Inventory of Reservoirs of Key Significance for Water Management in Poland—Evaluation of Changes in Their Capacity

Abstract

Dam reservoirs constitute an important element of protection against floods and hydrological droughts, and they ensure the possibility of producing electricity. Loss of reservoirs’ storage capacity has a significant impact on the management of their water resources, including flood protection and counteracting the effects of drought and the possibility of producing electricity. The paper presents changes in the capacity of 47 reservoirs in Poland that have the status of key objects of protection against floods and hydrological drought. Based on the collected, unpublished data, the changes in capacity from the beginning of the reservoirs’ existence to 31 March 2021 were calculated, which allowed us to determine the total amount of lost capacity and the pace of the processes taking place. From the beginning of operation (average operation time 48 years), the capacity has decreased by about 5%, which means that almost 200 million m3 less water is stored. Detailed analyses of the lost capacity also allowed for an illustrative presentation of forecasts for further changes in the short and long term. The results obtained represent a unique contribution to future national strategies for the management of sediment and reservoirs’ flood reserve and reduction of drought. The presentation of this problem seems to be important also in the context of climate change.