Hydrochemistry of Medium-Size Pristine Rivers in Boreal and Subarctic Zone: Disentangling Effect of Landscape Parameters across a Permafrost, Climate, and Vegetation Gradient

Round 1

Reviewer 1 Report

The aim of the current manuscript was to study two big pristine rivers  (Taz and Ket) of boreal and subarctic zone in western Siberia and extract useful conclusions regarding their hydrochemistry. The authors performed several samplings along the rivers and their tributaries over the time period of two distinct seasons (Spring and Summer flooding’s) and recorded additional information regarding the existing vegetation coverage, temperature and other important surface characteristics. Afterwards they performed chemical analysis followed by statistical treatment in order to investigate   existing relationships between the elements concentration and other characteristics such as the morphology of the landscape. The results of their analysis among other reveals that the existing vegetation, bogs and permafrost controlled the major and trace element concentration pattern. Finally very interestingly, the authors were able to infer some predictions regarding the future concentrations of several elements. In particular at the northward regions, the highly mobile elements like DIC, Ca, Sr and U are expected to be increased by a factor of 3.

The current work is very interesting and can be published in Water because it includes extensive experiments on real world cases and the authors through their analysis assess environmental influence in water quality. A minor revision is recommended. 

 1.       Line 164: “The SUVA was measured via ultraviolet…”. When using less popular abbreviations like “SUVA”  the authors should define earlier their definition (Specific UV absorbance).

2.         Line 234-236: “The spatial variations of elements … between two seasons”. The authors here declare that the differences in concentrations were rather temporal rather spatial. This statement is also repeated in the conclusions lines 439-441. However these two statements might create the misunderstanding that was found no important variance spatially along the river line and thusly more than 1000km of water sampling was performed needlessly. The authors should clearly pronounce somewhere in the text, similar to what stated in paragraph defined by lines 280-294, the importance of the spatial variable of concentration along the length of the rivers. This should make clear that the spatial information   contained in the samples gathered is important.

3.     Line 288-289: “larger but did not any …River basin (Table S4)”. Move the word “any” after the word exhibited, so it is written “larger but did not exhibited any systematic…”.

4.         Line 315: “Noteworthy than neither the watershed…”. Replace the word “than” with “is that”.

5.         The rivers (Taz and Ket) were selected because they were untouched by humans. It would be really interesting for the authors to include a comment regarding whether any unexpected levels of concentration were found, indicating human pollution or human intervention in the sampled regions.

Author Response

Responses to Reviewer No 1

The current work is very interesting and can be published in Water because it includes extensive experiments on real world cases and the authors through their analysis assess environmental influence in water quality. A minor revision is recommended. 

We thank the reviewer for positive evaluation of our work and performed all necessary changes in the manuscript as requested.

1.      Line 164: “The SUVA was measured via ultraviolet…”. When using less popular abbreviations like “SUVA”  the authors should define earlier their definition (Specific UV absorbance).

We revised the text as necessary and provided the units of SUVA₂₅₄.

2. Line 234-236: “The spatial variations of elements … between two seasons”. The authors here declare that the differences in concentrations were rather temporal rather spatial. This statement is also repeated in the conclusions lines 439-441. However these two statements might create the misunderstanding that was found no important variance spatially along the river line and thusly more than 1000 km of water sampling was performed needlessly. The authors should clearly pronounce somewhere in the text, similar to what stated in paragraph defined by lines 280-294, the importance of the spatial variable of concentration along the length of the rivers. This should make clear that the spatial information   contained in the samples gathered is important.

The reviewer made a very good point that we should clearly distinguish weak spatial variations within each basin (often the main stem and tributaries exhibiting similar concentrations) but sizable variations in solute concentrations between the northern and southern river. We therefore revised the text as necessary, including Results and Discussion (sections 3.1, 3.4) and first paragraph of the Conclusions. However, we disagree with the statement that our more than 1000 km of water sampling was useless, simply because one has to perform such a sampling to demonstrate the negligible variations in solutes along the river length. Further, we did observe sizable variations among the tributaries, depending on the land cover and this was essential information for identifying the main controlling landscape factors.

3.     Line 288-289: “larger but did not any …River basin (Table S4)”. Move the word “any” after the word exhibited, so it is written “larger but did not exhibited any systematic…”.

We corrected the text accordingly; thanks for catching this!

4. Line 315: “Noteworthy than neither the watershed…”. Replace the word “than” with “is that”.

We revised the text accordingly.

5. The rivers (Taz and Ket) were selected because they were untouched by humans. It would be really interesting for the authors to include a comment regarding whether any unexpected levels of concentration were found, indicating human pollution or human intervention in the sampled regions.

The reviewer made an excellent proposition. The concentration of all major (i.e., nutrients) and trace elements that could be used for tracing anthropogenic activity within the river basin were not high enough and did not exhibit sufficient spatial variations to be related to any human activity. Fr example, there were no ‘spikes’ in element concentration of the main stem of both rivers; such spikes could have indicated the presence of local pollution activity. The variations, by a factor of 2 to 3, of some solutes among the tributaries were clearly insufficient to suggest any direct human impact; rather, such variations merely reflected natural factors such as land cover. Only in the case of the Taz River basin, we observed elevated concentrations of Ni and Cu in the northward directions, which could be tentatively linked to far-range (> 300 km) atmospheric transfer from the Norilsk smelters. We developed this possibility in the revised text (section 3.2).

We thank the reviewer for his/her very useful comments and remarks.

