Regional Hydrogeochemical Evolution of Groundwater in the Ring of Cenotes, Yucatán (Mexico): An Inverse Modelling Approach

Round 1

Reviewer 1 Report

The paper "Groundwater Quality Evolution Model in the Ring of Cenotes, Yucatan, Mexico" by Pérez-Ceballos and coauthors is very interesting and I enjoyed reading it, but need some minor changes before being accepted. Although the study is not novel, the authors apply classical methodologies to determine the aquifer hydrochemistry in an area where it had not been used until now. The study area, the Ring of Cenotes, is very interesting for international readers because support several water bodies which were designated as RAMSAR sites. Therefore, the aquifer is very vulnerable so studies like this one will allow us to better understand its characteristics in order to improve the management of the water resources in the region. Perhaps the main weakness of the study is the lack of a better description of the aquifer geology, which I consider very important in order to understand the hydrochemical aspects that are cited throughout the study. Finally, I strongly recommend to change the ms title to better reflect the content of the study: Regional hydrogeochemical evolution of groundwater in the Ring of Cenotes, Yucatán (Mexico): an inverse modelling approach.

Specific comments:

L92: Missed Fig. 1

L97: From May to August instead of during May to August

L98: May is dry instead May is drought

L110: It is not necessary use see (18,27-30)

L111-L112: What kind of carbonate rocks?

L112. Rocks from the Oligocene need a lithological description

L114-115: Something missed in the parenthesis. Perhaps Fig1?

L115-116: Something missed

L117: RC, near the…

L118: It must be described the hydrogeochemistry characteristics of Region 2

L119: RC, characterized by…

L120: show that calcite instead of shows

L121: RC, and

L122: and seawater instead of and with seawater

L124-125: It is necessary to describe the characteristics of the Eocene aquifer in order to justify this affirmation. Are there gypsums in the Eocene carbonates? Which and how is the influence of dolomite in the sulfate enrichment?

L128: Icaiche formation and Chicchancanab lagoon are not described previously and it doesn’t appear in Fig 1.

L110-L128: geology is not well described, and it affects to the hydrogeochemistry understanding.

L134: during four periods, instead of during the four seasons. Only spring, autumn and winter are represented in the sampling

L145: Evolutionary trajectories? It is better only Trajectories

L146-147: the same. It is not clear the idea of evolution trajectories (why evolution?) Trajectories don’t evolve, water characteristics evolve

L155: SI means instead of mean

L164: surficial minerals? I don’t understand the meaning of surficial in this sentence

L165-166: Revise reactions; unify H₂CO₃ in (2) and (3) and L166

L167-170: Revise sentence

L169: …minerals over their trajectories?: minerals don’t move

L176: estimated? Instead of estimates?

L180: (a) from where? (b) from where?

L181-182: indicate recharge region in Fig.1

L184-185: again evolution trajectories

Figure 2: I don’t understand this figure. Water composition is the same in the four areas. Which is the sense of this figure?

L203: it would be interesting to describe the hydrogeochemical facies in each area. For example using Stiff diagrams into a map

L211: Fig 3d must be explained due to its difference respect 3a, 3b and 3c

L211: R-MD is not in figure 3

L212: Its is convenient beginning another paragraph for Saturation index

Figure 3: c) SP3; it doesn’t appear MD in the graphs; It is necessary to explain in the text the differences in the d) graph, which is clearly different than a), b) and c) tendencies (probably due to meteorological reasons as you explain latter?)

Figure 4: d) Percentage instead of The percentage;

L241-242: rSO₄/rCl ratio in contrast to rCl showed

Figure 5: Hydrogeochemical evolution along trajectories; the same as figure 3 (It is necessary to explain in the text the differences in the d) graph, which is clearly different than a), b) and c) tendencies)

L286: …except SP4 where… Why?

L297: dolomitization is not the dolomite precipitation but the transformation of calcite in dolomite.

L297: was mainly due instead of was due mainly?

L298: available in the ground? I think it is better to use in the rocks

L301-306: it is necessary to improve the lithological description of each segment to understand the interpretation

L311: Groundwater at the RC…instead of The RC…;  tendencies instead of evolutions;

L313: (R-MD-D), which were suggested, instead of

(R-MD-D). These ….evolutions were suggested

L315-316: I suggest: Celestium trajectory, from the recharge area to the cost, showed an increase of sulfates associated to the dissolution of gypsum from the Eocene aquifer, also likely.

L327: dolomite precipitation (dolomitization): see L297

L331-341: you must explain the influence of seasons more than the influence of sampling periods. Taking into account figures 3d and 5d

L350-351: are you sure that 0.5 is a good correlation?

L359: R²>0.5 (Not in gypsum: 0.466)

Figure 9, L367: with rainfall instead of the rainfall?

L384: meteorological tides (they haven’t been studied in this paper)

L389-390: Better: …(cenotes 17 and 19) and in R-MD (cenotes 10 to 16) located at 20 km and 30 to 62 km respectively from the Dzilan Bravo’s shoreline.

L393: space between Ticul, and

L393-394: agricultural practices in the area likely also contribute to the increasing of sulfates concentration: please, explain why and how.

