This study examines historically measured groundwater levels on observation wells of the Zagreb and Samobor-Zaprešić aquifers since the 70-ies of the 20th century until today. The analysis also entails older groundwater level maps dating from the 60-ies of the previous century, which off er additional insight into the historical groundwater levels. The analysis of the existing groundwater levels and historical groundwater levels has identifi ed changes of those levels in certain areas of the aquifer, special reference being taken to developments which, with time, led to the deceleration of negative trends of groundwater levels in certain parts of the aquifer. The most signifi cant such developments in the past 50 or so years are the construction of the weir of the Zagreb cogeneration plant (TE-TO) in the Sava River and the occurrence of hydrologically above-average favourable years like 2013/2014, which have been separately analysed. The analysis has found that today's groundwater levels in the Zagreb and Samobor-Zaprešić aquifers are generally lower by approximately 3 to 6 m in comparison with the historical levels from the 60-ies of the last century.