三峡水库水质时空变化特征及影响机制研究OACSTPCD

The reservoir ecological environment after the construction and operation of the Three Gorges Project has been a great concern.The water quality conditions in the reservoir are complex and constantly changing.However,the spatio-temporal varia-tion characteristics and influence mechanisms of the water quality in the reservoir under the reservoir scheduling still need to be explored.Based on the monitoring data over 11 Yangtze River mainstream cross sections and 2 tributary cross sections in 2021,we utilized the water quality index(WQI)to evaluate the water quality in the reservoir,and combined principal component analysis(PCA),Pearson correlation analysis,one-way ANOVA and random forest(RF)methods to investigate the spatio-temporal characteristics and influence mechanisms of water quality in the Three Gorges Reservoir under the influence of reservoir schedu-ling.The results showed that:①From the spatial scale,the changes of each water quality parameter had obvious spatial heteroge-neity.The overall water quality condition had improved from upstream to dam site(Zhutuo to Wuxiakou section),and the water quality condition of Zhuyangxi section was the worst.②From a monthly perspective,different water quality parameters and WQI changed with reservoir storage.TP and CODMn concentrations generally showed the characteristics of flood season(June to Sep-tember)＞drawdown period(January to June)and storage period(September to October)＞high water level period(October to December).DO,pH and WQI,on the contrary,decreased in the drawdown period,were relatively stable in flood season,and gradually increased during the storage period.The ecological scheduling benefited the water quality in the reservoir.Two ecological schedules,from 29 May to 3 June and from 16 to 22 June,to promote the reproduction of drifting spawning fish,probably resulted in a significant improvement in water quality in the reservoir in June.④Various statistical analysis tools combined with RF meth-ods showed that there were significant correlations between different water quality parameters.TN,TP,NH3-N and CODMn were significantly positively correlated(r＞0.3,p＜0.01),pH and DO were significantly positively correlated(r =0.428,p＜0.01),and all parameters significantly affected the WQI in the Three Gorges Reservoir(p＜0.01),with turbidity being the most impor-tant parameter affecting the water quality in the Three Gorges Reservoir.The results of this study can provide a theoretical basis for the sustainable development of the water environment and the rational allocation of water resources in the Three Gorges Reser-voir.