Changes in Lake Inundation and Shrinkage Within the Framework of Coevolutionary River-Lake state

Abstract

The Dongting Lake (DTL) area constitutes a naturally interconnected lake wetland. Alterations in river-lake relationships are poised to profoundly modify the ecological condition of lake region. This study aims to investigate the co-evolutionary attributes and ecological response mechanisms involving the Yangtze River, the Four Rivers within the DTL basin (DFR), and DTL itself during extreme hydrological events. Amidst the trajectory of wetland contraction, the impact of shifts in river-lake relationships on the wetland's state remains unclear. Thus, we employ cross-wavelet transformation and the multifractal method to establish a framework for co-evolution between rivers and lake. Through this framework, we analyze the varying progression of hydrological relationships within the river-lake system and their corresponding responses. The findings reveal that instances of low-water events in DTL predominantly manifest during winter and spring. These low-water events exhibit a propensity to occur frequently and irregularly, except during July-August, coinciding with the Yangtze River's flood regulation period. Additionally, the DFR-DTL system demonstrates a wider periodicity and more pronounced positive continuity, serving as the principal impetus behind the ecological evolution of DTL. Simultaneously, alterations in the inundation status across DTL regions display an ascending trend from west to east. The predominant influence of the Yuan River and the Yangtze River leads to the majority of water degradation areas being concentrated in the western DTL region, where sedimentation is particularly severe. The changes in river-lake relationships showcase substantial variability and exert distinct impacts on DTL's hydrological evolution through a range of confluence regions.