Deep Groundwater as an Alternative Source of Water in the Ogaden Jesoma Sandstone Aquifers of Somali Region, Ethiopia

Round 1

Reviewer 1 Report

The aim of the paper and its scope is very interesting and valuable. After correcting and supplementing it deserves to be published.

1.      The title and introduction refer to climate change. This is an important issue, climate change affects water scarcity. further part of the research refers to the designation of alternative access to water to protect against the effects of these changes. I suggest changing the title to: “The use of deep groundwater as an alternative source of water in ...”

2.      Line 84, Figure 2. The map of ethnic groups is not related to the topic. On the Map Location (..) there is no description of which administrative units have been included.

3.      Line 128. On the basis of Figure 2 you can’t tell what depth there are groundwater.

4.      Line 131. Figure 3. The scale in numeric format is not needed. It makes it difficult to read the map.

5.      Add a diagram of the thematic layers which were used.

6.      What other places have been designated by experts? Explain why it was decided to drill in the selected location.

7.      What weight has been given to the thematic layers.

8.      Based on Figure 2, it is not possible to determine at what depth groundwater is.

9.      Line 138. Table 1. The symbols X, Y, Z are not explained.

10.  In Material and methods, complete the information about VES method (methodology, principle of scientific research, equipment).

11.  Why you pumped only on stage 1. In European countries, pumps are pumped at 3 degrees. Please quote the general methodology of testing pumps for Ethiopia.

12.  Has the filtration coefficient been calculated for the aquifer based on the trial pumping?

13.  Line 195. Which empirical calculations (formulas, assumptions) were used to calculate the well's efficiency.

Author Response

Reviewer 1

1	The title and introduction refer to climate change.   This is an important issue, climate change affects water scarcity. further   part of the research refers to the designation of alternative access to water   to protect against the effects of these changes. I suggest changing the title   to: “The use of deep groundwater as an alternative source of water in ...”	Title has been changed as suggested
2	Line 84, Figure 2. The map of ethnic groups is not   related to the topic. On the Map Location (..) there is no description of   which administrative units have been included.	Ethnic group map has been removed
3	Line 128. On the basis of Figure 2 you can’t tell what   depth there are groundwater.	The text has been changed a new figure 2 added.
4	Line 131. Figure 3. The scale in numeric format is not   needed. It makes it difficult to read the map.	The figure has been edited as necessary.
5	Add a diagram of the thematic layers which were used.	Added
6	What other places have been designated by experts?   Explain why it was decided to drill in the selected location.	Some text has been added
7	What weight has been given to the thematic layers.	Weightage has been added
8	Based on Figure 2, it is not possible to determine at   what depth groundwater is.	This has been resolved with the addition of a new figure
9	Line 138. Table 1. The symbols X, Y, Z are not   explained.	These have been deleted
10	In Material and methods, complete the information about   VES method (methodology, principle of scientific research, equipment).	This point is not clear
11	Why you pumped only on stage 1. In European countries,   pumps are pumped at 3 degrees. Please quote the general methodology of   testing pumps for Ethiopia.	In Africa, a single test pumping is followed. I have added some text.
12	Has the filtration coefficient been calculated for the   aquifer based on the trial pumping?	Not included
13	Line 195. Which empirical calculations (formulas,   assumptions) were used to calculate the well's efficiency.	Revised

Reviewer 2 Report

General comments

remote sensing such as GRACE are not used or highlighte din the method

also scaling down of the remote sennsing to site specific (groud truthing) is not explicitly mentioned

The none-uniquness  problem solution of the inverse method (geophsyics) solution  is not mentioned.

Resilence and climate change are mentioned but with out much detail to the study area in terms of water resource. It needs to be assessed or left out/remove.

Methodology

The three phased approach needs to be presented in a flow chart  and how those relate to each other via feed back/loop etc. It lacks clarity and the flow of the idea gets in disarray.

The hydrogeological conceptual model lacks quanitative resource /reserve estimate.Moreover, hydraulic parameter (storage) is not explictly assessed and employed for resource estimate.  Multi-layer aquifer assessment (shallow vs deep aquifers) is not addressed via inter leakage/upward/diownward gradient etc, despite a huge meaning interms of climate change and resilence. T this can be done using

Through flow method

Hydrograph fluctuation method ( Area, Storage coefficent, seasonal hydraulic fluctuation)

groundwater balance method ( please see sugested references below)

Technical words suich as:

initial CAPEX (Capital Expenditure) investment and

Value For Money (VfM) are shown up in the discussion with out details in the proceeding sections.

