三峡水库蓄泄水过程对香溪河库湾水华影响的对比分析

通过对比分析蓄、泄水期间三峡水库干流及支流香溪河库湾的水流、水温、浊度、营养盐等指标,研究了蓄、泄水过程中控制库湾水华的主要因子.结果表明,泄水过程中香溪河库湾叶绿素a浓度显著大于蓄水过程,水华暴发强度差别显著.蓄、泄水过程中以透明度的差异最大,其次依次为表层流速、表底温差、混合层深度、氮磷比、浊度、总氮、水体稳定系数、真光层/混合层深度比等.泄水期间各因子对叶绿素a浓度不存在单一限制作用,藻类生长受各因子的协同作用影响,在观测时段内泄水过程中各因子的变化对藻类生长的限制并不显著;而蓄水期间强烈的倒灌异重流作用加剧了库湾水体的垂向掺混,增大混合层深度,较小的真光层与混合层深度比对藻类生长起到显著的抑制作用.

Comparative analysis of the impact of discharging and impounding process of Three Gorges Reservoir on the algal bloom in the Xiangxi Bay

Water flow velocity, water temperature, turbidity, nutrients and other environmental parameters of Yangtze River and the Xiangxi Bay (XXB) were monitored. Differences of these parameters between discharging and impounding stages were analyzed in order to probe the main factors controlling algal bloom. It showed that the concentration of Chlorophyll a of discharging Period was significantly greater than that in impounding stage. In these two periods, transparency, near surface current velocity, water temperature differences between surface and bottom, mixing depth, rate of nitrogen vs. phosphorus, turbidity, total nitrogen, relative water column stability and rate of euphotic depth and mixing depth were significantly different. During the discharging stage, the discharging process did not limit algal growth. However, during the impounding stage, strengthening density current intrusion intensified vertical mixing and increased the mixing depth in the bay. Thus, smaller ratio of euphotic vs. mixing depth played a key inhibition role on algae propagation.