Abstract
This publication is to confirm the existence of a correlation between lakes under hydrometric supervision and unmonitored lakes using formulas for calculating thickness of ice cover observed on lakes located within the same physico-geographical unit. The article presented herein covers lakes located on the upper Radunia River in the central part of the Kashubian Lakeland. Lake Raduńskie Górne has been under constant hydrometric supervision of the Limnological Station of Gdańsk University for over 60 years. The study covers three spring lakes: Stężyckie, Bukrzyno Małe and Lubowisko. The cover thickness was measured during the period of 2003–2006 and in 2016. Analysing the measurement data gathered during field research and the data obtained from the station allowed formulas for calculating ice cover thickness to be established. The formulas were tested in 2016 with the use of the fieldwork data. The result confirmed that the formulas can be used to calculate thickness of ice cover with considerable accuracy.