Observations of the Impacts of Hong Kong International Airport on Water Quality from 1986 to 2022 Using Landsat Satellite

Round 1

Reviewer 1 Report (Previous Reviewer 4)

The second (revised) version of the article is presented. The effort is devoted to the analysis of a long-term retrospective series of satellite and field monitoring data in relation to the task of assessing the anthropogenic impact of construction of Hong Kong international Airport. The authors carefully and thoroughly treated the consideration and elaboration of the previously submitted comments, the manuscript was promptly and well supplemented and corrected. Two comments can still be made that generally do not detract from the benefits of the work.
1) In the previous review, it was suggested:
«2.5 Despite the fact that the authors have processed a large array of data and applied original methods and presets of data processing, the article does not contain scientific conclusions concerning remote sensing and/or the processes of extracting useful data from remote sensing products. What new scientific contribution to the field of remote sensing (and not oceanology or ecology) was made as a result of this study?»
In response to this remark, the authors made some conclusions and added them to the article. However, from my point of view, this block should be supplemented. It would be appropriate to declare (as a result of the effort) that useful bands were found for the problem being solved, with an explanation of the physical background that confirm such a choice of spectral range.
2) It remains unclear to me how a modern model based on artificial intelligence could worsen the results of determining the desired parameters when adding objective (albeit not strongly related to the process under study) data. It seems to me that such data can be of arbitrarily little contribution, but they should not be harmful (except for the cost of computing resources). I think that readers may have similar questions, so it would be appropriate in the article to give the results of a test in which the accuracy achieved both with a complete data set and with using only the selected bands. In the responses to the review, the authors mentioned such a test.

Thank you very much for your work!

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 2 Report (Previous Reviewer 5)

The comments are in the attached file.

Comments for author File: Comments.pdf

English language still definitely needs revision, both for grammar and for meaning.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report (Previous Reviewer 4)

Dear authors!
Thank you for your work and prompt answers!
With best wishes!

Author Response

Thank you very much for your careful and thorough review for this paper.

 

Best regards

Reviewer 2 Report (Previous Reviewer 5)

English language has improved, I suggest to check the punctuation in lines 130 - 132.

English language has improved, I suggest to check the punctuation in lines 130 - 132.

Author Response

Thank you very much for your review. The manuscript has been revised according to your comments.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

This paper is already in a good shape. No more comments.

Reviewer 2 Report

1. The latitude and longitude displayed in Figure 1 are unclear, which may increase the resolution of Figure 1.

2. The punctuation is missing in Line 139.

3. The satellite data used in the paper are Landsat data. What are the advantages of Landsat data in the study? The authors may add references for clarification.

4. Maybe an analysis of the zone of Hong Kong port on 2 December 2020 should be added to the research in Figure 8?

5. “To more clearly depict the temporal variations of water quality in different regions of the NWBHK, this study divided the bay into three areas: A, B, and C. (Line354-356)” Can the authors explain how to divide the three areas in detail?

6. Line 384,“......, which decreased from 1990 to 1992 (from 0.05 mg/L to 0.05 mg/L)” maybe there is an error in the data?

7. Figure 13 (c) top border missing. Please keep it consistent with (a) (b).

8. Line 517-518, The format has an error.

Reviewer 3 Report

Dear authors the current research paper (which is very interesting as an application) should be modified in its structure

as well as rewrite the abstract in which you have to mention clearly the task. A scheme that you can follow is :

Abstract

1.  Introduction

2. Description of the research area

3. Data used and methodology

4. Results

5. Discussion

6. Conclusions

References 

Acknowledgments (in case that you have to mention any)

The authors study the water quality over the International Airport of Hong Kong for the period 1986-2022 using  Landsat-5 TM and Landsat-8 OLI images.  

 By analyzing the temporal variations and spatial distributions they found that:  During the construction period of HKIA, the construction activities could 

cause the rise of SPM (suspended matter) as well as for PO4P and DIN concentrations of water (orthophosphate-phosphorus and dissolved inorganic nitrogen) 

based on the BPNN algorithms.  The impact of Tuen Mun River on NWBHK increased, while the impact of Tung Chung River on decreased. 

 Finally, the interception impact of the International airport to the transportation of pearl river became stronger.    

 

The abstract should be rewritten. Also in the introduction section authors should mention the research questions and why it is essential to support the solution.

Do the authors know what happened in the area now? Also, I think that the authors should mention similar works of other research groups.

 

 

 

Reviewer 4 Report

1. A brief summary
The presented article is devoted to the analysis of a long-term retrospective series of satellite and field monitoring data in relation to the task of assessing the anthropogenic impact of the construction of Hong Kong International Airport (HKIA) in the Northwestern Bay of Hong Kong. The article undoubtedly required significant efforts related to the collection, processing and analysis of various data. The article is generally compiled appropriately, but it is recommended to finalize it. Specific comments are provided below.

