大型分层水库翻库特性及溶解氧响应研究

翻库对分层水库的水生态环境具有重要意义。通过在大型深水水库潘家口水库的原位监测结合垂向二维水动力-水质-水生态模型对翻库特性及溶解氧(DO)响应进行研究,分别对2018和2020年的水环境过程进行模拟。结果显示,水温分层导致了DO垂向分层,表层DO与气温相关性强,底层DO在分层后持续下降至0,秋季翻转是底层复氧的主要途径。2018年平均运行水位较2020年高14.2 m,表层温水层最大厚度2018年比2020年增加了近10 m,水库翻库从库尾逐渐向坝前推进。在库尾到坝前的距离约30 km的水域,2018年翻库的历经时间比2020年缩短40 d,坝前DO的垂向均匀时间滞后于水温7~10 d。水库水位较低时,翻库产生的表层水体DO下降幅度更大,降幅为3~4 mg/L。分别对水库不同断面可用势能指数(APE)对分层稳定性的过程进行分析,水库在不同年份和不同位置断面的翻库日期与夏季混合循环期的平均APE指数大小具有较好的相关关系。研究为探求大型深水分层水库水环境演变规律,科学合理进行调度提供理论基础。

Turnover characteristics and dissolved oxygen responses in a large stratified reservoir

Turnover has important eco-significance to the stratified reservoirs.By in-situ monitoring in Panjiakou Reservoir,a large and deep reservoir in northern China,associated with a vertical 2-dimensional hydrodynamic-water quality-water ecological model,the reservoir turning characteristics and dissolved oxygen(DO) response were studied.The environmental evolution processes in 2018 and 2020 are modelled respectively,and the results show that water temperature stratification leads to vertical stratification of dissolved oxygen(DO).The surface DO has a correlation with the air temperature,and the bottom DO continues to drop to 0 after stratification.The autumn turnover is the principal way of the bottom aeration annually.The average operating water level in 2018 was 14.2 m higher than that in 2020,and the maximum thickness of the epilimnion in 2018 is nearly 10m greater than that in 2020.The reservoir turnovers started from the tail of the reservoir to the region in front of the dam.The duration of turnover in 2018 was 40 days shorter than that in 2020 in the analyzed domain which is about 30km from the tail to the dam.The vertical mixing time of DO lags behind the water temperature by 7 to 10 days.Surface DO was strongly influenced by the turnover and dropped 3-4 mg/L in the period with the relatively low water level in 2020.The annual available potential energy index(APE) of each section was utilize to analyze the stability of stratification.When the water level of the reservoir is low,the DO of the surface water body produced by the reservoir turnover will drop more,with a drop of 3-4 mg/L.The annual variation process of the available potential energy index(APE) of different sections of the reservoir is analyzed respectively.The dates of turnover of different locations in the two years have a good correlation with the average APE index in the summer mixing cycles.The study explored the regular pattern of water environmental evolution in the deep and stratified reservoirs,admin and some theoretical results for optimal operation.