三峡水库支流水华机理及其调控技术研究进展

A review on the mechanism and its controlling methods of the algal blooms in the tributaries of Three Gorges Reservoir

三峡水库自2003年蓄水以来,水库干支流水环境状况及支流水华问题已成为广泛关注的问题,国内外不少科研单位及学者对此进行了大量的研究。本文在介绍三峡水库蓄水以来水库水质状态及支流水华情势的基础上,系统总结了关于三峡水库干支流水动力特征及其环境效应、水华机理及其调控措施的研究发现,并提出了有待进一步研究的内容。主要研究发现包括:(1)三峡水库蓄水后支流库湾普遍存在分层异重流现象,产生的原因是干支流温度差及泥沙浓度差引起的水体密度差,其中水体温度差是主要因素;(2)在分层异重流的驱动下,支流库湾水体呈现"双混斜"及"半U"型特殊水体分层模式,支流库湾营养盐也主要来自于水库干流倒灌;(3)流速变缓只是支流暴发水华的表观原因,分层异重流驱动下的混合层(Zm)与临界层(ZCr)的关系变化才是决定水华生消的关键;(4)水库水位升降可通过影响分层异重流的形态、改变支流水体分层状态进而调控支流水华的生消过程,基于此提出了防控支流水华的"潮汐式"生态调度方法。如何将上述新发现上升为具有三峡水库特色的系统理论与方法,实现支流水华的精准预测预报,开展能够协调水库传统效益和防控支流水华等生态效益的三峡及上游梯级水库群联合多目标优化调度实践,应是今后进一步努力的方向。

Since the initial impounding of the Three Gorges Reservoir（TGR） in 2003,the problems of algal bloom in some tributaries have been attracting much attention, and many research works have been done by some scientists and research institutes. In this paper,the condition of the water environment and algal blooms is firstly introduced, the hydrodynamics and its effects on the ecosystem are analyzed, research progress of the mechanism of the algal blooms and its controlling method is reviewed,and the future research aspects are discussed. The review of new findings includes that（1） a bidirectional density currents（BDCs） could be a common flow pattern in the tributaries of the TGR,which are caused by the density difference related to the water temperature and the silt concentration,in which water temperature is the dominant factor;（2）under the BDCs,the thermal stratification in the tributary bays present a＂double mixolimnion-thermocline＂pattern near the estuary and a＂half Ushape＂pattern near the backwater end,and the nutrients in the tributary bays are mainly from the mainstream through water intrusions;（3）the trig-ger of the algal blooms depends on the relationship between the mixing depth（Z_m） and euphotic depth（Z_（eu））,but not on the flow velocities directly;（4）the tide-type ecological operation method of TGR could effectively control the algal bloom through affecting the stratified density current. The further study should focus on how to predict the algal bloom accurately using some new theory and methods,and to develop a multiple-objective optimal operation of the cascade reservoirs in the whole Yangtze River upstream area.