HAI RIVER

WadeGiles romanization Hai Ho, Pinyin Hai He, river in Hopeh province, China. The name Hai properly belongs only to the short stream from Tientsin that discharges into the Po Hai (Po Gulf) at T'ang-ku some 43 miles (70 km) away. It is, however, also used as the general name for the extensive system of tributary streams that discharge into the sea through this channel. The system has a drainage area of some 80,500 square miles (208,500 square km), including almost the whole of Hopeh, the eastern slopes of the T'ai-hang Mountains in Shansi province, and the northeastern corner of Honan province. The principal tributaries are the Ch'ao River, rising in the mountains north and northeast of Peking; the Yung-ting River, flowing southeastward from around Chang-chia-k'ou to the south of Peking; the Ta-ch'ing River, flowing eastward from the T'ai-hang Mountains to join the Hai at Tientsin; and the Tzu-ya River, flowing northeastward from southwestern Hopeh toward Tientsin, with its further important tributary, the Hu-t'o River, from the T'ai-hang Mountains west of Shih-chia-chuang in western Hopeh. The area of the Hopeh Plain drained by the Hai River system is flat. The rivers have low gradients and are often built up above the level of the surrounding land by the silt they have carried down from the T'ai-hang uplands. The depth of the rivers is variable because the area is one of seasonal variations in rainfall, with dry winters (during which many of the streams dry up to a trickle) and heavy summer and autumn rainfall; rains in the T'ai-hang Mountains particularly produce serious flooding in the lower plains. The Hai River's channel itself is quite inadequate to carry the amount of floodwater discharged. In recent centuries floods have been almost an annual occurrence. In 1939 Tientsin itself was submerged for a month. These floods not only have caused loss of life, crops, and property but have also raised the alkali content of the soils of frequently inundated regions in much of Hopeh, thereby greatly reducing their productivity. Since 1963 the Hai River Basin has been the subject of a comprehensive water-control project. On the upper courses of the tributary streams, 1,400 retention dams have been constructed, several of them (such as the Kuan-t'ing Dam on the Yung-ting River, west of Peking) of considerable size and designed as dual-purpose installations for irrigation and for the production of hydroelectricity. These works have been allied with afforestation, soil conservation, and field-terracing programs in the uplands. In the plain itself, the major rivers have been embanked to give protection against flooding, and their channels have been cleared and canalized using the massive mobilization of local labour. As a result, many of the Hai River's principal tributaries have been canalized or directed into new channels and given separate outlets. The Hai River thus no longer has to carry the entire flow of all these rivers in flood. These major works have been integrated with a large-scale construction program of subsidiary drainage and irrigation works that is designed to reduce the incidence of flooding and to ameliorate the consequences of drought. To improve irrigation facilities still further, a huge number of wells have been dug and pumping stations constructed to supplement the irrigation system with subterranean water.