Are the Fouta Djallon Highlands Still the Water Tower of West Africa?

Round 1

Reviewer 1 Report

The reviewed manuscript aimed to investigate an important topic about the 'water tower role' of Fouta Djallon Highlands. This kind of topic requires a holistic approach and extensive data analysis. However, in my opinion, this study should have been involved more geological analysis but finally, the manuscript has not failed in its aims and related results. The authors have involved novel remote sensing applications and hydrological derivatives to support their findings. As a summary, the findings of this manuscript can be accepted for publication after correcting and answering my issues listed below:

• Figure 1: the image resolution seems to be low for me in the reviewed manuscript. I recommend to improve it to make it more easily readable.
• Figure 2: the second item in the legend should be corrected to 'sandstone'
• Line 99: to be changed to 'Figure 2' from 'figure 2'
• Line 102: to be changed to 'estimated' from 'estimate' 
• Line 103: to be changed to 'into three' from 'in three' then replace the 'with' with a 'by'
• Line 122: what did the authors mean by 'generalized groundwater'? Please describe this term for the possible future readers.
• Line 125: the authors refer to a relatively old (30 years old) reference in terms of the water mineralization rates. Do they think this has not changed by then?
• Line 159: to be changed to 'Figure 3' from 'figure 3'
• Figure 3: I suggest to rephrase the title of the figure. Please use a more suitable way to express the 'trends' of rainfall which tends to decrease in the title. Also my other concern is related to the 'a' and 'b' signs, which should be placed in a more visible way. What are the dots representing? Please try to express it as well because maybe it is not clearly evident for all future readers.
• Figure 4: It is really difficult to read the values plotted of the isochrones due to the extremely small letters. Please redesign this figure.
• Line 164: a dot is missing from the end of the sentence.
• Line 184: to be changed to 'Figure 5' from 'figure 5'
• Line 185: a dot is missing from the end of the sentence.
• Line 210: to be changed to 'Figure 4' from 'figure 4
• Line 229: to be changed to 'Mann-Kendall's Tau test' from 'Mann Kendall Tau'. By the way, why the authors found this test to be an 'efficient trend detection method'? Please clarify your decision.
• Line 232: A sentence has to be started with capital letters.
• Figure 5: For me, this Figure is not informative. How can we distinguish the 16 separete basins? The legend does not support the understanding of this figure. Please redesign this figure.
• Figure 6: the 'a' to 'e' signs should be placed in a more visible way. Another issues that please use dots as decimal places on the y-axis instead of commas. Moreover, why the authors plotted points on the line graphs on a, b and c parts and not plotted on the rest? Please create unified figures.
• If there is an empty rectangle on Figure 87 representing the detailed map of Figure, then why there is another rectangle showing the position of Figure 8?
• Line 396: to be changed to 'Mann-Kendall' from 'Man-Kendall'. By the way, what is a 'Pvalue Test'? It has not been described clearly in the methods.
• On Figures 7 and 8 we cannot see any blue pixels or patches. Why? I have not found any explanations from the authors.
• Line 402: to be changed to 'Figure 9' from 'figure 9'
• In Lines 414, 418 and 420 the authors used two types of 'Figure mentions'. Please make it in a unified way.
• Figure 11: Why the authors used this extremely long figure caption? It needs to be done in the body text.
• Figure 12: the 'a' and 'b' signs should be placed in a more visible way.
• Figure 13: the 'a' and 'b' signs should be placed in a more visible way.
• Figure 14: Please redesign the figure to be in harmony with Figure 6.

Also I have to highlight that the Abstract does not include too much things in terms of the methodology which is an important part. I suggest to improve the Abstract as well.

Author Response

Response to Reviewer 1

 

• Figure 1: the image resolution seems to be low for me in the reviewed manuscript. I recommend to improve it to make it more easily readable.

Response: The 3 maps of Figure 1 were re design in order to make them more readable

• Figure 2: the second item in the legend should be corrected to 'sandstone'

Response: the correction was made

• Line 99: to be changed to 'Figure 2' from 'figure 2'

Response: the change was made

• Line 102: to be changed to 'estimated' from 'estimate' 

Response: the change was made

• Line 103: to be changed to 'into three' from 'in three' then replace the 'with' with a 'by'

Response: the change was made

• Line 122: what did the authors mean by 'generalized groundwater'? Please describe this term for the possible future readers.

