|Reviewer 2 |
Yira et al.: Impact of climate change on water resources in a tropical West African catchment using an ensemble of climate simulations
The authors included the my comments in an appropriate manner and significantly improved the manuscript. Nevertheless, I request to revise the following (minor) points.
1.) Referring to point 2 of the Reviewer 2 comments concerning the different scales of climate models (50x50 km2) and the Danu catchment size (200km2):
Autors reply:“Only considering climate variables of the nearest RCM grid point to the Dano catchment would be meaningless since the nominal resolution of RCMs does not correspond to the effective resolution (..).”
This was exactly the point I was refering to with this comment.
Authors reply: “Therefore, we had to consider a larger RCM domain to represent the simulated climate within the Dano catchment (20 nodes domain was applied). (...) To overcome these issues we adoped the “one node at a time approach” and the 20 nodes were used”. and article p. 8, L. 130ff: “ Due to the discrepancy between the RCM-GCM data resolution and the hydrological modelling domain the data of eache node were seperatly used as climate input for the hydrological simulation model. Therefore, for each period (..) 20 simulations corresponding to the 20 nodes are performed per RCM-GCM (... and) then calculated as arithmetic mean.”
I totally agree with your reply. Actually, I see this “one node at a time approach” as the main methodical innovation of this study. This appoach enables the use of climate model input for very small scale catchments which are smaller than the size of one climate model grid cell and, hence, an approximately climate impact analyses for very small scale catchments. I recommend to highlight this more clearly in the study.
Refering to that:
P 19, L 467: “The approach appears suitable to display the ,results of climate change impact on catchment hydrology.” -> I recommend to highlight: ...on catchment hydrology of small scale catchments!
2.) The study focuses mainly on the analysis of climate model simulations with a hydrological focus and uses an hydrological model to simulate river discharge on a small scale. I think, the titel does not capture the content of the study as it refers to “water resources”, which include other hydrological aspects than precipitation, evapo(transpi)ration and river discharge. Here I rater suggest to use the term “hydrological conditions” (or similar).
3.) This comment is also roughly related to point 2.
p19, L. 465ff: “The ecological concept (..) in this study proved to fully capture climate change impact on the catchment hydrology as both discharge change signal, precipitation and (..) evapotranspiration change signal are consistently displayed by the E-P plot. (...) it further brings insights about the catchment environmental conditions (..).”
To my view, the study only focuses on hydro-climatical conditions and river discharge at the outlet station. It does not “fully capture climate change impacts on the catchment hydrology”, which includes also other aspects like interception, infiltation, subsurface runoff and groundwater flow. Also the new “insights about catchment environmental conditions”, instead of hydro-climatic conditions, are not clearly discernible to me.
4.) I suggest to include in the manuscript the author’s reply on the short calibration period and that it was shown by Yira et al. 2016 that both calibration and validation period reflect the rainfall pattern for a longer period.
5.) I further suggest to revise the section P. 18, L. 432ff:
P. 18, L. 432: “All the climate models that projects a precipitation increase result in an ETa increase.”
This is not surprisingly as all climate model simulations project/include an increase in temperature.
ff: “This indicates that the catchment ecosystem (as defined as the vegetation within the catchment and provided by the land use and land cover map of the catchment) is able to optimize the use of water and energy available in the environment, thus reducing unused water with temperature increase.
I do not understand this sentence, especially not the term “unused water” in this context.