Water Quality Variability and Related Factors along the Yangtze River Using Landsat-8
Round 1
Reviewer 1 Report
I have now reviewed the manuscript by Author et al., on “Long-time water quality variations and its factors in the main-stream of the Yangtze River using Landsat-8 data”. Overall, the paper may be a case study of a long-time water quality variations and monitoring, but the reviewer thinks that it cannot be published from this journal in the current form. The most serious problem is that the sentences are too much redundant. The followings are major comments, which should be addressed in addition to the above-mentioned serious drawback: 1. Literature review part is needed to be elaborated more; focus should be given water quality variations and monitoring as per climatic zone. 2. Rationale of study is missing and Hypothesis need to be address 3. Methodology section should be completed with some relevant information and a more complex discussion would be needed. 4. More complex discussion would be needed. I would like to see more discussion here about the possible application of this method to other places of the world. What do the authors propose? Comparisons with other studies have to be provided in the discussion section 5. I would like to see the information of figure to be inserted after the relevant texts 6. Conclusion part should be written is separate section and should be improved 7. Recommendations for future studies are not significant as per the findng of this study, so rewrite the future studies 8. Keywords should not be the repetitions of the title words, please find such words which are not in the title, this way search engines of the web will find your manuscript with higher probability. 9. Figures (1, 2,) need to be redrawn as the text aren’t clearly readable. Cartographical errors such as legends, texts are difficult to read, blue line depicts what (legend need to be update)?, scale unit in km as in the study area, the distance and area unit should be consistent and cartographical elements are missing. Please redraw and Map display should be balanced Following minor comments should also be addressed This paper need to address why a variety of factors are selected Some of the points are without references like Line 43-45 please provide the reference; Line 46-47 please provide the reference Abstract need to be rewrite Identify your purpose. Explain the problem at hand. Abstracts state the “problem” behind your work. ... Explain your methods. ... Describe your results (informative abstract only). ... Give your conclusion Please explain better the “novelty” of this study. Is this methodology used in previous studies? Is this methodology applicable for other areas of the world?Author Response
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Author Response.docx
Reviewer 2 Report
Overall comments
The study uses landsat 8 to measure chl-a, TN, and TP in three parts of the Yangtze River. The authors used in-situ data to develop a well validated empirical model. Seasonal patterns in water quality were investigated and seasonal changes in flow, temperature, precipitations, and shipping traffic were related to seasonal patterns in water quality.
Overall, I think the manuscript is fine. I encourage the authors to simplify this manuscript as much as possible by removing some description of the basin and choosing which results focus on. This manuscript focuses mostly on seasonal patterns, therefore perhaps reduce some of the background on empirical models in the introduction and set up why it is important to look at seasonal patterns in the Yangtze if that is the goal. The manuscript also requires some attention to English grammar.
Specific Comments
The results about land use and precipitation do not seem to add to your story. Consider removing to focus your results.
Title: I am not sure 2014-2020 is a long time and also this paper appears to be about seasonal patterns. Is that correct? Consider revising title to something like…
“Seasonal variability in water quality in the Yangtze River using Landsat-8”
“Water quality variability along the Yangtze River using Landsat -8”
Line 31: change “ratio increasement” to “an increasing ratio of total nitrogen to total phosphorus…”
Line 48: I am not sure these water quality types are well known (e.g. I, II, III, V, etc.). Consider removing this sentence and terms or explain them.
Line 49: I do not understand what is meant by “river lengths accounted for 68.1%... of river lengths”? Please explain or remove.
Line 50: What are “main over-standard items”? The main concerns perhaps?
Line 64-82: Consider simplifying this paragraph to the main points, I do not think we need the details of error metrics from many different papers.
Line 82: Consider starting a new paragraph here to line 90, it seems different than the sentences above.
Line 97: revise to “natural and human factors”
Section 2.1: Considering removing some details about the basin to simplify, for example details that are already in the intro, and the coordinates are not necessary.
Line 140: Correct to “in-situ”
Line 294: I thought MDWI not NDVI was used?
Line 295: Correct Yangtze river spelling
Line 301: Remove “through analysis”.
Line 329: I don’t know what this sentence means. The spatial distribution of water quality is counted separately? The figures are all over time. Did you look at each river reach over time separately?
Line 332: What is meant by the concentration “are significantly more significant”. Does this mean the upstream reach has a better model fit than the lower reaches?
