中文摘要：

三峡蓄水后的支流回水区平均流速在0.01m/s以下,因此将其近似视为静止水体,通过构筑光照对蓝藻种群垂直迁移影响理论模型,分别以1a和1d为研究期限,对蓝藻种群的垂直迁移进行模拟计算。结果显示：蓝藻垂直迁移过程具有明显季节特征,每年冬季,蓝藻处于休眠期,并停留在水底;4月蓝藻开始复苏,11月处于休眠期的过渡阶段,这两个月具有微弱浮力;5和10月蓝藻开始接近水表,易发生垂直迁移;6～9月蓝藻垂直迁移速率增加,易发生水华。计算表明：6和9月蓝藻上升/下沉速率较大,易发生快速的上浮/下沉垂直迁移运动,宏观上表现为水华的急剧暴发/消退;6月易暴发水华的时间为早上8点到10点,9月易暴发水华的时间为早上10点到11点,预测结果和实测资料具有良好的一致性。

英文摘要：

In this paper,since the water flow velocity below 0.01m/s,the following in the tributary backwater area after the Three Gorges Reservoir Area impounded,so it can be approximately regarded as static water.The paper carried on simulating calculation to the vertical migration of cyanobacteria species by building a theoretical model of illumination influences to its vertical migration,and setting ayear and a day as study period respectively.The results of the calculation revealed that the vertical migration of cyanobacteria had an obvious seasonal characteristic.Cyanobacteria stayed in the dormant period and remained at the bottom of water every winter,while they began to recover in April and entered dormancy in November when they had weak buoyancy.Cyanobacteria started to up to the water surface in May and October,and the velocity of cyanobacteria＇s vertical migration increased from June to September when algae blooms could happen easily.Meanwhile,the computed results demonstrated that the speed of rising/sinking of the cyanobacteria were higher in June and September,and the water body was prone to come up rapid migration of floating/sinking vertical migration.This phenomenon showed dramatic bloom outbreaks/fade at macro level. What＇s more,it was from 8：00am to 10：00am in June that the algal blooms easily occurred,and in September,the time was from 10：00am to 11：00am.Predicting results and observed data had a good consistency.