South Asia river-flow projections and their implications for water resources

Mathison, C.; Wiltshire, A. J.; Falloon, P.; Challinor, A. J.

doi:https://doi.org/10.5194/hess-19-4783-2015

Articles | Volume 19, issue 12

https://doi.org/10.5194/hess-19-4783-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/hess-19-4783-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 19, issue 12

Research article

|

07 Dec 2015

Research article |

| 07 Dec 2015

South Asia river-flow projections and their implications for water resources

C. Mathison, A. J. Wiltshire, P. Falloon, and A. J. Challinor

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Final revised paper (published on 07 Dec 2015)
Preprint (discussion started on 16 Jun 2015)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC C3152: 'Review of manuscript by Mathison et al.', Anonymous Referee #1, 18 Aug 2015
RC C3299: 'Review Comments', Anonymous Referee #2, 26 Aug 2015
EC C3352: 'Editor review', Bettina Schaefli, 27 Aug 2015
AC C3511: 'Authors reply to comments from reviewer 1, reviewer 2 and the editor', Camilla Mathison, 09 Sep 2015
- RC C3596: 'Reply to comments reg.', Anonymous Referee #2, 10 Sep 2015
RC C3597: 'Review of Mathison et al.', Anonymous Referee #3, 10 Sep 2015
AC C3671: 'Authors reply to comments from reviewer 3', Camilla Mathison, 15 Sep 2015

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (17 Sep 2015) by Bettina Schaefli

AR by Camilla Mathison on behalf of the Authors (25 Sep 2015) Author's response

ED: Reconsider after major revisions (28 Sep 2015) by Bettina Schaefli

ED: Referee Nomination & Report Request started (28 Sep 2015) by Bettina Schaefli

RR by Anonymous Referee #2 (30 Sep 2015)

RR by Anonymous Referee #3 (11 Oct 2015)

Suggestions for revision or reasons for rejection

I have re-reviewed the manuscript. I also went through Jones et al., 2004, which the authors cited last time in response to my comments on the need to provide additional 'control' runs and the need to provide additional detail on the 'downscaling' exercise. Following are my concerns:

While the presentation has improved (e.g. more text on models used), my major concerns remain unaddressed. Only minor, textual, revisions have been done. I therefore raise my concerns/provide my comments again in the following (no different from round1):

1) It is important, for completeness sake, that the authors provide an illustration of how RCM regionalises GCM fields. A passing reference to Jones et al. is not sufficient in this regard, especially since this appears to be the backbone of the entire paper. This will clarify not only how the RCM regionalizes GCM outputs but also why it may not necessarily be a downscaling exercise. It would be most suitable if the illustration is done in cartoons than in text.

2) The authors cite Jones et al. (2004) when they mention how they derived finer scale fields. This line (#17, page 8) is perhaps the only place in the paper which gives any indication of the method used for 'downscaling' (again its not clear to me why the authors call it downscaling when HadRM3 using the same physics as HadCM3, produces solution at finer resolution with coarser GCMs outputs only as lateral boundary condition at boundary pixels). Yet this is key to understanding the science behind the entire paper. It is therefore crucial. Given that authors themselves raise their lack of trust in observational data, they should provide additional control runs to assess 'Uncertainty in Regional Climate Change' (Page 12 of Jones et al., 2004). Here what is desired is not an exhaustive assessment using multiple RCMs but some effort in that direction. The need to do so also comes out in the 'validation' of the RCM in Fig 6 where RCM rainfall forced by the two GCMs match more closely with ERA forces RCM rainfall than with the observations. I would therefore reiterate my suggestions (from round 1) in the following:
- please update Figure 2 and provide precipitation maps corresponding to GCMs and ERA to provide an assessment of what we are missing if we donot resolve precipitation at a resolution finer than GCMs
- please provide runs (for the two GCMs and ERA) using either a statistical downscaling technique or another RCM (assuming it also has a landsurface scheme) and keeping the routing scheme the same
-please provide runs using HadRM3 without MOSES landsurface scheme and without the routing used but instead using a simple bucket model (e.g. runoff = max(0,P-EP) for hydrology.

The conclusions that are currently been drawn should then be further discussed in the light of the above (point 2). The above should ameliorate, though only to a limited extent, concerns regarding uncertainty in regional climate impact modeling and assessment.

I believe that potential HESS readers of this paper would miss out on excellent science that has gone behind regional climate modeling of the Indian subcontinent along the Himalayan ark if the above two points are not appropriately addressed.

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ED: Publish subject to minor revisions (Editor review) (29 Oct 2015) by Bettina Schaefli

AR by Camilla Mathison on behalf of the Authors (05 Nov 2015) Author's response Manuscript

ED: Publish as is (09 Nov 2015) by Bettina Schaefli

Short summary

South Asia is a highly variable region where there is concern over water and food security. The simulations presented suggest an increasing trend in water resources, in some cases almost doubling by the end of the century although this is masked by the large annual variability of river flows for this region. Future peak river flows still occur during the monsoon period, with a tendency for reduced frequency of lowest flows and increased magnitude of highest flows across the selected locations.