Both reviewers agree that the paper represents a novel and interesting contribution to the literature and the topic and scope of the paper are appropriate for HESS; however, the comments by the reviewers and the replies of the authors indicate that major revision and reconsideration are needed at this point in the process.

I now ask the authors to incorporate the revisions they have proposed in their responses and I will then send the revised manuscript out for further review. In this revision, please pay close attention to grammar and the required HESS preparation guidelines: http://www.hydrology-and-earth-system-sciences.net/for_authors/manuscript_preparation.html.

I look forward to receiving the revised manuscript.

I have re-read the revised manuscript, the author responses to the first round of reviews, and the reviews of the current version of the manuscript.

Both reviewers note that additional revision is needed for the paper to proceed. I find that Reviewers 1 and 2 both have expressed concern that the initial reviewer comments are not fully addressed, particularly with respect to the limited sample size utilized to support the author findings.

The authors initial response to this comment indicated that there is more data to support their findings but that the authors did not want to include these additional results because it would add too much length to the manuscript. I felt quite the opposite; if there are more data to support the findings, this would increase the quality of the manuscript and strengthen the case for the use of crowd-sourced information for hydrologic modeling. Since this is, as the authors rightfully point out, one of the first contributions on this topic, additional case studies are needed to convincingly argue that the use of crowd-sourced information is viable.

Another place of particular revision that is needed is in the separation of the results and discussion. While the authors may feel the current organization of the manuscript is clear to them, Reviewer 1 has stated it was not clear in their reading. I agree that it would be a cleaner presentation of the results to have these sections separated.

This manuscript has the potential to be an important and novel contribution to the literature and I believe that the changes requested by the reviewers are constructive and will further enhance and strengthen the contribution.

I look forward to reading the next revision of the manuscript.

Dear Authors,

I still find issues with the manuscript and agree with the comments of the Reviewer, with improvements needed in three areas: 1) editing for the English language, 2) clearer descriptions of the methods and modeling procedures, and 3) softening of the use of the crowd-source aspect of this study. I also ask that the reviews please carefully follow the HESS publication guidelines for equations and variables: http://www.hydrology-and-earth-system-sciences.net/for_authors/manuscript_preparation.html.

I continue to believe, as does the Reviewer, that the manuscript has value and has the potential to be a worthwhile contribution. These needed revisions will alter framing of the manuscript substantially and, therefore, I am recommending again major revision to address the remaining reviewer and editor comments.

I ask the authors to now respond to these comments and revise the manuscript. The manuscript can still be rejected at this point if the comments are not accounted for the in the revised version.

I thank the authors for their continued revisions and submission to HESS and I wish them all the best on this next set of revisions.

Kind regards,
Stacey

I first would like to thank both the authors and reviewers for their patience and diligence through this review process. I believe that the discussion and reviews have served to improve the manuscript and increase the impact that this publication will have, particularly through the expansion of additional catchments and scenarios as well as in the clarity and value of crowd-sourced data. The manuscript, I believe, is novel and highly relevant and certainly appropriate for HESS.

I do, however, still find numerous editorial corrections that need to me made, which I list below. Once these changes are made, I look forward to accepting the manuscript for publication in HESS.

Minor edits:

1. The use of HESS conventions should be followed. I ask the authors to please carefully review the guidelines and edit the manuscript accordingly. In particular the naming variables and the notations are not according the guidelines in several instances. See section 4 when discussing the NSE properties for example. Specifically (but not exhaustive):

a. Line 114: EnKF is not explained.
b. line 188: 3D-Var and 4D-Var are not explained before being abbreviated. It also not clear what is meant by these models.
c. In lines 403-404, the superscripts on Q appear to different in each line. Please review the tables and figures carefully to be sure they are stand alone and all variables are explained as the conventions followed. This is still not the case in several of the figures.

2. Do not abbreviate DA for “data assimilation.” I do not think this warrants an abbreviation and adds confusion for the reader.

3. I would refer to Experiment 1 and 2 in the singular. Each experiment has different scenarios but it is not necessary to call them Experiments 1 and 2; rather use Experiment 1, Scenario X when referring a particular experiment and Experiment 1 to refer to the set of all scenarios in Experiment 1.

