Analysing hydroclimatic changes in the Upper-Tisza catchment under mitigation and non-mitigation scenarios

Changing climatic conditions affect several sectors and processes in the environment, including river discharge. It is important to estimate the probable changes, as it may play an important role in flood defence, ecosystems, transportation, energy supply or water-management. Our ultimate aim is to analyse the runoff conditions in a small European catchment, namely, the Upper-Tisza basin. As a first step of our investigation, climatic conditions are analysed for the target area.

For the analysis the observation-based CARPATCLIM dataset and 11 regional climate model simulations from the EURO-CORDEX program are used. Three 30-year-long time periods are selected (1972–2001, 2021–2050, 2069–2098) and three different scenarios (RCP2.6, RCP4.5, RCP8.5) are applied to analyse the future conditions from an immediate reduction of anthropogenic greenhouse gas emission to a later reduction, and finally no mitigation throughout the 21^st century. Therefore, uncertainties emerging from both the applied model and the applied scenario can be assessed. Temperature and precipitation characteristics are calculated on a monthly basis for the entire domain, and for six hydrological stations (namely, Alsókalocsa, Bisztra, Királymező, Ökörmező, Rahó, Tiszabecs). Beside the mean values, different percentile values and climate indices are determined, e.g. the consecutive dry days, the number of precipitation days with more than 5, 10 and 20 mm, the highest one-day and five-day precipitation amount, the number of cold days and frost days.

According to our results, higher temperature values will occur in the entire area. The greatest warming in the Upper-Tisza basin is projected for January, when temperature increase can exceed 4.6 °C by the end of the 21^st century according to the multi-model mean under the RCP8.5 scenario. Precipitation is projected to increase in winter, while a precipitation decrease in summer is likely to occur according to the RCP8.5 scenario. Higher temperature (which may result in less snow) and altered temporal distribution of precipitation clearly have an effect on runoff conditions, so in order to analyse them in details, the next step of our research is to run the DIWA hydrological model driven by the different climate model simulations.