2. General concept comments
2.1 It is difficult for the reader to follow the methodology underlying the research. The study has diverse tasks (from identifying the stages of construction of the HKIA to comparing the impact of climatic and anthropogenic factors on the water area of interest).  Various data are used in various combinations, which were additionally sorted, culled and processed using various tools and tuning parameters. Beginnig from the 3rd section the article contains hard-to-read text arrays with a routine narration of quantitative observation results, which are difficult to understand and link them into a single interconnected set of results that provides foundation for conclusions. Consequently:
a) It is recommended to offer the reader a graphical scheme of the study, in which the initial data, operations, types of results and information connections between these elements will be provided.
b) It is recommended to provide more analytical, rather than descriptive text of the results of observations.
2.2 Attention is drawn to the strong positive anomalies of SPM (and other water parameters) in the west of the area of interest, for example, in Fig.8). These anomalies significantly exceed the effects associated with the construction of HKIA. In my opinion, these features should be considered using quantitative criteria and discussed in relation to the identified parameters of the impact of HKIA construction on the environment.
2.3 How justified was the use of only 4 satellite image bands (Line 297)? Perhaps these missed channels would improve (not radically, but still) the accuracy of restoring the parameters of the aquatic environment. The motivation for ignoring bands is unclear.
2.4 The block related to monitoring the construction process looks insufficiently. If the purpose of this block was to determine the stages of construction, then it would probably be easier to extract the stages from open source data. If the goals of this block are more meaningful, then at least quantitative results (for example, the dynamics of the built-up area) and their analytics should be added.
2.5 Despite the fact that the authors have processed a large array of data and applied original methods and settings of data processing, the article does not contain scientific conclusions concerning remote sensing and/or the processes of extracting useful thematic data from remote sensing products. What new scientific contribution to the field of remote sensing (and not oceanology or ecology) was made as a result of this study? I have no doubt that this contribution exists, and I recommend the authors to formulate such conclusion and add it to the manuscript.
2.6 [References] are not well developed, for example, the NDVI index is mentioned without reference to the original source, the formula for calculating Rrc is mentioned with references to works that only use (but not explain) this formula (which was originally proposed for MOD 09).
2.7 Please approach the formulation of phrases more carefully and observe the scientific style, some phrases raise questions, for example:
Line 158 – “Landsat-8 has 7 bands”. The mention of the ‘OLI’ device was missed. Moreover, in general, this device has more than 7 bands, it is better to mention this in manuscript, despite the fact that the authors did not use other bands in their effort.
Line 161 – “The serial number for the satellite 161 data is 122044”. This is not “serial” number; this is Worldwide Reference System (WRS) path and row numbers.
Line 212 – Chl-a abbreviation is declared, but is not used anywhere.
Line 325 –  The term "yearly" in this phrase is incorrect, since in fact the results given do not reflect fluctuations in SPM concentrations either within each year or in an interannual retrospective (only daily distributions are shown, and the given time series is not regular).
…And other…

3. Review and comments
3.1 The TITLE of the article does not include mention of in situ data, although these data provide a significant part of the results of the work.
3.2 Figure 1. The purpose of ABC polygons becomes clear only at the distant part of the article, it confuses the reader.
3.3 Section 2.2. Please specify the characteristics of in situ measurements, namely, specify the time frequency of ground-based measurements of water quality indicators and a list of measured indicators (this indicated only in the results).
3.4 Section 2.3. Please specify the description of the satellite data, namely, show the distribution of the images selected for the study by year and by seasons and evaluate its suitability for the research tasks.
3.5 Figure 3. It seems appropriate to mark the stages of construction in the illustration (they probably correspond to the horizontal rows of images, but this is not obvious).
3.6 Figure 8, Figure 10, Figure 11, Figure 14. The maps in these figures are unnecessarily small, which makes it difficult to study the processes directly near the HKIA. It is recommended to enlarge the maps (for example, by placing them in 4 rows of 3 columns, and place the scale at the bottom). The contours of the ABC zones should be added to these drawings. At the same time, the spatial coverage of the study area map (Fig.1c) and the maps of the results of determining the concentrations by satellite methods do not coincide (the results are given for a reduced area).
3.7 Figure 9 (b), Figure 12 (a, b), Figure 13 (a, b). Please adjust the ranges of the vertical scales so that they better reflect the actual values of the studied parameters (the lines of some graphs merge together).
3.8 Line 545. It seems appropriate to place the description of the climate change data used in section 2 together with other in situ measurements used.
3.9 Figure 18. Please add the stages of airport construction to the chart for the convenience of comparison with other charts.

Thank you very much for your work!

Reviewer 5 Report

Comments for author File: Comments.pdf