Characteristics and Causes of Long-Term Water Quality Variation in Lixiahe Abdominal Area, China

Round 1

Reviewer 1 Report

I have read with interest your paper title “Characteristics and Causes of Long-term Water Quality Variation in Lixiahe Abdominal Area, China”. It is a well written paper, rich of quantitative and empirical data.

Here, however, are suggestions on how to further improve it and to make it more accessible to the general public, with policy impact:

• Affiliations: where similar, it should not be repeated but the same number should be used. Please check MDPI guidelines.
• “Correspondence” has been written twice.
• Lines 17-19: specify the country
• Introduction: why this case study? Please argue and justify why this specific case study has been chosen.
• Introduction: what is the guiding research question? Please be more explicit and clearly state it at the beginning of the paper.
• Original contribution: please clearly show what is the gap in the literature you are contributing to fill; this should be done by reviewing all relevant literature and in showing the gap (see comments below about this).
• Methodology: please justify – not just describe – the methods of data collection and analysis you have used.
• Lines 39-47: why you chose only those previous studies (which represent only a certain school and geographical area of the scholarship)? Please consider including also the work of Sharifa Hind and of Prof. Taleb Odeh on index that impact water quality, see for instance their work on: 1) Alsharifa Hind, J., & Marwan, A. (2010). Assessing groundwater vulnerability in Azraq Basin area by a modified drastic Index. Journal of Water Resource and Protection, 2010. 2) Odeh, Taleb, "Over-pumping of groundwater in Irbid governorate, northern Jordan: a conceptual model to analyze the effects of urbanization and agricultural activities on groundwater levels and salinity." Environmental earth sciences 78.1 (2019): 40; 3) Mohammad, Alsharifa Hind "Understanding the impact of droughts in the Yarmouk Basin, Jordan: monitoring droughts through meteorological and hydrological drought indices." Arabian Journal of Geosciences 11.5 (2018): 103.
• Section 3: not clear and accessible to not expert audience. Please make it more accessible to non-expert and technical audiences.
• Section 3: add a map of the country/region.
• Lines: 83-88“Because it is located in the lower reaches of the Huai River, the water quality of the water from the upper reaches is generally poor. The water used in the area is mainly from Jiangdu water conservancy project and Gaogang water conservancy project, by which the high-quality Yangtze River water enters the area through Xintongyang canal and Taizhouyingjiang River to meet the demand for water for life, industry and agriculture”. Here it clearly comes up the issue of the conflict between different regional areas, demand and supply, and the challenge of ensuring a balance between the two. Please see similar work, which should be included, on how water scarcity (increasing water demand) pushes to supply solutions, impacting water quality. This scholarship has explored especially transboundary settings in water scarce countries, which I believe would be useful in enriching your paper as it would add the comparative aspect and relate your paper to more general scholarships in the field. See for instance:

On groundwater resources: “Villar, P. C., & Ribeiro, W. C. (2011). The Agreement on the Guarani Aquifer: a new paradigm for transboundary groundwater management?. Water international, 36(5), 646-660; SILVA, L. P. B. D., MACHADO, L. O., & RIBEIRO, L. (2009). Fronteira Brasil-Bolívia: interações e características do espaço fronteiriço. Anais... 12º Encuentro de geógrafos de América Latina. da Silva, L. P. B (2019). Production of scale in regional hydropolitics: An analysis of La Plata River Basin and the Guarani Aquifer System in South America. Geoforum, 99, 42-53. Ibid. The Guarani Aquifer System, highly present but not high profile: A hydropolitical analysis of transboundary groundwater governance” Environmental Science & Policy, 83, 54-62. ;

 

 

Finally, the conclusion should be clearer, and make a clear point, bring the argument together, linking it to the main question which should be in the introduction, and clearly answer the question in the conclusion. Be clear, and accessible. I hope this suggestions and recommendations will help the authors in improving their work. 

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

After reading the article I remark that the authors did a lot of work for this article. Still, I have the following questions and suggestions.

