Assessment of Empirical Methods for Estimating Reference Evapotranspiration in Different Climatic Zones of Bosnia and Herzegovina

Round 1

Reviewer 1 Report (New Reviewer)

The article “Assessment of empirical methods for estimating of reference evapotranspiration in different climatic zones of Bosnia and 3 Herzegovina” presents a consistent and well-defined analysis of ETo estimates regarding the evaluated models, however, some doubts need to be better clarified, to facilitate understanding.

- Do meteorological stations measure global radiation (Rs)? If they do, why make the estimates (gap-filling)? And why apply correction factors, since surface measurements would consider the astronomical, geographic and atmospheric effects of each location?

- Insert the percentages of daily failures (when there is not enough data to estimate ETo by PMF – Tar, Ur, Rs and Vento) in Table 1. Present the procedures/methodologies for filling these failures.

- In Table 2, explain the measurement units: n “insolation” is the annual or monthly sum? Are “u” measured at 10.0 m or already projected at a height of 2.0 m? Are “P” and “ETo” monthly or annual sums?

- The method evaluated in 2.3.3 is unnecessary, as the original HS method (2.3.2) and its local calibrations for each station (2.3.4) are already evaluated.

- As a suggestion, other simplified methods that may present good results for the region could be evaluated: Turc (1961), Hansen (1984), Holdrige (1959), Makkink (1957), Linacre (1977) and Romanenko (1961), among others.

- The biggest limitations for applying PMF in the estimation of ETo are the measures of winds, radiation, humidity and temperature (in this sequence). In this way, the authors, however, propose other simplifications of the PMF method, for example: using a standard wind speed or a standard solar radiation (Rs), both obtained based on the averages of the climatic regions. This would allow analyzing whether these possibilities would also present good results.

- The topic of Statistical evaluation of the method's performance is very interesting and consistent.

- Are the coefficients in Table 3 applied even to the measured Global Solar Radiation (Rs)? If so, provide justification.

- Figure 4, legend identification is not in English;

- Insert a map with the spatial distribution of ETo by PMF and another with the difference of the best simplified method (delta ETo)

Author Response

Dear Reviewer 1, we found your comment valuable and much appreciated, helping us to improve the manuscript and we are thankful for all useful comments and advices provided. The manuscript has been changed according to the suggestion.

• Meteorological stations in Bosnia and Herzegovina (BiH) only measure the duration of sunshine (n) using Campbell-Stokes heliograph. This means that they do not directly measure global solar radiation (Rs). However, it is possible to calculate Rs from n using the formulas proposed by the Food and Agriculture Organization of the United Nations (FAO) in their publication FAO 56. In this manuscript, two formulas are used to calculate Rs, the Angstrom formula and the Hargreaves formula. The Hargreaves formula was used when n was not measured, which is the case for first period of observation. Table 2 shows meteorological stations in BiH that had n measurements. During the second observation period (2018-2022), all analyzed stations had n measurements. Therefore, we corrected all calculated Rs values, as explained in lines 410-445.
• The percentage of the daily failures is given in Table 3. Please find procedures for filing these failures in lines 350-445.
• In the revised version of the manuscript, we added units’ explanation. Please find it in lines 286-292.
• Method evaluated under 2.3.3. is Trajkovic’s method and it should be mentioned because it is widely used and recognized. In his adaptation of original Hargreaves-Samani method (HS) he obtained a unique exponent of 0.424 which showed excellent applicability on territory of Serbia. Therefore, this method is cited in chapter 2.3.3.
• Thank you very much for suggesting for other empirical methods that we could use in our research. We are familiar with many of them but due to article size limitation we choose to test only 9 methods.
• Thank you for your comment. We greatly appreciate your review.
• Thank you very much for providing us with a positive feedback of our statistical evaluation chapter.
• Yes, these coefficients are used because global solar radiation (Rs) has not been measured in Bosnia and Herzegovina. We have given a more detailed answer regarding Rs in the first question of this review.
• Figure 4 legend has been fixed and is now in English.
• The spatial distribution of ET_o by the FAO-PM method is presented in the revised manuscript in Figure 5, while the map representing the difference between the best simplified method (HC method for all zones) and the FAO-PM method is in Figure 6.

