Temporal Variability of Velocity Structure according to Artificial Discharge in Yeoungsan Lake

Song, J.I.; Kim, J.W.; Yoon, B.I., and Woo, S.-B., 2017. Temporal variability of velocity structure according to artificial discharge in Yeoungsan Lake. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 274–278. Coconut Creek (Florida), ISSN 0749-0208. An estuary dyke makes a closed environment in an artificial lake such as Yeoungsan Lake, thereby restricting material circulation. Because the artificial discharge serves as an external force with dominant effects on the internal material circulation of the lake, the effects of this discharge need to be investigated. This study analyzed the water temperature and velocity data for Yeoungsan Lake to identify the change in water temperature due to the discharge and the mechanism of the two-layer velocity structure found after the discharge. During the discharge, the downstream velocity and water temperature of the bottom layer of Yeoungsan Lake rapidly increased. After the discharge, a two-layer velocity structure repeatedly appeared, with flows in the downstream direction at the surface layer and upstream direction at the bottom layer. The water temperature, which rapidly increased at the bottom layer during the discharge, rapidly decreased after the water was completely discharged. Consequently, the water temperature after the discharge remained higher than that before the discharge. The inflow of water mass from the upstream area during the discharge led to a spatial density difference and generated the two-layer velocity structure after the discharge. The vertical mixing due to this two-layer velocity structure after the discharge increased the water temperature at the bottom layer and decreased stratification.