Dear Dr. Yuedong Guo and co-authors. I have reviewed the original and revised manuscript with great care and while I appreciate that you have addressed many of the three reviewer's concerns, there are still a large number of technical and most certainly grammatical improvements that are required before this paper is suitable for publication.

Perhaps most importantly, the grammar in the manuscript must be edited. The English is still substandard which severely limits the reader's ability to appreciate the potential importance of this paper. This is at its most severe in the Discussion, which lacks focus and has a number of sentences where the verb and subject are far apart, there are peculiar uses of commas, sentences are disjointed or at times lack a subject, etc. Also, there are issues with tense, plural terms and articles. My simple suggestion would be to have a native English speaker or a colleague with a strong command of scientific writing edit the manuscript. This will not be a large task but as it stands it fall below the standard for publication in HESS.

From a technical point of view, you have made some good progress in addressing the reviewer’s comments, but there are still a number of outstanding issues that need to be addressed that I will outline in detail. This manuscript provides important new data on Eurasian systems and their broader context and the data appears abundant and of high quality. However, at times it reaches too far and the conclusions are not substantiated, even in the revised edition. Please note my concerns below.

1. The use of stable isotopes does not support the manuscript. At no point do you explain why there is a large offset between rainfall and the stream/soil water samples (I'm assuming snowmelt recharge?). The congruence between stream and near-stream values does not supported your response to reviewer 3 and reference to a figure (xx) exists. I suggest that the entire isotope analysis can be removed from the manuscript to more closely pursue the DOC quality story.

2. You have addressed the inter-annual variability and applied LOADEST. The link you have provided has changed (https://engineering.purdue.edu/mapserve/LOADEST/). Regardless, there is little explanation as to why there is this inter-annual variability. Later in the conclusion you state that there is a stable relationship between DOC and discharge - which is clearly not the case. More detail into the residuals and variability of the Q-DOC relationship is warranted because you lean very heavily on the premise that DOC is transport limited, but the relationship is not particularly stable year-over-year.

3. The issue of the riparian zone and its importance is not supported by data in this manuscript and should be revised (lines 473-481). There is not sufficient spatially explicit field data to resolve this level of process detail.

4. I have some issue regarding the system is not DOC limited based on the uncorrelated DOC vs temperature in the soils. The only way this could be evaluated (and it should be referenced) is with more data for a single depth-location vs temperature as opposed to pooled data.


Finally, it is noted that the original manuscript was very similar to the Guo et al. (2015) paper in the Journal of Hydrology. I would warn the lead author against self plagarization as many of the sentences were virtually the same.

Sean Carey, McMaster University

I would like to thank the authors for their diligent and thoughtful work during the review process. I believe this work is an important contribution to the literature.

Sean Carey, McMaster University