Modeling the Impact of Land Use Changes and Wastewater Treatment on Water Quality and Ecosystem Services in the Yongding River Basin, North China
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Authors,
The manuscript is written well with good contents. I left some comments for further improvement:
I observed that the authors are from USA and Germany but they selected the Yongding River Basin in China without any Chinese affiliation. Off course, it does not matter but my concern is that is there any similar basin area in USA, where this kind of study could be conducted. If yes, then why did you select the Chinese river basin? By this explanation in manuscript, the scope of your study could be enhanced.
You used CAM model for LU changes. The title could be “Impact of land use changes and wastewater treatment on water quality and Ecosystem Services in the Yongding River Basin: A modeling study”.
The abstract section is not fulfilling the requirement of standard abstract. I did not see any description of methodology and results. The authors only added the conclusive statement and the text only. You need to add your particular results in quantitative form.
In Introduction section, the novelty and the significance of the study need to be elaborated. Only, one sentence (Line 76) regarding the novel aspect is not enough. The significance of your study is given in line 113-117, that can be imported in Introduction section.
Figure 1: Choose a different color scheme for elaboration of different rivers. Current color scheme is not appropriate.
Figure 2: The information of increasing/decreasing the certain type of land use should be incorporated for better understanding of readers. May be, you can add it in figure 2 or in separate table.
Figure 7: the range of y-axis needs to be enhanced for COD, NH4, TP, so that the values could clearly be covered within the graph area.
The implications of the study are significant, emphasizing the need for considering land use and infrastructure in planning. However, the manuscript should also briefly mention the potential policy recommendations derived from the findings.
Comments on the Quality of English LanguageMinor grammatical corrections could improve readability.
Author Response
Attached are the responses to reviewers and the annotated version of the manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsWell written and informative paper - only a relatively few comments about suggested, primarily, additions. Easy to read, good graphics that are referenced in the text and an important topic. Comments are in the copy of the paper attached below.
Comments for author File: Comments.pdf
Author Response
water-3051903: Modeling the impact of land use changes and wastewater treatment on water quality and Ecosystem Services in the Yongding River Basin, North China
Replies to Reviewers’ Comments
Reviewer 2 Comments
General Comment:
Well written and informative paper - only a relatively few comments about suggested, primarily, additions. Easy to read, good graphics that are referenced in the text and an important topic. Comments are in the copy of the paper attached below.
Response:
Thank you for the reception of our work. As we also mentioned to the other reviewer’s replies, we appreciate this positive feedback, as it was a challenging task to combine different concepts and methods to produce a holistic assessment. We tried to do our best to adequately address all your suggestions, please find our point-by-point replies below.
Comment 1: It would be helpful if the country map were larger and on the watershed map that the main channel might be more highlighted or the tributaries be identified - where is Zhangjakou City? From the text it looks like the component of the watershed that was tested lies totally in the city.
Response 1: Thank you for the comment. The edited map has now a larger representation of the country, and the City of Zhangjiakou has been added. We have also highlighted the thickness and color gradation of the rivers to address a comment from the other reviewer.
Comment 2: What is the major source of animal waste in the city?
Response 2: Thank you for the attentive comment, we have removed this phrase.
Comment 3: I am not familiar with these models but assume that they are appropriate for providing the desired information.
Response 3: Thank you. We have used these models in the past for other occasions and study areas, and we have further supported them in the text with relevant references.
Comment 4: Does this mean that the green area in Fig 1 is the city of Zhangjiakou - if so that needs to be clearly stated in the Figure 1 title as now it simply says "study area" Are all the sampling sites in the urban area?
Response 4: The comment has been addressed. We have added a new layer in Figure 1 to show the city of Zhangjiakou. The study area is the Yongding River in Zhangjiakou City, which accounts for 47.5% of Zhangjiakou’s total area. The figure legend has been revised to make this clear.
Comment 5: Where is Table S1? What is meant by typical load per unit - what constitutes a unit? How different WWTPs are present in the study area?
Response 5: The reviewer is right. In the revised text we have corrected the expressions, and we hope that now these phrases are clear. Moreover, at the beginning of section 3.2, we clarified how the pollutant discharge is assessed, and cited the supplementary material. The supplementary material includes all the supplementary figures and tables, which have also been uploaded in the submission. Given the large size of the study area, there are 16 different WWTPs within it. The information about their treatment capacities and efficiencies is known, but their specific location information was not available.
