Overview of the Chemical and Isotopic Investigations of the Mareza Springs and the Zeta River in Montenegro
Round 1
Reviewer 1 Report
Review of " Overview of chemical and isotopic investigations of Mareza springs and Zeta River in Montenegro", manuscript submitted to "Water" by Katarina Živković et al.
The research reported uses hydrochemical and isotopic data to characterize the Zeta river and the Mareza karstic aquifer. Together with isotopic data of precipitation (oxygen and hydrogen isotopes), the values obtained are used to model the dynamics of the aquifer (mean transit time and the fraction of young water), as well as the provenance of humidity feeding precipitation and the (characteristics of the) possible recharge area.
Overall, the research is well fundamented, and its results are interesting and of potential practical use, and as such the manuscript deserves to be published.
There are, however, some issues that I feel should be addressed by the authors before publication can proceed. Among these, there are two questions that worry me most:
On the one hand there is the amount of trust that can be placed on the data. The analyses done cover a very short time, corresponding to just one year. Particularly the precipitation data are very variable, and I wonder how representative are they of the longer-term precipitation in the area. The various water lines defined by the authors are probably only representative of the data used, and little more.
On the other hand, the choice of stations for sampling precipitation is probably not the best possible one. Along the text, the authors convincingly argue that the isotopic data of ground- and river-water point to recharge by precipitation falling at lower temperature, and therefore higher altitude. Using isotopic data of precipitation collected in the middle-lower course of the drainage network for modelling purposes is probably not the best choice, and I wonder how this influences the modelled values (in terms of transit time and the relative contribution of stored / new water to the discharge ...).
Other that the above fundamental questions, there are other minor ones that I have detailed below and marked on the text (see attached file), and that will also require an explanation. An, of course, there are some grammar and spelling questions (many corrected in the attached file; some others not) that the authors may want to consider.
Overall, I have enjoyed reading the manuscript; find it interesting and think that should be published after moderate revision.
Specific comments follow:
L 97.- Fig. 1: Figure 1 is of rather poor quality, and it could (and should) easily be improved, for example by an equal area image from Google Earth, or equivalent.
L 102-103.- "... sampling period (from February 2017 to March 2018)". Seems too little time, given the normal climatic variability at a local scale. Danger of lack of representativity, and therefore biased conclusions. A period of at least two years -ideally not less than three- would have been desirable to derive more trustworthy conclusions.
L 115-117.- There has to be something wrong here ...Annual precipitation of 1900-2150 mm was indicated above. Here, however precipitation amounts one order of magnitude lower "mean annual precipitation of 146.7 mm) are reported ... Values of mean annual precipitation in Fig. S1 are in the region of 100-200 mm. There has to be an error somewhere. IAEA-GNIP values for Dubrovnik are >1000 mm/year, so I suspect Fig. S1 is wrong ...
L 118.- Fig. 2: Further to my comment relative the representativity of the sampling period chosen, note that precipitation of March'17 is about 1/4 of that of March'18. This surely has an effect on isotopic composition. On Table S2, isotopic values of precipitation in March'17 are very different from those of Feb.'18 ... It seems evident that there are serious issues with the representativity of such a short sampling period ...
L 122-123.- I want to believe that the authors used rain gauges for collecting precipitation samples. The way this is written it could be understood that P1 is water from the Zeta river, and P2 water from the aquifer ... Please, state unequivocally!
L 125.- " ... from wells along both sides of the river ...". Ambiguous again: RU and RD are river water (free flowing) or are well waters? If samples were taken from wells, technically those are groundwaters!
L 165.- Is this value correct? 2pi/365 = 0.017214, and this is the value reported in ref. [38] (Rodgers et al.'2005)
L 175.- Table S3; Table S2 gives the values on precipitation.
L 207.- " The hardness (CV) ...". ?????? CV has not been defined before. What does it mean?
I can understand what a "conduit flow type" spring is, and the difference with diffusive flow springs, but these different types have not been identified and differentiated anywhere in the text.
In Table S1, "hardness" is given as mg/L of CaCO3. What is CV? Why its units are in %? Do you mean the "coefficient of variation? If so, where are the raw data?
