**Jianzhong Lu \*, Haijun Li, Xiaoling Chen and Dong Liang**

State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China; lihaijun@whu.edu.cn (H.L.); xiaoling\_chen@whu.edu.cn (X.C.); liangdong@whu.edu.cn (D.L.)

**\*** Correspondence: lujzhong@whu.edu.cn; Tel.: +86-27-6877-8755

Received: 30 October 2019; Accepted: 19 November 2019; Published: 21 November 2019

**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.

**Keywords:** hydrodynamic model; remote sensing; sand dredging; suspended sediment concentration (SSC); spatiotemporal analysis; Poyang Lake
