POSSIBLE IMPACT OF CLIMATE CHANGE ON THE DISCHARGE OF TWO SPRINGS FROM CENTRAL NORTH BULGARIA.

Many studies confirm a shift to warmer climate in South East Europe. In Bulgaria, warming trends have been registered since the end of the last century, and different scenarios show increased air temperatures in the future. In the face of climate change, it is a challenge to assess its effect on water resources. The aim of the paper is to evaluate the possible impact of climate change on the discharge of two springs from the Lovech Tarnovo karst basin. This study uses the monthly water balance method to compare the future regime with the baseline regime for two karst springs. For calculations, the software WaterbalANce is applied, which is based on the Thornthwaite–Mather method. The monthly time series of temperature and precipitation for simulations are used from the meteostations neighbor to the springs (stations Pleven for Krushuna and Veliko Tarnovo for Musina). For the purposes of this study, monthly water balance calculations are performed for the baseline scenario S00 (1976–2000) and a set of future climate development scenarios Snn. The first index refers to absolute change of temperature, and the second – to relative change of precipitation. The scenarios S10 and S20 mean change only of temperature, +1.5°C and +3.5°C respectively. The S11 and S21 scenarios assume a 10% decrease in precipitation in addition to the corresponding temperature changes. The input data for any scenario other than the baseline scenario are obtained by corresponding changes in the time series of temperature and precipitation. The results of the water balance calculations show the negative impact of the increased temperature (flow reduction for the Musina spring by 13% and 25%, respectively, only for temperature change, +1.5°C and +3.5°C, respectively). An additional 10% reduction in precipitation will lead to a 33% and 44% drop in average discharge, respectively. Similar results are obtained for the flow rate of the Krushuna spring. Overall, these results show the serious negative impact of future climate change on the discharge of the studied springs. [ABSTRACT FROM AUTHOR]