|I commend the authors on the review work. The suggestions of both referees have been considered with utmost care, and all points are addressed. This includes expanding the modeling framework to include the 1D flood modeling step, therefore capturing also the effects at the seawards boundary, much expanding the scenarios contemplated, and including many more simulations. It is quite impressive that the authors have been able to carry out and document so much work in a short time. The explanation of the methods is far clearer, and Fig. 2 is excellent. Calibration and validation of model results is high quality, and figures are generally far superior now. The new version is a much more solid and superior study in many respects, and conclusions/implications can be drawn with much more confidence. What authors could not implement in the revision, e.g., a more accurate topography in parts of the analysis, is satisfactorily motivated. I recommend publishing the article, pending some minor suggestions that the authors should consider, focusing mostly on the general presentation of the study and on the methods.|
L. 13: scenarios are mentioned here as though it was already clear that any scenarios were included, whereas this is not the case.
L. 14-18: In those sentence there is repetition that could be substituted by some indications of in which direction climate change and hydrological development, respectively, alter discharge. That will be an obvious question still in the mind of the reader after having read the abstract.
L. 25: the first part of the closing sentence of the abstract seems not very informative. So far the reader has not received any indication about the heterogeneity or complexity of the region, and does not have the chance to learn anything meaningful here. Similarly for the ecological fragility: it’s mentioned here for the first time and not much is said about it.
L 39: flooding creates damage even if short-lived. Also, please check punctuation (also on line 49).
L 59: since most of those papers will be explained individually in the following, it’s probably not necessary to cite them all together in that line. Also later in the paper, a bunch of studies are cited repeatedly, mostly needlessly.
L 60: Hoang et al 2016 present results for several stations of the Mekong. To which does this result refer?
L 73: it doesn’t seem obvious to the reader that “These hydrological alterations are likely to intensify when considered cumulatively”. In the previous sentence you report opposing outcomes on dry season flows, so that one expects alternations to compensate each other .
Please check that whenever a results from previous studies is reported that evokes climate change, the scenario to which it is associated is also reported here, so the reader can evaluate if any discrepancies are attributable to different study set ups or to different scenarios.
L 186: the reader is referred to Triet et al. 2020 for the forcings of MIKE11, among which the sea level rise data used in this study. That study seems to only include a 43 cm sea level rise scenario. Is that what is used in this study, and is that appropriate for both climate scenarios included here?
L 240: It is fine that the reader is referred to the previous study for further details on scenarios, but it would seem important that some more information is included also here on how the effect of the reservoir is included in the simulations. What assumptions are made about the way those 126 dams are operated? It seems plausible that based on that the peak flow lamination and the environmental flows may change massively.
Table 2. I find the name codes of the scenarios needlessly confusing. E.g., why sometime ‘Irrigation_low’ is included in the name, and other times ‘LI’? why scenarios including climate change sometimes have the notation CC and sometimes not. If it’s too much trouble, the authors may leave names as they are.
Fig. 6. Another puzzling choice is to have the two baseline maps on a different scale than the rest of the maps here. This does not have to be changed, but I wanted to point it out in case the authors agree that this is bizarre and does not facilitate visual comparison.