Abstract
The research was carried out in three Łęczna-Włodawa lake-catchment systems, during the hydrological years 2007–2009. The observed lakes varied in terms of basin morphometry and catchment features. The hydrological functioning of the lakes resulted from three main factors: (1) storage capacity of the lake basin, (2) catchment area and relief, (3) human impact on water distribution. The vertical water exchange ratio in Lake Sumin was almost four-times higher than flushing time. In Lakes Rotcze and Syczyńskie horizontal water exchange, presented as flushing time was significantly higher than the vertical one.