水利工程兴建后洞庭湖径流与泥沙的变化

EFFECT OF WATER CONSERVANCY PROJECT ON THE CHANGES OF RUNOFF AND SEDIMENT IN DONGTING LAKE

本文根据1951—1988年洞庭湖及其入湖河流的水文泥沙资料,研究大型水利工程兴建后洞庭湖径流与泥沙的变化。研究表明,近40年来洞庭湖的径流量减少了29.2％,输沙量减少了48.7％。引起水沙变化的主要原因是荆江四口分流河床的淤积,使荆江入湖的径流量与输沙量减少。1966—1972年下荆江三个弯道裁弯取直,使荆江河床下切,导致荆江及其分流水位的下降,也促使荆江分流的流量与输沙量的减少。40年来洞庭湖水流变化的趋势对洞庭湖、江汉平原与长江中下游的防洪较为有利。

Hydrological data from 1951 to 1988 show that the average runoff of Dongting Lake was 3019×10(8) m3/a. of which 54. 6 % came from four inlet rivers (Xiangjiang River, Zishui River .Yuanjiang River and Lishui River), 37. 1 % from three diversion waterways (Ouchi Waterway, Songzi Waterway and Hudu Waterway) of the Jingjiang River and the rest 8.3 % from other so_urces. The average sediment load transported into Dongting Lake was 193×10（6）t/a, of which 82. 3% came from three diversion waterways and 17. 7 % from four inlet rivers. From 1951-1958 to 1981-1988, the runoff volume and sediment load of Dongting Lake were decreased by 29. 2 % and 48. 7 % respectively as a result of the follows; (1) the deposition of three diversion waterways of the Jingjiang River; (2) curve cut-off in the lower reaches of the Jingjiang River. The decreases in runoff and sediment of Dongting Lake have favorable effects on the flood control at Dongting Lake, Jianghan Plain and the middle reaches of the Changjiang River.