赣江入鄱阳湖尾闾东西河分流比变化规律分析

Analysis on variation of flow diversion ratio at tail-streams of Ganjiang River

赣江尾闾在南昌段的裘家洲、扬子洲首次分为东、西河,其分流比变化特性直接影响到下游河道的稳定、防洪、航运、水生态水环境等方面的安全问题。影响分流比的因素众多,主要选取了过流条件和入湖水位两个因素,采用资料分析和模型试验的方法,分析了赣江东、西河分流比变化规律及其影响特征。对1998年以来裘家洲分流口东、西汊的断面演变状况进行了对比分析,结果表明:西汊在不同水位条件下的过水面积增大是西河分流比增大的主要因素;西河入湖水力比降降低幅度较东河要小,东河甚至出现了倒比降,这些均是影响分流比的重要因素。为此,进行了试验研究,试验结果表明:东河入湖水位对分流比的影响相较于西河而言更为显著,水位的变化幅度与分流比的变化呈线性相关关系,而且随着流量的减少,对分流比的影响更为敏感;西河分流比的变化与流量呈线性关系,东河分流比与流量则呈幂函数关系。

The Ganjiang River separates into two river branches(East and West) at Qiujia and Yangtze sandbars,the tailstream area of Nanchang reach. The flow diversion ratio of the East and West branches directly determine the stabilization,flood control,navigation and water environment safety of downstream river channels. The flowing conditions and water level at lake entrance were selected as two factors impacting diversion ratios. Using data analysis and model test,the variation laws and features that influence the flow diversion ratios were analyzed to provide basis for keeping the diversion ratio within a reasonable range.Comparison was made to analyze the bifurcation cross-section variation at the Qiujia sandbar since 1998.The results show that the cross-section area increase under different water levels in the West branch is the major factor for a higher diversion ratio; hydraulic gradient of the East branch reduced more than that of the West branch,the East branch even experienced a negative growth occasionally. The model test results indicate that compared to the West branch,water level of the East branch at the lake entrance has more significant impact on the diversion ratio; the variation of water levels is linearly correlated to the changes of diversion ratio and in the condition of lower flow,the diversion ratio is more sensitive to water level; the diversion ratio of the West branch varies linearly with the flows and the diversion ratio in the East branch shows a power function relation to water flows.