4. These specific edits are not exhaustive so please complete a thorough proof-reading of the manuscript.

a. line 16: Change “need of involving” to “growing inclusion of”
b. line 19: Change to read: “to participate in the collection…”
c. lines 21-22: Delete “if not discouraging”
d. lines 23-24: Delete “with the characteristics described above”
e. lines 26-28: Nice sentence.
f. line 39: Change to read: “…forecasting and uncertainties…”
g. line 40: Change to read: “…uncertainty of the model…”
h. line 43: Change to read: “…are two of the most used approaches to update a model when…”
i. line 48: Change “very expensive” to “cost prohibitive”
j. lines 49-50: Change to read: “For this reason, improvements to monitoring technology has led to…sensors to measure..”
k. line 51: Change to read “…defined in the paper as a “social…”
l. line 53: Change to read: “that, due to their reduced cost and voluntary labor by citizens, result in a more…”
m. line 55: EU-FP7 is not spelled out first before its use.
n. line 55-56: Delete “, which also sponsors this research” and replace to read “…(2012-2016) and various other projects that proposed to assess the usefulness…”
o. lines 78-80: Delete this sentence.
p. line 86: Change “just” to “only”
q. line 92: Change to “(the expertise level of the crowd), credibility (the volunteer group), and performance of volunteers as they relate to accuracy…
r. line 93: Change to “levels of the model.”
s. line 98: Change to “at an operational level”
t. line 100: Add a comma after “real-time”
u. line 103: Add a comma after “mean”
v. line 104: Delete “Regarding the variable life-span” as this does not make sense.
w. lines 105-106: Change “sent just” to “taken”
x. line 107: Change to read “…and accuracy of the measurement.”
y. line 109: Change “has been” to “was”
z. line 112: Change to read ”However, it was not considered that the…”
aa. line 121: Delete “not pre-determined, or”
bb. line 130: What is meant by the “appropriate time”?
cc. lines 139-141: Change sentence to read, “In light of the reviewed approaches, this study uses a pragmatic method, due in part to the…”
dd. line 143: Delete the word “novel”
ee. lines 144-146: This is a confusing sentence.
ff. lines 150-152: You do not discuss the study areas yet so I would remove these specifics from the introduction.
gg. line 165: Remove “which is funding this research.”
hh. lines 216-219: Very nice addition to the text.
ii. lines 225-228: This is a confusing sentence. Consider revising to: “In contrast, crowdsourced water level observations…of citizens at random moments (when a citizen decides to send data). Thus, from the modeling viewpoint, …”
jj. line 454: Delete “the”
kk. line 460: Pick either “estimate” or “calibrate” - it is confusing to have both there.
ll. line 473: Change to read “…model - KMN - under…”
mm. line 496: Change to “frequencies”
nn. line 497: Change to “random accuracies”
oo. line 522: Can you be more specific in referencing the settings rather than using A or B?
pp. line 521: Decide whether to have a “the” in front of CSD or not. Then make this consistent across the manuscript. See example on this inconsistency on line 495 and line 521.
qq. line 536-537: This sentence does not make sense. Please clarify.
rr. Section 3.3: Only one of the study catchments is mentioned here; why are the others not mentioned?
ss. line 537: Change to “forces”; also this sentence is not clear.
tt. line 552: Change to “…model performances and consequent NSE value.”
uu. line 582: Change to read “…difference that they are…”

I thank the authors once again for their patience in this process. At this point, the paper is accepted. However, I offer a few additional suggestions that I hope will be incorporated into the final published paper:

- p. 18, line 509: It is still a bit awkward to reference sub-catchment B of setting A. To clarify, add the figure references such as "sub-catchment B (fig. 2) of setting A (fig. 1)."

- Consider mu_Nse instead of mu(Nse), where the Nse is the subscript on the mean and standard deviation symbols.

- Review the captions for the figures. Many of them are still not stand-alone. The abbreviations are not explained in the captions. And a period is missing at the end of the captions.

I wish the authors all the best on this and their future research.

With kindness,
Stacey