洞庭湖萎缩对湖内洪水影响

Study on the effect of Dongting Lake′s shrinkage on the flooding

为了更好地理解湖泊萎缩对湖内洪水过程的影响,在假定洞庭湖将继续萎缩的前提下,通过建立荆江—洞庭湖水动力模型,定量分析洞庭湖萎缩对湖内洪水的影响。研究结果表明,湖内水位及洪峰流量随湖泊面积的萎缩而增加,洪峰水位到达时刻随着湖泊萎缩而提前。若遇1996年型洪水,洞庭湖面积若从目前的2670km^2减小至1380km^2时,西洞庭湖及南洞庭湖内最高水位将抬高2.0m左右,东洞庭湖水位将抬升0.4m左右,城陵矶站点洪峰水位到达时刻将提前约11h,洪峰流量增加约4800m^3/s。因此,若洞庭湖湖泊面积在目前基础上(面积2670km^2)继续萎缩,湖区特别是西洞庭湖及南洞庭湖将面临更为严峻的洪水灾害。虽然湖泊萎缩对西洞庭湖与南洞庭湖内水面坡降影响较小,但东洞庭湖内水位同时受湖泊萎缩及长江来流的影响,水面坡降发生较大变化,在距离蔡家洲80~110km(鹿角站附近)河段水面坡降出现大幅增大。

In order to better understand the effect of the lake shrinkage on the flood process in a large lake,a quantitative analysis of the relationship between the lake shrinkage and the flooding in Dongting Lake was conducted,for which Jingjiang-Dongting Lake hydrodynamic model was applied and different scenarios of water area in the Dongting Lake were assumed.The results show that the water level and peak discharge will increase,and the peak time will occur earlier with the shrinkage of the lake.The water level in the West and South Dongting Lake would increase by around 2.0 m and the water level in the East Dongting Lake would increase by around 0.4 m if the area of Dongting Lake was shrunk from 2 670 km^2 to 1 380 km^2 when the 1996-type flood occurred in Dongting Lake.Moreover,the arrival time of the peak water level at Chenglingji station would be about 11 hours earlier,and the peak discharge would increase by about 4 300 m^3/s.Hence,the flood disaster would be more severe in the Dongting Lake area if the lake continues to shrink from now on.In addition,the water surface slope changes a little in the West and South Dongting Lake.But the water surface slope increases a lot near the Lujiao station due to the water level in the East Dongting Lake is affected by both of the lake shrinkage and the water level in Yangtze River.