为研究三峡水库汛期调度对支流水华的抑制效果,于2022年6月24 日-7月3日,跟踪监测三峡水库调度前期、调度期、调度后期代表性支流小江的藻类群落结构与水体理化因子,采用Kruskal-Wallis秩检验分析调度前后的水环境变化,采用Pearson相关分析和逐步回归分析探究藻类与环境因子的关系,采用RDA分析探究不同环境因子对藻类群落结构变化的贡献度,构建结构方程模型解析水库调度对水华的影响.结果显示,调度前期小江常年回水区发生蓝藻水华,以叶绿素a浓度表征的藻类生物量最高达到58.33 μg/L;通过调度水位抬升后,藻类生物量降至6.41 μg/L.回水区水温、pH值、总氮(TN)浓度降低,总磷(TP)浓度、硝酸盐(NO3--N)浓度升高(p<0.01);逐步回归分析结果表明藻类生物量受水位变化过程中的TN、NO3--N、磷酸盐(PO43--P)、水温、电导率(Cond)和化学需氧量(COD)的影响,共解释了 79%的生物量变化.结构方程模型表明,水位抬升能降低COD浓度,显著降低支流水体的叶绿素a含量.研究结果表明通过适当的水库调度能够有效抑制三峡支流水华,这可为水库生态环境管理和保护提供依据和新的解决方案.
In the aim of investigating the inhibitory effect of Three Gorges Reservoir(TGR)operation in flood sea-son on water bloom in its tributaries,we monitored the algal community and environmental parameters of water body in Xiaojiang River,a representative tributary of TGR,before,during,and after TGR operation from June 24th to July 3rd,2022.We employed the Kruskal-Wallis rank test to analyze the changes in water environment,the Pearson correlation and stepwise regression analysis to examine the relationship between algae and environmental factors,and RD A to assess the contribution of different environmental factors to the variation of algae community structure.Additionally,we constructed a structural equation model to analyze the influence of reservoir operation on water bloom.The results demonstrated a significant decrease in algal biomass characterized by chlorophyll a concentration(from 58.33 μg/L to 6.41 μg/L)after the operation in the permanent backwater area where severe bloom occurred.In the whole backwater area,water temperature,pH value,and TN concentration decreased,while TP concentra-tion and NO3-N concentration increased(P<0.01).Stepwise regression analysis revealed that algal biomass was primarily influenced by total nitrogen(TN),nitrate(NO3--N),phosphate(PO4--P),water temperature,electri-cal conductivity,and chemical oxygen demand(COD),explaining 79%of the biomass variation.The structural e-quation model indicated that water level rise led to a reduction in COD concentration and an evident decrease of chlorophyll a concentration.This study conclusively shows that proper reservoir operation can effectively inhibit wa-ter bloom in the tributary of the Three Gorges Reservoir.These findings provide a basis and a solution for reservoir eco-friendly management practices.