Research Hotspots and Trends in Soil Infiltration at the Watershed Scale Using the SWAT Model: A Bibliometric Analysis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This could be a very useful and interesting paper with some modifications to the figures.  My major comment deals with the figures that are so important in the paper.  They need to be larger with clearer descriptions of what lines, nodes, etc. mean.  Even with magnification of 400% or higher I could not read words in the colored legend lines in most of the figures.  I tried to explain the problems I had in each of the figures.  Major attention needs to be given to a clearer presentation of the figures.

Comments for author File: Comments.pdf

Author Response

Comment 1: The figure (Figure 1) could be larger, difficult to read the material in the boxes at the top and headings in the dark blue above the green boxes in the bottom of the diagram.

Response 1: Thank you for pointing this out. We have revised Figure 1 to make it more readable, ensuring that the content within the boxes at the top, as well as the headings in dark blue above the green boxes at the bottom of the diagram, are sufficiently clear and comprehensible (on page 4).

Comment 2: Again, this figure (Figure 2) could be larger to make it easier to ID the dates with the circles on the graph

Response 2: Thank you for your comment. We have adjusted Figure 2 to improve its clarity and make the individual items easier to identify (on page 4).

Comment 3: In Figure 3,

1) The figure needs to be larger, difficult to read the small names, and dates on the legend box at the left - I could not read any of the years in the dark blue even when magnified an name of authors in the smallest font are difficult to read.

2) If each node represents an author why are there not more names on the figure? For example, which of the nodes actually represent Melesse, AM?

3) I do not see differences in line thickness which is supposed to represent higher degrees of cooperation.

Response 3: Thank you for your valuable comment.

Regarding 1), we have revised Figure 3 and increased the font size of the author names and the years in the legend box on the left to improve readability. We hope this revision addresses your concerns (on page 5).

Regarding 2), in Figure 3, each node represents an author, with the node positioned at the center of the corresponding name label. To ensure clarity and readability, only authors with a higher number of publications are labeled. We have clarified and revised both the figure and the related content accordingly. For your convenience, the revised paragraph is attached below for your kind review.

   “Each node represents an author, with larger nodes indicating more frequent occurrences.” (Page 5, lines 158 to 159)

Regarding 3), we apologize for the confusion. The lines between nodes indicate the presence of cooperative relationships between authors; however, they do not represent the degree of cooperation through line thickness in Figure 3. We have revised the main text to clarify this point and eliminate any potential misunderstanding. For your review, the revised content is provided below.

   “Lines between nodes indicate that they have a cooperative relationship. Figure 3 shows that there are currently two major core research teams in this field: those centered on Steenhuis, Tammo S., and Easton, Zachary M., and those centered on Arnold, J.G., and that the teams are essentially in an independent research phase among themselves.” (Page 5, lines 159 to 163)

Comment 4: I do not see any difference in thickness of rings (Figure 4). Not sure what is meant by high centrality.

Response 4: Thank you for your insightful comment. We have reworked Figure 4 to clearly highlight the difference in the thickness of the purple ring. Additionally, we have added the necessary explanations to the caption to enhance the figure’s readability.

Comment 5: A minor comment: In the heading -center the Institution ranking over the institution & Publications. You might put (ARS) after AgResearch Service.

Response 5: As you suggested, we have revised the contents accordingly in Table 1.

Comment 6: Not sure what threshold k=5 and time slice =1 mean minimum of 5 pubs, time slice would be annual?

Response 6: Thank you for pointing out this issue. “k” actually refers to the scaling factor in the g index, which is used to control the density of the network. We have specified and corrected the definitions of g-index and k, as

   “the g-index determines the number of nodes (articles, authors, countries, or journals) displayed in the network visualization. By adjusting the scaling factor k, the density of the network can be controlled.” (pages 4, lines 149 to 151)

Additionally, we have clarified that the time slice is set in years, as the statement on top of page 5, line 152 “… and the time slice was set as 1 (year)”.

Comment 7: I cannot read the number of pubs in the legend on the left (Figure 5).

Response 7: Thank you for pointing out this issue. We have modified Figure 5 (on page 7) enhance the clarity of its elements. In this figure, the node size is utilized to indicate the number of publications originating from the corresponding institution.

Comment 8: In Figure 6,

1) I cannot read the number of citations in the legend box on the left. Does each dot represent a journal?

