Abstract
The paper presents the analysis of the transformation of Lake Osieckie, the largest lake in the Holy Cross region until 2016. It is a valley lake that according to cartographic materials had undergone no changes in the shoreline since ca. 1938. The nearby activity of a sulphur mine required building three dikes on the lake, dividing it into four independent water bodies. The paper presents the analysis of their morphometric properties in comparison to those of the original lake. Although the basins of the new lakes are of natural origin, the currently existing four lakes can be described as quasi-natural.