Evaluation of the Groundwater and Irrigation Quality in the Zhuoshui River Alluvial Fan between Wet and Dry Seasons
Round 1
Reviewer 1 Report
It is very importanr to include a figure showing the location of the shallow aquifers and the 4 aquifers (a cross section for example), or at least a table with the depth location of each of the 4 aquifers.
Please check the attached pdf file for correction suggestions and comments.
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The collection of water quality data are valuable. To predict water quality as a response to wet and dry seasons hydrological simulations are required. Then time lag can be accounted for.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The paper by Chang et al. evaluates the groundwater quality of an alluvial fan area and discriminates the collected data between dry and wet seasons. First, this article needs a strong English edition. However, the main concern of this manuscript is that it refers to groundwater contamination with ammonia and nitrates; however, the levels of both compounds in groundwater are low. I think the authors may rewrite this part and discus why the low levels of nitrates are found in this agricultural area, whereas there are moderate levels of ammonia (maybe by the high recharge in the unconfined aquifer and non-direct recharge in the confined aquifers, or maybe to the reducing conditions in groundwater, or maybe the two processes are responsible….). Also, although the arsenic concentrations are very high, the authors did not try to explain these high Arsenic levels. Rainfall and surface water infiltration carrying organic matter from recently accumulated biomass may play a critical role in releasing arsenic and iron present in the sediments, due to the oxidation of organic matter consume high rates of dissolved oxygen, promoting the release of As due the reductive dissolution of Fe-oxyhydroxides (As is bound to these Fe-oxyhydroxides). Furthermore, this may explain the low concentrations of dissolved oxygen found in groundwater and also may help to explain the low levels of nitrates (there is little nitrification in a reducing environment). Please read:
Saha et al., 2010. Evaluation of hydrogeochemical processes in arsenic-contaminated alluvial aquifers in parts of Mid-Ganga Basin, Bihar, Eastern India
Other specific issues are:
A correlation analysis between variables (maybe Pearson) may help to explain some processes occurring in groundwater, which also may elucidate the concentration values of some variables in groundwater
Why the dissolved oxygen concentrations are very low? (because reducing conditions???) What factor promotes this condition???
What is the meaning of the error bars in all the Figures?
Please report de ammonia nitrogen as NH4+ in all the manuscript (including tables). There are several mistakes such as NH3+ (This is not an ion, is a neutral molecule).
The analytical procedure for the measurements of major ions and TOC should be described
Line 16: Eliminate the Word “Area”
Line 32: “whereas aquifer 2 is less affected” instead “and aquifer 2 are less affected”
Line 34: “could represent a risk” instead “could be risk”
Line 46 “the Water Resource Agency (WRA)”
Line 70: “The National Chiao”
Line 72: “the WRA” instead “the Water Resource Agency”
Line 80: 2, 6 and 30 hours correspond to ??????????
Line 80: Where is the subject in this sentence (In consequently, showing that the deeper)???
Line 82: “analysis showed that” instead “analysis to show that”
Line 90-91: , and also the groundwater quality may be affected
Line 94: “Owing to” instead “with”
Line 97: “groundwater quality in the” instead “groundwater quality data in the”
Line 99: “were” instead “was”
Line 104: “covers” instead “with”
Line 124: “surface water cannot recharge deeper” instead “surface water cannot be easily recharged to deeper”
Line 127: “clay is larger” instead “clay larger”
Line 129: “was” instead “were”
Line 130 “affected” instead “affect”
Line 152 “such as chloride” instead “of chloride”
Line 179 “and” instead “or”
Line 183: Where is the verb in this sentence (spatial and temporal distribution of uneven rainfall in Taiwan due to global climate)???
Why are negative values in the groundwater table levels? (Table 1)
209 – 210. It is important to comment that As concentrations are higher that the guideline value of 0.010 mg/L for safe drinking water proposed by the World Health Organization
Lines 254 – 257. I believe this explanation of the Dissolved Oxygen levels in groundwater is not right. Confined aquifers may have low dissolved oxygen values because there is not a direct recharge from rainfall to groundwater!
