Seasonal Groundwater Recharge Characterization Using Time-Lapse Electrical Resistivity Tomography in the Thepkasattri Watershed on Phuket Island, Thailand
Round 1
Reviewer 1 Report
I recommend the authors for a well-written interesting article that provides an example of an application of ERT for seasonal groundwater recharge discussion in a watershed in Thailand, which allows identification of recharge zones. The study provides an interesting case study that may be useful in many other areas for detecting recharge mechanisms.
Please go carefully through my comments below, some of them are minor editorial comments, but some more substantial comments are also included.
Page 1
- Title: Change to “in the Thepkasattri Watershed”
- Line 14: delete ‘very’
- Line 17: The objective of this study ‘was’
- LIne 19: delete ‘by’
- Line 21: ‘showed’ – use past tense for study description, please check throughout
- Line 25/26: ‘preferential groundwate recharge zones’ and ‘groundwater discharge zone’, to be specific
Page 2
- Line 54: Be specific: ‘Descloitres et al. [5] selected an’. Also please add the study location (Country, climate)
- Line 57: add country and climate (Panama?).
- Line 60: ‘to characterize the Dry Creek watershed,…”
- Line 61-63: Reformulate. Better to not use significant – or did they find a statistically significant relationship between? Then say that. ‘Therefore, it might be possible to identify infiltration pathways in base rocks …’/
- Line 66: ‘water movement in the vadose zone’
- Line 68: ‘On Phuket Island in Thailand’
- Line 73: ‘in the Thepkasattri watershed’
- Line 72 – 76: Please state the objectives of the study here clearly, or formulate as research questions. It is in the sentence but needs to be more clearly formulated.
- Line 80: Please convert both areas to km2
- Line 81: Which ‘both mountains’? Maybe ‘from the surrounding mountain slopes’?
- Line 83: ‘and form two main streams’
Page 3:
- Figure: Label the 3 maps with (a), (b), and (c) and refer to the maps in the caption, instead of referring to ‘left hand side figure’ and ‘lower right’
- Line 88: ‘Geologically, …’
- Line 91: ‘by an unconfined aquifer’; ‘the aquifer is further divided into’
- Line 95 and Figure 2: Is it possible to draw a more complete geological cross – section? Is there more well log data available? At least a sketch across the two watersheds would be helpful. I see that this was developed as part of the study later on…
- Line 96: ‘potential aquifer? Better to just say ‘aquifer’ or formulate more clearly
- Line 99: ‘which were computed’ (data are plural)
- Line 103/104: ‘during the dry season’, ‘during the wet season’
- Line 104: scanty? Replace with ‘scarce’
- Line 105: groundwater flow direction is not visible in figure.
Page 4:
- Figure 2: Please show both figures based relative to the same elevation, then the differences etc become more obvious.
- Line 111/112: is this mean total monthly rainfall? Over which period was this mean calculated? Also please add the period over which the mean total annual rainfall was calculated.
- Line 119: Please explain what you mean with a ‘Werner array’
- Line 121: ‘are given’
- Table 1: Please add year and days of surveying. How long did one survey take?
- Line 127/128: Please round up to no decimal figures, there is likely too much uncertainty to show that. Again, add the period over which the average was taken.
Page 5
- Line 128: This is not a trend but a seasonal rainfall variability.
- Figure 3: Mean total monthly rainfall? Over which period? Also, be consistent with calling it rainfall or precipitation. Can use rainfall here, as there is no snowfall (precip includes both). Change y-axis label to Rainfall.
- Line 133: The data from the
- Line 139: I think it is better to not call the wet season data ‘monitoring dataset’ as both wet and dry season data are monitoring data. Just keep it with ‘wet season data’ maybe? Or choose other label.
- Line 143: ‘at different years:’
- Line 144: …’by the Department of Groundwater Resources (DGR) in 2007 but stopped functioning in 2016, while the second piezometer was installed by … at the College of Disaster Prevention and Mitigation … . ‘
- Line 148: Do the two small streams have names? Might be easier to refer to them by name…
- Line 149: data are plural – please check throughout the article.
- Line 151: through pumping?
- Line 152/153: This statement is not true – water level fluctuations can be influenced strongly by nearby pumping, so it is indeed very difficult to conclude from one well over a large spatial area… Maybe if there was no pumping at all in the aquifer, but according to the description, the aquifer is well pumped. Please reformulate / delete sentence.
- Line 155: Again, this is not a ‘trend’ but a seasonal pattern or fluctuation.
- Line 156: Please ensure again that all is written in past tense – this was observed in the past over the study period, this is not a general statement. Please ensure throughout article that the correct tense is used.
Page 6:
- Figure 4: Need to add legend for the figure. Increase size of axis labels, hardly readable. Figure caption: Needs more information. Which well, which dates, where was precipitation measured. Need to add precipitation station location to map in Figure 1. Was it in the watersheds? Also need to reformulate the sentence, delete ‘data wise’
- Figure 5: need to add a, b, c to the figures. And if there is space, even the month label – that makes it easier to read. What is meant with the ‘resistivity log’ (red arrow)? Was it not logged all along the line?
- Line 165: add ‘(low resistivity)’
- Line 166: ‘In the March tomography’, ‘does not’, ‘indicated’ (not demarcated)
- Line 170: ‘beginning of the profile (0m)…’
- Line 175 – 180: Please clarify this paragraph.
