Analysis on the evolution and driving mechanism of low flow regime from 1956 to 2022 in Poyang Lake,China
Changes in the low flow regime of Poyang Lake will greatly affect the security and stability of regional water resources,water environment and water ecology.The analysis of the causes of extreme hydrological events in Poyang Lake and the early warning of disasters under complex conditions are currently difficult problems that need to be broken through.This paper,based on the analysis of the hydrological process of annual water replenishment and water withdrawal in the lake area,explores the evolution law and driving mechanism of the low flow regime in the lake area by using the methods such as the staging analysis of"river-lake relationship".The results show that:(1)during the post-Three Gorges period,the dry regime in the lake area was significantly intensified,the annual minimum water level at Xingzi station dropped by 5.7％on average,and the low water intensity and low water days increased by 36.9％and 26.6％on average,respectively;(2)in the single factor analysis,the number of low-water days in the lake area is more affected by the flow conditions of the Yangtze River than the low-water intensity and minimum water level;in the multi-factor analysis,six explanatory factors comprehensively explained the evo-lution of the three above-mentioned low flow variables in the lake area,and the R2 values obtained by the three re-gression models were 0.83,0.83,and 0.70,respectively;(3)contribution analysis shows that the overall aggra-vation of the dry in the past 20 years is mainly due to the comprehensive impact of changes in the Yangtze River wa-ter flow conditions;taking the decrease in the annual minimum water level in the lake area as an example,the var-iation in the water level and flow relationship of rivers and lakes contributes 138.0％,Hankou runoff reduction con-tributes 8.4％,and Hankou runoff increase(mitigation)during the replenishment period of the Three Gorges Reser-voir contributes-34.2％.This study will provide a reference for the decoupling of the driving mechanism of the low flow regime in Poyang Lake and the study of drought early warning.
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