Reviewer 2 Report (New Reviewer)

This article is a comparative analysis between nine empirical methods for estimating reference evapotranspiration. The topic is interesting and the outputs are insightful for the scientific community. However, some points need to be revised/improved are listed below:

Line 56. Give some examples from the literature about the use of the aforementioned techniques for reference evapotranspiration measurements. Also, provide its advantages/disadvantages and associate accuracies and costs in different environments (eg https://doi.org/10.2166/ws.2021.142, https://doi.org/10.13031/2013.20414 )

Line 77. It is suggested to add a comment about the importance of the selection of the appropriate evapotranspiration method to drought estimation and climatological parameters as found in recent studies (https://doi.org/10.3390/hydrology10030064, https://doi.org/10.3390/w15040626)

Line 84. Better describe the FAO Penman-Monteith and add some comments about the vegetation conditions such as “The reference concept relates to a growing reference grass crop and is represented in FAO-24 by climate types calibrated with lysimeter data from various locations. However, many have pointed to weaknesses in the FAO-24 methodologies for implementation on a global scale.”

Line 145. Please clarify the novelty of this research in comparing several methods with reference ones in a agriculture environment. What’s new in your approach? There are several similar approach in the literature.

Line 161. Describe the instruments of the meteorological station and their characteristics.

Line 183. Decrease the scale of the figure 2.

Generally ,the article is well structure and worth publication after the necessary revision.

Author Response

Reviewer 2:

Dear Reviewer 1, we found your comment valuable and much appreciated, helping us to improve the manuscript and we are thankful for all useful comments and advices provided. The manuscript has been changed according to the suggestion.

Line 56: Examples for direct methods of measuring ET_o and their advantages and disadvantages are given in lines 57-79.

Line 77: A comment was added on the importance of choosing the appropriate evapotranspiration method for drought assessment and climatological parameters. Please find it in lines 124-132.

Line 84: A proposed description of the FAO-PM method as well as comments on vegetation conditions have been added to the new manuscript. Please find it in lines 107-124.

Line 145: The novelty is clarified in the new manuscript. Please find it in lines 184-208.

Line 161: The instruments used to measure weather parameters in BiH are described in lines 293-300.

Line 183: The scale of Figure 2 has been reduced in revised manuscript.

Thank you very much for providing us with a positive feedback on our work. We greatly appreciate your review.

Round 2

Reviewer 1 Report (New Reviewer)

In the second review of the article entitled “Assessment of empirical methods for estimating of reference evapotranspiration in different climatic zones of Bosnia and Herzegovina” ID water-2562356 submitted on 07/31/2023, the authors made changes to the text, in addition to the inclusions of Table 3 and Figures 5 and 6. All previous comments/suggestions were accepted or justified. The article is eligible for publication in Water.

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

Water management during crop growing with climate change is complex. The estimation of reference evapotranspiration using FAO Penman-Monteith needs input data, often unavailable at agro-meteorological sites. Therefore, studies focusing on assessing empirical methods for estimating reference evapotranspiration are essential.

This study presented an exciting result for the recommended empirical methods for estimating reference evapotranspiration in Bosnia and Herzegovina.

The empirical methods recommended in this study will help to improve irrigation scheduling by requiring fewer input parameters for ETo calculation.

Before recommending a paper for publishing, some questions need to answer.

(1)   Equation (3) has an Error! (Bookmark not defined), I recommend rewriting equation (3).

(2)   In equation (13), what does the R refer to?

