Experimental study on the effect of the Three Gorges Project on water level in Lake Poyang

三峡工程运行改变了长江中下游水沙情势,影响了鄱阳湖湖区水位,造成了水资源利用、水质、湿地和生态等方面的新问题.实测日水位资料分析认为:湖区水位年内变化可分为低水、涨水、顶托倒灌和退水4个阶段;顶托倒灌阶段湖区水位基本由长江干流控制,另外3个阶段湖区水位受湖口流量和长江干流的共同影响,受影响程度与水位站位置、湖口流量和长江干流相互作用强弱有关;三峡工程运行没有改变鄱阳湖水位高水湖相、低水河相的基本特征,但对水位造成了一定影响.开展物理模型试验探索三峡工程运行对湖区水位的影响程度,结果表明:蓄水期三峡工程运行造成湖区水位降幅较大,枯水年都昌站平均(最大)降幅为0.94 m(2.58 m),枯水年湖区水面面积减小68%;增泄期会增加湖区水位,都昌水位最大增幅约1 m,平水年湖区面积增加约32%;枯水期三峡工程运行对鄱阳湖水位基本无影响.;The operation of the Three Gorges Project(TGP) modified water sand regime in the middle and lower reaches of Yangtze River, affected on water level in Lake Poyang and correspondingly brought series new problems on water resources utilization, water quality, wetland and ecology. Analysis of daily water level turn out:yearly variation of water level in the lake includes four stages-low level stage, level rising stage, backwater stage, and recession stage; water level in lake is determined by Yangtze discharge in backwater stage, and is affected by both Yangtze discharge and discharge at Hukou station in the other three stages. The operation of TGP does not change the basic feature of Lake Poyang-lake-like with high water level and river-like with low water level, but actually changes values of water level. Physical model experiments have been carried out to study the effect of TGP on water level in Lake Poyang, and the results indicate:TGP impoundment caused decline in water level, the average(maximal) value of decline at Duchang station is 0.94 m(2.58 m), and corresponding decline ratio of water-surface area of Lake Poyang is 68%; TGP pre-discharge caused increase in water level, the maximal value at Duchang station is about 1 m, corresponding increase ratio of water-surface area is 32%; the operation of TGP in dry season affects little on water level in Lake Poyang.