The manuscript received two reviews. Overall, the reviews were positive but suggested important points regarding the limitations of the method proposed in the manuscript as well additional analysis to illustrate the limitations and strengths of the methodology.

The authors have responded to these comments in detail, although in some of their responses, it is unclear if their responses were incorporated into the manuscript - even if only as additional text to comment on potential limitations. For example, Reviewer #2 points out limitations of this method that likely would exist in data sparse regions. The authors make a nice rebuttal but it is not clear if the authors propose to add text to address this comment. I believe that the reviewer's point should be discussed in the text even if there is not a quantitative assessment completed to test the limits of applicability in data sparse regions.

Therefore, in the next stage where the authors will submit their revision and final responses, I ask that they define clearly where the text is modified to address the reviewer comments. I do thank the authors for adding additional analyses to address the point regarding sensitivity, making sure this work is distinguished from an earlier publication on this method, and in toning down the language regarding the performance of the method.

Given that new analyses and figures are proposed to be added to the revised manuscript, I will send out the revised manuscript to the previous reviewers to ensure their comments have been addressed.

Dear Authors,

Your revised manuscript has been reviewed. Both reviewers (who also reviewed your initial submission) agree the manuscript has been much improved and their comments were addressed. Reviewer #2 has two additional and specific minor but important comments to address in the next round of revision related to uncertainty and the use of only one year for analysis.

If these comments are addressed, I do not see a need for additional review and I look forward to the acceptance of this paper.

Very kindly,
Stacey

Thank you for considering the minor but important additional comments from the reviewers of the revised version. I accept your response to comment #1 on the point raised regarding why this method might be more advantageous than a purely statistical method but I think the text would benefit from adding your response to two places in the paper:

Abstract (line 15; suggested text begins and ends with **):

**The ISR methodology advances prediction of streamflow in ungauged basins by accounting for a physical representation of the river system that is not generally handled explicitly in more-commonly applied statistically-based models.**The key advantages of this approach are that it (1) maintains all the physical consistencies embodied by a diffusive wave routing model (flow confluence relationships on the river network and the resulting mass balance, wave velocity and diffusivity), (2)....

Introduction (last paragraph):

I believe repeating and including some of the text from your response to this reviewer comment somewhere in the last paragraph of the introduction would be helpful and to also add a citation to the PUB textbook (Bloschl et al, 2013) with your comments. This citation references these statistically-based models and then the text from your response notes the clear advancement of the ISR approach over the methods in Bloschl et al (2013).

Citation: Blöschl, G., et al., eds., 2013. Runoff prediction in ungauged basins. Synthesis across processes, places and scales. Cambridge: Cambridge University Press.

I hope that you find these minor points easy to include. I believe that making this clear distinction will further strengthen the reader's understanding of this contribution.