A Connectivity Approach to Agricultural Diffuse Pollution in Tropical Montane Catchments Dominated by Swidden Landscapes
Round 1
Reviewer 1 Report
This paper addresses the important issue of describing the generation and transport of pollutants (sediment and pesticides in this case) within moderately complex hydrological catchments. Application of this research to a developing economy (Laos DPR) is important as there will always be insufficient resources to conduct detailed direct assessment of pollutant transport in these locations.
The methods are described clearly and in sufficient detail that the techniques can be applied elsewhere. The results are reported concisely, with appropriate statistical testing and the implications of the research are indicated with suitable restraint.
Author Response
Response to Reviewer 1
This paper addresses the important issue of describing the generation and transport of pollutants (sediment and pesticides in this case) within moderately complex hydrological catchments. Application of this research to a developing economy (Laos DPR) is important as there will always be insufficient resources to conduct detailed direct assessment of pollutant transport in these locations.
The methods are described clearly and in sufficient detail that the techniques can be applied elsewhere. The results are reported concisely, with appropriate statistical testing and the implications of the research are indicated with suitable restraint.
Response: Dear reviewer, thank you for taking the time for reading our paper and your positive comments.
Best regards
Author Response File: 
Author Response.docx
Reviewer 2 Report
Title. The title is a bit misleading, in that the insights about diffuse pollution are not the strength of the paper, rather it’s the approach for hydrological (and sedimentary) connectivity. There is no actual data on pollutants, and no modelling of pesticide transport inclusive of processes like sorption-desorption and decay. There is useful methodology development on elucidating sources and sinks, and this should be clear in the title. Authorship. Jumping to conclusions here, but it looks like none of the authors of the paper are Laotian. There is mention of some help from locals in the acknowledgements. As this is an agricultural systems paper, clearer voices of lived experiences from inhabitants would enhance the credibility of the paper. This would also diminish perceptions of scientific colonialism (though clearly well-meaning). The journal should request author-level contribution from a Lao PDR research partner. Before the authors retract the paper in righteous outrage, I can assure them that the benefits from more deep insights from local researchers will improve the paper and demonstrate a genuine partnering attitude of the authors. Overall. An important paper as a case study of applying a methodology to identifying connections between sources and sinks in uplands with changing landuse. Whilst there is little new insights about the system of upland land management, the methodological development is sufficiently novel to warrant publication. The authors do a good job in discussing the limitations and pathways for going forward. There is a lot of current investment planned in areas similar to that studied here (for example the ASSET program). Presumably the authors are familiar with the CIRAD crew active in Laos and NW Vietnam. They should find the paper useful. A few specific comments. Some English improvement needed, but overall well written. Some editing needs listed, but a good read over by someone needed to pick up others. Ln 20. Relationships (or is). Ln 74. …absorbed…you mean adsorbed (nothing gets absorbed by soil particles…absorbed by soil, sure, but for a particle surface reaction you mean adsorbed). Study area. Essential to include soil information, particularly aspects relevant to erosion. What is the soil type (I am not sure what the requirement is for naming in this journal….USDA, FAO, national). Ln 251. ….resolution. Ln 264. 20 space m Tables 3 and 4, ln 550, elsewhere. Unwarranted number of significant figures. Ln 398 villagers not villagers’. Ln 443-446. Swidden or cleared for on-going “permanent” cropping? Table 6 needs more explanation about what is being shown. Does it reflect rotation (with transition back to forest after 1 year) or expansion of cropping during the study period (a time of expanding cropping throughout Lao PDR. Discussion. Lots of stuff here covered earlier and not really needed here. Focus on discussing what can be inferred from the results, the limitations, what the most useful insights are, and next steps. Ln 705-715. A bit emotive, but OK. It would be useful to have provided some data on pollutant levels in the vulnerable areas identified.
Author Response
Response: Dear Reviewer, many thanks for the valuable and constructive comments of the reviewers. An attempt was made to accurately apply all comments to the text of the article. Revisions were made to the text of the article and figures. Each point of comments has been answered in this document. Best regards.
Author Response File: Author Response.docx
Reviewer 3 Report
Excellent work.
Some minor comments:
1. Please move the section "2. Study area" to "3. Materials and methods".
2. The subtitles "3.1 Connectivity" and "5.1 Methodological issues" are too short. Please put more words on them.
3. In Fig. 7.3, there is a human picture. Please remove the picture and add some text if needed.
Author Response
Response: Dear Reviewer, many thanks for the valuable and constructive comments of the reviewers. An attempt was made to accurately apply all comments to the text of the article. Revisions were made to the text of the article and figures. Each point of comments has been answered in this document. Best regards.
Author Response File: Author Response.docx
Reviewer 4 Report
I want to thank the authors for their paper and their scientific contribution. The paper is well written. The methodology and scientific tools are cited. However, I believe there is some minors points that should be cited:
- The introduction is well structured but it is really too long and I was pretty lost while reading it.
- In the study area, I found a problem in knowing location of the region of interest. It would be more convenient if you add the coordinates grids of the region borders. You should also try to add the geographic coordinates of the first and second map of the study area figure (figure 1).
- Random forest of supervised classification is very precise and good algorithm. However, I didn't find the usefulness of putting table 1. A simple notice in the text of the average pixel for each training sample will be enough. In addition, A rule-of-thumb is that training sites should not occupy more than 5% of a land cover. Is this applicable for this case ?
- It is really original to apply this advance algorithm (Random forest) for shifting cultivation purpose and especially for very short period. The classification average error matrix marked a good classification. You could however add rely on other parameters like spectral separability of training samples or kappa index of the supervised classification.
-Why you have not showed interpreted classification image for each year ? It could be useful in remote sensing to visualize most changing sensitive areas. Also, I think change detection matrix will be very useful to visualize changes between land use classes.
- the result and discussion is perfectly structured and exhibits the phenomenon very good. Especially the land use transition and the structural connectivity results.
- In general, the paper is very good and can be published in this format.
Author Response
Response: Dear Reviewer, thank you very much for this comment and many thanks for the valuable and constructive comments of the reviewers. An attempt was made to accurately apply all comments to the text of the article. Revisions were made to the text of the article and figures. Each point of comments has been answered in this document. Best regards.
Author Response File: Author Response.docx
