Contribution of different hydrodynamic conditions caused nutrients released, and algal blooms growth in large quantity and deteriorates water quality. Important factors related to climate variation, such as water temperature, precipitation, wind, solar radiation, and human activities can influence trophic conditions in the water column. A field survey was conducted at Meiliang Bay during spring and summer seasons and in diverse hydrodynamic conditions. The study aimed to investigate the variation of wave shear stress generated by strong wind and vessels. The results show that different hydrodynamic conditions influence the various wave shear stresses. The measurement results showed that the shear stress increased in direction with increasing wind speed and significant wave heights. Wave shear stress τ has a maximum value = 0.2 (Nm2) during weak wind 1.5-2.5 m/s and significant wave height = 0.20 (m) while, it has a maximum value = 0.8(Nm2) with strong wind range from 4.5 to 10 (m/s) corresponding with the significant wave height which has maximum value = 0.65 (m) in 2014. Also, wave shear stress τ has maximum value = 0.25 (Nm2) with maximum significant wave height = 0.6 (m) during passages vessels in 2016. It ranges from - 0.8 to 0.8 Nm2 with maximum wave amplitude value U = 0.4 m/s passages heavy ship in 2018. Also, the means of nutrients: total phosphorus (TP), total dissolved nitrogen and phosphatase have similar values while total Nitrogen (TN), total dissolved nitrogen (TDN), Ammonia (NH4) and Phosphate (PO4) have the maximum means values and more sensitive for resuspension in the water with the strong wind and heavy vessels movement conditions. The results indicated that the bottom layer has a major impact, with strong winds and vessels' induced waves.
Furthermore, the shear stress generated by those forces impacted directly on the boundary of the lake and caused sediment resuspension leading to release nitrogen. The worst water quality was noted in 2014 and 2016. It also declined at the end of summer 2018, and this results maybe because of climate change and decline wind speed in the tropical and subtropical area and south Asia. The outcomes of this paper give a clear idea about the processes happening in the lake and which force is more effective on the boundary and released nutrients that encourage algal blooms in these seasons.
Keywords: Vessels; Hydrodynamic; Waves; Shear stress; Meiliang Bay; Lake Taihu