Hybridization of DRASTIC Method to Assess Future GroundWater Vulnerability Scenarios: Case of the Tebessa-Morsott Alluvial Aquifer (Northeastern Algeria)

Round 1

Reviewer 1 Report

For groundwater modeling need to be clarified related to the:

1. Conceptual model

2. Boundary condition of the numerical model

3. Hydrogeological parameters of the numerical model such as number of layers, thickness of every layer, distribution of K value

4. Calibration process related to the number of well observasion and statistical of calibration process

5. Piezometer level countur is crossing the water level label in the supplementary file

Author Response

For groundwater modeling need to be clarified related to the

1. Conceptual model.
2. Boundary conditions.
3. Hydrogeological parameters of the numerical model such as number of layers, thickness of every layer, distribution of K value.
4. Calibration process related to the number of well observation and statistical of calibration process.

 

Response: Thank you for your suggestion. All the information have been added in the text

Line 325-338: Hydrogeological conceptual models are collections of hypotheses describing the understanding of groundwater systems and they are considered one of the major sources of uncertainty in groundwater flow and transport modeling. According to the basic hydrogeological information, the following boundary conditions were set in the steady-state groundwater model. The aquifer was considered as unconfined with a heterogeneous layer. The entire study area received recharge by rainfall (flow boundary). The wadis of the region (El Ksob wadi, El kebir wadi and Chabro wadi) were defined as the second flow boundary. In some lateral boundaries, the boundaries were closed and considered watertight (no-flow boundary). Conversely, some boundaries were simulated as open flow boundaries where hydraulic gradients allow flow across these boundaries (fractured limestones of the Maastrichtian and Turonian). The boundary conditions are given in Figure 4 and all the aquifer’s parameters are shown in Table 2.

Finally, the simulation was developed over a period of 20 years (period 2010-2030).

Table 2. The aquifer parameters used for model setup and calibration.

Parameter	Value	Unit
Groundwater level Number of layer Aquifer thickness Hydraulic conductivity Specific storage Recharge Withdrawal (wells) Stream leakage Boundary limits	1.0–78 1 150–300 2 x 10-5–3 x 10-4 8–22 84,354 36,986 195,320 147,953	m U m m/s % m3/day m3/day m3/day m3/day

Calibration process related to the number of well observation and statistical of calibration process

Response: Thank you for this remark. The Figure and paragraph have been added in "3.2.1. Steady-state model" section.

Line 351-356: Figure 6 shows a scatter diagram of the observed heads and calculated heads in 17 monitoring wells. Clearly in the steady state, the measured groundwater levels of the observation wells match very closely with the calculated values (with a coefficient of determination R² = 0.96)."

 

Figure 6. Relationship between calculated and observed heads in meters (May 2010).

Piezometer level contour is crossing the water level label in the supplementary file

Response: The Figure S2 has been corrected.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript presents a local case study. It would be worth supplementing it with an overview of DRASTIC methods and modifications. 

Author Response

1.The manuscript presents a local case study. It would be worth supplementing it with an overview of DRASTIC methods and modifications.

Response: Some examples of application and modification have been added in the introduction section. Anyway, since it is not a review paper, we referred in the text to 2 well know reviews.

Line 78-83: Several modifications have been proposed in the last years: Busico et al. [14] achieved the optimization of rating methods combining statistical analysis with parameter objectivation, Khosravi et al. [26] enhanced DRASTIC performance using artificial intelligence and Duc-Vu et [27] al combined DRASTIC and Modflow to increase vulnerability performance. A complete review of all methodologies and modifications is available in Machiwal et al. [1] and in Taghavi et al. [28]

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

This is a very good study wherein numerical groundwater modeling and DRASTIC model have been used to assess the present and future groundwater vulnerability to contamination.

I have some suggestions that the authors must undertake in order to improve this manuscript.

