Industry-Driven versus Natural Groundwater Flow Regime at the Dead Sea Coastal Aquifer

Round 1

Reviewer 1 Report

This paper would be acceptable with minor revision.

1) some evidence for the hydraulic parameters should be cited.

Author Response

Line numbering in the responses refers to the revised manuscript (when "all markup" of the "track changes" is selected in the "review" panel).

1) some evidence for the hydraulic parameters should be cited.

Response: References were added to the manuscript [33-35] for justifying the following model parameters and boundary conditions: hydraulic conductivity (line 366), specific storage (line 372), anisotropy (line 372), east and west concentration boundary condition (lines 261,263). Dispersivities values were added to the manuscript (200 and 20 m for longitudinal and transverse respectively) and referenced (lines 283-285).

Reviewer 2 Report

The authors provide results of a modeling study aimed at estimating future leakage rates from evaporation ponds south of the Dead Sea. While a very interesting topic, I found that the contributions are minor, compared to what is already known from historical data. In addition, the results presented have a high degree of uncertainty, which is not quantified by the authors.

1. Section 3.2: I am not sure why halite precipitation is considered in the water balance of Equation (1)? Halite is a salt mineral, and not a hydrologic pathway, so why is it included?
2. Section 3.2: “all values include some errors or uncertainties”: could you indicate which variables might have a higher degree of uncertainty? And what degree (%) of uncertainty is expected?
3. Equation (2) is for a confined aquifer. Is the aquifer system confined? Are there any portions that are unconfined? If the aquifer is unconfined, then Equation (2) must be changed to reflect this, using the appropriate terms (e.g. specific yield).
4. I assume that the solute in Equation (3) is total salinity? Please make this clear in the text. Is there any reason to believe that salt in the aquifer is conservative? Or should equilibrium chemistry (e.g. precipitation-dissolution) be included? In other words, does salt mineral dissolution increase salinity concentration in the aquifer, and/or does the salt concentration in the aquifer reach sufficient levels so that precipitation occurs? If so, then Equation (3) is not sufficient to simulate the transport of salt in the aquifer system.
5. Line 256: what is the rationale for setting C = 0 mg/L along the western boundary of the model domain? Does the groundwater really have no salt along the western edge? That does not seem right, for any semi-arid or arid aquifer where salt minerals are present. The results in Figure 9B also point to this: the model shows that there are very low salinity concentrations in the entire western region of the model domain. This does not seem likely.
6. Lines 310-312: already stated in the Methods section. Delete.
7. Lines 282-284: this seems like the model used 10-year, 8-year, 5-year, and 4-year time steps. In other words, groundwater head and salinity concentration are only calculated at these specific intervals. Is this true?
8. From the results (e.g. page 12) it seems like the aquifer is unconfined, particularly since there is interaction between the leakage from the evaporation ponds and the aquifer. Please clarify this. If this is the case, the model needs to be re-done using unconfined groundwater flow equations.
9. The groundwater model is being used to predict future leakage rates. However, the model is test only for groundwater head measured in the 2017-2020 time period (and it seem like a single measurement at each monitoring well). How can we be certain that the model is correctly simulating groundwater flow rates?
10. For leakage rates: please show the comparison between data-estimated and model-estimated leakage rates. This will help the reader see the accuracy of the model.
11. In general, the text is confusing in that leakage is discussed in several ways: leakage from the canals, and leakage from the embankments of the ponds. It took a while for me to understand that you are simulating leakage from the evaporation ponds into the aquifer, and then simulating groundwater flow between the ponds and the Dead Sea. Please make this clearer, particularly in the Abstract and final paragraphs of the Introduction.
12. I do not see the need for the salinity transport model. I did not see how it is used to estimate leakage rates. Also, there are no presented groundwater salinity data, so the spatial values in the maps in Figure 9B and 10 cannot be tested/verified. I suggest eliminating this from the paper, unless there is an aspect that I did not see in relation to the objective of the paper, which is to estimate future leakage rates.
13. In general: I am not convinced of the need for this paper. In lines 467-468, the authors state that “This paper demonstrates how the conflict between anthropogenic development and natural forces in the Dead Sea region has evolved with time.” However, this has already been demonstrated using historical data, as shown and mentioned by the authors themselves. The only contribution is to predict leakage rates from evaporation ponds for the next 20 years. I do not see how this is helpful, particularly since boundary conditions, weather patterns, pumping rates, etc… in the coming codes are unknown, and therefore the predicted leakage rates have a high degree of uncertainty. I would like the authors to a better rationale for the need of this modeling study, when historical data already shows the stated conflict.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Very nice and interesting work.

My only comment is that more references in the Introduction (literature review), concerning especially the methodological framework that is used in the paper (e.g. similar case studies), would be helpful to demonstrate its validity and impact. This is just a suggestion. The paper is OK even without it.

Author Response

Line numbering in the responses refers to the revised manuscript (when "all markup" of the "track changes" is selected in the "review" panel).

Reviewer 3 comment: My only comment is that more references in the Introduction (literature review), concerning especially the methodological framework that is used in the paper (e.g. similar case studies), would be helpful to demonstrate its validity and impact. This is just a suggestion. The paper is OK even without it.

Response: We have added references [5-7] to the Introduction, as suggested. These references demonstrate coexistence between man and natural hydrological systems due to research effort. Yet, we didn't find similar cases of leakage between two saline lakes having anthropogenic different levels.