2) The purple rings all look the same thickness - do you mean the size of the ring? Why does Hydrologic Processes not have a ring - you list it as one of the top three journals that published the 141 most cited papers.

Response 8: Thank you for your valuable feedback.

Regarding 1), we have enlarged the legend box and revised the layout in Figure 6 to improve readability, particularly the citation numbers. In this figure, each dot represents a journal, and the size of the node corresponds to the number of citations it has received.

Regarding 2), In Figure 6, we were focusing on the number of citations of the journals, and the larger node size indicates more citations, but not the thickness of the purple circle. The purple rings appear to have similar thickness because their centrality values are comparable, as explained in Section 3.3 Analysis of Country and Institution. In the revised paper, we have modified the related statement about the purple circle that may causing any confusion.

Hydrological Processes does not display a ring because its centrality did not reach the visualization threshold, despite being among the top three journals in terms of publication count. Additionally, to facilitate a clearer understanding, we have incorporated a list of the top five most-cited journals in Figure 6.

Comment 9: In Table 2,

1) You might indent the first line describing each paper to make it easier to identify what content goes with what author.

2) In looking at this table in this elongated format, I would recommend that the author information be lined up with the first sentence of the paper description.

Response 9: As you advised, we have adjusted Table 2 accordingly, which has significantly improved its readability.

Comment 10: I think SWAT should be capitalized as it is throughout the paper.

Response 10: Following your suggestion, we have capitalized “SWAT” in Table 3.

Comment 11: Each dot in this figure (Figure 7) represents a keyword? In this figure, the thickness of the rings actually varies which I do not see happening in numerous of the other figures where you mention ring thickness and therefore my earlier question as to whether thickness really means size of the ring.

Response 11: We would like to clarify that the thickness of the purple ring and the size of the node are two independent parameters. The node size represents different metrics depending on the context of each figure—such as the number of citations or the number of publications—while the thickness of the purple ring specifically reflects the centrality value.

In addition, we have revised the figures to more clearly illustrate the meaning of the purple ring about centrality. For your convenience, the updated definition of the purple ring is provided below.

   “The purple rings represent the mediated centrality of the node, and their thickness reflects the centrality value.” (Page 3, lines 123 to 124)

Comment 12: The figure (Figure 8) is confusing even after reading the supporting text. Keywords - watershed modeling - what level of strength is involved with the beginning and end - watershed modeling had reached a given strength by 2006 but that strength ended in 2010 - is that what the blue line is showing - it would be helpful to have years indicated below these lines.  Is the red line for watershed modeling basically showing the dates of 2006-2010?

Response 12: Thank you for your valuable comment. We have revised the description in the text to clarify the meaning of the strength and duration of the keyword bursts, and we have added explicit explanations and year indicators below the lines in Figure 8. We hope these revisions make the figure clearer and easier to understand. For your reference, the revised relevant content is provided below.

   “The light blue line represents the keyword has not yet appeared in the period, the dark blue line represents the keyword appeared in the period, and the red line represents the period when the use of the keyword increased significantly (which indicates a significant increase in academic interest in the keyword during that period).”  (Page 11, lines 291 to 295)

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Author,

Thanks for the invitation to review the review manuscript titled Research Hotspots and Trends in Soil Infiltration at the Watershed Scale Using the SWAT Model: A Bibliometric Analysis. We understood that infiltration is one of the processes that has a significant impact on the water cycle, which impacts runoff, groundwater recharge, and ecosystem health. The research of soil infiltration using the Soil and Water Assessment Tool model has garnered continuous attention from scholars. “Land use” and “climate change” were currently the hotspots of interest in this field. Notably, two countries, China and Ethiopia, have contributed the most in these areas. The study used the CiteSpace 6.3.R1 tool, information visualization analysis software. 

The author needs to clarify why the USA, China, and Ethiopia have many publications related to the field of “Soil Infiltration at the Watershed Scale Using the SWAT Model.” What are the prominent basins they focus on? What is the level of publication in this field in Asia and Southeast Asia? For example, why is Japan less published than other countries?
Figure 1: the text in this figure is too small; the author needs to increase the size
The author needs to clarify the goal of this manuscript to enhance its clarity. Are the results of the research useful? Why care about countries, institutes, ...? What are hotspots? What does it mean to identify hotspots, because it does not necessarily mean that they are hydrologically problematic areas?

