Impacts of Climate Change on Irrigation Water Management in the Babai River Basin, Nepal

Round 1

Reviewer 1 Report

General review:

The paper is interesting with many methods used. But there is significant question of the paper relevance, as GCMs were used for climate scenarios and not RCMs.

Units should be unified - there are m3s-1 and m3/s in the text.

There are several formatting errors: no scpaces, too much spaces.

 

Detailed review:

48 the MMZ abreviation has to be explained at the first appqearance

71-79 This paragraph is too general and speaks of generally known facts. 

108 IWD abbreviation has to be explained at the first appearance. I assume it is irrigation water demand.

169 GCM data is too general and are used to calibrate regional climate models (RCMs). Why RCMs were not used in the research? There are several RCMs developped within the Coordinated Regional Downscaling Experiment (CORDEX) for South Asia (CORDEX-SA), also with Australian Climate Futures framework specifically for Western Nepal.

196 Bias correction had to be done on RCMs and not GSMs.

263 CWR abbreviation has to be explained at the first appearance. I assume it is crop water requirement.

268 sunshine hour - did you mean day length?

278 export > expert?

288 Which parameters were selected for initial SWAT calibration?

291 explain what is  GWQMN.gw (Threshold depth of water in the shallow aquifer required for return flow to occur?)

297 two years were escaped??

355 From the Figure 5 it is not seen that future rainfall will decrease in Nov. & Dec., as stated in paper. Changes in future rainfall are similar for Jan-April and for Nov. & Dec and are very small (not significant).

384 Figure 6: more tick marks on the y axis are needed

401 fellow land??

406 IWD under CC will increase not only for September, as stated in paper, but also for Jan, Feb, Mar, Apr, May and June, as seen from Table 6.

434 Figure 8 is the same (eith added EF) as Figure 6 - Figures should be merged (EF presented already in Figure 6).

421-427 The amount of water for environmental flow tells much less than percentage. In April the amount of EF water is smaller (7 times) than in August, but it represents 81 % of the natural flow, therefore in this month not much water is left for water use.

446 - 452 Water use for EF EMC categories are not seen in Figure 9, but in text it is duscussed as they are. Authors have to add a table with this data  - water balance for each month and different scenarios and EMCs. 

Are there really no other water demand in this region (e.g. domestic water demand or industry)?

Absolute number for water deficit (m3/s) does not tell much. For instance, water deficit in May is small (44m3/sec), but stream flow in May is around 20m3/s (cannot be seen better from the Figure 9), so the deficit is 2 times larger than stream flow, so such irrigation water demand is not susuatinable! Therefore the irrigation demand scenarios for future have to be change -this should be also the goal of such study. From the map it could be seen that there is a dam - this was not discussed in the paper, nbut is crutioal information.

It should be explained also in conclusions: 541-553 --> What are solutions and proposals to improve crop and irrigatiom managament, as there is not sufficient water for irrigation

521 Conclusions have to be rewritten, as they have to be written according to guidelines for writing conclusions. 

 

 

 

 

 

 

 

 

 

References

link for the referenece 11 does not work

Author Response

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Reviewer 2 Report

The work is interesting and practically significant, although it was carried out using standard methods that are now very popular. Despite the known limitations of using SWAT models, which the authors outlined in the Conclusions, readers still overlook a lot. It primarily concerns the quality and interpolation of the initial data underlying this modeling. This is an essential point of research, which the authors of such works are usually reluctant to publish. But this is in vain. It would be nice if the authors in the appendix materials provided at least some primary data. All of this would increase the credibility of the work.

Comments:

• You have previously published a study on a neighboring river basin: Mishra, Yogendra, Nakamura, T., Babel, M. S., Ninsawat, S., & Ochi, S. (2018). Impact of Climate Change on Water Resources of the Bheri River Basin, Nepal. Water, 10 (2), 220. https://doi.org/10.3390/w10020220. What are the differences and similarities between the forecasts? There is little emphasis on benchmarking forecasts in your work.
• The predictive changes you have outlined do not convince me until you prove the statistical significance of the differences between the predicted variables (including total river flow and environmental flow) under different scenarios. Otherwise, the practical value of the results obtained is minimal.
• Section 2.1. It lacks the elevation map of the analyzed river basin.
• Table 3. Hector? Maybe “hectare”? "Crop area under a current condition and future condition …".  I don't understand what future condition you are writing about.
• Table 6. Under the table, please explain what CI and μ are.
• At the end of the manuscript, I would recommend listing the abbreviations used.

