长江中游监利段近10年水位流量响应关系新特点

为了掌握三峡水库试验性蓄水以后长江监利河段水位流量响应关系新特点,以监利水文站为代表,采用数理统计、影响因素相关分析等方法进行了研究。结果表明:三峡水库蓄水后,尤其是试验性蓄水后监利河段河床冲刷,同水位过水面积增加,但监利站水位流量关系随断面冲淤调整的特征与下荆江裁弯及三峡水库蓄水初期河床冲刷引起的水位流量关系变化特征有较大不同。下荆江裁弯引起监利站各流量级相应水位降低0.62～0.95 m;蓄水初期(2003～2008年),监利站实测流量点群中心线同流量对应水位比蓄水前有所下降。试验性蓄水期(2009～2018年),同流量对应水位仅在枯水期有明显降低,随着流量级增加,水位降低幅度逐渐减小,当流量超过平滩流量,对应水位基本无变化。水面比降是监利段水位流量关系的主要影响因素,河床冲刷是次要影响因素;该河段水位流量特征的变化受洞庭湖出流顶托影响不明显。

New characteristics of water level and discharge relationship at Jianli section in middle reaches of Yangtze River in past 10 years

In order to explore the new water level and discharge relationship at Jianli section in the middle reaches of Yangtze River since the experimental impoundment operation of the Three Gorges Reservoir, statistics and correlation analysis were carried out to study it with the monitoring data of Jianli Hydrological Station. It is concluded that after impoundment of the Three Gorges Project, especially after the experimental impoundment, the riverbed in the Jianli section was scoured, and the area of water passing through increased at the same water levels. However the water level and discharge relationship characteristics of Jianli section caused by riverbed scour were quite different compared with that of cut-off project of lower Jingjiang Bay and the initial impoundment of TGR. The lower Jingjiang Bay cut-off project caused drop of water level about 0.62～0.95 m at each flow level, and in the initial impoundment of the Three Gorges Reservoir(2003～2008), the water level corresponding to the center line of point group of measured flow decreased compared with that before the impoundment. In the experimental impoundment stage(2009-2018), the water level corresponding to the same flow decreased significantly only in dry seasons, and as the flow discharge increased, the decrease amplitudes of water level were gradually mild. Especially when the flow approximately exceeded the bankfull flow, the water level corresponding to the same flow basically remained unchanged. The analysis showed that water level gradient was the primary factor for water level and discharge relationship in the Jianli reach, the riverbed scour was a secondary factor, and the backflow effect of the Dongting Lake had not significant effect on the water level and discharge relationship.