From plot measurements to catchment modelling: Forest role in coping with floods and droughts in the Gradaščica River catchment

The Gradaščica River catchment is a small torrential catchment (≈160 km²) in central Slovenia, with mainly forested and agricultural land, entering the urban area of Ljubljana in its lower reach. It is one of the case studies of the European SpongeScapes project, which aims to enhance the ‘sponge’ function of soils, groundwater, and surface waters. The project combines field measurements, upscaling, and hydrological modelling to improve catchment resilience to floods and droughts. Since 2014, a research plot has been established in the catchment to monitor precipitation interception, throughfall, and stemflow of deciduous and coniferous trees, as well as their effect on local water balance. These data were upscaled and used to model the influence of forest cover on the water balance of the catchment. A Wflow SBM model with 200 m resolution and an hourly time step, driven by precipitation, air temperature, and potential evapotranspiration, was developed to simulate hydrometeorological extremes (e.g., floods and droughts) of varying magnitude and to assess the impact of forest share, type, and location on catchment hydrology.Acknowledgements: The authors would like to acknowledge the financial support provided by the European Union’s Horizon Europe Research and Innovation Programme, within the scope of the project “SpongeScapes” (Grant agreement No. 101112738). The study was also partially financed by the Slovenian Research and Innovation Agency (ARIS) within the research program P2–0180 and project J2-4489. The research is also supported by the UNESCO Chair on Water-related Disaster Risk Reduction and the Slovenian national committee of the IHP UNESCO research programme.