ЗМІНИ ВОДНО-БАЛАНСОВИХ СКЛАДОВИХ В МЕЖАХ ЛІВОБЕРЕЖЖЯ СЕРЕДНЬОГО ДНІПРА ЗА 1961-2020 рр.

Abstract

The article examines the changes in water balance components within the left bank of the Middle Dnipro during two hydroclimatic periods, 1961-1990 and 1991-2020. The research also covered six key river basins on the left bank of the Middle Dnipro, including Psel, Sula, Vorskla, Trubizh, Supii, and Zolotonoshka. The examination of the modifications in the components of the water balance during the period of the climatic norm from 1961-1990 and the modern climatic period from 1991-2020 revealed a decrease in the average long-term values of precipitation in general by -7.3 mm, river runoff by -5.2 mm, and total evaporation by -2.1 mm. The amount of rain on the left bank of the Middle Dnipro was different in each river basin. In the Psel and Sula basins, there was a significant increase in precipitation, with a difference of 18.4 mm and +0.9 mm, respectively. In the Vorskla, Zolotonoshka, Trubizh and Supii basins, there was less rain by -2.2 to -51.7 mm. The opposite scenario was observed in the variation of total evaporation in the respective river basins. Thus, in the three largest river basins of the Psel, Sula and Vorskla, it increased from 5.6 to 26.7 mm, in all other basins the total evaporation decreased from -0.3 to -47.6 mm. But despite various changes in precipitation and total evaporation, there is a reduction in the volume of river runoff from -1.6 to -8.6 mm. The negative dynamics of river runoff indicators are attributed to negative cumulative values of precipitation and total evaporation. The main cause of these changes is the increase in the average annual air temperature across all studied basins by +1.2 °C, leading to an increase in climate aridity indicators within the left bank of the Middle Dnipro by +0.9 %. Similarly, there was a drop in the runoff coefficient by 0.9 %. In essence, changes in water balance components in the studied area result in more water volume from atmospheric precipitation going towards total evaporation, leading to a loss of the water volume that forms river runoff. This serves as a clear example of the influence of the global increase in air temperature on the reduction of water volume in rivers within the left bank of the Middle Dnipro.