三峡工程运行对洞庭湖与荆江三口关系的影响分析

THE IMPACT ANALYSIS OF THE RELATIONS BETWEEN DONGTING LAKE AND THE THREE OUTLETS OF JINGJIANG RIVER AFTER THE THREE GORGES PROJECT OPERATION

三峡水库于2003年6月1日正式开始蓄水,其防洪、发电、航运等综合效益日益明显。根据水文泥沙观测资料,采用BP(Back Propagation)神经网络、变差系数法、双累积曲线法等方法分析三峡工程的运行对洞庭湖与荆江三口关系的影响,结果表明:(1)从年际和年代际尺度上看,长江上游降水量减少和三峡工程建设等人类活动是影响洞庭湖水沙变异的主要因素;(2)长江中下游荆江三口分流分沙锐减,并呈现三口口门趋于淤积,藕池河和虎渡河逐渐走向衰亡;(3)从洞庭湖泥沙沉积量过程线来看,2003—2010年洞庭湖的累计泥沙淤积量仅为2301×104t,比多年平均值减少95.6%;(4)运用BP神经网络对洞庭湖出湖水量和沙量进行模拟,结果显示模拟精度满足洞庭湖出湖水沙预测的需要。

Since impoundment on June 1,2003,the Three Gorges Reservoir(TGR) began to play comprehensive roles in flood control,power generation,and navigation,etc.In order to study the changes of erosion,hydrological response,relationship between river and lake,variations in the condition of water and sediment movements in the Dongting Lake area since the operation of TGR.Hydrological and sediment observation data were analyzed systematically to understand the water and sediment in-and-out of the TGR.In addition,by applying the BP Neural network,variation coefficient and accumulation curve of water and sediment were calculated or depicted,to study the material transportation from the Dongting Lake to the Changjiang(Yangtze) River,and the variation of water and sediment within the lake.Results show that:(1) in inter-annual and inter-decadal scales,reduction of precipitation in the upper reaches of Changjiang River and the construction activities of TGR are the main factors causing variation of materials in the lake;(2) the sharp decrease of flow-in water and sediment downstream the TGR has caused siltation at the Sankou Section(the three outlets of Jingjiang River) and the demise of other two tributaries who are no longer function as a normal river; and(3) the accumulated amount of sediment in Dongting Lake in 2003—2011 is merely 2301×104 t,a 95.6% reduction of that in 1994—2002.In addition,using BP neural network could simulate precisely the amount the runoff and sediment in Dongting Lake,providing a tool for effective utilization and scientific management over the complicated river-basin system.