Review Reports

Round 1

Reviewer 1 Report

The summary is too long and should be redone. In the material and methods it is difficult to understand the areas in CA or CT system. The results show the climatic conditions in a very extensive way, but the results of the work are described in tables, 2, 3, 4 and 5. These tables must be developed and highlighted. This chapter should be redone to allow a better analysis of the results and to facilitate the discussion. 

Author Response

Thank you very much for your constructive and useful comments. In the revised version, we tried to address all the comments provided. All edits are provided using the “track-change” in the revised manuscript. The “Blue” colored texts in the response document are those included in the manuscript as a response to the comments.

Author Response File: Author Response.docx

Reviewer 2 Report

This is an interesting study on the water resources in an agricultural region of East Africa (Ethiopia) that is based on high-resolution water table fluctuation and river discharge sampling. 

The study is well described and likely very valuable for a region strongly impacted by droughts. However, there are several limitations that should be addressed. These are summarized below:

1. Novelty of approach - Overall, this study reads very much like a scientific report (i.e., case study) rather than a research paper. The objective is simple: quantify irrigation potential using simple recharge and runoff calculations. The problem is that the methods applied are very simplistic (i.e., recharge should be quantified using a daily water balance model rather than point-scale water table fluctuations) and the paper does not discuss the limitations and simplifying assumptions of each of the applied methods. The study also does not critically discuss current scientific literature on the topic of baseflow and groundwater recharge quantification. For example, the filter method used in the baseflow estimation is very subjective and the model output is very much dependent by the filter parameter (herein referred to as beta) and the applied number of passes (best results are usually obtained with 2-3 passes; see commented in the attached pdf). The authors provide no justification for their applied value despite the fact the the overall results very much depend on the choice of appropriate filter parameter and pass number. (As a side note, the filter method applied should not be used on regulated streams with surface water diversions, channels, dams, etc. The authors do not elaborate on streamflow modifications in the study area). Similarly, the water table fluctuation method has several limitations (valid only for unconfined aquifers, assumes no drawdown and rebound due to pumping cycles, etc.). The authors should clearly highlight some of the limitations and give at least some error estimates in their quantifications.
2. Method description. It is still not clear why baseflow and recharge outputs (from the WTF) methods were used as separate inputs. Shouldn't the baseflow be a proxy for recharge (given that it is often used used as a recharge calibration target for water balance models)? Also, shouldn't the baseflow value be comparable to the recharge value estimated by the WTF method? A comparison of these results may help narrow down the filter parameter and the optimum choice of applied passes. It is also not really clear why a "low flow" amount from flow duration curves was needed.
3. Tranferability of results. Can the authors - based on the findings of this study - make any comments on water availability in similar settings and can the authors provide any information on the study's limitations? For example how representative is the applied study period (2015 - 2017) for capturing long term trends in irrigation potential and future climate change scenarios? What can be improved for a more refined  understanding of surface and groundwater irrigation potential?

I have included more minor comments as sticky notes in the attached pdf

Comments for author File: Comments.pdf

Author Response

Thank you very much for your constructive and useful comments. In the revised version, we tried to address all the comments provided. All edits are provided using the “track-change” in the revised manuscript. The “Blue” colored texts in the response document are those included in the manuscript as a response to the comments.

Author Response File: Author Response.docx

Reviewer 3 Report

In my opinion the work is prepared to publish

Reviewer 4 Report

It is striking that the study was carried out for the years 2015 to 2017 and is sent for publication in 2021.
The focus of the paper is scientifically correct and formatting.

Round 2

Reviewer 1 Report

The changes request are introduced

Author Response

The reviewer do not like to sign the review report. However, we do not see any further comments.  

Reviewer 2 Report

I find the revisions of this article unacceptable. It does not appear the authors did any quantitative improvements to the original manuscript that were required ion my original review. The statements on individual revision comments are also somewhat vague. The biggest flaw is that the baseflow constraints are based on a subjective input parameter (beta value of 0.925) that has been highly criticized in recent research. The authors mention some regression analysis with "manual" separation techniques, but it is not at all clear how these were derived. If the beta value is not objectively constrained, the baseflow estimates become highly uncertain and that will have rather large impacts on the irrigation estimates. It is also not clear why low flow runoff, baseflow and recharge were used as in dependent proxies for irrigation potential as recharge and baseflow should be equal. Ideally, the authors should have used the WTF-derived recharge estimate to calibrate baseflow outputs and thereby estimate the appropriate beta parameter. Because of this and many other flaws, I recommend having this article reviewed by a 3rd independent reviewer. The authors should also be given more than 2 weeks to complete the revisions.

Author Response

As you suggested to invite a third reviewer, we agree and OK with it. Please see attached document for detailed response. 

Author Response File: Author Response.pdf