Dear Dr. Gaborit,

thank you for replying to the comments of the two reviewers. From those, you will have noted that both reviewers find the presented results potentially interesting, and suggest that the topic may be suitable for publication in HESS.

However, you will also have noticed that both reviewers have serious concerns about the clarity of writing and overall quality of presentation of the manuscript. Your replies to the reviewers address these concerns to some extent. But after having read carefully the revised manuscript that you attached to your reply to reviewer 2, I am concerned that this may not constitute the major revisions which the reviewers are seeking, and which I fully support.

One example is section 1.4: I agree with reviewer 2 that the calibration procedure presented here is very hard to follow and requires revision (and may well benefit from a diagram). For instance, when you mention that calibration was performed on "the GRIP-O gauged area", do you mean that the model was calibrated on each of the gauged subbasins individually, or some kind of aggregate? If the former, how were the parameters then transferred to the ungauged area; if the latter, how was the aggregate obtained? It is important to keep in mind that reproducibility is a corner stone of scientific publication. I do not think that this is already achieved in the version that you attached in your reply to reviewer 2, especially if one considers that a considerable number of readers of HESS may not be thoroughly familiar with the GEM-Hydro setup.

These considerations lead me to request major revisions. The manuscript will be sent back to the reviewers, with the specific request to evaluate whether their concerns about presentation and transparency of the model implementation and evaluation have been addressed adequately, in addition to any scientific concerns.

Such revisions would also give you the opportunity, as reviewer 1 suggests, to increase the scientific relevance and perhaps even the streamline some of the content.

Depending on the availability of the original reviewers, I may also seek the opinion of a third reviewer.

At this point, I cannot guarantee that your manuscript will eventually be published in HESS; this will entirely depend on the thoroughness with which you will be able to address the reviews, which I believe are very thorough and constructive.

Kind regards
Wouter Buytaert
handling editor

Dear Dr Gaborit,

thank you for submitting your revised manuscript. Please find below the reviewers' evaluation of the new version. In view of the nature of the comments, I am afraid that I have to ask for further revisions. With your revision, please provide me with a detailed rebuttal of each of the comments. A final decision on your manuscript will be made depending on the quality of both your revision and your reply to the reviews.

Kind regards
Wouter Buytaert
handling editor

The manuscript has improved further, and I think that in terms of content it is now suitable for publication. However, in terms of presentation the manuscript is now very long (>9000 words, compared to 5000 - 7000 for a typical manuscript). For a technically quite straightforward topic like this, that is probably not necessary and may unnecessarily reduce the manuscripts accessibility, clarity and impact. Hence I request the authors to make one more revision and try to trim the manuscript with perhaps 500 - 1000 words. This would also be an opportunity to scan the manuscript one more time for colloquial language (such as on p.6 and p.17, where "a tremendous amount" should be quantitative and scientific).

Kind regards,

Wouter Buytaert
handling editor

Dear Dr Gaborit,

thank you for making the effort to make further amendments to your manuscript. I am happy to accept it for publication.

Kind regards

Wouter Buytaert
handling editor