Effectiveness of Rain Gardens for Managing Non-Point Source Pollution from Urban Surface Storm Water Runoff in Eastern Texas, USA

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript entitled “Effectiveness of Rain Gardens for Managing Non-Point Source Pollution from Urban Surface Storm Water Runoff in Eastern Texas, U. S.” proposes the evaluation of the effectiveness of three rain gardens positioned next to each other as structural BMPs. Despite presenting very old data, the topic is interesting and current. However, there are some points that, in my opinion, should be improved so that the manuscript can be considered for publication in this journal.

1) INTRODUCTION: I suggest that the Introduction section be separated from the Literature Review section. This section should focus on providing a brief contextualization of the topic, delimit the research gap, the objective, and highlight the novelty of the research. Conceptualizations and in-depth analyzes of the topic should be placed in the Literature Review section.

2) LITERATURE REVIEW: Although the journal allows for the fusion of the introduction and literature review sections, in my opinion this manuscript would benefit if the sections were presented separately. Then, I suggest creating a literature review section. The literature review aims to indicate the state-of-the-art on the subject. Although the authors provide a quantitatively sufficient list of references, it is necessary to delve further into the methodologies and results obtained in previous studies. As well as substantiating the most important concepts for understanding the research. It is not possible to guarantee a solid theoretical background without broadly discussing the results of previous research on the subject. 30 references were cited only in section 1. However, few of them had their content properly explored.

3) REFERENCES: References must be improved. Authors must work to make the study denser and supported by updated scientific evidence. Considering the 48 scientific references cited, only 13 are current (less than five years since publication). In other words, currently, the data presented by the authors as a theoretical basis for the research can be considered outdated.

4) FIGURES AND TABLES: Figures and tables must be positioned throughout the text, close to where they are cited for the first time. It is extremely inefficient for the reader to be forced to look for these elements at the end of the manuscript every time they need to observe them to follow the reasoning presented in the text.

5) FIGURE 1: The figure caption indicates that: “The map indicates the contributing drainage areas for each rain garden, including surrounding impervious surfaces such as parking lots, sidewalks, and buildings”. Although they are visible on the map, I do not consider these areas to have actually been indicated by the authors. I suggest that the figure be updated, including graphic elements that effectively indicate these contributing areas for each rain garden.

6) FIGURE 1: In my opinion, the images used by the authors to specify the research region are not clear. The gradual reduction of the area (Texas - Nacogdoches County - Nacogdoches City) should be better worked out graphically.

7) SECTIONS 2.3 AND 2.4: In my opinion, it would be very interesting to present schematic figures illustrating the "Structural Design" and "Cross Sectional Structure" of the studied Rain Gardens. This way, the reader will be able to follow the descriptions made in these sections by viewing the figure.

8) LINE 188: I believe this is Figure 2, not Figure 32, is that correct?

9) LINE 251 (Formula 1): I suggest that authors indicate the meaning of each term in the equations used, even if they are obvious, to avoid any misunderstanding on the part of readers.

10) LINES 253-257: In my opinion, this paragraph would be better located in the Materials and Methods Section.

11) TABLE 2: I found no reference to Table 2 in the text. Table 1 is cited on line 154, and Table 3 on line 261. Is Table 2 really relevant to the manuscript?

12) SECTION 3.1: Considering that the study period occurred approximately 11 years ago, I believe it would be interesting to also analyze precipitation conditions in subsequent years. This way, it is possible to identify whether this was a typical year or not.

13) FIGURE 3: Although the graphs are positioned perfectly aligned, it is interesting that the elements on the horizontal axis are also included in the "(a) Total concentrations" graph, so as not to create doubts for the reader as to the element analyzed.

14) CONCLUSION: Authors must include the limitations of the study in the conclusion section, which are probably many, given that it is an experimental study.

Author Response

Comment 1: The manuscript entitled “Effectiveness of Rain Gardens for Managing Non-Point Source Pollution from Urban Surface Storm Water Runoff in Eastern Texas, U. S.” proposes the evaluation of the effectiveness of three rain gardens positioned next to each other as structural BMPs. Despite presenting very old data, the topic is interesting and current. However, there are some points that, in my opinion, should be improved so that the manuscript can be considered for publication in this journal.

Response 1: We sincerely thank the reviewer for recognizing the relevance of our research topic and for acknowledging the current importance of evaluating rain gardens as structural BMPs. We made the major changes in introduction; we separated it into “1. Introduction” and “2. Literature review”. We have cited more recent literature to frame the findings in a contemporary context.

Comment 2: 1) INTRODUCTION: I suggest that the Introduction section be separated from the Literature Review section. This section should focus on providing a brief contextualization of the topic, delimit the research gap, the objective, and highlight the novelty of the research. Conceptualizations and in-depth analyzes of the topic should be placed in the Literature Review section.

