Experimental Investigation of Water Temperature Influence on Suspended Sediment Concentration

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Health of coastal ecosystems depends on the quantity and quality of suspended sediments brought by the rivers from land to the estuary. Behaviour of suspended sediments depends on water and sediment characteristics. Water temperature affects suspended sediment behaviour but has not been fully understood. Increase in water temperature due to global warming creates ecological issues. In the present study, influence of water temperature rise on suspended sediment concentration (SSC) has been studied under controlled laboratory conditions. Experiments were conducted in an annular flume using kaolin (d50 = 6.9 μm) at different water temperatures (T = 30o, 40o, and 50 °C) and salinities (S = 0, 1, 2, 5, and 10 g/L). Results show that both SSC and particle size increased with an increase in water temperature, but both decreased with an increase in water salinity. For S ≥ 2 g/L, the influence of water temperature on both SSC and settling velocity of suspended sediments was more significant compared to S < 2 g/L. For a unit increase in water temperature (°C), the SSC increased by 0.18%, 0.30%, 0.73%, 0.89%, 2.05% and settling velocity decreased by 1.71%, 2.15%, 3.64%, 3.17%, 3.45%, for water salinities of 0, 1, 2, 5 and 10 g/L, respectively. Empirical equations for determining the SSC at any time t and at any length L along the flow direction have been developed and verified.
Coastal ecosystem, Floc size, Settling velocity, Suspended sediment concentration, Water temperature