Minor comments

The article requires editing. To mention few:

line 89 ( needs space between "andthe")

Figure 2( Legend- Transmissivity - "m2/day". "2" should be superscript

Few references below-to address the coments above:

§   Yihdego Y and Webb J.A., 2015 “Use of a conceptual hydrogeological model and a time variant water budget analysis to determine controls on salinity in Lake Burrumbeet in southeast Australia” Environmental Earth Sciences Journal. 73 (4):1587-1600. http://link.springer.com/article/10.1007/s12665-014-3509-x

Yihdego, Y, Khalil, A (2017). Groundwater Resources Assessment and Impact Analysis Using a Conceptual Water Balance Model and Time Series Data Analysis: Case of Decision Making Tool. Hydrology, 4(2), 25. doi:10.3390/hydrology4020025. https://www.mdpi.com/2306-5338/4/2/25

Author Response

Reviewer 2

1	The three phased approach needs to be presented in a flow chart  and   how those relate to each other via feed back/loop etc. It lacks clarity and   the flow of the idea gets in disarray.	This is now included
2	The hydrogeological conceptual model lacks quanitative resource /reserve   estimate.Moreover, hydraulic parameter (storage) is not explictly assessed   and employed for resource estimate.  Multi-layer aquifer assessment   (shallow vs deep aquifers) is not addressed via inter   leakage/upward/diownward gradient etc, despite a huge meaning interms of   climate change and resilence	Weightage has been included based on this recommendation
3	Technical words suich as: initial CAPEX (Capital Expenditure) investment and Value For Money (VfM) are shown up in the discussion with out details in   the proceeding sections.	These have been explained in the text
4	Editing of english	This has been included

Reviewer 3 Report

 Climate resilient deep groundwater investigation and 2 development in the Ogaden Jesoma sandstone 3 aquifers of Somali Region, Ethiopia

 

This manuscript used the WATEX three-phased approach in an area of  Somali Region, Ethiopia. Moreover, it emphasizes the need for a systematic understanding of the lithology with appropriate hydrogeologic investigation before drilling.

The topic is very interesting, especially in arid areas where it is important to drill productive well and to withdraw good quality groundwater.

However, the paper is very difficult to read.

First of all, the Watex method is not described but only a reference is reported. The geological setting is poor, and a geologic map and or cross section is lacking.

The results are not clearly supported by figures and tables.

 

I think that a more complete and clear description of methods and results must be inserted, before to accept and publish the paper.

ABSTRACT

LINE 31-32: the sentence is probably incomplete. Please, modify it.

 

INTRODUCTION

In the introduction is not clear what is WATEX technique and if it was used in the study area.

 

 

MATERIALS AND METHODS

Line 87-88: the word “that” can be removed

Line 89: andthe : separate and the

 

The explanation of the method must describe all the single steps. Instead in the paper only

references to the bibliography are reported (using the three-phase methodology outlined in (8)). The reader in this way has great difficulty understanding the method. Please, be more detailed and illustrate the method in a complete way.

line 103: what does it mean “a based-on experts’ judgement”?

 

RESULTS

HYDROGEOLOGICAL CONCEPTUAL MODEL

It could be useful to add  a geologic map of the area, and if possible a cross section.

Because of it is very difficult to understand the used method (there only a reference, but not a description) I’m not sure that the Hydrogeological conceptual model must be inserted in the results or in the method / study area. Is the reconstruction of Hydrogeological conceptual model the first  step of the method?

Otherwise, I moved it in the methods/ study area.

 

Line 122: “well logs showed”: The paper (15) is unpublished, and then the reader is not able to have an idea on the well logs. Please, insert in the paper a figure with well logs.

 

 Line 124: what are the reasons of the presence of brackish water?

 

Line 124-125: “Using the overlay methods outlined in (8), a conceptual model was developed and outlined in figure 2 below.”

It is not clear how the authors developed the conceptual model.

 

Line 122-130: “The conceptual model identified an absence of a retaining layer at shallow depth due to the high transmissivity of the sandstone formations. Recharge was noted to percolate deeper until it intercepts the underlying limestone or clay layers of the upper cretaceous formation. As per the interpretation  outlined in figure 2, the water bearing layers are expected to be located between depths of 300 m to  450m below ground level.”

These sentences are not supported by a clear description of the geologic setting.