Author Response

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Reviewer 3 Report

The paper is very interesting and important from the point of view of water management (river discharge, water availability, water supply). However, some minor changes in the article should be done. I give my comments below:

1. In Introduction section, the first paragraph should be extended. Climate change is the core of the article and it would be good if this issue will be described more precisely. Also, a good idea is to expand the literaturę on current works related to climate change's influence on water management. Nowadays, it is a matter of concern for many countries around the world.
2. Line 37 – You write „The rainfall varies from 150 mm to 5,000 mm…”. I assume that you mean annual rainfall amounts?
3. When the first time an abbreviation is given, the full name should be also given. Then we can use only the abbreviation. In line 48, you write „MMZ”, but the explanation of this abbreviation is given later, in the next paragraph. You also use the abbreviation „IWD” (Irrigation Water Demand) without explaining it anywhere in the text. Please, correct it in the text.
4. In lines 300-301 you write that the results for calibration and validation lie in the very good category. Could you please recall the ranges of NSE, PBIAS, R2 for specific category of model fitting (in lines 247-248 you mention, according to Moriasi et al., the values for which the simulations can be considered satisfactory)?
5. In lines 320-322 you mention the changes in minimum temperature, but you write that „minimum temperature under RCP 8.5 is around…”. Please correct it.
6. In line 361 you are referring to Figure 6, and in line 371 – to Figure 7. However, the figures are shown further in the text. The figures should be given just after mentioning them in the article.
7. In Table 7, there are given the Environmental Management Classes (from A to F), but there is no clarification within the text. It would be good if you could give some short description of these classes – the results became clearer for the reader.
8. I also suggest to slightly change or clarify the titles of the second and third section (2. Data and method, 3. Methods) – now „methods” are replicated and thus may raise some concerns about the contents of these sections.
9. Some minor comments on figures:

- Figure 1b: the legent may be removed (the descriptions are given directly in the map.

- Figure 5: The maximum rainfall amount is about 600 mm, so the vertical axis may end at this value. Similarly, in Figure 6 and 8: The maximum streamflow is below 250 m3s-1, so the vertical axis may end at this value. The scale on the axis should be more accurate (for example, every 50 m3s-1).

10. Small language mistakes:

- Line 59: It should be „have BEEN done”

- Lines 108 and 109: „predicting” and „analyzing” instead of „predict” and „analyze”.

- Line 163: „To date” or „till date” instead of „to till date”.

- Line 193: I guess it should be „in hectares” instead of „hector”.

Author Response

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Reviewer 4 Report

The paper analyzes the impact of climate change on water management, and more specifically irrigation in the Babai River basin located in the western part of Nepal. In my opinion, while the submission is interesting, it requires a number of amendments before the final acceptance for publication. Major shortcomings are:

1. Page 1, line 48: abbreviation MMZ needs to be explained for the first time in this line (not in line 54).
2. The literature citation in the whole text needs to be corrected in accordance with the “Instructions for Authors”.
3. Page 3, lines 129 and 138: values such as the average rainfall 1467.94 mm should be rounded to the nearest whole number (1468 mm).
4. Page 3, line 131: please change notation “2570Km2” into “2570 km2”. Also, please change notation “annual mean runoff” into “annual mean flow” or “annual mean discharge”, including that in lines 132 and 133.
5. Page 3, line 132: value 86.01 m3s-1 should be rounded to 86.0 m3s-1.
6. Page 3, line 136: the same with 31.01 ° C and 17.81° C – need to be rounded to 31.0 ° C and 17.8° C, respectively.
7. Table 1: please separate clearly the meteorological and hydrological stations, and verify the presented values of rainfall and temperature (they need to be rounded). What is the meaning of abbreviations such as ASL, TX, TN? They don’t seem to be logical, regarding that in Table 5 different abbreviations are used ( T max, T min). Please correct.
8. Figures 4 and 9: the figure legends need to be added. What is the meaning of the box-whiskers chart? Please explain.
9. Figure 6: according to the figure caption the observed data of the monthly mean streamflow are from 1975-2005, but according to Table 1 the hydrological data for gauge Chepang are from 1991-2014. Please explain this inconsistency. Moreover, the vertical axis labelling should be changed into “streamflow (m3s-1)”. The same in Figure 8.
10. Page 19, line 472: in sub-chapter “3.8 Discussion and Summary” there is a lack of a real discussion. Please correct.
11. The list of references requires numerous improvements. Please refer to the “Instructions for Authors” for details.
12. The English language has to be improved, including grammar and punctuation.

Author Response

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Round 2

Reviewer 2 Report

Dear Authors,

Thank you for revising the manuscript. However, I believe that the studied river basin's elevation map is necessary to publish. You can place it in the appendix materials immediately after the paper's text or in another way. But the reader should have a clear idea of the distribution of heights in the studied river basin since the relief (topography) is one of the most important factors regulating the flow of water in rivers.

Author Response

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