LUAN RIVER

WadeGiles romanization Luan Ho, formerly Lei Shui, or Ju Shui, Pinyin Luan He, Lei Shui, or Ru Shui, river in Hopeh Province, China. The Luan River rises in northern Hopeh and flows northward into Inner Mongolia through steep gorges; it passes north of the town of To-lun, the ancient Mongol capital Shang-tu, from which its upper course is named the Shang-tu River. Its course then swings to the southeast, to join its tributary the Hsiao-luan River. It is only below this point that it is properly named the Luan River. It then flows southeastward across the mountains in the northeast of Hopeh. In the region of Ch'eng-te (Jehol) it is joined by the Je River, as well as by the Niu and Pao rivers. It passes through the Great Wall of China at Hsi-feng K'ou and then flows onto the eastern fringes of the North China Plain. In its lower course it receives the Che River and Ch'ing-lung River. From Lo-t'ing it divides into a number of distributaries, discharging into the Gulf of Chihli through a delta some 30 miles (50 km) wide. The Luan River is 545 miles (877 km) long and flows through an area of 17,220 square miles (44,600 square km). The river's upper stream is precipitous, with many rapids. Below Ch'eng-te, however, it is navigable for small craft during the summer. Because of this it was of considerable importance during earlier times as the only water route into the Ch'eng-te region for military supplies, and it was also used as a trade route from parts of Hopeh (then in the former province of Chihli) to the regions beyond the Great Wall. Because of steep hills and deep ravines at its upper reaches, the river overflows its banks during the rainy season. The flow of water is much-reduced in winter, and for some months the river is icebound. The whole of its upper basin, which was extensively forest-covered until the 19th century, has suffered severely from soil erosion caused by deforestation and unsuitable methods of cultivation. The Luan River project diverts river water into the Ch'iu-chuang reservoir of the Huan-hsiang River. The project has provided for improved water supply for industrial and agricultural use and increased electricity output. At the same time, capacity for flood control has been enhanced.