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East Asia is the location of the continent’s longest river, the Yangtze, which flows 6,300 km (3,900 mi) eastward from Tibet to the East China Sea. The Huang He (Yellow River) also rises in the Tibetan highlands, flowing east across central China to its mouth at the Yellow Sea. The Zhu Jiang (Pearl River) rises in southwestern China and flows through the southern part of the country on its route to the South China Sea.
In Southeast Asia the major rivers flow southward between mountain ranges. The Mekong rises in eastern Tibet and flows southeast to the South China Sea. The Salween also originates in Tibet, where it is called the Nu Jiang, flowing south to the Andaman Sea. The Irrawaddy, which rises in the mountains of northern Myanmar, also empties into the Andaman Sea.
The major rivers of South Asia have their sources in the Himalayas. The Ganges rises in the western Himalayas and passes eastward through India. Just north of the Bay of Bengal it joins the Brahmaputra River, which rises beyond the Himalayas and then empties into the bay. The Indus River emerges from the western end of the Himalayas and flows through Jammu and Kashmir and western Pakistan into the Arabian Sea.
The only large rivers of Southwest Asia are the Tigris and the Euphrates. Both rivers rise in Turkey and flow southward through Syria into Iraq, where they join before emptying into the Persian Gulf.
The three longest rivers of Russian Asia are the Ob’, the Yenisey, and the Lena, all of which are more than 3,600 km (2,200 mi) long. These rivers rise in southern Siberia and flow northward into the Arctic Ocean.
River basins in tropical and temperate Asia support the highest population densities. The Gangetic Plain, which lies between the Himalayas and the Deccan Plateau; the basins of the Irrawaddy, Mekong, and Chao Phraya in Southeast Asia; and the basins of China’s great rivers, especially the Yangtze, Huang He, and Zhu Jiang rivers, are all densely settled. These valleys have fertile soils for agriculture and the rivers serve as a means of transportation.
Some of Asia’s important rivers flow into inland lakes. The Jordan River rises in the mountains of Lebanon and Syria and flows southward into the Dead Sea, a saltwater lake seven times more salty than the ocean. At 408 m (1,340 ft) below sea level, the surface of the Dead Sea is the lowest point on Earth. The Syr Darya and the Amu Darya of Central Asia both drain into the Aral Sea, also a saltwater lake. Since the 1960s the diversion of much water from the Syr Darya and Amu Darya for irrigation has caused the Aral Sea to shrink to less than half its former size. In 1988 the lake split in two, forming the Large Aral Sea, which receives water from the Amu Darya, and the Small Aral Sea, which receives water from the Syr Darya. The decreased water intake has also increased the salt content of the lake. The Caspian Sea is the largest saltwater lake in the world. Lake Balqash in Kazakhstan is another major saltwater lake.
Lake Baikal in southeastern Siberia is the deepest lake in the world and the largest freshwater lake in Asia. The Tonle Sap, a shallow lake in western Cambodia, is the largest lake in Southeast Asia. It provides a lucrative source of fish for local residents. The Tonle Sap becomes more than three times its normal size between June and October when floodwaters of the Mekong River empty into the lake.