Wind impacts on suspended sediment transport in the largest freshwater lake of China

Abstract

Poyang Lake, the largest freshwater lake in China, is distinguished by complicated suspended sediment (SS) dynamics. Apart from lake currents, wind is an important form of natural disturbance in driving SS transport. Combining field data, laboratory experiments, and numerical simulations, we gained valuable insight into wind impacts on SS dynamics in Poyang Lake. (1) Lake current patterns exert great influence on the level of wind impacts. Due to reduced sediment carrying capacity, SS under weak current suffers from stronger wind influence than under strong currents. (2) Wind speed determines the degree of wind impact, not only affecting horizontal SS transport, but also regulating vertical dynamics. Winds exceeding critical intensity can enhance horizontal transport through both surface drift and Stokes drift at different water depths, triggering sediment suspension to feed the loads in overlying water. (3) Wind impact is influenced by lake morphology. The broad water surface in the central lake permits formation of continuous waves, leading to the largest SS fluctuation, from −10.05 mg·L−1 to +20.17 mg·L−1, while average variation in the south and north part of the lake is only −6.59 mg·L−1 to +10.36 mg·L−1. (4) SS in four reserves are characterized by notable wind impact, while in the other two reserves SS show no obvious departure from values without wind.

Keywords

• numerical experiment
• poyang lake
• shear stress
• suspended sediment
• wind