TUNG-T'ING LAKE

WadeGiles romanization Tung-t'ing Hu, Pinyin Dongting Hu, large lake in northern Hunan Province, China. It lies in a basin to the south of the Yangtze River. The lake is connected to the Yangtze by four channels; some 40 percent of the river's waters (more in flood periods) flow into the lake. The lake is also fed from the south by almost the entire drainage of Hunan Province, with the Hsiang River flowing in from the south and the Tzu, Yan, and Li rivers from the southwest and west. The waters of the entire lake system discharge into the Yangtze at Yeh-yang. The lake's size varies greatly from season to season. Its normal size is about 95 miles (150 km) from east to west and 60 miles (95 km) from north to south, while its area is 1,089 square miles (2,820 square km). In flood periods its water level may rise by as much as 50 feet (15 m), and the inundated area may increase up to 7,700 square miles (20,000 square km). The lake, like P'o-yang Lake farther east, acts as a huge retention reservoir for the Yangtze. In the flood season, from June until October, the Yangtze waters flood into the lake. At this time, not only the Yeh-yang outlet but also two of the inflow channels (the T'ai-p'ing and Ou-ch'ih streams) are navigable by large craft, which can also pass up the southern rivers. From October to April, however, more water is discharged from the lake than enters it, the water level falls, and much of the lake's area becomes dry land. Much construction work has been done to supplement the role played by Tung-t'ing Lake in regulating flooding on the Yangtze. In the northwest angle between the lake and the Yangtze, a huge artificial retention basin was built in 195456, with floodgates through which the Yangtze can be diverted in time of need. The basin is kept empty, and its floor is under cultivation, except during the flood season. Called Ta-t'ung Lake, it is regulated by a great barrage (dam) across the T'ai-p'ing Stream entrance to Tung-t'ing Lake. Between the 1930s and the 1950s, much of the land along the lake banks and inside the dikes surrounding Tung-t'ing Lake was reclaimeda fact hastened over the years by the gradual silting up of the lake from the huge amounts of sediment carried in by its inflowing rivers, especially the Yangtze. As a result, the area of the lake was said to be 400 square miles (1,000 square km) less in the 1970s than it was in 1937. At one time, as a result of such reclamation, the lake was almost divided in two and no longer fulfilled its regulatory function adequately, causing floods on the lower courses of the various rivers flowing into the lake. In the 1950s, however, such reclamation was prohibited, and works were undertaken to reconnect the different sections of the lake system. Tung-t'ing Lake provides a communication link between the various rivers of Hunan and also between northern Hunan and the Yangtze, the cities around the lake's margin being the chief agricultural collection and distribution centres for a fertile plain. The lake is also a fishing ground, particularly during winter, being noted for its carp. The Changling Oil Refinery, built in 1971, is located on the edge of Tung-t'ing Lake and provides fuel oil for the province.