Michał Lorenc, Renata Dondajewska and Lech Kaczmarek
The results presented in this paper of water level fluctuations in selected lakes of Wielkopolski National Park have a preliminary character, contributing new information to the knowledge on this area. Five lakes situated in three distinct tunnel valleys were selected for research: Jarosławieckie, Góreckie, Budzyńskie, Witobelskie and Łódzko-Dymaczewskie. The water level was measured from December 2006 till January 2008 and from January till December of 2012 with ca. monthly frequency. An increase in the water stage was noted in the autumn-winter period, which was rather unusual. The comparison of years 2007 and 2012 indicated higher water levels in the latter. The amplitude of the water level was higher in flow-through lakes due to the reaction to precipitation in early spring as well as different catchment features. Specific water level fluctuations in Lake Góreckie are probably related to the influence of groundwater of the Wielkopolska fossil valley.