三峡水库香溪河库湾特殊水温分层对水华的影响

三峡水库蓄水后,香溪河库湾暴发了多次藻类水华.通过分析香溪河库湾2008年全年水温分层及水华暴发的空间特性,研究了水体分层特性与水华空间分布的关系.结果表明:三峡水库库首江段在3至4月份出现了水温弱分层现象,垂向温差在1～2℃,基本不暴发藻类水华;香溪河库湾中下游水体因受长江倒灌异重流的影响,呈"阶梯"型分层模式,上游水体因受低温来流底部异重流影响,呈"半U"型分层模式;香溪河库湾水体主要进行"水平"而非"垂直"能量交换,呈现下游深水区水温分层较弱、上游浅水区分层反而较强的特殊空间分布特点;受库湾水温分层结构的影响,香溪河库湾下游近河口段水域水华暴发强度低,上游水域水华暴发强度高;水华暴发率和水体稳定率能够分别反映香溪河库湾水华暴发程度和水体稳定程度特性,二者相关性显著.结合临界层理论能够很好地解释三峡水库干支流水华暴发过程.

Effects of special vertical layered water temperatures on algal bloom in Xiangxi Bay of Three Gorges Reservoir

The algal bloom occurs in some sections of Xiangxi Bay after the Three Gorges Reservoir(TGR) impounding.The spatiotemporal distribution of layered water temperature and algal bloom in 2008 was monitored.The results show that there was a weak stratification from March to April in TGR;the vertical temperature difference was only limited within about 1-2℃;and no algal bloom occurred in the main stream of TGR.There was a weak stratification in downstream of the bay because of the adverse slope density flow from the main stream of TGR and a strong stratification in upstream because of the process of bed down slope density current from the incoming flow with low water temperature.As a result,the grade of algal bloom in downstream of the bay was more serious than the upstream.There was high correlation coefficient between algal bloom occurring ratio and the water vertical stability ratio.The relationship between the algal bloom and the stratification can be summarized as the critical depth theory.