(3)   Line 528, 529, and 530, “This deviation was much larger than the results obtained in BiH, where the average value of MAE for the common irrigation season in both zones was 0.51 mm day-1” this sentence is hard to read, suggesting rewriting the sentence.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript compares the performances of ten empirical methods for estimating reference evapotranspiration on a daily basis at 20 meteorological stations for two periods 24 (2000-2005 and 2018-2020) in Bosnia 3 and Herzegovina. It has some major drawbacks and requires a major revision. Detailed comments are provided in the following:

1.      Title: I suggest replacing “for the estimation” with “for estimating”.

2.      Line 19: for estimating reference evapotranspiration (ETo)

3.      Line 20: “Such as” and not “as”

4.      Line 22: What are “PMT2, PMT1,3 and PMTlok”? Define or remove them.

5.      Line 22: “With that of” instead of “with”

6.      Line 23: Add the long version of “FAO”.

7.      Line 27: Add the long version of “RMSE”.

8.      Abstract: The current abstract is confusing. It gives random results of different methods, while the reader can hardly understand and follow the logic behind the comparative analysis conducted in this study. I suggest rewriting the abstract by providing a clear path for presenting the results.

9.      Novelty: The novelty of this study is limited as it does not provide a new perspective on the estimation of reference evapotranspiration. It merely compares different methods for a new dataset, while the comparative analysis suffers from a suitable ranking method. For this purpose, the authors are advised to exploit the ranking method used in the literature (like 10.1155/2021/6627011) to delineate which method is the best.

10.  Data: From which source did you get the data? It is necessary to acknowledge the source of the data in the text.

11.  Lines 45-55 and 65-74: The introduction should not start with the climate of Bosnia and Herzegovina. It is better to present it as a case study and focus on comparing the estimation methods available for predicting reference evapotranspiration. Thus, any parts of paragraphs of the introduction section described the case study should be moved to the materials and methods section.

12.  Lines 56-64: This paragraph does not relate adequately to the topic of this paper.

13.  Introduction: It should be reorganized to show the problem statement and the importance of estimating reference evapotranspiration.

14.  Introduction: A comprehensive literature review should be presented in the introduction on the comparison of different available methods for predicting reference evapotranspiration. The current introduction just mentions selective papers instead of reviewing the related papers.

15.  Introduction: The novelty of the manuscript should be clearly stated in the introduction.

16.  Figure 1: The details of this figure are not clear. Modify it.

17.  Line 203: Add an appropriate reference for “any” equation that is not from your work. For example, you may use 10.1155/2021/9945218 for citing the indices used in your work.

18.  Equation 3: Check and correct the equation.

19.  Line 320: Is it “the methods’ performance” or “the methods performance”?

20.  Line 343: Is it “model’s performance” or “model performance”?

21.  Line 348: Is “Mean Relative Error (ARE)” correct? It seems that “ARE” is the abbreviation of “Absolute Relative Error” and not “Mean Relative Error (ARE)”. Also, the corresponding formula (i.e., Eq. 23) indicates MARE. Check and correct.

22.  Line 352: I suggest adding “Nash Sutcliffe criterion” as a performance evaluation Criterion.

23.  Figure 2: Omit the black border lines in this figure.

24.  Line 415: I disagree with this statement as Figure 4 clearly indicates R^2=0.2408, which indicates a very low correlation.

25.  Table 4: For improving the comparative analysis, I suggest adding a ranking analysis to the results obtained in this table.

26.  Table 4: I suggest presenting the best results in bold font in the table.

27.  General comment: I suggest that a native speaker checks the language of the text as many mistakes are observed. For example: “There is a possibility that a larger difference could occur in areas of BiH characterized by specific orography and climate dynamics which might require larger data set that we were not able to obtain for all stations.”

28.  Line 581: What do you mean by “In accordance with the stated findings on the climate variation in the BiH”?

29.  Conclusion: I think that this section requires a major revision as it does not provide a suitable conclusion of the study. It should have a take-home message.

30.  Lines 597-598: I disagree with “as this research is a pioneer work and a great effort to get knowledge about daily values of ETo” as many studies have conducted on the same topic in the literature.

31.  Line 796: This is not a reference. Check and correct.

Author Response

Please see the attachment. 