Comment 6: What kind of treatment do rural residents use, is each rural residence required to have a treatment system such as a septic system? Is farmland export primarily surface runoff or is subsurface tile also used? Is the assumption that all RLP is non-point?
Response 6: The rural residents use the rural centralized wastewater treatment facilities. Due to the investment limitation, the rural wastewater treatment facilities are not as highly efficient as the urban wastewater treatment plants. Here the RLP refers to the wastewater pollutants of rural residents, we did not consider other wasters or diffuse sources, thus it's a point source. In this work, we assumed that the farmlands export primarily surface runoff to simplify the calculation results. In future work, we should consider the subsurface tile of farmland pollutant export. We have added a comment to clarify this also in the text.
Comment 7: It would be helpful if the "Supplementary Material" was introduced on line 146.
Response 7: In the revised paper we have followed your suggestion, thank you for pointing this out.
Comment 8: does "planting" only mean pollution from the planting process?
Response 8: Thank you for the comment. Yes, “planting” means pollution from the planting process. We have also explained that in the text.
Comment 9: What is meant by breeding sources- are these pollutants only associated with the areas where "breeding" goes on or does this also cover this also include the day-to-day production of pollutants during the life of the livestock and poultry? And the latter are only from livestock and poultry that are free-range on the land?
Response 9: The reviewer is right; we have clarified this in the text, adding everywhere an explanatory phrase “captive breeding” throughout the text, to clarify that we consider captive breeding and the production of pollutants during the life of the livestock and poultry. In this study area, the livestock and poultry are not free-range on the land, they are captive breeding.
Comment 10: It might be helpful to define USD/ha/yr in a table footnote.
Response 10: In the revised paper we have followed your suggestion, thank you for pointing this out.
Comment 11: The urban area will increase fastest in relation to what? There is nothing to which its increase is being compared..
Response 11: Thank you for the detailed comment; in the revised paper we have corrected this expression.
Comment 12: Figure 2. These maps are so small I cannot see any changes between any of the years at the scale shown. Even the water bodies look the same size in all of them and if this is in the city, the urban area seems very small - is this area on the fringe of the city? So the maps are showing no change over time which is your major conclusion. It would helpful if the river was highlighted on the maps.
Response 12: The reviewer is right; we have now edited the Figure 2 to address your reasonable comments. We have enlarged the maps and added a bar diagram to show the quantified increases and decreases of the different land use types during the study period.
Comment 13: I am not sure it is possible in this kind of a study - but it would be helpful if some statistical analysis could be applied to help verify if differences did or did not exist.
Response 13: In this work, we selected three stages (2017, 2025, 2035) to show the pollutant load and spatialized them instead of year by year. So, based on three data points in each category, it is not enough to make a statistical analysis for pollutant load comparison or time-series analysis. However, the trend of pollutant loads in Figure 3 is clear. Therefore, we think the results here are proper in this study.
Comment 14: The size of these maps is better in showing that actual changes that exist between years.
Response 14: Thank you, we hope that in the revised paper now the figures are clearer.
Comment 15: Not sure that you really need to show cents in the values of the table.
Response 15: Thank you for the comment, but these decimals in the table are not cents (as the units are 106 USD), so we believe it is useful to keep them, to give a complete picture of the monetary values estimated.
Comment 16: It almost looks as though there may be higher values of COD in 2035 than 2025 in the northern segment of the SW and E segments- is that simply a result of significant population growth?
Response 16: Thank you for the attentive comment, we have now addressed it: That was our fault, as the wrong color label was kept there for the COD layer. We have now revised Figure 9. Thank you again for pointing this out.
Comment 17: The web address shown on line 2 did not work for me after several tries.
Response 17: The reviewer is right because this statement was the default text of the journal’s paper template. The link is indicative, and after acceptance and publication, they will upload our Supplementary Material, so the link will be valid. For now, we have uploaded the actual file of the Supplementary Material which the reviewers can access with our submission files.
We would like to thank again the Reviewer for the constructive feedback and willingness to improve the presentation of our work. We hope that in the revised paper, we have adequately addressed all comments raised.
Author Response File: Author Response.pdf