L401: analyses,

L409: two different trajectories with different evolution

L413-414: The marine intrusion influences (without there)

L418: with rainfall instead of with the rainfall

L420: sampling (SP4)

L422: is possibly instead of in possibly

L421-424: it requires a better explanation

Author Response

Dear Reviewer 1,

We thank for your generous comments on our manuscript. We have edited the manuscript to address your concerns.

We consider that the title you proposed, “Regional hydrogeochemical evolution of groundwater in the Ring of Cenotes, Yucatán (Mexico): an inverse modelling approach”, is adequate and fits much better the ideas of the manuscript.

In general, we added a paragraph to explain in a better way the geology of the Yucatan peninsula and a more detailed explanation of the halocline. Additionally, as suggested, we included the significance value of the correlation analysis between rainfall and the percentage of seawater towards Dzilam. The discussion and conclusions of the manuscript were also revised and improved.

We improved figures 1, 3, and 8. In figure 1, we added the midpoint of the modeling and the direction of the underground flow. In figure 3 we added MD that was missing. Figure 2 was replaced by another figure where the halocline is shown in the recharge and coastal zone.

Thank you very much for your comments that were very valuable to improve the manuscript.

Sincerely,

Rosela Pérez-Ceballos, PhD.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear Authors,

I read your manuscript with interest, being Yucatan one of the most amazing karst area in the World. My comments deal with some point which, in my opinion, needs revision in order to improve quality and clarity in exposing results.

I'm not a native english, so I apologize you for my concise and maybe rough expressions.

One of the most critical point of this manuscript is not considering the sampling distance from the halocline as a factor which can affect the seawater contamination without a real chemical evolution of the water directed towards the coast.

Furthermore, some results need more discussion. For example: how do you explain the chemical differences in the R samples collected in the same aquifer in the recharge zone?

English needs attention and possibly a revision by a mother tongue.

After revision, abstract and conclusion should be rewritten accordingly.

 

Here are some items which in my opinion require revision.

Lines 44-40 - It is important to consider the role of coastal dynamics and in particular of the sea level variations during the Quaternary in the evolution of karst aquifer and their effects on present flow pattern.

Line 47 - The fractures are not produced by weathering phenomena, but by tectonics and stress release. Chemical alteration only causes their enlargement. To be corrected.

Lines 51-52 - I think it is necessary to explain briefly how an impact structure of 66 Ma ago can morphologically affect landforms developed in Eocene-Miocene rocks, which are much younger.

Lines 60-62 – It looks like an anticipation of the results.

Lines 62-63 – Is the depth of halocline known? If yes, please discuss this point.

Line 94 - I would provide some information on the hydraulic gradient instead of defining it generically “flat”. What is the elevation asl of the water table in the sinkholes intercepting the groundwater?

Line 98 - I suggest "from June to October" instead of "between Jun and October".

Lines 99-100 – I suggest citing the source of the rainfall data.

Line 112 - Which kind of rock is the Oligocene formation?

Figure 1 - The symbol of what I believe to be faults and/or lineaments is missing in the legend. A sketch, vertically exaggerated profile from recharge area to coasts (towards C and D) along sampling sites could improve the comprehension of the hydrodynamic setting. I suggest adding it to the figure.

Line 133 - 22 sinkholes are indicated in the figure 1, not 18.

Line 134 - The periods indicated are not properly "the four seasons", summer is lacking. I suggest writing “for four different periods within a year”.

Lines 139-140 - Is there any data on the thickness of the freshwater lens? The distance of analyzed samples from the halocline can significantly vary going towards the coast, mainly in the area closest to coastline, and this distance can influence any phenomena of contamination by marine waters.

Table 1 - Due to the uncertainty of the analytical methods, two decimals look excessive for the temperature and for most of the main chemical components. I suggest inserting only one decimal number.

Lines 188-190 - Significant averages cannot be obtained from 3-4 measurements unless the standard deviation is very small. I suggest discussing the statistical significance of the average concentrations in Table 1 and, if possible, adding all analytical data as supplementary materials.

Lines 206-208 - Could the increase of chloride be due to a reduction in the thickness of the freshwater lens above the halocline? Please, consider this possibility in the discussion section.

Lines 209-210 – An increasing of chlorides in the D samples occurs also in 3d diagram.

Figure 3 – There is something wrong in diagram 3a. The arrow from MC to C indicate a loss of SO4, not of Ca. Please correct. Arrows shoving chemical evolution must be parallel to one of the sides of the triangle.

Lines 209-211 - Figure 3 maybe requires more description.

Figure 7 – Are rainfalls related to sampling periods? Please describe how rainfall averages have been obtained.

Lines 315-316 – I am not sure understanding well, but there is not an increasing of sulfates from MC towards the coast related to seawater mixing; Fig. 3 show a decrease of SO4.

Lines 336-341 – This point should be furtherly discussed. Is quite surprising that sulfates increase significantly during SP4 at Dzilam Bravo but not at the recharge zone and at Celestum, where during SP4 rainfalls are lower (see. fig. 7)

Lines 345-350 - It is not clear to me which rainfalls values are considered. Figure 7 and figure 8 show average rainfalls without specifying whether it is a multi-year average, or a spatial average based on data from several stations. Please explain better in the text. A different estimate of rainfall could change significantly the R2 indexes in figs. 8 and 9.

