m in places. This section of the river is known as San-sia. In its lower reaches, the river under the name Changjiang flows through the plains, first the Jianghan and then the Great China Valley. The river valley is well formed and has many rapids and branches. The width of the riverbed reaches 1 to 2 km and the depth is 20 to 30 m. It opens into the East China Sea near Shanghai with two main branches, and at the same time creates a delta with an area of approximately 80,000 km². There are many lakes in the river valley, the largest of which are Tung-ching-chu and Po-yang-chu. These lakes largely regulate the flow of the river downstream.
The river has over 700 tributaries. Among the largest are:
The river receives the largest supply of water in the summer thanks to the monsoon rains. The melting of snow and glaciers in the mountains also contributes significantly to the upper flow. In the summer, the water level in the Szechuan basin reaches more than 20 m, and in the lower reaches 10 to 15 m. In the gorges, the difference between the highest summer and lowest winter water levels is up to 40 m. The average water flow is 31,900 m³/s, which corresponds to the annual outflow 960 km³. This makes it the fourth wateriest river in the world (behind the Amazon, Congo and Orinoco). In the lower reaches, there is a significant influence of sea tides, which are manifested up to a distance of 750 km from the mouth near the city of Jiujiang. The river carries 280 to 300 Mt of sediment annually to its mouth, causing rapid growth of the delta (approximately 1 km in 35 to 40 years). For the most part, the water in the river has a yellow tint, so the name of the Europeans Blue River does not correspond to reality. In the plains of the lower stream, a significant part of the deposits is deposited in the bed, silting it up and raising it above the surrounding terrain. To prevent flooding of adjacent areas