Characteristics of water level fluctuations in Polish lakes – a review of the literature / Charakterystyka wahań poziomu wody w jeziorach polskich – przegląd piśmiennictwa

Water level fluctuations (WLF) in lakes are a natural feature that can be modified by human activities. The article presents a review of literature on the water level fluctuation in Polish lakes, their amplitude, periodicity and trends. WLF controlled by natural conditions and also those induced by human activity were considered. Although anthropogenic water level fluctuations in most Polish lakes seem to fall within the range of natural fluctuations, in some cases economic activities (e.g. the use of lakes for energy generation purposes) can lead to strong disturbances of the hydrological regime, causing an ecological instability that makes it impossible to maintain/achieve good ecological status. This, in turn, makes it necessary to define good ecological potential, being an environmental objective for such water bodies, which is less rigorous compared with good ecological status. The article indicates the need to expand the methods for the assessment of lakes in the country with new biological indicators to assess, in accordance with the Water Framework Directive requirements, the impact of hydrological alterations on biota