What does it means: “The conceptual model identified an absence of a retaining layer at shallow depth due to the high transmissivity of the sandstone formations”? Why the authors say “the water bearing layers are expected to be located between depths of 300 m to  450m below ground level”?

 

GEOPHYSICAL SURVEY

138: “interpreted water quality condition from VES survey”.

 

139-140: “The results of the VES indicated that groundwater generally occurs at depths below 300 m depth in the Auradu limestone and 450 m to 500 m depth in the Jessoma sandstone.”

Because of the VES are not located on a map, it is impossible to check the information. Please, insert a mp with geographic denomination.

 

Tab. 1 is not clearly described (see also the revision of figures and tables). Aquifer resistivity and remark (water quality???) are connected on the base of what? Do you used a reference?

Do you have also indication of EC?

 

Figure 4. Electrical logging of well 1. The figure is not clear. What is SP? What are the three lines? the figure must be described in detailed.

 

Line 157-161: “For drilling purpose, the VES site 5 was selected as the specific site for well siting at a depthof 600 m. Resistivity readings were taken during the drilling to interpolate the electrical conductivity  of the well and its potential to produce saline or brackish water. The results from this study are outline  in the figure 4 and they showed a gradual increase of resistivity meaning the presence of a fresh water  with lower conductivity.”

Gashamo well 1 and ves site 5 are the same point?

“Resistivity readings were taken during the drilling”. How?

“interpolate the electrical conductivity  of the well”. Where are these data?

 

FIGURE

Figures have a low resolution. Please, improve the resolution

 

Figure 1. Location of the study region.

I think that more than the ethnic groups, it could be more useful to have a geological or hydrogeological map. Please, modify it.

 

Figure 2. Hydrogeological conceptual model for Gasham.

In legend the authors added BH with T data, but this simbol is not present in the figure. Please, add it.

 

Table 1. please, modify “water le vel depth” in “water level depth”.

Please, describe what are

X

Y

Z

Estimated SWL

What is remark? Is it water quality???

 

Figure 3. Conceptual model of the lithologic formation.

The figure must be improved adding the lithologic formation in the cross section.

 

Author Response

Reviewer 3

1	First of all, the Watex method is not described but   only a reference is reported. The geological setting is poor, and a geologic   map and or cross section is lacking.	This is a modified version   of the Watex and the weighting and the methodology have now been included
2	LINE 31-32: the sentence is probably incomplete.   Please, modify it.	Modified
3	Line 87-88:   the word “that” can be removed. Line 89: andthe : separate and the	Done
4	The   explanation of the method must describe all the single steps. Instead in the   paper only	Done
5	It could be   useful to add  a geologic map of the area, and if possible a cross   section.	Done
6	Expert judgement	This is explained using   the added text and weightage table
7	Line 122:   “well logs showed”: The paper (15) is unpublished, and then the reader is not   able to have an idea on the well logs. Please, insert in the paper a figure   with well logs.	The government of the Somali   region are not forthcoming in giving this log. It is therefore not included
8	Line   124: what are the reasons of the presence of brackish water?	Text has been added
9	Line 124-125:   “Using the overlay methods outlined in (8), a conceptual model was developed   and outlined in figure 2 below.”	Included now
10	Line 122-130:   “The conceptual model identified an absence of a retaining layer at shallow   depth due to the high transmissivity of the sandstone formations. Recharge   was noted to percolate deeper until it intercepts the underlying limestone or   clay layers of the upper cretaceous formation. As per the interpretation    outlined in figure 2, the water bearing layers are expected to be   located between depths of 300 m to  450m below ground level.”	Correct
11	138:   “interpreted water quality condition from VES survey”.	Table focusses now on   water depth only
12	139-140: “The   results of the VES indicated that groundwater generally occurs at depths   below 300 m depth in the Auradu limestone and 450 m to 500 m depth in the   Jessoma sandstone.” Because of   the VES are not located on a map, it is impossible to check the information.   Please, insert a mp with geographic denomination.	The text has been modified   to reflect the results. Due to security reasons and access in this volatile Somali   region, we can not provide a further map.
13	Gashamo well   1 and ves site 5 are the same point?	Yes
14	I think that   more than the ethnic groups, it could be more useful to have a geological or   hydrogeological map	This has been modified
15	In legend the   authors added BH with T data, but this simbol is not present in the figure.   Please, add it.	Done
16	Table 1. please,   modify “water le vel depth” in “water level depth”. Please, describe what are X Y Z Estimated SWL  What is   remark? Is it water quality???	The table has been   modified
17	Figure 3. Conceptual   model of the lithologic formation. The figure   must be improved adding the lithologic formation in the cross section.	This has been modified