Response 2: We agree with this comment. We separated the previous introduction section into “1. Introduction” and “2. Literature review”.

Comment 3: 2) LITERATURE REVIEW: Although the journal allows for the fusion of the introduction and literature review sections, in my opinion this manuscript would benefit if the sections were presented separately. Then, I suggest creating a literature review section. The literature review aims to indicate the state-of-the-art on the subject. Although the authors provide a quantitatively sufficient list of references, it is necessary to delve further into the methodologies and results obtained in previous studies. As well as substantiating the most important concepts for understanding the research. It is not possible to guarantee a solid theoretical background without broadly discussing the results of previous research on the subject. 30 references were cited only in section 1. However, few of them had their content properly explored.

Response 3: We agree with this comment. we have revised the Literature Review to go beyond listing references and instead offer a more critical and thematic synthesis of the state-of-the-art.

Comment 4: 3) REFERENCES: References must be improved. Authors must work to make the study denser and supported by updated scientific evidence. Considering the 48 scientific references cited, only 13 are current (less than five years since publication). In other words, currently, the data presented by the authors as a theoretical basis for the research can be considered outdated.

Response 4: We agree with this comment. We updated the reference and added 6 more recent publications. The total number of references is 55.

Comment 5: 4) FIGURES AND TABLES: Figures and tables must be positioned throughout the text, close to where they are cited for the first time. It is extremely inefficient for the reader to be forced to look for these elements at the end of the manuscript every time they need to observe them to follow the reasoning presented in the text.

Response 5: We were terribly sorry for the inconvenience of reading the main text and figures and tables. The figures and tables were at the end due to the template provided by the journal. In the revision manuscript, we positioned them in line with the main text and also kept them at the end as well.

Comment 6: 5) FIGURE 1: The figure caption indicates that: “The map indicates the contributing drainage areas for each rain garden, including surrounding impervious surfaces such as parking lots, sidewalks, and buildings”. Although they are visible on the map, I do not consider these areas to have actually been indicated by the authors. I suggest that the figure be updated, including graphic elements that effectively indicate these contributing areas for each rain garden.

Response 6: We agree with this comment. There was an error in that the map in figure 1 did not have the contributing areas delineated. We changed this figure out with one that indicates the rain garden locations and contributing areas.

Comment 7: 6) FIGURE 1: In my opinion, the images used by the authors to specify the research region are not clear. The gradual reduction of the area (Texas - Nacogdoches County - Nacogdoches City) should be better worked out graphically.

Response 7: We agree with this comment. We updated the image indicating where Nacogdoches County and City are in relation to the state of Texas as an inset as the reviewer suggested.

Comment 8: 7) SECTIONS 2.3 AND 2.4: In my opinion, it would be very interesting to present schematic figures illustrating the "Structural Design" and "Cross Sectional Structure" of the studied Rain Gardens. This way, the reader will be able to follow the descriptions made in these sections by viewing the figure.

Response 8: We agree with this comment. We added two more figures, one of the cross-section designs and one with an overview showing the layout from above.

Comment 9: 8) LINE 188: I believe this is Figure 2, not Figure 32, is that correct?

Response 9: We agree with this comment. We’ve corrected it into Figure 2.

Comment 10: 9) LINE 251 (Formula 1): I suggest that authors indicate the meaning of each term in the equations used, even if they are obvious, to avoid any misunderstanding on the part of readers.

Response 10: We agree with this comment. We’ve added the meaning of each term after the equation.

Comment 11: 10) LINES 253-257: In my opinion, this paragraph would be better located in the Materials and Methods Section.

Response 11: We agree with this comment. We moved this paragraph to section 3.5 Water sample collection, line 303-308.

Comment 12: 11) TABLE 2: I found no reference to Table 2 in the text. Table 1 is cited on line 154, and Table 3 on line 261. Is Table 2 really relevant to the manuscript?

Response 12: We agree with this comment. We added the reference to Table 2, it is under section 3.9 Statistical analysis, line 359.

Comment 13: 12) SECTION 3.1: Considering that the study period occurred approximately 11 years ago, I believe it would be interesting to also analyze precipitation conditions in subsequent years. This way, it is possible to identify whether this was a typical year or not.

Response 13: We agree with this comment. We add the monthly mean precipitation from 2015- 2024 into Table 3 that was aligned with the data of study period and the period before the study. The precipitation is increasing over time.

Comment 14: 13) FIGURE 3: Although the graphs are positioned perfectly aligned, it is interesting that the elements on the horizontal axis are also included in the "(a) Total concentrations" graph, so as not to create doubts for the reader as to the element analyzed.

Response 14: We agree with this comment. We added the horizontal axis in the "(a) Total concentrations” panel.