1. In the abstract, line 25 what does it mean the letter a near 0.25-0.50. The same for line 28 and others in the article content.
2. Please explain the significance of  -0.068/a 
3. The introduction is too general. Please provide a more specific introduction.
4. 90% of the references cited in Introduction and Methodology are articles written by Chinese authors. I am sure that there are also other important papers of authors from other countries treating the wavelets topic and with contributions in the modeling direction using wavelets. Therefore, please add such references.
5. Please provide the abbreviation for the first time when you are using them (line 58, 268)
6. Please add a blank after 1025 al line 82.
7. lines 90, 271 - COD is not a pollutant, but a chemical indicator that reflects the content of the organic substance in the water. 
8. line 90 and line 104, 208 s.a:  The COD_cr values and COD_Mn are different due to the chemical procedure of retrieving the values. Therefore, please be consistent and discuss either COD_cr or COD_Mn allover in the article.
9. lines 88-92: Please explain the significance of the pollutant load. 94000 tones appear to be a huge amount...
10. line 120. There is a dot, instead of a comma.
11. formula (3): rikL and rikU - are they capital U and L or not? There is no concordance in the notation in formula (3) and the explanation of the significance  - lines 123-124.
12. What software did you use for wavelet analysis?
13. lines 157-165 should be removed or summarized since they are well-known.
14. line 185: Please provide the results of the statistical test that allow you to assert that there is a trend of the series. 
15. lines 185-186: Generally when the WQI decreases the water quality decreases as well. If you used another standard, please provide it in English.
16. Please provide the limit values for classification of the water quality as very good, good and so on.
17. Please provide the definition of the overproof rate.
18. Table 1. COD values are higher in July -Sept and lower in Oct-Dec. Why?
19. The measurement unit m/L or mg/l - please be consistent
20. In Table 3, how did you determine the characteristic period? Please provide an explanation.
21. Figure 4. A better option for proving the existence of a decreasing/increasing test is to perform a Mann-Kendall trend test, followed by Sen's slope in the case when the null hypothesis in the Mann-Kendall test is rejected. Otherwise, the linear model should be significant as a whole and the F test for its significance should be also performed.
22. Please check the formatting of the reference. For example, at the first reference, put dot instead of a column.
23. In  Conclusion it is a bit strange that the pollutant concentration increases and the water quality increases as well. Please double-check the results that lead to this conclusion.
24. The quality of Fig 4 should be improved.
25. What software did you use for drawing the figures?
26. Please provide the output of wavelet decomposition and the code source.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thanks for sending the updated version and for revising it. It looks improved. Nevertheless, I still feel that my comment was not addressed properly, while you write in your answers that you have. Please revise accordingly, as I feel that passage is still weak and would benefit from revision according to this point:

• Lines 39-47: why you chose only those previous studies (which represent only a certain school and geographical area of the scholarship)? Please consider including also the work of Sharifa Hind and of Prof. Taleb Odeh on index that impact water quality, see for instance their work on:

 

• 1) Alsharifa Hind, J., & Marwan, A. (2010). Assessing groundwater vulnerability in Azraq Basin area by a modified drastic Index. Journal of Water Resource and Protection, 2010.
• 2) Odeh, Taleb, "Over-pumping of groundwater in Irbid governorate, northern Jordan: a conceptual model to analyze the effects of urbanization and agricultural activities on groundwater levels and salinity." Environmental earth sciences 78.1 (2019): 40;
• 3) Mohammad, Alsharifa Hind "Understanding the impact of droughts in the Yarmouk Basin, Jordan: monitoring droughts through meteorological and hydrological drought indices." Arabian Journal of Geosciences 11.5 (2018): 103.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The authors addressed almost all the suggestions of the reviewers. Still, there are some minor changes to be done.

1. Concerning COD -if the analysis is about CODMN,  you should remove the description related to CODCR for consistency 
2. You should mention in the article, not only in the answer to reviewer what software was used.
3. Concerning the use of t and F test, it not advisable to use such tool without checking the R2 value and testing hypothesis on residuals. Please provide the results for Man-Kendal trend test and Sen's slope.
4. Answer 14. We can't guess in a scientific article. Please provide the MK test results for those assertions.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 3

Reviewer 1 Report

Looks much improved, and I think the writing of Hind Mohammad improved your conceptualisation of the issue.

One minor thing before acceptance: please replace the outdated reference number 2 with: 

Hussein, (2018). The Guarani Aquifer System, highly present but not high profile: A hydropolitical analysis of transboundary groundwater governance. Environmental Science & Policy, 83, 54-62.

Much better to have a reference discussing the challenges around groundwater dated 2018 and with the depth of the discussion of the Guarani, rather than the 1970 reference you have used. Other than this, ready to go. 

Author Response

We have replaced the reference 2 with Hussein's.

Author Response File: Author Response.docx