Response: We change by : “the total absence of generalized watertable and continuous groundwater reservoir”; groundwater in the FD is characterized by a lot of small water table.

• Line 125: the authors refer to a relatively old (30 years old) reference in terms of the water mineralization rates. Do they think this has not changed by then?

Response: Yes, that is true; so we added some measurements done in the FD in March and May 2019; the value measured at this time was coherent with the ones cited of the Didier Orange (1990) reference

• line 129-134: “This relatively old finding remains overall coherent and aligned with a series of small sampling tests made in the FDss by the authors in March and May 2019. In 28 samples taken at an elevation of less than 800 m, the mineral concentration of water was in average 55 mg.l^-1 (SD 74, with values ranging from 6.5 to 414) and in 14 samples taken at an elevation higher than 800 m, the mineral concentration was in average 24.5mg.l^-1 (SD = 14.8, values from 6.5 to 53)”.

• Line 159: to be changed to 'Figure 3' from 'figure 3'

Response: the change was made

• Figure 3: I suggest to rephrase the title of the figure. Please use a more suitable way to express the 'trends' of rainfall which tends to decrease in the title. Also my other concern is related to the 'a' and 'b' signs, which should be placed in a more visible way. What are the dots representing? Please try to express it as well because maybe it is not clearly evident for all future readers.

Response: the title was changed and completed by: “Figure 3. Rainfall evolution in the Fouta Djallon mountains since 1923; 3a: Konkouré, Corubal and Gambia rivers basins; 3b: Senegal and Niger upper basins. Dots represent the Annual Total Rainfal (ATR), in mm.

”

• Figure 4: It is really difficult to read the values plotted of the isochrones due to the extremely small letters. Please redesign this figure.

Response: the values were plotted in greater  letters

• Line 164: a dot is missing from the end of the sentence.

Response: the change was made

• Line 184: to be changed to 'Figure 5' from 'figure 5'

Response: the change was made

• Line 185: a dot is missing from the end of the sentence.

Response: the change was made

• Line 210: to be changed to 'Figure 4' from 'figure 4

Response: the change was made

• Line 229: to be changed to 'Mann-Kendall's Tau test' from 'Mann Kendall Tau'. By the way, why the authors found this test to be an 'efficient trend detection method'? Please clarify your decision.

Response : we completed the sentence as follows :

“Mann-Kendall’s Tau test is an efficient trend detection method [31] and has been used for this data type for other regions of western Africa [32,33,34]. Mann Kendall’ Tau test can be submitted to null hypothesis (P value) testing that the data come from a population with independent realizations and are identically distributed. It has been retained a significance at 0.001 for this paper meaning that a sample as extreme as that observed would occur 1 time in 1000 if the null hypothesis was true”.

• Line 232: A sentence has to be started with capital letters.

Response: the change was made

• Figure 5: For me, this Figure is not informative. How can we distinguish the 16 separete basins? The legend does not support the understanding of this figure. Please redesign this figure.

Response : the figure was redesigned

• Figure 6: the 'a' to 'e' signs should be placed in a more visible way. Another issues that please use dots as decimal places on the y-axis instead of commas. Moreover, why the authors plotted points on the line graphs on a, b and c parts and not plotted on the rest? Please create unified figures.

Response :the changes suggested were made

We changed commas by dots

Points have been plotted in all the figures; previously, we put points only in the figures were isolated yearly data obliged us to plot points to represent all the years; in order to homogenize the figures, all the figures are now plotted with points

• If there is an empty rectangle on Figure 7 representing the detailed map of Figure 9?, then why there is no another rectangle showing the position of Figure 8?*

Response: the title of the figure was changed and it is now as follows: “Figure 7. Vegetation (forest density higher than 15%) in 2000 and 2019; and vegetation loss and gain (GFC product, [29] for the 16 basins. The empty brown rectangle is the area covered by map of figure 8. The empty blue rectangle is the area covered by map of figure 9. The empty red rectangle is the area covered by map of figure 11”

• Line 396: to be changed to 'Mann-Kendall' from 'Man-Kendall'. By the way, what is a 'Pvalue Test'? It has not been described clearly in the methods.

