Soil moisture in relation to lake fluctuations in a river-lake-basin system: A case study of the Poyang Lake region, China

摘要

Lake fluctuations in river-lake-basin (RLB) systems are highly complex because of the significant interactions of various hydrological variables. Clarifying these interactions would be helpful for understanding the physical mechanisms of lake fluctuations and improving responses to extreme hydrological events (i.e., drought or flood). Though numerous studies have been carried out to investigate the flow between rivers and lakes (river-lake interaction), research on the hydrological processes between a lake and its surrounding basin (lake-basin interaction) remains rare. This study investigates lake-basin interactions by examining the changes in the water distribution between the land and a lake with an examination of the Poyang Lake region, China. Specifically, this study first estimates water storage by employing the water balance model. Then, the spatial and temporal correlations between the lake area and soil moisture are examined to capture the lake-land interaction. The results show that the region's annual water storage has decreased in recent decades and varies in different months. Specifically, more water in the region is stored in the lake before July, and increasing amounts of water are held on land after that. Spatially, soil moisture is low in the region near the lake in summer because of the high radiation of water reflectance, which enhances evapotranspiration. By contrast, soil moisture is high in other seasons because of the flow from top to bottom. It can be concluded that soil moisture could mitigate the change in water storage due to the shrinkage of Poyang Lake, which is characterized by significant spatial and temporal variabilities. The results of this study help elucidate the dynamics and distribution of water resources in similar RLB systems, support water management and promote local sustainable development.