The analysis and presentation of results is interesting. Regarding the protocol I have next comments:
I believe that we should try to gather additional data to enhance the physical interpretation of the results (if we have time to focus on this?). At the moment, effect of basin size, baseflow index and aridity index is available for all selected catchments but other potential controls are limited to some of the catchments (e.g., glaciers, soil, lakes). Especially effect of elevation could be analysed also for other catchments (and not just for Austrian catchments). If the digital elevation model is not available for some specific areas we could use SRTM digital elevation model (as already proposed). Further, we might even focus on some other topographic indices.
I also agree with previous posts and I could provide rainfall (average annual rainfall amounts or maximum 12-h or 24-h rainfall amounts for different return periods) and air temperature (monthly or annual) data for the Slovenian catchments.
I agree with Thirel that scatter plots would maybe be better option than boxplots (e.g., Fig. 6) and using colours or different point types we could add additional information to these figures (e.g., in case of Fig. 6 colours could be used to separate catchments based on geographic location-country).
Thank you for great work.