Lines 353-354 – What does it mean “rainfall previous to SP1, SP2...? Previous what? Which period you consider before field sampling? Please clarify this matter in the text.

Lines 373-376 – The effect of different confinement extension on sea water contamination requires more discussion and preferentially a sketch figure showing the geometry of aquifers and hydraulic heads in the coastal sectors.

Line 422 – I guess “is” instead of “in”.

 

Author Response

Dear Reviewer 2,

We thank for your generous comments on our manuscript. We have edited the manuscript to address your concerns.

We consider that the title proposed, “Regional hydrogeochemical evolution of groundwater in the Ring of Cenotes, Yucatán (Mexico): an inverse modelling approach”, is adequate and fits much better the ideas of the manuscript.

In general, we added a paragraph to explain in a better way the geology of the Yucatan peninsula and a more detailed explanation of the halocline. Additionally, as suggested, we included the significance value of the correlation analysis between rainfall and the percentage of seawater towards Dzilam. The discussion and conclusions of the manuscript were also revised and improved.

We improved figures 1, 3, and 8. In figure 1, we added the midpoint of the modeling and the direction of the underground flow. In figure 3 we added MD that was missing. Figure 2 was replaced by another figure where the halocline is shown in the recharge and coastal zone.

Thank you very much for your comments that were very valuable to improve the manuscript.

Sincerely,

Rosela Pérez-Ceballos, PhD.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors present a groundwater quality evolution model in the Ring of Cenotes in Mexico. They present some modelling results based on very old data of regional scale. In the opinion of the reviewer, much more interesting would be to compare historic and current models. Majority of results were of good agreement with literature data and this is why they do not bring significant novelty. How many sinkholes were analyzed: 18 (from the text) or 22 (from Figure 1)? It should be clarified. There are some little corrections in the text which should be changed:

1. page 3, line 98, is Jun should be June
2. a dot in Eq. 3 and 4 after the bracket is not necessary
3. unit mg L-1 in Table 1 for NO3- should be below the NO3-
4. page 6, line 194 and other pages (line 212-213, 215) what is the meaning of y between Fig.1 and Fig.2 for example?
5. the description below Figure 3: SP3 is missing
6. It is not so clear if ternary diagrams were prepared based on concentrations or equivalents
7. please indicate and discuss the critical value of R2 for 4 measurements (p=0.05). It is not a proof for statistical significance when R2>0.5 only. The overall discussion concerning correlations should be verified according to the critical values of R. 
8. Was Pearson's or Spearman's correlation coefficient used to determine R2? Were there any limitations for using Pearson's or Spearman's correlation coefficient checked (i.e. data normality).

 

Author Response

Dear Reviewer 3,

We thank for your generous comments on our manuscript. We have edited the manuscript to address your concerns.

We consider that the title proposed, “Regional hydrogeochemical evolution of groundwater in the Ring of Cenotes, Yucatán (Mexico): an inverse modelling approach”, is adequate and fits much better the ideas of the manuscript.

In general, we added a paragraph to explain in a better way the geology of the Yucatan peninsula and a more detailed explanation of the halocline. Additionally, as suggested, we included the significance value of the correlation analysis between rainfall and the percentage of seawater towards Dzilam. The discussion and conclusions of the manuscript were also revised and improved.

We improved figures 1, 3, and 8. In figure 1, we added the midpoint of the modeling and the direction of the underground flow. In figure 3 we added MD that was missing. Figure 2 was replaced by another figure where the halocline is shown in the recharge and coastal zone.

Thank you very much for your comments that were very valuable to improve the manuscript.

Sincerely,

Rosela Pérez-Ceballos, PhD.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Dear Authors,

I read your manuscript with attention and I found it was significantly improved respect to previous version.

Despite this, in my opinion, some changes and corrections are still necessary before the paper can be accepted for publication.

English language and style is not yet quite satisfying. English is not my first language but I have done some corrections that you could consider in order to make the text more clear and readable. I found several unnecessary repetitions, for example regarding the location of study site.

Here is some major remarks.

Table 1 could be better placed in the Resuts section.

In Fig. 3, blue arrows indicate also a decreasing trend of sulfate, not always a gain. You should insert a thrird arrow with different color in the legend and in the diagrams.

Fig. 9 is not discussed in the text and it could be removed from the manuscript.

Several minor corrections and comments are in the pdf as annotations.

Best regards

Comments for author File: Comments.pdf

Author Response

Dear Reviewer 2,

Thank you for providing valuable feedback that helped to improve our manuscript.

Sincerely,

Rosela Pérez-Ceballos, PhD.

Author Response File: Author Response.pdf

Reviewer 3 Report

Presented explanations are satisfactory.

Author Response

Dear Reviewer 3,

Thank you for providing valuable feedback that helped to improve our manuscript.

Sincerely,

Rosela Pérez-Ceballos, PhD.