洞庭湖近几十年来湖盆变化及冲淤特征

洞庭湖是我国著名的五大淡水湖泊之一,位于长江中游荆江段南岸,湖南省境内.历史时期,曾经是我国第一大淡水湖,直至新中国成立初期,湖泊面积仍然有4350km2,居我国淡水湖泊之首位.但由于洞庭湖承纳“四水”,吞吐长江,长江大量水沙涌入洞庭湖,造成了湖盆迅速淤高,加之由此诱发的人类大规模地湖泊垦殖活动,湖泊急剧萎缩.目前,洞庭湖已退居鄱阳湖之后,为我国第二大淡水湖泊.湖泊的严重泥沙淤积,已经造成了湖泊调蓄长江中游洪水功能的严重衰退,不但危及湖南省的防洪的安全,而且危及长江中下游地区的防洪安全,研究洞庭湖的湖盆冲淤演变具有重要意义.本文根据1974、1988和1998年洞庭湖125000水下地形资料,并针对洞庭湖具有显著上下游水位落差的实际,分不同高程和不同水位情况下,分析洞庭湖湖泊面积和容积演变特征,探讨洞庭湖近几十年来的湖盆变化及冲淤规律,试图揭示洞庭湖湖泊调蓄能力的变化过程.

Analysis of the Lake Basin Change and the Rushing-silting Features in the Past Decades of Dongting Lake

Dongting Lake, which is one of the five biggest fresh water lakes in our country, is located in the south bank of Jingjiang river of the middle reaches of the Yangtze river as well as in Hunan Province.The Dongting Lake was the biggest fresh water lake in history, which is still the biggest one with the area of 4350km² up to the initial period of the foundation of P.R.China.The area of the Dongting Lake gets small rapidly because of enormous sands from the Yangtze river and reclamation, resulting the rising-up of the basin.Today, Dongting Lake has become the second largest behind Poyang Lake and the function to adjust and preserve the flood of the Yangtze River has become seriously weak because of the sands and mud silting, which threatens the safety of flood prevention not only of Hunan Province but also the middle and lower reaches of the Yangtze River.In the article the feature of the evolution of area and capacity of the Dongting Lake is analyzed according to the different height and water level, and the change of lake basin and the rule of rushing and silting are probed, so that the changing process of the adjustable and preserval ability of the Dongting Lake is revealed.Based on the topographical data of 1: 25000 under water in 1974, 1988 and 1998, the real situation that the water level changes in the upper and lower of the Dongting Lake is discussed.