Lines 272 – 273. It would be useful if the authors use references for other countries rather than China. For example, the authors may introduce the high As levels in groundwater as follow: “As other worldwide areas [References], the coastal zone of the Zhuoshui River alluvial fan is an area with high arsenic content in groundwater”
Examples of recent papers describing worldwide areas with high Arsenic content are (the authos may cite these papers):
In México:
Mora et al., 2021. Mapping salinization and trace element abundance (including As and other metalloids) in the groundwater of north-central Mexico using a double-clustering approach. Water Research 205, 117709
In Bangladesh:
Mihajlov et al., 2020. Arsenic contamination of Bangladesh aquifers exacerbated by clay layers. Nature communications 11 (1), 1-9
In Europe:
Banning A. 2021. Geogenic arsenic and uranium in Germany: Large-scale distribution control in sediments and groundwater
Journal of Hazardous Materials 405, 124186
Line 293: “two times higher than”
Lines 296 – 302. I cannot see that the values of nitrate and ammonia indicate groundwater contamination. In fact, the nitrate concentrations are very low (the threshold value of natural nitrate concentrations is 3 mg/L). Therefore, it is not common these low nitrate concentrations in an agricultural area. The authors may discuss this indicating that the recharge in the unconfined aquifer is high (because there are no high seasonal variations). Thus, the high recharge may dilute the nitrate levels until values of 1.4 mg/L. On the other hand, confined aquifers may not show nitrate contamination because there is no a direct recharge coming from surface waters.
Lines 303-305. Similarly. I can not see in Fig. 5 that the ammonia levels exceed the Taiwan standard of 3 mg/L. The mean values of ammonia showed in this Figure are 2.2 and 1.9 for aquifer 1 and 1.1 and 1.3 for aquifer 2
Lines 331 – 333. This is the same that that written in lines 48 – 50. Please delete this….
Line 347: “were be”????? This paper needs a strong English edition…..
Line 273. I can not see high nitrate concentrations…
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Review of version 2 by Peter Klint Jensen
Evaluation on the groundwater and irrigation quality in the Zhuoshui River alluvial fan between wet and dry season
Tawei Chang et al.
New summary
Ground- and irrigation water quality of the Zhuoshui River alluvial fan is of mayor importance for domestic water supply and irrigation water. The challenge is the violation of water quality standards valid in Taiwan due to seasonal or future climatic changes. Water quality data in many wells have been collected. The data are grouped with respect to four groundwater reservoirs in the alluvial fan. The authors find that the long-term groundwater level is not significantly affected by hydrological conditions. Except for groundwater temperature, bicarbonate and TOC, other groundwater quality parameters are not affected either. The parameters “wet” and “dry” seasons can therefore not be used to predict the water quality. It is concluded that the long-term groundwater level is a more usable quality predictor. The authors provide recommendations on the choice of reservoirs for groundwater exploitation.
General remarks:
The second version of the paper presents the analysis clearly to the reader. The results are important for future planning of water exploitation with regards to the health of the population.
Abstract
No comments.
- Introduction
56: ”Hsu (2018) [4] indicated … ” Please revise the English language.
88: Previous conclusions on the relation between precipitation and water quality appear to be contradictory. Please indicate here that this paper offers a new look on the subject.
- Materials
123: “The aquitard 1 is located under the aquifer 1” Please correct 1.
- Results
262: “Figure 2” Please explain the difference between the superscripts a and b. Some of the uncertainty bars are placed above the columns. Please place them correctly. The same in fig. 3, 4, 5, 6, 7, and 8.
268: “Surface water..” This sentence is too long.
226: Please help the reader by explaining the meaning of ORP, DO ….
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
The paper has been improved. I recommend publication after the following mistakes are corrected:
Line 81 using
Line 117 There are
Line 124 recharge the deeper
Line 157 groundwater quality data include
Line 160 include iron
Line 161 coliforms
Line 201 analyzed using a TOC analyzer
Line 207 which include
Line 211 show
Line 212 pollutants of more public concern in groundwater
Line 213 show
Line 214 “between” instead of “of”
Line 215 “for” instead of “of”
Line 219 higher than the guideline
Line 291 recommended by de World…
Line 223 groundwater has been used
Line 233 risk for public health
Figures 2 and 9 captions …..statistical results
Line 270 dry season are higher levels than those found during the wet season
Line 273 there are no significant differences in the dissolved oxygen and redox potential levels between wet and dry seasons
Line 280 aforementioned behavior in
Line 299 The infiltration of organic matter during rainfall….
Line 301 the release of
Line 304 statistical
Line 313 areas using groundwater of aquifer
Line 344 of both aquifers
Line 346 parameters such as groundwater temperature
Line 366 landscape is
Lines 369 -370 Owing to the
Lines 372 “they also affect” instead of “which also affects”
Line 381 “has” instead of “have”
Caption figure 6 and 9…….in both aquifers
Line 389 nutrient elements
Line 397 Consequently, the use of groundwater
Line 399 public health
Line 399 dry season
Line 405 area, application
Line 450 except for the major ions, aquifer 1 is
Author Response
The authors thank reviewer’s comments on our manuscript. All correction suggestions have revised according to reviewer’s comments.
