Dear authors

You already uploaded detailed comments to the reviewers. So please change the manuscript according to the comments and your reply. There are some points I want to add a comment.

1) Reviewer One questioned your objective of the paper and you answered:
„However, we believe that the innovation of this paper should not be sought in these aspects but rather in the fact that through a simplified model (i.e. a conceptual model), we are able to assess hydrological processes in the Lake Tana basin, which would be complex to do if a more sophisticated model were used (one would immediately encounter problems due to data scarcity). The insights that are gained learn a lot about the hydrology of this system, which up till now was less understood."
If you want to demonstrate that a simple model works better than a complex one, you should apply a complex model and compare that to your simple model. It would be nice to see, but I do not see that in the paper.
You agreed to the reviewer that type of model used does not fully allow to gain additional insight in hydrological responses but you argue that you gained (at least) some insights about the hydrology of this system, (i.e. catchment). This is not convincing for me but for me the main interesting point of the study and the reason why I would see a revised paper published is the following: In data scarce regions we have the problem that we have not enough data to run complex physically based models. But also it is difficult to run reliable conceptual models, because the lack of data for calibration or verification. So we need clever simple models that try to use all available information on hydrology. One such available information on hydrology is topography and I would guess that in region such as the upper Nile basin topography is a good proxy for the variability of most of the catchment characteristics. Hence I would like to see the story of the paper directed towards the question if a simple topography driven model structure is a good choice for such regions. What is the difference to a benchmark model that is based on different basic assumptions?

2) Concerning the quality of the model and the analysis of model errors: Please add some more model performance indicators and parameter uncertainty studies, but just add more indicators is not too helpful as many indicators are highly inter-correlated. I think it would be helpful to discuss the simulation performance of some single events in much more detail based on hydrological understanding and to discuss some simulation results such as the modelled soil moisture variability. Are the patterns plausible? Are there some observations of hydrological variables which may support the model results? (e.g. variability of groundwater level which give hint to simulate groundwater recharge. )

Hence please revise the paper as recommend by the reviewer point by point and take into account the editors notes.

Best regards
Ralf Merz

Dear authors,
thank you for the thorough revision of the mansuscript. The paper certainly improved and is ready for publication after some minor technical corrections indicated by the reviewer and listed below.

Best regards
Ralf Merz




1. L2: Is it better to change ‘…regions of the…’ into ‘… regions, such as the…’?
2. L73: is there a duplicate space?
3. L118: Where is Dessie et al. (2014) in the references list?
4. L159: is it a mistake to use ‘looks quit’? and shall it be changed to ‘quite’.
5. L169: change QSe2 into Italic, and make sure all the symbols are consistent, such as ‘NSE’ in L489.
6. L398: change ‘b’ into appropriate size.
7. L448: is it better to change ‘0.0’ to ‘0’. Is it better to use ‘with lower absolute values’?
8. L462: change ‘this paper model’ into ‘Wase-Tana model’.
9. L476: where is (delta)t in your equation. Please make sure the units are consistent in the left and right parts of equations.
10. L479: Shall you change from ‘all units are in mm’ to ‘all units are in mm/d’, or ‘mm per time step’?
11. L510: remove ‘indicators’.