Lake Žuvintas is classified as a shallow eutrophic lake. Floating islands formed of aquatic vegetation are particularly characteristic of this lake. Silting processes of the lake have a negative impact on the water quality and environmental state. The turbidity of the lake and formation of a mud layer depend on some abiotic factors such as water inflow to the lake (discharge and water quality), meteorological parameters (wind, participation and temperature), variation of the lake water level, chemical composition of the bottom soil and the aquatic vegetation in the lake. Some measures of water management are proposed with the aim to improve the ecological state of Lake Žuvintas. These could be the regulation of the lake level with sluice regulators, improvement of the water quality of the river inflowing to the lake and cleaning the lake surface from water vegetation. Only mathematical modelling is used to predict the impact of sediment processes in the lake under different management scenarios. The aim of this research was the modelling of sedimentation processes in Lake Žuvintas during flood periods according to the scenarios of the lake management. For this purpose, the hydrodynamic model of the lake as the background for sediment transport modelling was constructed and calibrated. The two-dimensional modelling system MIKE 21 was used as a software.

Keywords: Lake Žuvintas, hydrodynamics, sediment transport, MIKE 21 modelling system