Line 347: Delete obvious, and chance annual variation cycles, to “annual cycles”. Change “fitting” to “fitted”.
Line 407: Change to, “It’s an important source of pollution to rivers”.
Figure 12. This is a bit confusing. It’s the same graph repeated 3 times with different axes correct? If so, only show the lines that match the axis for each graph.
Line 449: Delete the first sentence of this paragraph. Start with “Studies have shown..”
Line 489: Change to “water quality indicators”.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The submitted manuscript is interesting, but the authors must make important modifications and organize the information better in order to evaluate it seriously.
First of all, it should be organized following the instructions to the authors and the sections should follow the outline proposed by the journal for the articles. Without justifying why, the material and methods section has been divided separating the study area (unnecessary) and the results have been divided into a section 5 where the discussion has been included as a subsection. The instructions indicate that the discussion should be a first level section, usually section 4.
On the other hand, there must be some automated processing error in the treatment of the bibliography that has made most of the references incomplete and missing (at least) the name of the journal where it has been published.
Regarding the image dataset used, the number and temporal distribution of the images used should be detailed as well as the reference of the image download. There is no explanation of the Google Earth procedure used for this purpose. The methodology also does not describe the procedure used for image processing, computer applications, statistical treatment; without this it is not possible to try to reproduce the calculations.
On the other hand, the procedure used is arguable to present it as novel when it is based on the usual techniques used for satellite images from 1980 to the present, based on simple relations between bands and normalized relations. And in other cases I do not find the differences, for example between FT9 and FT12, I think it is the same. I do not understand then, how in Figure 4, the results are different.
The procedure of field measurements should also be better explained, as it seems to explain that several spot measurements have been taken in each of the five zones where it has been sampled several times on one occasion in September 2020. In this case, it is expected that there is therefore only spatial variability in terms of quality and that temporal variability will therefore not exist, being a homogeneous response throughout the satellite year.
As for the results presented, the variation of river quality would be estimable by the satellite images considering the variables influenced by the optical properties of the water. In the variables used only chlorophyll has that property, while N and P are not related, so expositionally the relationships between N, P and chlorophyll are fully causal because the first two are the variables that influence the second. It would have been desirable for the quality model to use variables such as water color, transparency and temperature. In the paper only chlorophyll is measurable with an image and all the rest are statistical coincidences. Then it is very necessary to better write up how to relate N and P through chlorophyll values to optical properties.
Once everything is improved, the discussion should be properly worded and concluded.
Therefore, it is proposed to reject the manuscript as currently drafted and resubmit for re-evaluation once the title has been improved and reworded.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
My comments were successfully responded to by the authors. As a result, I recommend that the manuscript be published.
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
Nice work with revisions.
Line 93: Perhaps change “river is in a moderately nutrient state..” to “the river has moderate nutrient concentrations and there has never been a bloom.”
Line 98: I think “long-time” should be “long-term”, correct?
Line 247: What bands were actually used in this best band combination? That would be useful for the readers to know.
Line 345. I think there is a word missing in the sentence. Perhaps, “The goal of this study is to retrieve…”?
Lines 489-502: This paragraph already exists on lines 454-466. Decide where this paragraph should be and delete the repetitive paragraph. It could work in either location.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
Author make an effort to modify the manuscript, and the results are better. Only some tips to review now.
The introduction must be reviewed because some references number are bad ordered. especially review that [10] is after [12]. I think that [9] is repeated or bad numbered. Please, review it.
I am not sure that "features" would be the adequate word to describe the equations. I suggest to correct by an expert of english language in a better technical english vocabulary. I propose Characteristics, Properties or Functions. And review the construction of paragraphs, and do not repeat "features" or the word replacing it (section 2.3.1. B, C, D). And in all the results section.
Review mistakes in line 237.
Section 3.1. Is unnecessary to repeat the equations here, only refer as equation (6), equation (2) or equation (4) as necessary.
I propose that figure 9, 10 and 11 and its related comments will be better situated in Results section, not discussion. In Discussion, must be the comments about the results and comparisons betweeen the results of the work and other works about the quality of waters, coincidences and discrepances.
And finally, remember to format the bibliography as the style of the journal indicates. Attention to the abbreviation of titles of the journals and the dots.
Author Response
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Author Response File: Author Response.docx
Round 3
Reviewer 3 Report
Manuscript has modified according to my proposals. But note that must review the style of references according to journal instructions.
Author Response
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Author Response File: Author Response.docx
