基于常量离子示踪技术的香溪河库湾分层异重流特性研究

DENSITY-STRATIFIED FLOW OF XIANGXI BAY AT THREE GORGES RESERVOIR BASED ON THE TRACER PRINCIPLE OF INORGANIC ION

2012年9月26日对三峡水库干流及香溪河库湾的水流特性及常量离子进行监测,以分析蓄水期间三峡水库香溪河支流库湾水动力特性。结果表明:香溪河库湾镁离子空间上呈下游低上游高的梯度变化,钠离子呈下游高上游低的梯度变化,河口处水中常量离子的楔形区与流速纵剖面矢量图中流向上游的楔形区的位置和厚度基本一致。监测期间香溪河库湾存在显著的分层异重流特性,在河口处,长江水体从中层倒灌进入香溪河,为中层倒灌异重流;上游水体由香溪河底部流入长江干流,为底部顺坡异重流。

The Three Gorges Dam, the largest hydroelectric dam in world currently, is located at Sandouping of Yichang City, Hubei Province. While it has brought far-reaching economic and other benefits in flood control, hydroelectric power, and greater navigation access to the Yangtze River in central China, it also has many negative impacts on ecology and environment. Since the initial filling of Three Gorges Reservoir （TGR）, eutrophication and algal bloom have been observed in some tributaries, which arouse the attention from the scholars both home and abroad, and have been carried out a large number of researches. Since the initial filling of TGR, the hydrodynamics of the Xiangxi Bay（XXB） has also been changed. Regulation of water level in reservoir and the physical and chemical difference of water in XXB and steam stream, cause the frequent water exchange between steam stream and tributaries in the TGR. The hydrodynamics of the XXB could be generalized as a density-stratified flow, and could not be simply simulated by one-dimension model. The upstream water mainly flowed out of the bay in a process of downslope-bottom density current, meanwhile, the TGR mainstream water flowed into the XXB in a flowed reverse density current. SO42 ,CI-,Na＋,Ca2＋,Mg2＋,K＋,F are constant ion in water. The content of some ions in the water is relatively stable, which have chemical conserved. In this paper, XXB was as the study location. On September 26th, 2012,hydrodynamics and inorganic ion were measured in XXB, the largest tributary bay in the TGR, to study hydrodynamic characteristics of XXB at TGR. Based on the tracer principle of inorganic ion, spatial distribution of inorganic ion in XXB suggest that inorganic ions in XXB exist gradient trend. The concentration of Mg2＋ is low in downstream and high in upstream in space, the concentration of Na＋ is contrary,and they form wedge-shape while diffused to upstream. The wedge- shape is the same with that of the velocity distribution profile diagram. The water is from the steam stream, and it back flows into XXB. It verified the stratified density currents in XXB. Velocity distribution profile diagram in XXB suggests that the water back flows into XXB in the middle of the estuary, which is the middle density currents; while the water in the upstream flow into XXB at the bottom, which is the upstream slope density current. Stratification movement of the water in XXB is obvious. Finding out the hydrodynamics in XXB is a basic work to solve eutrophication.