Characteristics of thermal stratification in head area of Three Gorges Reservoir and ecological effects in different operation periodsEI北大核心CSCD

为了解三峡水库库首2003—2018年的水温变化特征及其对生态环境的影响，基于庙河断面实测资料，采用LSTM-Logistic模型模拟分析了库首多年水温结构特性，并探讨了其变化对库区支流库湾水华的影响和对坝下鱼类产卵水温的影响。结果表明：LSTM-Logistic模型能较好地适用于三峡水库，准确地模拟水温的逐日变化过程；2006—2013年，三峡水库库首每年4—6月均出现了水温分层现象，从2014年开始，水温垂向差异变小，水温不分层，且春季、秋季和冬季水温升高，下泄水温进一步平坦化；三峡水库库首水温长期变暖的趋势，会使支流库湾倒灌异重流潜入深度上移，从而改变异重流倒灌形式，降低库湾水华风险；梯级水库蓄水缓解了春季下泄低温水的不利影响，但秋冬季水温的升高对中华鲟繁殖造成了进一步威胁。

Characteristics of thermal stratification in head area of Three Gorges Reservoir and ecological effects in different operation periods

In order to investigate the variation of water temperature at the head area of the Three Gorges Reservoir (TGR) from 2003 to 2018 and its impact on the ecological environment, the LSTM-Logistic model was used to simulate the multi-year water temperature process based on the field data at the Miaohe hydrological station. The influences of its variation on algal blooms in the tributary bay and the spawning water temperature of the downstream fish are discussed. The results show that the LSTM-Logistic model is applicable to the TGR, and it can accurately simulate the daily variation of water temperature. From 2006 to 2013, thermal stratification occurred at the head of the TGR from April to June. In 2014, the vertical differences of water temperature began to decrease and stratification disappeared. The average water temperature increased in spring, autumn, and winter, and the discharge water temperature further flattened. The long-term warming trend of the water temperature at the head area of the TGR will reduce the depth of the plunging point of the density current from the tributary bay, affect the pattern of the density current, and reduce the risk of algal blooms in the tributary bay. After the impoundment of the upstream cascade reservoirs, the impact caused by cold discharge water in spring is partly mitigated, while the increase of the water temperature in autumn and winter further threatened the spawning of Chinese sturgeon.