Abstract
Wind from different directions induce waves-waves to collid at the central zone of Taihu Lake. It causes exchange in water bodies and release of internal nutrients which increases algal bloom. This study aims to analyz the impact of the interactions between waves-waves collision from different directions and different sources such as traveling ships and explored factors, causing sediment resuspension. The results were achieved to collect high-frequency data for measuring wind speeds, currents, waves, and suspended solid concentration (SSCs). The results indicate that the water exchange and the turbidity highly escalated when wind speeds reached 5 m/s. The surface flow velocities are very high, about 80 cm/s or more according to the raw data after calibrating the instruments. This finding is very important in the processes of sediments dynamic. Maybe in these wide area, high waves –waves collide leading to constructive interference from different sources generate waves. Sediment processes were categorized into three period A, B, and C corresponding to three shear-stress thresholds. Period A: Sediment bottom particals was stable with τw < 0.01 N/m2. It did not change through this period and the averaged suspended solid concentration (SSCs) was approximately 50 mg/L. Period B: Sediment resuspension was small with a range between 0.01 ≤ τw < 0.1 N/m2. It jumped up slowly and the averaged was in the range of 50 to 70 mg/L. Period C: Sediment resuspension was moderate with shear stress 0.1 ≤ τw < 0.8 N/m2. The form of the sediment bed was changed at the second period, this shows that increase of the shear stress activated the sediment in this period. The bottom SSCs increased quickly from 60 to 350 mg/L in average. Outcomes of this paper presents the main factor causing sediment resuspension, which may assist further studies and estimate the real reasons for internal nutrient release from different waves induced waves-waves to collide in Lake Taihu. Key words: Eutrophication, central zone, shear stress, different direction wind, waves-waves collide, constrictive interference.
Highlights
The result indicates the generated waves from different directions and the high waves from the north. This finding is very important to a view point on different waves from different wind directions, which should be in considered by researchers in Lake Taihu
Results from this study indicate that measured influences of waves and currents depended on wind conditions; in the presence of wind speed conditions (< 4.5 m/s). in some cases, the bed shear stress was contributed ; but this did not result in sediment resuspension process
The present study eludicated that the factor of sediment resuspension processes during interactions between currents and waves is generated by wind
Summary
Excess nutrient loading in shallow lakes, reservoirs as well as freshwater bodies have become a critical. The prevalence of water eutrophication is a difficult function to evaluate amongst the affecting factors (Martin et al, 2008; Yang, 2008). Excessive nutrient loading into surface water system is considered to be one of its main factors (Fan et al, 2004; Tong et al, 2003; Xiao-e and Yang, 2008; You et al, 2007). Eutrophication phenomena are excessive nutrient loading especially in shallow lakes. It is considered as a result of internal nutrients release from sediments (Qin, 2009; Qin et al, 2006; Zamparas and Zacharias, 2014)
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