Abstract
A recent dramatic decline in water level during the dry season in China’s largest freshwater lake (Lake Poyang) significantly influenced water availability and biogeochemical processes. To learn the potential causes of water level decline, this study investigated the hydrodynamic response to bathymetric changes during three typical hydrological years by scenario simulation using Environmental Fluid Dynamics Code (EFDC). The simulation results indicated that bathymetric changes resulted in a water level decrease during a low water level period. Inter-annual variation in the decrease rate implied that water level in typical dry and wet years were influenced more significantly than that in moderate hydrological years. A spatial gradient in the distribution of water level changes was also observed, which was mainly concentrated in the main channel. Water velocities also slowed down, weakly corresponding to the decrease in water level during the low water level period. Overall, bathymetric changes caused by sand mining contributed to water level and velocity variations, influencing the stability and sustainability of the lake ecosystem. This study can potentially enhance our understanding of the hydrodynamic processes in Lake Poyang and support water resource management.
Highlights
Lake Poyang, the largest freshwater lake in China, plays an important role in water storage, transportation, and ecological maintenance [1,2]
We investigated the effects of bathymetric changes caused by sand mining on the hydrodynamic conditions in the typical wet, dry, and moderate hydrological years in Lake Poyang
These results proved that the model was able to capture the variation in the water level of Lake Poyang
Summary
Lake Poyang, the largest freshwater lake in China, plays an important role in water storage, transportation, and ecological maintenance [1,2]. Hydrodynamic conditions in Lake Poyang are associated with the ecological evolution of and biogeochemical processes in aquatic ecosystems. The water level fluctuation is closely related to drought and flood occurrence and frequency [4], water quality deterioration [5], phytoplankton biomass and distribution [6,7], wetland exploitation and conservancy [8]. The water level of Lake Poyang has a large seasonal fluctuation of around 10 m. There is a large fluctuation in the inter-annual water level, and the probability of having a year with a low water level is higher than a year with a high water level [10]. Owing to the inter-annual fluctuation, Lake Poyang Basin frequently faces extremely high and low water level events, especially in recent decades. Devastating floods occurred in 1954, 1983, Water 2019, 11, 1469; doi:10.3390/w11071469 www.mdpi.com/journal/water
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