Projected changes of extreme runoff characteristics under climate change conditions – case study for a Central/Eastern European catchment

Regional climatological conditions play key roles in the different processes of the whole hydrological cycle (especially in runoff), therefore, projected climate change can substantially modify them in the future. These changes may result in various environmental and socio-economic hazards (e.g., floods, landslides, droughts, water scarcity, sustainability of food production). In order to decrease the overall exposure to potential future damages, it is essential to estimate and evaluate future climatic trends and prepare detailed assessments of hydrologic responses, with special regard to the runoff extremes. Thus, this study focuses on impacts of climate change on runoff extremes over a relatively small catchment area. The applied methodology is shown for a Central/Eastern European watershed. Specifically, extreme hydrological characteristics (both high and low) are analyzed for the Zagyva-Tarna catchment located in the northern part of Central Hungary. For the investigation the DIstributed WAtershed (DIWA) hydrological model is used, considering several aspects i.e., topography, land use, soil type. Historical meteorological and runoff data are available for 30 years to analyze trends in the recent past. Future climate simulations are provided by the RegCM4 regional climate model (taking into account the RCP4.5 and/or RCP8.5 scenario) adapted for the Carpathian Region by the Department of Meteorology, Eötvös Loránd University.

First, calibration and validation of DIWA distributed hydrological model are completed for the joint watershed after the confluence of the two small Hungarian rivers (until the cross-section located in Jásztelek, Hungary at 47.5°N 20.0°E) using historical meteorological and runoff data. After that, characteristics of extreme hydrological events in the past and in two future 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 catchment of Zagyva-Tarna.