1. Use a lat/long grid coordinate system in your maps for global audience

2. Study areas figure needs to be revised. Use different insets to provide the location of your study area with reference to World, Europe, Algeria and finally study area

3. No need to use DEM to represent the study area. Instead, I would suggest using natural color composite images for this purpose.

4. The final map caption, Fig. 10 DRASTIC MAP, needs to be revised to provide a better illustration of this figure, such as a Vulnerability map showing...

6. Add a section on the limitation and future scope of this work.

7. Improve the literature review and discussion. Use the latest references about the DRASTIC modeling from mountainous regions of the world such as the Himalayas and the Alps

 

Best of luck and serve humanity!

 

Author Response

Dear Authors,

This is a very good study where in numerical groundwater modeling and DRASTIC model have been used to assess the present and future groundwater vulnerability to contamination.

I have some suggestions that the authors must undertake in order to improve this manuscript.

1. Use a lat/long grid coordinate system in your maps for global audience

Response: Thank you for your suggestion. It is easy to put the Lat/Long grid coordinates system in the maps established under GIS, while the hydrogeological modeling work (under Modflow) the UTM system is the most practicable (easily used). For this reason, we have chosen the UTM, datum WGS 1984 coordinates system which is globally recognized.

2. Study areas figure needs to be revised. Use different insets to provide the location of your study area with reference to World, Europe, Algeria and finally study area

Response: The study area figure has been corrected.

3. No need to use DEM to represent the study area. Instead, I would suggest using natural color composite images for this purpose.

Response: Thank you for your suggestion. But, instead of presenting two maps, one map of geographic location and another map to present the topography, this map was (DEM) chosen to provide the geographic location and topography description of the study area. Please see the paragraph after Figure 1. However, the title of the Figure 1 has been corrected.

4. The final map caption, Fig. 10 DRASTIC MAP, needs to be revised to provide a better illustration of this figure, such as a Vulnerability map showing …

Response: Thank you for your suggestion. The caption of figure 10 has been modified.

Figure 10. DRASTIC map. Three groundwater vulnerability classes have been defined: 1) 52 < Vi ≤ 100: Low vulnerability (green color), 2) 101 < Vi ≤ 140: Average vulnerability (yellow color) and 3) 141 < Vi ≤ 157: High vulnerability (red color).

 

6. Add a section on the limitation and future scope of this work.

Response: Thank you for this remark. The paragraph has been added.

 

Line 523-537: The new proposed approach considering the hybridization between a numerical model (Modflow model) and a groundwater vulnerability method (DRASTC) for predicting actual and future groundwater vulnerability assessment represent a step-forward the canonical concept of static representation of vulnerability. The possibility to forecast short and long term situations, accordingly the most suitable climatic and socio-economical scenarios is a valuable tool for groundwater management. At the regional scale, this proposed concept can be easy adapted and in the different aquifers types (karst, fissured or porous) and climatic regions. On the other hand, the suitability to regional scale assessment is contemporary the main conceptual drawback since the numerical simulation requires detailed aquifer information not everywhere available, especially for national scale. Moreover is of paramount importance to include in the assessment the pollutants’ transport dynamic and nitrogen formation and removal processes both in vadose and saturated zone [53] along with the role of fracture and sinkholes in nitrogen leaching [54] to ensure proper management of land and water resources.

 

7. Improve the literature review and discussion. Use the latest references about the DRASTIC modeling from mountainous regions of the world such as the Himalayas and the Alps.

Response: Some examples of application and modification have been added in the introduction section. Anyway since it is not a review paper we referred in the text to 2 well know reviews.

Line 78-83: Several modifications have been proposed in the last years: Busico et al. [14] achieved the optimization of rating methods combining statistical analysis with parameter objectivation, Khosravi et al. [26] enhanced DRASTIC performance using artificial intelligence and Duc-Vu et [27] al combined DRASTIC and Modflow to increase vulnerability performance. A complete review of all methodologies and modifications is available in Machiwal et al. [1] and in Taghavi et al. [28]

Author Response File: Author Response.pdf