Response : the description was given in methods : « “Mann-Kendall’s Tau test is an efficient trend detection method [31] and has been used for this data type for other regions of western Africa [32,33,34]. Mann Kendall’ Tau test can be submitted to null hypothesis (P value) testing that the data come from a population with independent realizations and are identically distributed. It has been retained a significance at 0.001 for this paper meaning that a sample as extreme as that observed would occur 1 time in 1000 if the null hypothesis is true”.

• On Figures 7 and 8 we cannot see any blue pixels or patches. Why? I have not found any explanations from the authors.

Response : the following sentence was added: “Few blue pixels appear in Figures 7 and 8, partly due to the low vegetation gain, partly due to methodological reasons.. Bebele basin (Tene River at Bebele stream gauge station) which is designed in Figure 7 and 8 is not considered in this analysis, due to its very poor data set.

• Line 402: to be changed to 'Figure 9' from 'figure 9'

Response: the change was made

• In Lines 414, 418 and 420 the authors used two types of 'Figure mentions'. Please make it in a unified way.

Response: the change was made

• Figure 11: Why the authors used this extremely long figure caption? It needs to be done in the body text.

Response: the change was made, and the long sentence removed from the caption to the body text

• Figure 12: the 'a' and 'b' signs should be placed in a more visible way.

Response: the change was made

• Figure 13: the 'a' and 'b' signs should be placed in a more visible way.

Response: the change was made

• Figure 14: Please redesign the figure to be in harmony with Figure 6.

Response: the figure was redesigned completely in harmony with Figure 6

Also I have to highlight that the Abstract does not include too much things in terms of the methodology which is an important part. I suggest to improve the Abstract as well.

 

Response: the abstract was completely re written and includes currently a short description of methodology

Otherwise, the change in figures graduation (dots instead of commas) was also made in the 16 concerned figures of Supplementary Material

 

 

Reviewer 2 Report

There are many problems with the English in this paper. Suggest extensive editing by a native English speaker. Try to standardize figures and make sure the reason is given or justified for each figure that is presented. Make sure all jargon and local colloquial terms are defined and used consistently. I started to note some of the English mistakes or incorrect word choice but this file is only a partial list.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2

 

line 85 : It is never defined what this refers to?

 

Response : The  sentence was completed and precised; otherwise, Fouta Djallon and Guinean Dorsale are well distinguished in Figure 2

 

line 114-115 : what does this phrase mean??

 

Response: the sentence was completed as follows: “However, no clear difference can be noticed in their hydrological behaviors, most probably due to their similarly high levels of imperviousness”

 

line 133: Not the correct word.

 

Response : the sentence was changed as follows: “The impervious geology of most of the FD mountains”

 

line 151: English needs work.  Poor water storage?

 

Response: the sentence was changed as follows: “This location is very rainy, but it allows very poor water storage”

 

line 255-256: These are different graph types, standardize

 

Response: standardization was made !!

 

Overall, Reviewer 2 said : “There are many problems with the English in this paper. Suggest extensive editing by a native English speaker. Try to standardize figures and make sure the reason is given or justified for each figure that is presented. Make sure all jargon and local colloquial terms are defined and used consistently. I started to note some of the English mistakes or incorrect word choice but this file is only a partial list.”

 

Therefore, the whole text has been revised, by the English native co-author as well as the two colleagues living or have lived long time in countries where the language is english (England and Autralia)

 

Authors kindly acknowledge the reviewers for their revision which allows us to propose an improved version of manuscript

 

Round 2

Reviewer 2 Report

The English language is greatly improved in this revision.  Below are a few areas where it can be further improved.

Line 71  Change "spots" to a less colloquial term such as "receives some of the greatest rainfall in West Africa" 

There are still problems with plural words, including precipitations and behaviors.

Multiple instances of confusion between "in" and "on"

Some confusion between "is" and "are"

 

Author Response

2^nd round Revision

 

Changes

1- Figure 1b was modified in order to be more similar than figure 1c

 

2- According to the reviewer 2 suggestions:

2-1- Line 71 

We Changed "spots" by "receives some of the greatest rainfall in West Africa" 

2-2- Precipitations and behaviors were replaced by their singular mode precipitation and behavior

2-3- Confusion between "in" and "on", and between "is" and "are" were checked and marked

 

3- According to the 2^nd reviewer, 2 english speaker colleagues proposed some other improvements;
This improvement was overall applied in the results, discussion and conclusion part, as suggested by Reviewer