The assessment of changes in the long-term water balance in the Krupinica River basin for the period 1931–2020

The study is focused on the evaluation of changes in the hydrological balance of the Krupinica River basin to the Plášťovce station for the entire 90-year period as well as for the three 30-year subperiods 1931–1960, 1961–1990 and 1991–2020. In the first part of the study, the hydrological balance is processed in an annual step on the basis of measured series of average monthly flows from the Krupinica: Plášťovce; monthly precipitation totals on the Krupinica catchment area and average monthly temperatures in the catchment area. The hydrological balance in the monthly step was processed in the second part. Changes in water resources in the river basin over the three mentioned time subperiods were analyzed. The long-term annual precipitation total in the Krupinica River basin for the whole period was 660 mm, the annual runoff depth was 182 mm and the balance evaporation was 478 mm. A comparison of 30-year periods shows a significant decrease in the runoff of Krupinica – from 231 mm to 144 mm. This was even more pronounced in the runoff coefficient – it fell from 0.32 over 0.27 to 0.21 in the last period 1991–2020. In the third part, a simple regression relationship between runoff, precipitation and air temperature was derived to estimate the future development of the annual runoff from the basin. The relationship shows that a 100 mm decrease in precipitation in the Krupinica River basin will cause an average decrease of 52 mm in runoff. And an increase in the average annual temperature by 1°C in the Krupinica River basin results in a decrease in runoff of about 33.5 mm.