西南地区典型河道型水库水温结构及水动力机制研究

Study on water temperature structure and hydrodynamic mechanism of river-type reservoirs in southwest China

大型河道型水库在发挥水电效益的同时,其特有的水温分层对水环境的影响不容忽视。现有研究多偏重于水温垂向差异及时空演变规律研究,对于其形成过程的水动力影响研究尚不够深入。本研究利用数学模型模拟分析西南地区典型河道型水库—乌东德水库水温结构变化过程,发现水动力条件是水温结构形成的决定性因素,主温跃层的形成和演变取决于温差异重流导致的水动力机制。2—3月来水下潜于水库底部,二者界面形成主温跃层,并不断向库区下游发展;4—6月来流形成中间流,其上和其下分别形成两个温跃层;7月入库水流为上浮流,其下形成主温跃层;坝前局部区域水体主温跃层因取水孔口动力抽吸作用等温线出现局部收缩。

For a large river-type reservoir that is operating for hydroelectric benefits,the impact of its unique water temperature stratification on the water environment cannot be neglected.Most of the previous studies focus on the vertical variation in water temperature and its temporal evolution,lacking an in-depth examination on the hydrodynamic effect during its formation.This study uses mathematical models to simulate and examine the varying process of water temperature structure in the Wudongde reservoir,a typical river-type reservoir in the southwest region.We find that hydrodynamic conditions are the decisive factor in forming certain water temperature structures,and the formation and evolution of the main thermoclines depend on the hydrodynamic mechanism caused by thermal density flow.From February to March,the incoming water plunges into the reservoir bottom,forming a main thermocline at the interface between the two layers,and continuously developing as it advances further downstream at the bottom;From April to June,the inflow plunges down as an intermediate layer,with two thermocline layers formed at its upper and lower edges separately;In July,the inflow stays on the surface as an upward floating flow with a main thermocline below it.In the case of the water intakes,the dynamic suction effect of its orifices causes the main thermoclines to contract locally in certain areas near the dam.