三峡水库支流神农溪库湾倒灌异重流特征及成因分析

三峡水库蓄水以来，库区干支流水动力变化显著。探明三峡水库支流库湾倒灌异重流的成因对库区水华防控调度十分关键。基于2018年野外观测数据，对神农溪库湾水流速度，水温，浊度等因素进行分析。结果表明：库湾春冬季由于水温变化不大，泥沙含量很低，干支流密度差较小，导致倒灌异重流呈无规律状态；夏秋水温变化较大，泥沙含量大幅升高，水体多以中、底层倒灌形式从干流潜入库湾。库湾在汛期受泥沙含量较高的影响，导致水体密度增大形成异重流，且大部分出现在库湾中底层，其他月份异重流是由水体温差形成的，温差是倒灌异重流的主要成因；汛期6~8月，干支流泥沙含量升高，泥沙含量对水体密度的贡献率增大，最大为75%；其他月份水体密度主要受水温影响，水温对水体密度的贡献程度在各月均超过80%，最大贡献率为95%。

Characteristics and Causes of Density Flow in the Shennong Bay of the Three Gorges Reservoir

Since the impoundment of the Three Gorges Reservoir, the hydrodynamics of the mainstreams and tributaries in the reservoir have changed significantly. It is very important to find out the reason of the density flow in the bay of the Three Gorges Reservoir. Based on the field observation data of 2018, the water flow velocity, water temperature and turbidity of Shennong Bay were analyzed. The results show that the water temperature in the Shennong Bay was not changed greatly in spring and winter, the sediment concentration was very low, and the difference of the mainstream and tributary was small, which leaded to the density flow in an irregular state. The water temperature in summer and autumn changed greatly, the sediment concentration increased greatly, and the water body most of them were submerged into the reservoir bay from the mainstream by means of medium and bottom inversion. In the flood season, the reservoir was affected by the high sediment concentration, which leaded to the increase of water density and the formation of density flow, and most of them appear in the middle and bottom of the reservoir bay. In other months, the density flow potential was formed by the temperature difference of the water body, and the temperature difference was the reverse irrigation. From June to August,the main cause of density flow was the sediment concentration of the difference between the mainstream and tributary increased, the contribution rate of sediment content to water density increased, up to 75%; the density of water in other months mainly affected by water temperature, the contribution of water temperature to water density exceeded 80% in each month, and the maximum contribution rate was 95%.