A Meta-Analysis of Environmental Tradeoffs of Hydropower Dams in the Sekong, Sesan, and Srepok (3S) Rivers of the Lower Mekong Basin
, Ali Farshid 1, Gregory Goodrum 1, Curtis A. Gray 1,2, Sapana Lohani 1,3, Christina N. Morrisett 1, Liana Prudencio 1 and Ratha Sor 1,4
Thomas Wilding
Round 1
Reviewer 1 Report
See attached comments
Comments for author File: 
Comments.pdf
Author Response
Please see the attachement.
Author Response File: Author Response.pdf
Reviewer 2 Report
A lot of work has gone into pulling this body of research together. It is well written. Where the paper strays into unsubstantiated statements, I have pointed them out in the comments below so these can be rectified.
Line 33 - A "high tradeoff" is ambiguous. It could be high benefits or high losses? Suggest change "tradeoffs" to "losses".
And throughout the article, I find the "tradeoff" terminology is often innappropriate. If a community accepts the loss of a fishery for the gain of cheap power, then they have made a trade off. There is an implied balance, based on full knowledge of gains and losses. But when talking about the environmental effects or losses as stand alone points in this article (especially ones communities may not even be aware of), then you're no longer talking about tradeoffs. Revise accordingly throughout - "environmental losses" vs "economic gains" would be considered, and only labelled a "tradeoff" if the balance of the two is acceptable to someone.
Line 40 - You can confidently say dams provide renewable energy, but not that they're carbon neutral. Change text accordingly. See:
doi.org/10.1371/journal.pone.0161947
doi.org/10.1093/biosci/biw117
Line 70 - "Much of the biodiversity... comes from... flow variability". Reword. It would be difficult to quantify how much biodiversty "comes from" flow variability, since that requires knowledge of evolutionary history. Can you find articles to support a statement more along the lines of "many species depend on flow variability..."?
Line 79 - change "large population" to "many people", given population is ambiguous in this context (people or fish?)
Line 106 - There is some very useful new information in this section. But it seems to repeat topics covered in the introduction. Restructure accordingly.
Line 119 - again "gave rise to... biodiversity" is not (and probably cannot be) substantiated. Instead talk about species dependence on flow variability.
Line 140 - I don't know what "All databases precede 1990" means. It implies you only used literature published prior to 1990 - perhaps you meant the opposite? If so revise wording accordingly.
Line 175 to 187 - parentheses not closed. (e.g., [39, 40].
Line 189 - I see this article reaches the same conclusion as the article links I provided above. Hydropower is not carbon neutral.
Line 206 - Given the small size of the 1990 dam, and your conscious decision not to find EIA completed for the dams, I think your are overstating the lag between construction and science publication. Would be more accurate to state only construction of bigger dams generated piublished research?
Line 210-216 - Delete sentences. Given you did not review the EIA, you are not in a position to present opinion on their scope or worth. The conclusions of other authors do not belong in your results. Instead cite them in the discussion.
Line 349 - this statement would have more impact if you indicated the quantities. Does it block connectivity for 1km of stream habitat or 100km? How many species would be blocked?
Line 355 - I don't understand this sentence - "Giving up Cambodia’s mainstem Mekong River dams and the Sekong Dam supports research showing that specializing rivers for human or environmental benefits provides greater economic and environmental benefits than building dams on all rivers." For example, what is "specializing rivers"? Please reword.
Line 360 - this paragraph is great. But some wording needs attention. Reword "were especially compelling for sustainable decision-making". Do you mean "made a compelling case for decision making that better recognised environmental impacts"?
Line 363 - was it "hydropower generation" that channged migratory access, or the dam itself regardless of hydropower? If it they analysed the added generation potential across multiple dams then please state that.
Line 379 - Good points made in this section.
Line 417 - suggest delete "stated simply".
Line 447 - suggest reword "avoid overestimating hydropower development benefits". perhaps change to "avoid overestimating the net benefit of hydropower development"
Line 479, 487, 545, 554, 571 - incomplete references
Figure S1 - change m3/s to superscript
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
See attached comments
Comments for author File: Comments.pdf
Author Response
We apologize that our previous revised manuscript did not upload correctly. To combat the problem we have put all of our files into a single document.
The single document that we uploaded contains:
- clean version of our revised manuscript
- clean supplemental information for our revised manuscript
- tracked-changes version of our manuscript (line numbers correspond to our response to reviewers document)
- tracked-changes supplemental information for our revised manuscript
- response to reviewers
Formatting comments were added to the right side of the document when we uploaded it. We cannot control this as the submission system requires a word document rather than a pdf.
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
Thank you for updated files. I believe the paper has been properly improved and it is now ready for publication
