Changes in the hydrological balance in the Litava river basin during the 90-years period 1931–2020

During last twenty years, a number of extremely dry years have occurred in a number of European river basins. In Slovakia, the lowland streams of southern Slovakia have been particularly affected by drought. One of these streams is the Ipeľ River. In this basin we have three continuous observations of daily flows since 1931: from Krupinica at Plášťovce, Litava at Plášťovce, and from Ipeľ at Holiša station. The first part of the paper is devoted to the statistical analysis of the Litava flow series. In the second part, the hydrological balance in the Litava basin for the three subperiods (1931– 1960, 1961–1990, and 1991–2020) in annual time step has been elaborated. The first thirty years 1931–1960 were the wateriest (runoff was 205 mm). In the last thirty years, the runoff coefficient was only 0.2 (runoff 131 mm) in Litava basin. In the final part of the study, the BILAN balance model (in a monthly step) was used to compute the contribution of several runoff components in the Litava basin during period 1930/31–2019/20. The long-term average baseflow accounts for 40.7% of the total modelled runoff, interflow accounts for 46.8% and direct runoff accounts for 12.5% of the total modelled runoff.