From Drever (1997), "the hardness of a water is the concentration of ions in the water that will react with a sodium soap to precipitate an insoluble residue. It is usually reported as mg/L of equivalent CaCO3. From the atomic weights involved, eq. CaCO3 = 2.5 (mg Ca / L) + 4.1 (mg Mg / L).
Doing the appropriate calculations using the data of Table S1, the results do not correspond with those reported, particularly as it regards river waters.
Please check.
L 231-232.- Figure 7: If both figures share a common number ("Figure 7") there should be a single, common figure caption.
Most important for this figure and for others in the manuscript: We do not have the actual data plotted; in Fig S1 only average, max, min are given, so it is not possible to reproduce the plot, should it be needed.
L 234-235: Figure 8: One figure, one caption!
L 271-272: Figure 11: Same comment; one figure, one caption.
L 315.- Ref. [57] is the same reference than [38]
L 321.- Precipitation data are Table S2
L 325.- [23]: Is this the most adequate reference? I would have used the original definition instead (Craig, 1961; ref. [75])
L 332.- [61]: Hoefs is a general isotope textbook; very good, but again, probably not my reference of choice ... Works by Craig, Gat, Wassenaar, ... would perhaps be better suited. Even the book by Clark & Fritz, if you prefer a review, general book ...
L 348+.- Eq. (4): I would not stress much this relationship; with only one year of data, it is probably not representative ...
Figure 13: An "L" is missing in GMWL in Fig. 13
L 361.- Figure 14: The label of Y-axis is on top of the axis marks
L 363-365.- Can be rephrased!
L 378.- " ... with slightly lower mean d excess value for long term period of 12.2‰". How can you determine this, without longer-term data for Podgorica?
L 394.- "... Local Spring Water Line (LSWL) ...": LSWL is not labelled in Fig. 16, nor mentioned in the figure caption.
In any case, the basis for discussing spring and/or surface water lines should be properly argued. Personally, if at all, I would talk about correlation, but would be weary of "defining" new lines without a thorough discussion of the arguments in support of such a definition ...
... Particularly with so few data ...!
L 399.- Figure 15: It is not possible to individualize data from each spring
L 401.- Fig. 17: Figure 17 is not referred to in the text.
L 406-408.- Unsupported by data! Precipitation sampling ends in Feb.'18, so you cannot mention the period "Nov. - March". In the period Nov.'17 - Feb.'18 there is a trend towrds lower 18O values (Fig. 12), but Jan.'18 is obviously anomalous.
Comparing with the period March - May'17, you cannot state that precipitation was "heavy"; if anything, just the opposite. This is obviously more evident if you consider summer months ...
Confusing, to say the least!
L 414.- [75]: Do not understand the reason for citing Craig '61 here!
L 416.- " ... no isotope data for these streams is available". What sort of effect would the authors expect from these tributaries onto the isotopic results?
L 421-421+.- I insist on my preventions regarding definition of new "surface water" lines ...
In any case, what values have been used to define LSRWL? Rivers + Springs? On what theoretical grounds? What does such a line tell us?
An what about the statistics of the values used?
L 422-425.- No wonder! Mixture of Atlantic and Mediterranean air masses.
L 426.- Figure 20: Fig. 20 is not cited in the text. The choice of symbols does not allow easy individualization of analyses from individual springs.
The only difference with earlier figures is the inclusion of river data. Is that justified? What additional information do we gain from it?
L 427.- " Regarding the δ values leads to the conclusion ...": Rephrase
L 441.- 2Pi/365 = 0.017214
L 446.- Figure 21: There are obvious outliers in precipitation data. Has this been considered during modelization? Same observation applies to Fig. 22
L 462-463.- " The differences are attributed to the small intermittent tributaries": Reasonable, but unsupported by data.
L 658-660.- [57]: Is the same ref. than [38]
Supplementary material, Table S1: Hardness CaCO3 mg/L
Comments for author File: 
Comments.docx
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
This manuscript, entitled ‘Overview of chemical and isotopic investigations of Mareza springs and Zeta River in Montenegro’ aims to investigate the chemical and isotopic composition of Mareza springs and Zeta River and precipitation waters in Montenegro, West Balkans.
Water chemistry and stable isotopic composition (δ18O and δ2H) of monthly precipitation samples are presented, in order to determine the Local Meteoric Water line for the study area, and compare the behavior of Mareza karst springs and the Zeta river water. Based on them, the origin of and mean transit time of spring and river water were determined. The results may provide a good basis for future studies in the area as well as in similar hydrogeological systems.