Reviewer 2 Report

This manuscript, water-1816601-peer-review-v1- entitled "Hydrochemistry of medium-size pristine rivers in boreal and subarctic zone: Disentangling effect of landscape parameters across a permafrost, climate and vegetation gradient," is well written and has potential, but it should be more organized.

In my opinion, a careful revision of the English language should be carried out as there currently are some unclear sentences. I recommend accepting this manuscript after revision. The main concerns are as follows:

1)     The abstract should be rewritten, and many sentences can be used in the introduction.

2)     The introduction should explain more about the importance of the applied methodology.

3)     More literature review about the other methods is needed. The manuscript could be substantially improved by relying and citing more on recent literature about contemporary real-life case studies of sustainability and/or uncertainty, such as the followings.

·        Barbieri, M., Barberio, M. D., Banzato, F., Billi, A., Boschetti, T., Franchini, S., ... & Petitta, M. (2021). Climate change and its effect on groundwater quality. Environmental Geochemistry and Health, 1-12.

·        Eskandari, E., Mohammadzadeh, H., Nassery, H., Vadiati, M., Zadeh, A. M., & Kisi, O. (2022). Delineation of isotopic and hydrochemical evolution of karstic aquifers with different cluster-based (HCA, KM, FCM and GKM) methods. Journal of Hydrology, 609, 127706.

4)     Quantitative results should be provided in the abstract to make it more comprehensive. The results of the paper Should be added in the abstract section. Also, The main aim of the study should be clearly mentioned in the abstract.

5)     I recommend providing a table containing the advantages and disadvantages of the applied methodology based on the literature review and comparing the applied and similar methodologies.

6)     For readers to quickly catch your contribution, it would be better to highlight significant difficulties and challenges and your original achievements to overcome them more straightforwardly in the abstract and introduction.

7)     Providing a comprehensive flowchart is highly recommended by researchers, so please add a flowchart representing the methodology in the paper.

Author Response

Responses to Reviewer No 2

This manuscript, water-1816601-peer-review-v1- entitled "Hydrochemistry of medium-size pristine rivers in boreal and subarctic zone: Disentangling effect of landscape parameters across a permafrost, climate and vegetation gradient," is well written and has potential, but it should be more organized.

We thank the reviewer for positive evaluation of our work and revised the organization of the text as recommended by reviewers

In my opinion, a careful revision of the English language should be carried out as there currently are some unclear sentences. I recommend accepting this manuscript after revision.

We carefully edited the English of the manuscript in the revised version.

The main concerns are as follows:

• The abstract should be rewritten, and many sentences can be used in the introduction.

We shortened the Abstract and moved a part of information to the Introduction. We also provided some quantitative information obtained in this study and presented the aims of the study as requested by the reviewer in his/her comment No 4.

• The introduction should explain more about the importance of the applied methodology.

Good point. In the present study, we used a coupled hydrochemical/landscape (land cover) approach that allows revealing the main environmental factors controlling the hydrochemical composition of the river water.  We added this information in the revised text of the Introduction.

3)     More literature review about the other methods is needed. The manuscript could be substantially improved by relying and citing more on recent literature about contemporary real-life case studies of sustainability and/or uncertainty, such as the followings.

• Barbieri, M., Barberio, M. D., Banzato, F., Billi, A., Boschetti, T., Franchini, S., ... & Petitta, M. (2021). Climate change and its effect on groundwater quality. Environmental Geochemistry and Health, 1-12.
• Eskandari, E., Mohammadzadeh, H., Nassery, H., Vadiati, M., Zadeh, A. M., & Kisi, O. (2022). Delineation of isotopic and hydrochemical evolution of karstic aquifers with different cluster-based (HCA, KM, FCM and GKM) methods. Journal of Hydrology, 609, 127706.

We thank the reviewer for indicating these valuable recent works and we carefully cited them in the revised version (Introduction).

• Quantitative results should be provided in the abstract to make it more comprehensive.The results of the paper should be added in the abstract section. Also, the main aim of the study should be clearly mentioned in the abstract.

We revised the Abstract via adding more quantitative results obtained in this work and removing some qualitative information. Note however that the overall approach employed in the present work is a first-order (qualitative, rather than quantitative) identification of the main landscape parameters (land cover) controlling hydrochemistry of the river water. Providing exact numbers behind the degree of the impact of each parameter requires high-resolution seasonal study and will be a focus of future research.

• I recommend providing a table containing the advantages and disadvantages of the applied methodology based on the literature review and comparing the applied and similar methodologies.

We thank the reviewer for this very constructive comment. We could only partially address this issue in the beginning of revised section 3.4, but we did not revise the manuscript further in response to this comment. First, our work is, primarily, a research report and not a reviewer paper where we would discuss and compare various approaches. Second, we used quite well established methodology, consisting in pairwise correlations and Principal Component Analysis when establishing the relationship between the hydrochemical composition of the river water and land cover parameters.

• For readers to quickly catch your contribution, it would be better to highlight significant difficulties and challenges and your original achievements to overcome them more straightforwardly in the abstract and introduction.

We agree with this valuable remark and provided some difficulties/challenges of our approach (limited seasonal coverage, lack of elementary export fluxes) in the revised section 3.4. We also cited relevant works where some of these limitations were resolved.

• Providing a comprehensive flowchart is highly recommended by researchers, so please add a flowchart representing the methodology in the paper.

This is an excellent proposition and we added such a flowchart summarizing our approach in the revised text (new Fig. 1).

We thank Reviewer No 2 for his/her valuable comments and remarks