Changes in water balance components of river basins in the Slovak Republic and Ukraine

Abstract

This study examined the long-term changes in water balance in five river basins located in Slovakia and Ukraine. Despite small increase in precipitation between 1961-1990 and 1991-2020, the study found a clear trend of decreasing water discharge, accompanied by an increase in evaporation and a significant decrease in the runoff coefficient. Data from two Slovak rivers and three Ukrainian rivers were used, chosen based on three criteria: the presence of at least two meteorological stations within the river basin, a long-term observation period, and minimal human impact on river runoff. The results of statistical analysis indicate that the Belá river basin in the Tatra Mountains had the smallest decrease in the runoff coefficient (-1.28%). The largest decrease in the runoff coefficient (-34%) was observed in the Sula River catchment area with the smallest altitude and the most eastern location. On average, the runoff coefficient decreased by 14% in studied basins. The study highlights the importance of monitoring water balance changes, particularly in regions where water resources are limited.