Numerical Study of Remote Sensed Dredging Impacts on the Suspended Sediment Transport in China’s Largest Freshwater Lake

Jianzhong Lu,Xiaoling Chen,Dong Liang,Haijun Li

doi:10.3390/w11122449

Abstract

As the largest freshwater lake in China, Poyang Lake plays an important role in the ecosystem of the Yangtze River watershed. The high suspended sediment concentration (SSC) has been an increasingly significant problem under the influence of extensive sand dredging. In this study, a hydrodynamic model integrated with the two-dimensional sediment transport model was built for Poyang Lake, considering sand dredging activities detected from satellite images. The sediment transport model was set with point sources of sand dredging, and fully calibrated and validated by observed hydrological data and remote sensing results. Simulations under different dredging intensities were implemented to investigate the impacts of the spatiotemporal variation of the SSC. The results indicated that areas significantly affected by sand dredging were located in the north of the lake and along the waterway, with a total affected area of about 730 km2, and this was one of the main factors causing high turbidity in the northern part of the lake. The SSC in the northern area increased, showing a spatial pattern in which the SSC varied from high to low from south to north along the main channel, which indicated close agreement with the results captured by remote sensing. In summary, this study quantified the influence of human induced activities on sediment transport for the lake aquatic ecosystem, which could help us to better understand the water quality and manage water resources.

Highlights

As one of the most important factors of water environment variations, suspended sediment carries a large amount of pollutants, including nutrients and heavy metals, affecting the water turbidity, bottom elevation evolution and hydrodynamic process in the long term
The results showed lower accuracy during the annual dry period, the reason for which may be as follows: (1) the shorelines changed from a lake into a river channel during the dry period on account of water recession, and the hydrodynamic characteristics changed a lot while the model parameter conditions remained the same as during the previous wet period, meaning the uniform model condition may result in more error during the dry period, or (2) sand dredging activities have changed the bottom bed seriously since 2001, and the bathymetric data used was measured in 2000
The main purpose of this study was to reveal the characteristics of hydrodynamic variations and their impacts on the suspended sediment concentration (SSC), caused by sand dredging activities at the spatial and temporal scale, in Poyang Lake, the largest freshwater lake with high turbidity in China

Summary

Introduction

As one of the most important factors of water environment variations, suspended sediment carries a large amount of pollutants, including nutrients and heavy metals, affecting the water turbidity, bottom elevation evolution and hydrodynamic process in the long term. Human activities like sand dredging in the navigation channel and harbor, building artificial islands by dredger, and lifting sediment into water in the coastal zones have great impacts on the suspended sediment concentration (SSC) in an aquatic ecosystem [8]. These processes and influences can be described with the help of the numerical model [9,10,11]. Considering that the numerical model is able to simulate the water flow and

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Conclusion