三峡水库坝下水温变化及其对鱼类产卵影响

Assessing water temperature variations and impacts on fish spawning downstream of Three Gorges dam

三峡水库的运行改变了坝下河段天然水文情势,为研究三峡-葛洲坝梯级水库对中游河道水温的影响程度,应用滑动平均法、Kendall秩次相关检验和Spearman秩次相关检验分析宜昌站水温年际变化趋势,利用水库对河流水温影响的评价指标量化评价水库对宜昌站水温过程的影响程度。研究表明,由于葛洲坝水库调节库容较小,葛洲坝水库蓄水对宜昌站水温影响较小;三峡水库蓄水后,宜昌站水温波动效应明显增强,主要表现为明显的滞迟效应,均化程度呈逐年加深趋势;三峡水库蓄水改变了坝下河道原有的天然水温过程,水温的滞迟效应表明三峡水库运行导致的水温变化使中华鲟的繁殖时间推迟29天左右。此研究结果为面向生物保护的三峡水库生态调度提供科学支撑。

Operation of the Three Gorges reservoir has caused changes in the natural hydrological regime. To evaluate the impact of the Three Gorges-Gezhouba cascade reservoirs on the middle Yangtze, we analyze the annual variation in water temperature at Yichang hydrological station, using statistical approaches of moving average, Kendall＇s rank correlation, and Spearman＇s rank correlation, and focusing on water temperature quantified with evaluation indicators. The results show that the Gezhouba reservoir has a slight impact on the water temperature at Yichang because of its small storage capacity. Since impoundment of the Three Gorges reservoir, water temperature has shown larger fluctuations featured with a hysteretic effect, and the peak-valley differences have decreased year by year. The impoundment has significantly impacted the natural river water temperature below the dam. The period of higher water temperature within a year has manifested a tendency of time delay, which is an evidence showing that the reservoir has caused changes in water temperature. Our analysis indicates that under this circumstance, the spawning time of Chinese sturgeon should have been delayed for about 29 days. This study would be useful to the ecological operation of the Three Gorges reservoir facing biological conservation.