Reviewer 4 Report

The study describes a three-phase methodology of climate resilient deep groundwater development of wells in the Ogaden Jesoma sandstone aquifers of the Somali Region, Ethiopia. While the topic is interesting to readers, the current version of the manuscript is poorly organized with several grammatical errors. The writing and contents of the research is very hard to follow. Overall the English is poor, and requires editing from a native English speaker. Based on these points, I recommend major revisions of the manuscript. My specific comments are as follows:

1.       Abstract: Too much background information. Description of methodology and results is insufficient. Should clearly and concisely mention the stages of the mentioned three-stage methodology. Overall, abstract requires a judicial rewriting.

2.       Page 1, Line 31: Incomplete sentence. Please add the missing words to complete the sentence.

3.       Page 2, Line 47: Please revise the sentence " This far higher than the global average which notes that...." for better readability.

4.       Page 2, Lines 50-53: The sentence "Recent reviews.......groundwater recharge" requires revising and rewriting.

5.       Page 3, Line 86: Are you referring to a specific project?

6.       Methodology lacks clarity. So far I understand, the research is based on earlier published documents. Although you gave credit to this published work, the three-phase methodology and the steps are not clearly articulated in the methodology section of the current version of the manuscript. For readability and better understanding of the contents, the methodology followed in this research must be clearly mentioned.

7.       Page 4, Lines 116-125: Did you gather this information from your own conceptual model? If yes, you need to provide a description of the conceptual model along with the initial and boundary conditions in the methodology section. If not, these texts should appear in the background and methodology section.

8.       Page 5, Line 135: Provide brief description of the Vertical Electrical Soundings (VES) in the methodology section. You don’t need to mention the methodology again in the result section.

9.       Page 6, Lines 157-159: Again you are mixing up results and methodologies.

10.   Page 6, Lines 159-161: Grammar error (The results from this study are outline). More explanations with interpretation of the results are needed here.

11.   Page 6, Lines 171-173: ‘Reverse circulation……to avoid collapse” might go to methodology section.

Author Response

 Reviewer 4

1	Abstract:   Too much background information. Description of methodology and results is   insufficient. Should clearly and concisely mention the stages of the   mentioned three-stage methodology. Overall, abstract requires a judicial   rewriting.	The abstract has been modified and edited.
2	Page 1,   Line 31: Incomplete sentence. Please add the missing words to complete the   sentence.	Done and included
3	Page 2, Line 47: Please revise the sentence " This   far higher than the global average which notes that...." for better   readability.	Is has been added to the sentence
4	Page 2, Lines 50-53: The sentence "Recent   reviews.......groundwater recharge" requires revising and rewriting.	Done
5	Page 3,   Line 86: Are you referring to a specific project?	Modified
6	Methodology   lacks clarity. So far I understand, the research is based on earlier   published documents. Although you gave credit to this published work, the   three-phase methodology and the steps are not clearly articulated in the   methodology section of the current version of the manuscript. For readability   and better understanding of the contents, the methodology followed in this   research must be clearly mentioned.	We have now added some more clarity around the   methodology. Some journals prefer to reference other work and we acknowledge   the need to improve this section.
7	Page 4,   Lines 116-125: Did you gather this information from your own conceptual   model? If yes, you need to provide a description of the conceptual model along   with the initial and boundary conditions in the methodology section. If not,   these texts should appear in the background and methodology section.	Yes and now included as recommmended
8	Page 5,   Line 135: Provide brief description of the Vertical Electrical Soundings   (VES) in the methodology section. You don’t need to mention the methodology   again in the result section.	Now clear
9	Page 6, Lines 157-159:   Again you are mixing up results and methodologies.	Text has been modified
10	Page 6, Lines 159-161: Grammar error (The results from   this study are outline). More explanations with interpretation of the results   are needed here.	Changed
11	Page 6,   Lines 171-173: ‘Reverse circulation……to avoid collapse” might go to   methodology section.	Done

 

 

Round 2

Reviewer 1 Report

My comments have been taken into account. I agree to the publication.

Author Response

Many thanks for the agreement

Reviewer 3 Report

The authors  answered to all the revisions.

Author Response

Many thanks for your agreement

Reviewer 4 Report

The authors have adequately addressed most of the concerns. However, the abstract still has 12 lines of background information.

Author Response

Further to your comment, the abstract has now been modified. See final draft.