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The Huai River itself and all its major left-bank tributaries have their sources in the mountains of southwestern Henan.
They flow eastward onto the Anhui Plain, subjecting it to disastrous floods.
The province stretches some 300 miles (480 km) from north to south and 350 miles (560 km) east to west at its widest point.
It is bounded to the north by the provinces of Shanxi and Hebei, to the east by Shandong and Anhui, to the west by Shaanxi, and to the south by Hubei. Shanxi Plateau, rising in places above 5,000 feet (1,524 metres).
Since 1957 more than 20 large dams, including those at Xianghongdian, Meishan, and Foziling, have been built.
Dikes were strengthened, with the result that no serious disaster has since occurred.
Consequently, soil salinity and alkalinity affect the whole area.
Zhengzhou, the provincial capital, lies in northern Henan at the point where the north-south Beijing-Guangzhou (Canton) railway crosses the Huang He and meets the Longhai line running from east to west; Kaifeng, the former capital, is located about 45 miles (75 km) to the east. Dabie ranges form a further extension of this axis, running in a southeasterly direction and marking the border between Henan and Hubei.
In 1949 the Huai basin became the communist regime’s first large water-conservancy program.
Six dams were quickly built in the upper reaches of Huai tributaries in Henan.
The Tongbai range is separated from the Funiu by a gap some 75 to 100 miles (120 to 160 km) wide cut by the Tang and Bai rivers, which are tributaries of the Han River.
This gap gives easy access from the Henan Plain to the central basin of the Yangtze River (Chang Jiang), a route much used from Han times onward in Chinese expansion southward. Until fairly recent geological times the mountains in the west formed the coast of a sea that, essentially, was the western extension of the present Bo Hai (Gulf of Chihli) and Yellow Sea.The higher land of the west is mainly mountain yellow-brown earth, better drained than the plains.