Is the Hydrological Function of Lake Wigry Changing?

The paper considers whether in recent years there have been changes in the structure of the water circulation in Lake Wigry, the main water body of the Wigry National Park. The volume and trends in the streams of water exchange in the lake have been assessed. They show that in recent years the horizontal water exchange is being reduced as the inflow to the lake is growing, mainly due to its main tributary, the Czarna Hańcza, while the outflow from the lake is decreasing. The paper examines whether these changes are reflected in the structure of the lake water circulation, which has been assessed on the basis of the lake water balance.