Integrated Hydrogeochemical Groundwater Flow Path Modelling in an Arid Environment

Round 1

Reviewer 1 Report

In this study, the flow path, water source and water chemistry evolution in groundwater were identified by isotopic tracers and NETPATH modelling in Jazan Province of Saudi. The findings are very interesting, which were based on comprehensive field investigation. Generally, the paper is well organized. I would like to recommend this paper to be published after some necessary revisions. The comments are listed below:

Superscript should be used for δ18O.

Lines 45, 51, 52: I think the citations [8-12], [13], [14] are not in a proper format.

The method (i.e., end member mixing model) that employs isotopes or conservative ions as tracers to quantify water sources is important, which should be described in the Introduction. The following references, regarding the theories and applications of this method, may be helpful and referred to:

1. M.G. Sklash, R.N. Farvolden, R.N. Farvolden. The role of groundwater in storm runoff. Dev. Water Sci., 12 (1979), pp. 45-65
2. Juan Gui, Zongjie Li, Ruifeng Yuan, Jian Xue.
   Hydrograph separation and the influence from climate warming on runoff in the north-eastern Tibetan Plateau, Quaternary International, Volume 525, 2019, Pages 45-53, https://doi.org/10.1016/j.quaint.2019.09.002.
3. Chengcheng Xia, Guodong Liu, Hongye Xia, Fangting Jiang, Yuchuan Meng. Influence of saline intrusion on the wetland ecosystem revealed by isotopic and hydrochemical indicators in the Yellow River Delta, China, Ecological Indicators, Volume 133, 2021, 108422,

Line 91: "discharges" instead of "discharging".

Line 121: The right expression should be " various concentrations were prepared".  What are the concentrations?

What are the instrumental errors for ion and isotope measurements?

Use superscripts for the valence of ions.

Lines 131-135: Do some spatial patterns exist in the distribution of pH, EC and TDS? Except for the ranges, more useful information is suggested be reported.

Equation (1): the right bracket is missing.

Lines 167-170: Figure 6 and Figure 7 should be mentioned after the text

Lines 251-254: This sentence is not clearly expressed, containing grammar errors. Please re-organize it.

Figure 6: why do you choose Mediterranean precipitation line for a comparison? You didn't mention it in the main text. Do you have a "local meteoric water line" based on local precipitation isotopes? Why is the evaporation line marked as "assumed"? It's not quite clear. More information should be provided for this part.

Author Response

Please find the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

General comments

The research fits well the scope of MDPI-Water, and can be published. However, some detail is missing and all the specific comments need to be addressed to fix the issues

Specific comments

Lines 16-36. Clearly say in the abstract the type of rock that you have studied

Line 23. “Unsaturated” is written with a different font size

Lines 27-28. Change “probably” into “likely”

Lines 27-28. “Which” to “dilution” the concept is unclear, please reward this part

Lines 34-35. Do not enter in such details in an abstract, remove the number of the wells

Line 42. Add literature on water / rock interaction that treats water isotopes 

  - Falcone, R.A., Falgiani, A., Parisse, B., Petitta, M., Spizzico, M.
and Tallini, M., 2008. Chemical and isotopic (δ18O‰, δ2H‰, δ13C‰, 222Rn)
multi-tracing for groundwater conceptual model of carbonate aquifer
(Gran Sasso INFN underground laboratory–central Italy). Journal of
Hydrology, 357(3-4), pp.368-388.

- Medici, G. and Langman, J.B., 2022. Pathways and Estimate of Aquifer
Recharge in a Flood Basalt Terrain; A Review from the South Fork Palouse
River Basin (Columbia River Plateau, USA). Sustainability, 14(18), p.11349.

- Jeelani, G., Lone, S.A., Nisa, A.U., Deshpande, R.D. and Padhya, V.,
2021. Use of stable water isotopes to identify and estimate the sources
of groundwater recharge in an alluvial aquifer of Upper Jhelum Basin
(UJB), western Himalayas. Hydrological Sciences Journal, 66(16),
pp.2330-2339.

Line 56. Un-clear the meaning of KSA. Explain the acronym

Line 57. “Only a few studies” please provide reference

Line 74. “Groundwater flow velocity”. Add “flow”  before “velocity”

Line 77. Add the 2-3 specific objectives of your research

Line 79. You need to explain the acronym before in the manuscript

Lines 93-84. The link between renewable water resources and rainfall is unclear. Please, explain the concept in better detail

Line 142. Ok mentioning the software, but what about the numerical code used for water-rock interaction? Did you use PHREEQC or an alternative code?

Lines 164-184. You used different font sizes in this paragraph.

Lines 268-269. First sentence of your conclusions unclear. Please, reward it

Lines 291-293. Please, revise the last sentence. All the aquifers are affected by rainfall recharge and evapo-transpiration. You need to explain better the novelty of your research.

Line 311. Add the relevant and recent references that have been proposed above.

Figures and tables

Figure 4. Increase graphic resolution

Figures 4 and 5. Make sure that in the caption and in the manuscript you mention the interpolation methodology for the water table

Figure 7. Or you insert the regression details (e.g., R²) or you remove the red line

Author Response

Please see the attached file.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have revised the paper carefully. I would like to recommend it to be published in WATER.