Processes of lake shrinkage as a result of the action of natural and anthropogenic factors in recent decades have been considerably accelerated. On the other hand, lake capacities may have increased as a consequence of damming. These changes are typically analyzed in relation to changes in lake area, while horizontal and vertical components are excluded. The aim of this study was to assess changes in morphometry in several lakes in central western Poland and to determine changes in water resources in selected lakes as a result of changes in their morphometry. These changes were analyzed based on archival data concerning the area and capacity of lake basins, collected from studies prepared by the Institute of Inland Fisheries in the early 1960s and current bathymetric studies. These investigations showed that within approx. 50 years a considerable decrease was recorded in the area of the analyzed group of lakes, amounting to 14.8% (i.e., 172.6 ha). As a result of changes in the area and shallowing of lakes, the water resources stored in lakes decreased by a total of 7.7%, which amounts to 3.6 million m³. Referring to the factors determining the above-mentioned transformations, it was found that both climatic and anthropogenic conditions were disadvantageous. While in the study period no trends were observed for changes in precipitation, a significant increase in temperature was found, thus contributing to increased evaporation. This situation was compounded by human activity connected with land reclamation operations or agricultural activity.