The Changes of Water Balance in the Eastern Slovakia

Abstract

The paper deals with assessment of the changes of the hydrological balance in the Topl'a River basin (Eastern Slovakia) up to the hydrological gauge Hanušovce nad Topl'ou during the period 1961/62-2014/15. Firstly we compared changes of hydrological balance of the Topl'a River basin in two separated periods: 1961/62-1987/88 and 1988/89-2014/15. From the 54-years annual data we derived the empirical relationship for the estimation of runoff on precipitation amount and air temperature. From it follows, that if precipitation amount will decrease by 100 mm then runoff will decrease by 50 mm. But if air temperature will rise by 1°C it will bring the decrease of Topl'a River runoff by 25.5 mm. Then we applied calibrated water balance model BILAN to assess the share of individual runoff components in monthly step. Base flow creates 50.38%, interflow 28.16% and direct runoff 21.48% from total Topl'a River runoff. Finally we used the BILAN model for simulation of runoff volume according to the four incremental scenarios - increasing air temperature and decreasing/increasing precipitation. The simulated mean monthly runoff volumes from the Topl'a River basin are the outputs of the model. If precipitation depth decreases by 100 mm, then runoff decreases by 77 mm. If air temperature will rise by 1°C it will bring the decrease of Topl'a River runoff by 29 mm. These values are higher than those from empirical equation. The worst scenario (increased air temperature by 1°C and decreased precipitation depth by 100 mm) indicates that the runoff from the Topl'a River basin will be reduced by 44% in comparison with actual status.