Author Response File: Author Response.docx

Reviewer 3 Report

The paper is a good study, but I recommend the authors to address the following issues prior to publication.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The manuscript was not modified as expected as important comments raised in the previous round of the review were not addressed adequately. One of the major problems with this article is lack of novelty. I suggest adopting a ranking analysis and/or a trend analysis to improve the work. The process of obtaining the ranking results shown in Table 6 is not clear. Detailed comments are provided in the following:

1.      Lines 19-26: The first sentence of the abstract is too long. Divide into at least two or three sentences.

2.      Line 20: Add a comma before “such as”.

3.      Line 26: Add “-” to the phrase “Food Agricultural Organization-Penman Monteith approach”.

4.      Line 29: Is it “zone” or “zones”?

5.      Line 30: Is it “observed by calibrated HC method” or “observed by the calibrated HC method”?

6.      Line 33: Is it “with HS method in MSH zone” or “with the HS method in the MSH zone”?

7.      Line 34: Correct “with FAO-PM method” as “with those of FAO-PM method”.

8.      Line 35: Is it “with HS method” or “with the HS method”?

9.      Line 36: You used past tense in many sentences in the abstract when you were referring to your work. However, this sentence is suddenly the present tense: “are obtained …”   

10.  Line 36: Is it “in DSH zone” or “in the DSH zone”?

11.  Line 37: Add a comma after “According to the regression coefficient (b)”.

12.  Line 38: Is it “in MAK method” or “in the MAK method”?

13.  Line 39: Is it “in MSH zone” or “in the MSH zone”?

14.  Line 40: Is it “in DHS zone” or “in the DHS zone”?

15.  Line 44: Is it “that HS method” or “that the HS method”?

16.  Line 44: Is it “in MSH zones” or “in the MSH zones”?

17.  Line 45: Is it “in DSH zones” or “in the DSH zones”?

18.  Line 47: Is it “showed high underestimation” or ““showed a high underestimation”?

19.  Line 47: Add a comma before “while”.

20.  Line 48: Is it “this method could not be used” or “this method cannot be used”?

21.  Line 49: Is it “the territory if Bosnia and Herzegovina” or “the territory of Bosnia and Herzegovina”?

22.  Abstract: The result part of the abstract is still confusing. It gives random results of different methods, while the reader can hardly understand and follow the logic behind the comparative analysis conducted in this study. I suggest modifying this part of the abstract by providing a clear path for presenting the results (from previous round of the review).

23.  Abstract: The abstract does not provide any information about the ranking results.

24.  Novelty: The novelty of this study is limited as it does not provide a new perspective on the estimation of reference evapotranspiration. It merely compares different methods for a new dataset, while the comparative analysis suffers from a suitable ranking method. For this purpose, the authors are advised to exploit the ranking method used in the literature (like 10.1155/2021/6627011) to delineate which method is the best (from previous round of the review). It is not clear how the ranking results shown in Table 6 were obtained. In other words, the ranking system you used is not clear. I suggest that you check the suggested reference, adopt a clear methodology for ranking different methods. You need to add the description of the ranking analysis in the materials and methods so that a future reader can replicate your work or at least understand how you calculate the ranking for each method. The ranking part is one of the most important aspects of this manuscript because it compares the performances of nine empirical methods for estimating reference evapotranspiration with that of FAO-PM. Without ranking the methods, your work does not have enough novelty to be published in this well-esteemed journal.

25.  Novelty: The manuscript just compared the performances of different methods for estimating reference evapotranspiration. In a bid to improve the quality of your work, I suggest adding a trend analysis method (like the conventional Mann-Kendall test used in papers like 10.1016/B978-0-323-91910-4.00033-9) to improve your article. The present manuscript does not contribute enough to the current literature as it is filled with studies like this one. I can prove my point if you have a glance over the references of your article.

26.  Line 55: Is it “by accurate calculation” or “by an accurate calculation”?

27.  Language: There are a lot of grammatical errors observed in the text. It should be corrected by a native speaker or a professional scientific writer.