- Line 187. Add ‘(medium resistivity)’
Page 7:
- Line 194: So the rainfall / groundwater level measurements are not from the same year as the tomography? Please be specific here, and need to add dates. Need to discuss if not the same years (how were the years different in terms of rainfall and seasonality??). On that note, it needs also be mentioned in the methods section, how the year of the survey compared to other years. Was it a relatively dry or wet year in comparison to the mean? The total annual rainfall given for the study year. Also in Figure 3, the monthly total rainfall for the study year should be added as line. This will help to understand the study years in context.
- Figure 6: See comments for Figure 5, same apply here, also relating to the figure caption and legend. There needs to be consistency between the figures too, please show either daily or monthly rainfall in both figures. I prefer monthly totals, as it is easier to see the seasonal change. Again, dates and locations need to be added to caption.
- Line 197: This is not clear from Figure 6. Either show a linear correlation figure, or remove this sentence.
Page 9
- Figure 8. Add a, b to figures. Refer to Figure 8 in previous figures where a ‘log’ is mentioned. Refer in Figure 8 back to the figures where the location of the log is indicated. What do you mean by active zone? Is that the soil + aquifer? Define in caption..
- Line 240: ‘The use of resistivity logs’. Define active zones (ie active water movement throughout the seasons?)
- Table 2: Define RMS in caption.Add full date (day, month, year)
Page 10: add a,b, to figure. Define RMS in caption.
- Line 264: ‘there are’
Page 12:
- Figure 10 appears very sudden (ensure in final layout that the figure appears below the first mentioning). But still – after the announcement in the abstract, I expected a sub-section where the hydrogeological profile is presented. It should be added to a new sub-section, where it is described. In the methods section, there is also need for a method sub-section on how this hydrogeological model was developed. Which well data were incorporated? What kind of elevation data were used? What tool/software was used? Also I don't think it can be called ‘ hydrogeological model’. This associates a numerical flow model. This is a sketch / hydrogeological cross-section, or a conceptual hydrogeological model. It would have been helpful to have a similar sketch already earlier in the method section, but I realize that the analysis was needed to develop this. Maybe refer in the method geological layer description to this already? So that the reader knows, he can peak ahead if he needs to gain understanding of the hydrogeology. This section also needs much more reference to literature. Is there any other information on the local hydrogeology?
- There is also a need for a small paragraph / two sentences that round the section and discussion up before moving to the conclusion (probably as part of the recommended hydrogeology section).
- In general, it is recommended that some more case studies and literature is incorporated to set the study in perspective. There is some discussion in the introduction, but it would be needed to have some more in the results/discussion section.
- In the conclusions, there is also a caution mentioned. This is mentioned in the results/discussion section for the data specifically, but should be more discussed in relation to the usability of this technique (expanding on lines 342-344 in the results/discussion section) and mentioning literature that discusses the challenges of this technology.
- Also, do not end the conclusions on this ‘negative’ note – if you discuss this aspect in more detail during the discussion, you can mention it just briefly further up in the conclusion. And conclude with a more summarizing and also forward-looking sentence that ties back to your introduction.
- Overall, please include more references.
Author Response
Thank you very much for the comments and suggestion; it helps a lot on improving the quality of the manuscript.
Please find attached the response for each comment and suggestion in the attached file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This study explores groundwater recharge characterization using Time-Lapse ERT, it is important to identify the ground water response from precipitation, it was great concern in the world. However, some revision was necessary, followings are some comments for consideration. (1)The highlights or new ideas did authors present in this research were not very clear, the author just say “no one has addressed the application of time-lapse ERT on two geologically contrasting vadose zones”, is novelty and originality in this study? What’s difference from other studies used two time-lapse ERT on geologically contrasting vadose zones? needs to be emphasized in “introduction”. (2)Line 46, not all of readers know the “time-lapse ERT”, well, please provide the more detail in this section or in “Materials and Methods” . (3)Line 40, provide the cited reference (4)Line 111-113, the “mean value”, how many years (5)The “discussion” was not enough, added more discussion, the author should make a comparison with other studies at least (6)Line 339-340, “…depends on the climatic condition of the study area”., this study just investigate “precipitation ”, no other climatic factors were involved. . (7)Line 340-344, please add more information in “discussion”, I think the readers was interesting to this point.Author Response
Thank you very much for the comments and suggestion; it helps a lot on improving the quality of the manuscript.
Please find attached the response for each comment and suggestion in the attached file.
Author Response File: Author Response.pdf
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
This paper explains that the time-lapse ERT method is used to study the recharge of groundwater in the valley with relatively simple hydrogeological conditions. The problems of this paper are as follows:
1. This paper is only an application of ERT geophysical exploration method to groundwater recharge research. The similar work in this field has been studied for decades, the manuscript is not innovative.
2. The description of hydrogeological conditions is too simple, and basic information such as the overall regional flow field and groundwater level dynamics are not provided;
3. Many conclusions of the manuscript are based on the guesses of geophysical exploration images only, rather than a rigorous scientific inference;
4. The standardization of scientific writing of papers needs to be strengthened.
5. For other specific suggestions, please refer to the manuscript.
Comments for author File: Comments.pdf
