The manuscript “Skilful seasonal forecasts of streamflow over Europe?" by Arnal et al., was reviewed by 2 experts in the field of hydrological seasonal forecasting. This investigation is also within the score of the Special Issue “Sub-seasonal to seasonal hydrological forecasting”, and the manuscript is well-structured with sufficient contribution in the scientific field. Both referees, including also myself, gave a very positive review and are in favour of its potential publication in HESS. However prior to this, it is important to address the various minor comments.

The authors replied very satisfactorily to Referee #1 and I therefore accept their suggested modifications to the manuscript. In particular, I see the referees suggestion to use climatology as a benchmark. In my view, benchmarking depends on the user’s forecasting experience/service, with more and more users introducing the ESP approach.,Therefore despite a potential dilemma “climatology vs ESP”, I would accept the already considered ESP approach. In addition, I would be very pleased to see a discussion on the EFAS (future) vision to improve forecast reliability.

Referee #2 raised a very exciting point in my view, which lies on linking the hydro-climatic processes to the seasonal forecasted accuracy/skill. This does not need to be numerical but rather in the form of a discussion.

I would like to thank the authors for this contribution and looking forward to the revised version of this manuscript.

Best regards,
Ilias Pechlivanidis

In this round of revision of the manuscript "Skilful seasonal forecasts of streamflow over Europe?", the authors successfully addressed all (minor) comments pointed out by the referees. As the requested revisions were only minor, review and final decision was given only by the editor. I am further pleased to see the authors' effort to identify potential links between hydrological forecasting skill and hydro-climatic characteristics at the basin scale. Although this has not been possible here (i.e. due to the spatial aggregation of the skill results to large geographical regions, which mask the spatial heterogeneity), I am pleased to read a more thorough discussion on this. I am therefore accepting these modifications in this revised version. Prior to final acceptance of the manuscript for publication, I would kindly ask the authors to address my two minor comments below.

P2 L18: Basin location is not a driver to affect the forecast quality. It is rather the 'physiographic characteristics of the basin’, which could occasionally have a spatial structure. Please remove 'location'.

P4 L10: Please mention the number of stations used in the calibration/evaluation. In addition I believe that it is misleading to imply that NSE > 0 has an explanatory power (NSE>0 means that the model is predicting better than the mean discharge). I would suggest you mention the mean and median NSE values for the calibration/evaluation stations instead.

Thank you once again for contributing to the Special Issue with this insightful investigation.

Best regards,
Ilias

The authors revised my 2 very minor comments and the article is in a acceptable level for publication. I am very pleased with this scientific investigation and would like to thank the authors for contributing to this Special Issue.

Best regards,
Ilias Pechlivanidis