Comment 15: 14) CONCLUSION: Authors must include the limitations of the study in the conclusion section, which are probably many, given that it is an experimental study.

Response 15: We agree with this comment. We add the limitations in the conclusion section. Line 831-835.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript entitled “Effectiveness of Rain Gardens for Managing Non-Point Source Pollution from Urban Surface Storm Water Runoff in Eastern Texas, U.S.” represents an interesting work addressing the environmental challenges associated with urban storm water runoff, particularly its profound effects on hydrology and water quality. An important aspect of the study is that the rain gardens were studied in the subtropical climate of east Texas, a region with extreme precipitation.

The study's significance originates from the need for investigations on anthropogenic surface-related water contamination (water from parking and building rooftops), which will enhance the aquatic environment's quality. Overall, it was an interesting challenge, but the methods and interpretation of the results in the context of the manuscript objectives are not very well done. The methods used in the article for determination of elements in water are not described, and the results are compared with local water quality regulations. The observations listed below require your attention.

Comments for author File: Comments.pdf

Author Response

Comment 1: The manuscript entitled “Effectiveness of Rain Gardens for Managing Non-Point Source Pollution from Urban Surface Storm Water Runoff in Eastern Texas, U.S.” represents an interesting work addressing the environmental challenges associated with urban storm water runoff, particularly its profound effects on hydrology and water quality. An important aspect of the study is that the rain gardens were studied in the subtropical climate of east Texas, a region with extreme precipitation.

The study's significance originates from the need for investigations on anthropogenic surface-related water contamination (water from parking and building rooftops), which will enhance the aquatic environment's quality. Overall, it was an interesting challenge, but the methods and interpretation of the results in the context of the manuscript objectives are not very well done. The methods used in the article for determination of elements in water are not described, and the results are compared with local water quality regulations. The observations listed below require your attention.

Response 1: We thank the reviewer for their thoughtful and encouraging comments, particularly for acknowledging the significance of our study’s geographic context and the relevance of investigating rain garden performance under extreme precipitation conditions. We expanded the “Water Sample Collection” and “Chemical Analysis” subsections to include the specific analytical procedures, instruments, detection limits, and protocols, clarified the regulatory comparison framework, and strengthened the linkage between the methods, results, and hypotheses.

Comment 2: 1. Line 108-117 move to 2. Materials and Methods.

Response 2: We agree with this comment. We have revised the paragraph to retain the hypotheses and the overall study framework, while relocating the detailed list of measured water quality parameters to the Materials and Methods section.

Comment 3: 2. Line 209-212 Choose one thing, either symbols (Cl, pH etc.) or element names. Please indicate by which methods the elements were determined (instrument name, manufacturer, city and country of origin).

Response 3: We agree with this comment. We added the relevant information after this part. Line 308-319.

Comment 4: 3. Line 214. Please indicate the accuracy of T and EC determination (instrument name, manufacturer, city and country of origin).

Response 4: We agree with this comment. We added the information. Line XX.

Comment 5: 4. Line 284. This is the first time you write that you have determined total and water-soluble copper concentrations. Describe the methodology and instrumentation in the Materials and Methods section. And why do you think it is important to consider these concentrations separately (applies to other elements as well)? What filters were used? Table 2 shows that the TCEQ maximum allowable concentration is 0.96 (is that for total copper?). You have a maximum value of 0.05 mg/L (line 285) for water-soluble and 0.09 for total. Why do you write that it “exceeds the water quality standard”? Please provide the MCL for copper recommended by USEPA.

Response 5: We agree with this comment. We have now added a full description in the Materials and Methods section explaining how total and water-soluble metal concentrations were determined. The copper standard listed in Table 2 is not a fixed value but derived from the TCEQ acute criterion for freshwater based on the equation presented. Given the measured hardness range at our study sites, the corresponding copper criterion ranges from 0.032 to 0.047 mg/L. Observed copper concentrations (max total = 0.09 mg/L; max soluble = 0.05 mg/L) are close to or slightly above these site-specific thresholds but remain well below the USEPA MCL for copper in drinking water (1.3 mg/L). The same as Lead and Zinc.

Comment 6: 5. Line 300. «Both values were below the TCEQ water quality standard of 0.36 mg/L». But in Table 2 Water Quality Standard for As is 0.34. According USEPA standard MCL for As is 0.01 mg/L. Are you shore that 0.36 mg/L is right values from TCEQ? It is very high concentration for As in water!

Response 6: We agree with this comment. We found that the stated TCEQ water quality standard of 0.36 mg/L for arsenic was incorrect. We corrected TCEQ water quality standard in Table 2 and the relevant content in 3.3.3 Arsenic.

Comment 7: 6. In discussion, you did not conclude how badly the rainwater coming from different facilities was polluted. Is there any danger in its chemical composition?

