Wind-induced hydrodynamic changes impact on sediment resuspension for large, shallow Lake Taihu, China

Abstract

Abstract The internal sediment release is a key factor controlling eutrophication processes in large, shallow lakes. Sediment resuspension is associated with the wave and current induced shear stress in large, shallow lakes. The current study investigated the wind field impacts on sediment resuspension from the bottom at Meiliang Bay of large, shallow Lake Taihu. The impacts of the wind field on the wave, current, and wave-current combined shear stresses were calculated. The critical wind speed range was 4–6\u202fm/s after which wave and current shear stress started to increase abruptly, and onshore wind directions were found to be mainly responsible for greater shear stress at the bottom of Lake Taihu. A second order polynomial fitting correlation was found between wave (R2 0.4756) and current (R2 0.4466) shear stresses with wind speed. Wave shear stress accounted for 92.5% of the total shear stress at Meiliang Bay. The critical wave shear stress and critical total shear stress were 0.13\u202fN/m2 for sediment resuspension whereas the current shear stress was 0.019\u202fN/m2 after which suspended sediment concentrations (SSC) increased abruptly. A second order polynomial fitting correlation was found between wave (R2 0.739), current (R2 0.6264), and total shear stress (R2 0.7394) with SSC concentrations at Meiliang Bay of Lake Taihu. The sediment resuspension rate was 120 to 738\u202fg/m2/d during 4–6\u202fm/s onshore winds while offshore winds contributed ≥ 200\u202fg/m2/d. The study results reveal the driving mechanism for understanding the role of the wind field in sediment resuspension while considering wind speed and direction as control parameters to define wave and current shear stresses.