28.  Line 61: Is it “[2,3,].” Or “[2,3]?

29.  Introduction: The novelty of the manuscript should be clearly stated in the introduction (from previous round of the review). Where did you state it clearly in the text?

30.  Figure 1: The details of this figure are not clear. Modify it.

31.  Line 203: Add an appropriate reference for “any” equation (like Eq. 1 or Eq. 2) that is not from your work. For example, you may use 10.1155/2021/9945218 for citing the indices used in your work (from previous round of the review).

32.  Lines 211-213: The text is full of grammatical and lexical errors. For example: “In the Figure 2. could be seen that on the territory of Bosnia and Herzegovina dominate forested land followed by agricultural land mainly concentrated in northern and northeastern part of the country [40].”

33.  Line 220. The text suffers from the correct use of articles. Why did you use “the” before the figure and table names? For example: “In the Figure 2” in line 211 or “In the Table 1” in line 220.

34.  Table 1: The name of the first and second columns should be “Weather Station” and “Period”, respectively, whereas the title of the first one is “Weather Station Period”, while the second one has no title in the first row.

35.  Table 1: Why did not you use the data between 2020 and 2023? Why is not your data up to date? Justify it in the text.

36.  Line 234: What is “ms-1”?

37.  Text: The main text has many typos, which clearly shows that it was not proofread before the submission. The authors are advised to check and proofread the whole text before any other submission.

38.  Table 2: Introduce these abbreviations: “ALT (m), LAT, and LONG”.

39.  Line 276: What is the difference between Table 1 and Table 3? It should be clearly explained in the text.

40.  Figure 3: The percentage of different land covers, especially hyperarid, is not clear in this figure.

41.  Figure 3: What is the added value of this figure? Justify it in the text.

42.  Line 304: Which software did you use for data analysis? Add it to the text.

43.  Line 334: Remove the comma after “where,”. Do similar corrections wherever it is required, like in lines 339, 346, and so on.

44.  Line 345: Why did you repeat Eq. 4?

45.  Figure 4: This figure is very plain and has no added value in its current format. Modify or remove it.

46.  Line 39: It is not acceptable to describe one figure by only one sentence.

47.  Line 460: Is “Mean Relative Error (ARE)” correct? It seems that “ARE” is the abbreviation of “Absolute Relative Error” and not “Mean Relative Error (ARE)”. Also, the corresponding formula (i.e., Eq. 23) indicates MARE. Check and correct (from previous round of the review).

48.  Lines 456-498: I suggest shortening the subsection of “Statistical evaluation of the methods performance”. Also, none of equations in this subsection has any references.

49.  Table 6: The procedure of the ranking analysis is not clear.  

50.  Line 607: Is it “climates’ dependent factors” or “climates dependent factors”?

51.  General comment: I suggest that a native speaker checks the language of the text as many mistakes are still observed (from previous round of the review). Where and what did you correct in the new version of the manuscript?

52.  Discussion: You need to discuss and justify why your results regarding some methods do not match with previous ones, particularly the one conducted in Serbia.

53.  Conclusion: I think that this section requires a major revision as it does not provide a suitable conclusion of the study. It should have a take-home message (from previous round of the review). It is just a repetition of the results section.

54.  Lines 597-598: I disagree with “as this research is a great effort to get knowledge about daily values of ETo” as many studies have conducted on the same topic in the literature. Is comparing different available methods for new data a great effort!?

55.  References: I think that this article should not have 81 references. It is not a review paper. I suggest removing the unnecessary and outdated (like 46 and 47) ones.

Reviewer 3 Report

Most of my comments are ignored or handled inadvertently, and I feel that if authors require time, they should take it rather than offering unfinished work. For example, research that were addressed are very important to the authors' work, yet the authors neglected the importance of those studies. It appears that authors are not at the  top of the literature, and the approach has not been well-managed. As a result, I propose that authors look through my earlier comments again.

Round 3

Reviewer 3 Report

Accept in present form