Response 7: We agree with this comment. We added a paragraph in discussion addressing the exceedances of water quality standards in the inflow samples and discussing the implications of specific contaminants of concern. Line 713-724.

Comment 8: 7. Line 530. USEPA standards are listed in Table 2 only for Hg, NO2, NO3 and Pb. But it is not clear if the waters satisfy these standards or not. Add USEPA water quality standards for other elements to the table and discuss them in the text.

Response 8: We agree with this comment. We have revised Table 2 to include the USEPA Maximum Contaminant Levels (MCLs) or Health Advisory Levels for all relevant parameters where applicable, including copper (Cu), arsenic (As), zinc (Zn), manganese (Mn), fluoride (F⁻), chloride (Cl⁻), and sulfate (SO₄²⁻), in addition to those already reported (Hg, NO₂⁻, NO₃⁻, Pb). Furthermore, we have revised the Results and Discussion sections to explicitly state whether observed concentrations of each pollutant exceed approach, or fall well below their respective USEPA MCLs. Line 389-410.

Comment 9: 8. Line 575. You have comprehensive analytical material and a large database, show on graphs the relationship of element distribution to pH or EC. This could clearly confirm your assumptions.

Response 9: We agree with this comment. We indicated that this can be the case and referenced the figures as suggested. Line 795.

Comment 10: 9. It is not clear from the text how the subtropical climate of the area affected the rain gardens. Please discuss this in the text. Did you find significant differences between the well-studied rain gardens in the temperate regions (line 101)?

Response 10: We agree with this comment. We modified the statement in the introduction explaining how this climatic regime poses distinct challenges to rain garden performance, particularly in relation to infiltration capacity, residence time, and pollutant removal dynamics. Line 49-57. We added a statement in the Discussion section to highlight how our findings differ from those commonly reported in temperate regions. Line 732-736. Subtropical systems often face short residence times, media saturation, and inflow volumes that exceed design storage. These conditions can reduce pollutant retention and increase the risk of bypass or overflow, particularly during back-to-back storm events.

Comment 11: 10. The measurements were made with HOBO loggers, it would be very interesting if you could provide graphs of variations in mineralization and temperature over a specific period of time (month, six months or year). This would greatly improve the understanding of climate and measurement periods.

Response 11: Unfortunately, we did not have all of the water temperature data for the study period, so we deleted the reference to that in the manuscript. The Hobo logger did normalize the measurements to 25 ℃ but we did not have the actual measurements of temperature saved.

Comment 12: 11. Line 188. (Figure 32)?

Response 12: We agree with this comment. We corrected the figure number.

Comment 13: 12. Lines 497, 499. 99%. [34]. - extra dots.

Response 13: We agree with this comment. We corrected the number.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

thank you for a very comprehensive work, which deals with the current problem in the field of NBS, with adequate structure and methodology, with excellent results and related conclusions.

Certain small corrections can improve your work in terms of:

1. In the introductory part, you should explain what is meant by extreme precipitation, primarily in relation to certain average values, especially for the research area,

2. Try to quantify the amount of pollutants originating from non-point sources,

3. Elaborate in more detailed way standards mentioned on lines 241 - 243,

4. Enrich the results/discussion section with precise key findings,

5. In present form conclusion is to scarce and must be improved with stronger reflection on quantitative findings, possible limitations of the study and more details concerning future researches.

All the best

Author Response

Comment 1: 1. In the introductory part, you should explain what is meant by extreme precipitation, primarily in relation to certain average values, especially for the research area,

Response 1: We agree with this comment. In the introduction section, we defined extreme precipitation based on climatological norms for eastern Texas, including the average annual rainfall and the intensity of short-duration events, supported by regional hydrological data. Line 52-54.

Comment 2: 2. Try to quantify the amount of pollutants originating from non-point sources,

Response 2: We did not observe any point sources of pollution during the study period and there were no permitted wastewater discharge permits issued for the contributing areas that would be consistent with point source pollution. We made a statement in the manuscript indicating that this was the case in line 209-211.

Comment 3: 3. Elaborate in more detailed way standards mentioned on lines 241 - 243,

Response 3: We agree with this comment. We improved the description of water sample collection and analysis.

Comment 4: 4. Enrich the results/discussion section with precise key findings,

Response 4: We agree with this comment. We revised the discussion section to quantify removal efficiencies for major pollutants and summarized with numerical values.

Comment 5: 5. In present form conclusion is to scarce and must be improved with stronger reflection on quantitative findings, possible limitations of the study and more details concerning future researches.

Response 5: We agree with this comment. We revised the Conclusion section to include quantitative synthesis of our key findings, critical reflection on the study’s limitations, and specific recommendations for future research.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

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