In this study, the distributed, physically-based DIWA (DIstributed WAtershed) hydrological model is coupled with the RegCM4 regional climate model. DIWA considers several aspects, e.g., topography and its relevant derivatives (slope, aspect, local drain directions, etc.), land cover, soil layers and their hydraulic properties, and simulates all relevant hydrological processes such as interception, snow accumulation and melt, infiltration, evaporation and transpiration, percolation, interflow, surface and stream runoff, etc. To run the hydrological model, gridded meteorological time series – daily minimum and average temperature, precipitation – are needed, which are provided by RegCM4 adapted for the target region.
Our analysis considers a relatively small catchment, namely, the Upper-Tisza basin (with an area of 9707 km2), which rises in the Ukrainian Carpathians and drains southwest into Hungary. It enters Hungary at the Tiszabecs discharge station. First, calibration and validation of DIWA distributed hydrological model are completed for the target catchment using historical meteorological and runoff data. After that, characteristics of extreme hydrological events in past and future (using new RCP scenarios) time periods for 30 years are assessed. Finally, statistical analysis based comparison of observed-past, modelled-past and modelled-future runoff data is evaluated for the Upper-Tisza catchment. The results can be used to provide recommendations for decision makers in order to mitigate climate change induced hydrological hazards.