Impact of Snowmelt Conditions on the Isotopic Composition of the Surface Waters of the Upper Ob River during the Flood Period
Round 1
Reviewer 1 Report
Isotopic observations from this region are still rare, and the results obtained may be of interest to researchers from other regions. I think that the article can be published without addition changes.
Author Response
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Reviewer 2 Report
The paper is fine. My only remark is to add few sentences on the geology (bed rock) of the river
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Reviewer 3 Report
The article reported the impact of snowmelt on the isotopic composition of the Upper Ob River surface water during flood period. The work is within the scope of the journal. This study has a certain degree of innovation, which is beneficial for us to study the composition and source of surface water during snowmelt periods. In my opinion, the manuscript is decent and has the potential to be published after minor modification. It could be improved if the issues below could be addressed by the authors:
1. Introduction
Ice is also an important link in the study of hydrological processes, where the δ18O distribution has certain reference significance for the research of this article, and detailed content can be referred to the following literature “Shulin Tang, Dahe Qin, Jiawen Ren, Jiancheng Kang, Zhijun Li. Structure, salinity and isotopic composition of multi-year landfast sea ice in Nella Fjord, Antarctica. Cold Regions Science and Technology 49.2(2007). doi:10.1016/j.coldregions.2007.03.005.”
2. Materials and Methods
2.1 Study area
What is the water depth of the study area?
2.2 Sampling
(1) The process of the experiment is not yet clear. What is the depth distribution of surface water sampling points? Why is the sampling depth set to 0.2 h?
(2) Please explain in detail the principles for selecting sampling points for the surface water samples and the bulk snowpack samples.
(3) Please add the period for collecting rain samples and the bulk snowpack samples.
2.3 Analytical methods
Line 146: The total number of samples mentioned is recommended to be placed in section 2.2.
3. Results
(1) Line158-166: The content is duplicated with the data in Table 1. My suggestion is to delete or replace the table with graphics. Additionally, this part of the data lacks analysis.
(2) Figure 3: Whether there is a certain linear relationship between discharge and isotopic composition, and why the relationship between discharge and isotopic composition in 2020 III - the second phase of the spring flood is different from other phases.
(3) Line 194-196: The text mentions “as a rule, lighter (by 0.2-0.3 ‰) isotopic composition of water is noted near the right gently sloping river bank relative to the high left bank, but at the end of the flood the situation changes to the opposite”. Why does the above phenomenon occur?
(4) Line 201-202: It is mentioned in the article that the average value of the isotopic composition of atmospheric precipitation was -19.8 ‰ for δ18O in the winter 2020-2021. But in Table 2, it appears as 19.8 ‰. Please check the calculation results.
(5) Table 3: “The isotopic composition of the snow cover in the catchment area of the Upper Ob above the studied river outlet section (Figure 1b) for the cold period of 2019-2020 (1) and 2020-2021 (2).” The above data is the same as the data in Table 2, it is recommended to keep only one.
4. Discussion
Line 279: The previous description is about 2020 and 2021. But what appears here are 2019 and 2020, please confirm again.
5. Conclusion
The conclusion should be clearly distinguished from the results, and further refinement is recommended.
Finally, the author also needs to carefully check the details, such as the punctuation mark of line 42, the expression of δ18O in Equation (2), the table style, etc.
see above.
Author Response
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Reviewer 4 Report
This manuscript needs further elaboration. It reports a sampling project of multiple water types, including surface water, precipitation, and snow packs. The precipitation samples are even event-wise in temporal resolution. Yet no time series variation was reported, thus missing the verification of possible contribution of precipitation to river supply. More description is needed in the sample section: In the study region in high latitudes, precipitation in the form of snow is expected to be significant during the study period; how often is snow sampled? As is understood, rain samples were collected event-wise; how about precipitation in the form of snow? Will snow be collected immediately after precipitating, or wait to be collected together in bulk snowpack sampling?
Secondly, the seasonal division is ambiguous. How is spring identified? This pertains to the comparison of spring initiation dates in L260. How is the date of complete melting of the snow cover in the catchment area judged? And how is the day of snow cover formation determined? Is it based on observation of a specific site or a large area? How are the two phases of spring flood defined? Normally, seasons are based on temperature and/or precipitation. Those climatic background information is missing in the manuscript.
Thirdly, results and discussions would benefit from more thorough description. What’s the temporal variation feature of precipitation isotopes? Is there any climatic controls over precipitation isotopes? What’s the sample period of those water reported in the manuscript? In Fig3 what do the color shadings mean? Why 4 shading blocks for three phases? Any explanation for the negative intercept of the LMWL presented in figure 2? From the current manuscript, conclusion 1 may not be founded, as little discussion was presented in the manuscript.
Fourthly, some key references such as 42-44 are not available in English, which prevented the reviewers from an objective judgement of those statement.
Language needs extensive improvement. Some sentences are confusing, and some words are wrongly spelt. For example, L68-69 usage of divide symbol between two numbers for temperature range is confusing. L71-72 the use of 'decade' is confusing, maybe change 'second decade of' to 'mid-', and 'the first decade of' to 'early'? L72 and L76, 'height' changed to 'depth'. L125 'ran' changed to 'rain'. Besides, comma needs to be changed to dot for all digit throughout the manuscript.
Author Response
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