Best regards,

Author Response

Comment 1: The author needs to clarify why the USA, China, and Ethiopia have many publications related to the field of “Soil Infiltration at the Watershed Scale Using the SWAT Model.” What are the prominent basins they focus on?

Response 1: Thank you for pointing this out. We have added a detailed explanation in the revised manuscript to clarify why the USA, China, and Ethiopia have a high number of publications in this field. Specifically,

1. There are relatively more researchers in the United States and China, and the SWAT model was developed by researchers in the United States, so there are relatively more articles from these two countries.
2. Watersheds such as the Blue Nile Basin in Ethiopia are key areas of global concern with significant climate change, attracting a large number of international collaborations and research.

In addition, we have included the prominent research watersheds that different countries focus on in Table 1 to provide a clearer reference and context.

For your review, the revised relevant content is provided below.

   “Firstly, Table 1 enumerates countries and journals that have demonstrated outstanding academic contributions in this field, alongside the principal watersheds studied by researchers from each country. Among the top five countries, there are three developed and two developing nations. The United States has published the most studies (72 articles), followed by China, Ethiopia, Canada, and Germany. There are relatively more researchers in the United States and China, and the SWAT model was developed by researchers in the United States, so there are relatively many publications from these two countries. In Ethiopia, river basins such as the Blue Nile Basin have garnered considerable global attention due to their pronounced susceptibility to climate change, consequently attracting extensive international collaboration and research efforts.” (Page 5, lines 173 to 182)

Comment 2: What is the level of publication in this field in Asia and Southeast Asia? For example, why is Japan less published than other countries?

Response 2: We appreciate your valuable comments. In the revised manuscript, we have added content to discuss the level of publication in Asia (including Southeast Asia). We also explained that countries in Southeast Asia, such as Thailand, Vietnam, and Indonesia, may have fewer studies in this field due to limited data availability and research funding. We have attached part of the revised paragraphs below for your kind review.

   “Among Asian countries, China, India, Iran, South Korea, and Japan are the principal contributors to research in this field. Conversely, Thailand, Vietnam, and Indonesia have comparatively fewer studies, potentially due to challenges related to data acquisition and limitations in research interests.” (Page 5 to 6, lines 182 to 185)

Comment 3: Figure 1: the text in this figure is too small; the author needs to increase the size.

Response 3: As you suggested, we have adjusted the size accordingly in Figure 1. In addition, we have made similar adjustments to other figures throughout the manuscript to enhance overall readability.

Comment 4: The author needs to clarify the goal of this manuscript to enhance its clarity. Are the results of the research useful? Why care about countries, institutes, ...? What are hotspots? What does it mean to identify hotspots, because it does not necessarily mean that they are hydrologically problematic areas?

Response 4: Thank you for the constructive comments. We have clarified the main goal of this study in the Introduction Section, as

   “In order to thoroughly understand previous research conducted using the SWAT model to analyze soil infiltration at the watershed scale, this study systematically reviews relevant literature from the past 25 years utilizing CiteSpace, a software tool for information visualization. Specifically, the objectives of this research are to elucidate: (1) the developmental trends of studies utilizing the SWAT model for watershed-scale soil infiltration analysis; (2) the primary research groups and international collaborative networks active in this field; and (3) the key research hotspots and anticipated future research directions. Ultimately, this work aims to provide a robust scientific reference for future scholars investigating soil infiltration at the watershed scale using the SWAT model.” (Page 2 to 3, lines 86 to 94)

Additionally, we have added the explanation of “why care about countries, institutions”. For your review, the added content is provided below.

   “In order to reveal centers of expertise and prominent research groups fostering international collaboration and knowledge exchange, we analyzed maps of collaborative networks and maps of institutional collaboration in 41 countries.” (Page 5, lines 168 to 170)

We have also explained the term “hotspots” to improve clarity and reader understanding in the footnote on page 2, as

“Hotspots: In our study, 'hotspots' specifically refer to key research topics identified through bibliometric analysis, rather than hydrological hotspots in the physical or environmental sense.”

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have responded appropriately to all of my comments and I believe that has improved the paper significantly. Tables and graphs have become more legible making them easier to review and understand thus making the paper more useful as the reader can concentrate on the information rather than spend time trying to interpret what the graphics are showing.

 

Reviewer 2 Report

Comments and Suggestions for Authors

Accept in current form