|I have already reviewed the previous version of this manuscript. In the revision the authors have really improved the accessibility of the manuscript and included much more interpretation of the results in an extended discussion. |
The Methods section is much improved, the collection of all the model information in Appendix 3 works well. Thanks for including some details, e.g. a short note on how transpiration decreases when root zone storage dries. Those pointers will really help readers (like me) to focus on the main message and not be distracted by searching. The discussion has much increased in size and enhances the quality of the manuscript. Most of my comments have been satisfactorily addressed or ruled out. Mainly on the new discussion, I have some more comments below. I propose to include a couple more aspects. Also I propose to bring some of the sections, especially in the „limitations“-part, to a resolution, e.g. how can those be tackled in the future?
I believe only minor revisions are required.
L 308 „We repeat this random sampling several times .. several model parameters“
Ok, I did not understand this ins the previous version. It remains unclear at this point:
How much is several, and what happens to the sample? Do you proceed with each individual realization or some aggregated (average) runoff coefficient?
L 279-281: It is really mostly the rooting depth that will be adaptable. I propose to include a short comment here, to help the reader make the association between rooting storage and rooting depth, which now change with vegetation type.
The role of the investigation of land use change is still a bit opaque in the manuscript. The Methods section says on lines 224-226: „These scenarios are meant as a sensitivity analysis in the spirit of trading space-for-time (Singh et al., 2011) to evaluate the effect of potential future land-use management on the overall water balance.“
I have interpret this to say that climate change scenarios will be evaluated in the light of the additional affect of land use change? This sounds very reasonable to me. But I wondered, why this idea was not taken up in the discussion? The „implications“ section of the discussion revolves mostly around climate change and I missed the reflection on the effects of the vegetation transformation. Can you more specifically return to the comment made earlier in the manuscript?
L 553-562 & L 565-579: Here you discuss one the one hand that present management practices affect the future and second the limitation that we do not know whether plants will be readily adapt to the root zone storages required in the altered climate. It would have been nice to have this connected a bit more, and given some idea on why the investigation is nevertheless useful. For example, it proposes an envelope of the hydrological response, which is based on the best of our knowledge. Furthermore, do you agree that the method can also be used to estimate the degree of adaptation in existing catchments? This would be one research outlook to improving the predictions.
L 609-612: I believe this has been added in response to one of my comments. It now comes a bit out of context here, and I propose to erase it. Mentioning the constant potential evaporation in the methods section works well. Adding a comment in the Methods section that swapping omega does not affect the HRUs would be helpful for readers like me.
L 639-640: „very interesting“ is a bit vague. Can you be a bit more specific? Why would it be and do you have an intuition how the water fluxes may change with adaptive roots compared to the original HTESSEL runs? Maybe also have a look at this publication in this context:
Stevens, D., Miranda, P. M. A., Orth, R., Boussetta, S., Balsamo, G., & Dutra, E. (2020). Sensitivity of surface fluxes in the ECMWF land surface model to the remotely sensed leaf area index and root distribution: Evaluation with tower flux data. Atmosphere, 11(12), 1–19. https://doi.org/10.3390/atmos11121362
L 650-651: „may allow us to estimate future ω or root-zone storage capacity values in a region where the future climate may resemble today’s climate elsewhere“
I am admittedly not sure where this is going. Can you be more specific on the expected insights? Do you propose to test how omega relates to root storage in different climates? This would be very nice and eventually help to validate one of the major assumptions of the manuscript, which is that omega changes due to vegetation and not climate.
Finally, I would really like to read a short discussion on how changes in climate dynamics would affect omega independently of vegetation in a future climate?
It is good to have all the model related details collected in this section. Very clear now.
It seems that some of the equations in Table S5 are potentially not correct? Should it not read dS_w/dt instead of S_w/dt? This is repeated in several lines. Also in the line relating to E_R: I am not sure I saw a definition of S_u.