This manuscript presents an interesting methodology that uses regionalized flow duration curves to constrain prediction uncertainty in water-balance modelling of ungauged basins.

We have received three positive reviews of the manuscript. The reviewers have provided very valuable comments that, if properly addressed, will help enhance the manuscript. They all agree that the paper’s contribution is substantial and useful, but also agree that some portions of the manuscript need to be improved. The authors, in the response letters have shown and they have carefully looked at these comments and have stated that the paper will be revised to account for the reviewers suggestions.

In my own opinion the paper is well written and its content is novel and valuable. After looking at the reviewer’s comments and my own assessment of the work I consider that the paper will be suitable for publication if the authors adequately address the reviewers’ comments, particularly those that will help improve the clarity of the methodology. Some of the major points raised by the reviewers that need to be carefully addressed in the revised manuscript are:

1) Reviewer 1 has pointed out some lack of clarity in the methodology section and has made some suggestions for improvement. D.A. Hughes also suggests including a discussion on the use of “uncertain results” for water resources management that will be extremely useful for the readership of HESS.

2) Reviewer 2, has listed a number of specific points that will help clarify the methodological approach (including selection of parameters ranges, a better explanation on the effect of precipitation uncertainty on simulation results, and clear explanation on the transferability of the methodology to a different study area).

3) Reviewers 2 and 3 have both pointed out the need to discuss the existence of alternative approaches for uncertainty estimation, and a justification for the selection of the methodology used in this study. It will indeed be beneficial to briefly discuss these alternative approaches, the rationale for the selection of this particular approach, and to include the appropriate references in the revised manuscript.

In summary, though the revisions needed are only moderate, they should address not only the main reviewer’s concerns (listed above) but also their minor comments, as this certainly will help to improve the revised manuscript.