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

Abstract

Poyang Lake, the largest freshwater lake in China, distinguishes itself by its 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 the wind impacts on SS dynamics in Poyang Lake. Several results stand out: (1) the lake current patterns exert great influence on the level of wind impacts. Due to the reduced sediment carrying capacity, SS under the weak current suffers from a stronger wind influence than those under strong currents; (2) The wind speed determines the degree of the wind impact. It not only affects the horizontal SS transport, but also regulates the vertical dynamics. Winds exceeding the critical intensity can enhance the 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 the lake morphology. The broad water surface in the central lake permits the formation of continuous waves, leading to the largest SS fluctuation, from -10.05 mg·L-1 to +20.17 mg·L-1, while the average variation in the south and north part of the lake is only from -6.59 mg·L-1 to +10.36 mg·L-1.(4) SS in four reserves are characterized by a notable wind impact, while in the other two reserves SS show no obvious departure from the values without wind.