It is an interesting paper, but a major revision is needed before its publication in Water.
General comments
All figures should be improved, in terms of axis titles.
A simplified geological / hydrogeological and a geomorphological map of the area should be presented in the manuscript as those settings are used for the interpretation of the results.
When presenting basic statistics instead of the original data ‘n’ should be included (this stands for the supplementary tables provided).
Comments
Line 42: Fissuring and high porosity lead to karstification of carbonate formations.
Line 42: Do you mean ‘…which promotes quick diffuse and restricted infiltration of water from the surface’ ?
Line 46-48: Due to the quick diffuse and the low water residence time, there is restricted infiltration of groundwater in a karstic aquifer.
Lines 66-69: It is not true that ‘In any area, groundwater chemical composition is unique because of typical isotopic and chemical fingerprint which the water obtained in processes such as soil/rock-water interaction during…’ The same composition may be resulted in any aquifer with analogues geology and lithology…
Line 125: Which samples came from ‘wells along both sides of the river’ ?
Lines 182-184: I don’t think that temperature data, alone, are enough for the statement ‘These results indicate a prolonged storage of major water mass in the aquifer and good homogenization; on the other hand, it points toward a distant water infiltration area with lower mean annual air temperature and higher altitude’
Line 192: There is no evidence presented, supporting the CO2 degassing during the warm period. In contrary HCO3 seems to be elevated in Zeta river water during that period (figure 6)
Line 215: Please remove ‘in limestones’. It is well known that dolomite is more robust than calcite to water dissolution.
Line 306: Please see my comment for lines 182-184.
Line 219: No evaporitic formations or minerals have been described in the bedrock in the relevant section.
Line 257: Replace ‘limestone rich’ either with ‘limestone’ or ‘calcite rich’.
Lines 262-263: The same stands for the EC.
Line 366 and throughout the manuscript including conclusions: Note that the study area of [71, ] Cruz-san et al. (1992) is Spain, just next to the Atlantic. Montenegro lays several thousand kilometers away at the NE Mediterranean and Alps and other mountain chains are in between. Only if you present meteorological data for such seasonal air movements you could convince the readers.
Author Response
Please, see the attachment to our response on comments and suggestion.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Second Review of " Overview of chemical and isotopic investigations of Mareza springs and Zeta River in Montenegro", manuscript submitted to "Water" by Katarina Živković et al.
The authos have largely considered the questions raised on a first review, and I am mostly satisfied with the result.
The main flaw of the manuscript remains, as it is not practical to enlarge the existing analytical database, due to the nature of the research performed, but I understand that the work reported is a useful initial step on wich to fundament future work, which is encouraged.
As far as the scientific content is concerned I believe that the manuscript should now be acceptable for publication.
However, there are a few details that the authors need to address before publication, including careful check of grammatical issues and additionally (line numbers relative to the revised, attached manuscript) ...:
L 98-99.- Fig. 2: Figure caption, and the heading of Table 1 should be separated in different lines.
L 113.- Should be Figure 3
L 146-148.- Consider the alternative text
L 152-153.- Common knowledge; delete!
L 174.- Might these be [42,43] as well? (by analogy with the original manuscript)
L 242-243.- Consider rewording
L 280-281.- Legend of Figure 7 and y-axis labels in the plots: The units of pCO2 are 10-x.x!!!
L312-313.- Figure 8 is not a dispersion (bivariate) diagram! The variables plotted are SO42+/Cl- ratio vs time!! Cannot refer to "correlation" (which has a statistical meaning), but rather variation, relationship, ...
L 364.- See comment
L 416.- See comment
Author Response
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Reviewer 2 Report
Authors have addressed my comments and suggestions and the manuscript has been improved since the original submission but I have still many doubts about the influence in water chemistry of Montenegro by air masses originating from the Atlantic Ocean. Please see my earlier comments. I think you could imply for an “Atlantic like isotopic signature”.
Furthermore please state to which papers/chapters of “IAEA Isotopic composition of precipitation in the Mediterranean Basin in relation to air circulation patterns and climate. IAEA-TECDOC-1453,2005,pp. 223” you are citing.
Author Response
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