Evaluation of Groundwater Sensitivity to Pollution Using GIS-Based Modified DRASTIC-LU Model for Sustainable Development in the Nile Delta Region

Round 1

Reviewer 1 Report

The paper need to be revised as reviewed in the paper especially the map of land use because it has the sam figure with hydraulic conductivity map.

The cross section ilustrates the lithological cross section instead of hydrogeological cross section must be clarified. The number of samples need to be mentioned and when the field campaign were done.

Interpolation method can be tried to change with another method for example kriging. The IDW will cause bull eyes in the result.

Comments for author File: Comments.pdf

Author Response

Reviewer: 1

Comment1: The paper need to be revised as reviewed in the paper especially the map of land use because it has the same figure with hydraulic conductivity map.

Reply: Thanks for your comment. We have corrected it and added a new figure of landuse map

Comment2: The cross section illustrates the lithological cross section instead of hydrogeological cross section must be clarified. The number of samples needs to be mentioned and when the field campaign were done.

Reply: Thanks for your comments. We have corrected it to the lithological cross section. We should mention here that we used this figure to illustrate the Bilqas Formation and Mit Ghamr Formation as reported in previous work only. (Ref 22, 23).

Comment3: Interpolation method can be tried to change with another method for example kriging. The IDW will cause bull eyes in the result. (This method will affect bull eyes in the interpolation result. Why the IDW was chosen as interpolated method?)

Reply: Thanks for your fruitful comments; we have already tried using kriging method but lead to disturbance in interpolation of values. Thus, we preferred to use IDW method. Moreover, the inverse distance weighted (IDW) method leads to predict the values of unobserved locations by using values of known location and creation of raster data set by digitization on ArcGIS software platform. In Addition, IDW works better in which there is hard breaks or changes within data, as reported in Chakraborty, et al. (2022).

Ref: Chakraborty, B., Roy, S., Bera, A., Adhikary, P.P., Bera, B., Sengupta, D., Bhunia, G.S., Shit, P.K. 2022.Groundwater vulnerability assessment using GIS-based DRASTIC model in the upper catchment of Dwarakeshwar river basin, West Bengal, India. Environmental Earth Sciences, 81(1):1-15. https://doi.org/10.1007/s12665-021-10002-3.

 

Comment4: In table 2. Ranges and ratings for Modified DRASTIC-LU factors (format to the top instead of center)

Reply: Thank you for your suggestion, we modified it

Comment5: Considering the land use map that is not appropriate, are the maps still valid?

Reply: Thanks for your comment and sorry for this mistake in editing but we already used appropriate land use map in building this vulnerability map

Comment6: has difference 10 points in the level from moderate to high and hight to very high

Comment7: Why the range has difference around 10 points in the different level of vulnerability? Why not directly difference value

Reply: Thanks for your comment and the range has difference around 10 points in the different level of vulnerability because we have making some steps in label format in software which leads to form 10 points. So, we have redesigned it with more accurate format and we obtained the range without any difference as shown in a new Figure (12).

Comment8: In Table 5. Statistics of sensitivity analysis according to single parameter (numbers in 3 digits, for example: 25.5)

Reply: Thanks, we modified it

 

 

 

 

 

 

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Section Abstract:

„…most the Nile Delta is high and very highly vulnerable with 50.68% and 39.53%, respectively….” – the value of 39.53 appears to be greater than 50.68 ?

Section 2. Materials and Methods:

-        there is no explanation of the symbols used in equations (1) and (2)

Section 3.2. Management of Data Layers:

“…model for groundwater susceptibility to contamination as shown in Equation (1b)

..” – there is no equation with the number 1b in the text

Section 4.3. Aquifer media (A)

-        “…The greater the permeability and contamination risk, the larger the grain size and the more cracks inside the aquifer…” - it seems to me that the effect is opposite, i.e. the larger the grain and the more fractures, the greater the permeability of the rock medium and the greater the risk of contamination of the aquifer

Section 4.4. Soil (S)

-        You used the abbreviation USDA for the first time, so it should be explained here or you will use citation (USDA, 2010)

Section 5 Creation of Vulnerability Map

-        “…weights using equation (1b)…” – please see comment for section 3.2

Section 5.1.2. Sensitivity Analysis of modified DRASTIC-LU Model

-        Please explain how the V index was determined / estimated

Tables

Table 2 – please explain why such a large Net recharge range (0.67 - 3.2) is rated 9

Figures

Figure 11 (a, b) – the figure do not match the title

Author Response

Reviewer: 2

Comment1: Section Abstract:

„…most the Nile Delta is high and very highly vulnerable with 50.68% and 39.53%, respectively….” – the value of 39.53 appears to be greater than 50.68?

Reply: Thanks for your comment, the value of 39.53 and 50.68 represented the area occupied by the red colour and buff colour of very highly and highly vulnerable to pollution as shown in Fig (12 b) and we calculated it as shown below::-

    Area= Pixel count *cell size (m) /1000000       to obtain the value with kilometer² unit

Then To calculate the percentage relative to the area of each class we applied the following equation:

   Area%= ​​ Occupied area/ Total Sum area of four classes*100

Comment2: Section 2. Materials and Methods:

       There is no explanation of the symbols used in equations (1) and (2)

Reply: Thanks for your advice. We have mentioned it in the manuscript.

Where D= Depth to water table, R= Aquifer recharge, A= Aquifer media, S= soil media, T= Topography, I= Impact of vadose zone, C= Hydraulic conductivity, LU= land use and subscripts r and w represent, respectively, the rating and weight of these factors.

 

Comment3: Section 3.2. Management of Data Layers:

“…model for groundwater susceptibility to contamination as shown in Equation (1b)

..” – there is no equation with the number 1b in the text

Reply: Thanks for your comment and sorry for this mistake. We have corrected it

 

Comment4: Section 4.3. Aquifer media (A)

        “…The greater the permeability and contamination risk, the larger the grain size and the more cracks inside the aquifer…” - it seems to me that the effect is opposite, i.e. the larger the grain and the more fractures, the greater the permeability of the rock medium and the greater the risk of contamination of the aquifer.

Reply: Thank you for your suggestion, we modified it

Comment5: Section 4.4. Soil (S)

      You used the abbreviation USDA for the first time, so it should be explained here or you will use citation (USDA, 2010)

       Reply: Thank you for your suggestion; we have added  (USDA, 2010).

Comment6: Section 5 Creation of Vulnerability Map

        “…weights using equation (1b)…” – please see comment for section 3.2

        Reply: Thanks for your comment and sorry for this mistake, we have corrected it

Comment7: Section 5.1.2. Sensitivity Analysis of modified DRASTIC-LU Model

        Please explain how the V index was determined / estimated

Reply: Thanks for your comment. We have determined V from vulnerability index where V value indicated to the total sum of vulnerability index as reported in equation (2)

V= DrDw + RrRw + ArAw + SrSw+TrTw + IrIw + CrCw+ LUrLUw

 

 

 

Comment8: Tables

Table 2 – please explain why such a large Net recharge range (0.67 - 3.2) is rated 9

Reply: Thanks for your comment. We have given rate 9 to these ranges based on to the ranges and rating of net recharges according to Aller et al. (1987).

Comment9: Figures

Figure 11 (a, b) – the figure do not match the title

Reply: Thanks, we have corrected it

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

minor change to the placing of table title and references 

Comments for author File: Comments.pdf

Author Response

Comment 1:- (minor change to the placing of table title and references) 

Thank you for your comments. We have modified all comments as required.

Author Response File: Author Response.docx