Drought Analysis for the Seyhan Basin with Vegetation Indices and Comparison with Meteorological Different Indices
Round 1
Reviewer 1 Report
The paper falls within the aims and scopes of journal. Also, the paper is reasonably well written and it reads well, the study in itself seems interesting enough for its report to be upgraded and further prepared for international publication. For this purpose, to be achieved, however, several things are needed, as follows.
- Title: It's a good title.
- Abstract: Well-prepared abstract. However, it was better that the research method was also mentioned in the abstract.
- Keywords: It is better that the "keywords" do not repeat the words of the paper title.
- Introduction: What was the theoretical basis? In other words, what was the "epistemological" background in this research?
- Materials and methods: This section is well presented. In this section, please describe the research method from different angles (type of quantitative or qualitative paradigm, type of experimental and non-experimental research design, type of data processing, validity and reliability, etc.).
- Results and discussion: Well, presented.
- Conclusion: What were the limitations of the research?
Author Response
We thank the reviewer for recommending our manuscript for publication in the journal of Sustainability and for her/his comments and valuable suggestions. We have revised the manuscript accordingly based on the comments and suggestions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This study is not novel or different enough from other previous studies. Lots of studies have analyzed drought situations using kinds of indices all over the world, as mentioned in the introduction part of this study (LN 71-82). I think this study only repeated the same procedures of applying the drought indices; even their usage or efficiency of application was verified. That is, this study shows any new insight or issue to the peer researchers. Something different objectives such as developing revised indices targeting the study basin or characteristics of NDVI and VCI different from other existing indices should be added. In addition, the significant result of this study is somewhat boring because the increasing trend of drought occurrence has been verified already.
These are the other comments:
The trend of VCI was not presented as a result of this study.
How was drought defined in this study, and how could it be determined with NDVI and VCI?
What do similar correlations of NDVI/VCI and other indices mean?
There are several misspells or grammar errors.
Too long paragraphs in the introduction and materials part should be restructured to be read more easily.
More abundant and specific discussions about the results are required.
Author Response
We thank the reviewer for recommending our manuscript and for her/his comments and valuable suggestions. We have revised the manuscript accordingly based on the comments and suggestions.
Author Response File: Author Response.pdf
Reviewer 3 Report
In this study, using remote sensing author studied the drought analysis for Seyhan Basin (a River Basin in Eastern Mediterranean, Turkey) using NDVI and VCI vegetation indices. In my opinion, the study is quite interesting, data looks robust, and manuscript is written well. However, I have few comments that can be considered for improving the quality of manuscript.
- Title should be catchy and easy to attract the readers.
- There are many places where the author's message is not clear due to improper phrasing and English language. Authors need to check that through the manuscript.
Author Response
We thank the reviewer for recommending our manuscript for publication in the journal of Sustainability and for her/his comments and valuable suggestions. We have revised the manuscript accordingly based on the comments and suggestions.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Even the author revised substantially, there are several parts still should be modified. The detailed comments are as follow:
- Introduction
- First paragraph of Introduction section is too long. I should be divided into two or more paragraphs.
- Please add the descriptions of specific indices used in five categories (e.g. SPI, GI)
- Please add the advantages of NDVI and VCI compared to other indices. Limitations of other indices also given to emphasize the usage of NDVI and VCI in this study.
- Among four research questions you set, how did you get an answer of “What is the frequency of the drought in this basin?” in this paper? I cannot find any comments or analysis about this question here. If you assess this question qualitatively, it should be analyzed in quantitative ways.
- Materials and Methods
- A whole structure of this section seems weird. There’s no figure of study area. Data and method explanations are intermixed, which interrupts readers’ understanding.
- I suggest the author to subdivide this section into “Study Area”, “Data” and “Drought Index”
- Results and Discussions
- Legend should be added in Fig. 6.
- As shown in Figs. 8 and 9, CC between vegetation indices (NDVI and VCI) and other indices was estimated quite low. If the indices used in this study gives little similarity to others, is it reasonable to use NDVI and VCI for drought indices? What is the reason this result came from? How can we overcome this crucial problem?
Author Response
#Response to Reviewer 2’ Comments
Comments and Suggestions for Authors
Even the author revised substantially, there are several parts still should be modified. The detailed comments are as follow:
We thank the reviewer for recommending our manuscript and for her/his comments and valuable constructive suggestions. We have revised the manuscript accordingly based on the comments and suggestions
- Introduction
- First paragraph of Introduction section is too long. I should be divided into two or more paragraphs.
The first paragraph is split into more appropriate sections
- Please add the descriptions of specific indices used in five categories (e.g. SPI, GI)
In this study, the calculation of plant indices is the main subject and in addition, the comparison with other indices made before.
For this reason, reference was made to the study in which detailed descriptions of other indexes were made.
The following explanation has been added to the introduction of the article.
“ - Comparison of vegetation indices with hydrological and meteorological indices for the Seyhan Basin. Meteorological indices are DI (Deciles Index), SPI (Standardized Precipitation Index), SPEI (Standardized Precipitation Evapotranspiration Index) and hydrological indice is SRI (Standardized Runoff Index). They were described in detail in the study of Asi Basin [21].”
- Please add the advantages of NDVI and VCI compared to other indices. Limitations of other indices also given to emphasize the usage of NDVI and VCI in this study.
The advantages and disadvantages of plant indices are added to the data section.
“Unlike other data collection methods that may take years, the remote sensing method allows extremely fast and rapid analysis. Using this method, comparably large areas can be analyzed using just one satellite image. With remote sensing, the required work for the selected area is minimized. Some areas that are easy to reach are selected and the accuracy of the data is tested. Also, with this method, it is easier to locate potential floods or forest fires over a large region which makes it easier to plan a rescue mission easily and fast.
On the other hand, this method also has some disadvantages as explained below.
Examining a small area can be costly. The variability of the weather may cause inac-curate measurements during image acquisition. Powerful active remote sensing systems such as radars that emit their own electromagnetic radiation can be intrusive and affect the phenomenon being investigated. A surveying engineering training may be required to correct, digitize, and analyze raw satellite images and check selected test sites.”
- Among four research questions you set, how did you get an answer of “What is the frequency of the drought in this basin?” in this paper? I cannot find any comments or analysis about this question here. If you assess this question qualitatively, it should be analyzed in quantitative ways.
We added it to the 2.4. VCI title.
“Dry periods are found depending on whether it is below the determined threshold values. According to Figure 3, the VCI graph shows a dry period every 9-10 years and a semi-arid period every 2-3 years. According to the NDVI graph, a dry period is observed every 5-6 years. Even this varies with different satellites. The rate of vegetation indices finding drought in the past years is less. The reasons for this are stated in the “data” header as the disadvantages of remote sensing.
In addition, it is appropriate to use vegetation indices in determinations such as land change, irrigation change and human intervention. Meteorological and hydrological indices, which have been measured for many years, should be used to accurately determine the severity and frequency of drought.”
- Materials and Methods
- A whole structure of this section seems weird. There’s no figure of study area. Data and method explanations are intermixed, which interrupts readers’ understanding.
- I suggest the author to subdivide this section into “Study Area”, “Data” and “Drought Index”
It was added figure of study area.
we have rearranged the titles of this section acoording to your suggestions
- Results and Discussions
- Legend should be added in Fig. 6.
- The legend was added in Figure.
- As shown in Figs. 8 and 9, CC between vegetation indices (NDVI and VCI) and other indices was estimated quite low. If the indices used in this study gives little similarity to others, is it reasonable to use NDVI and VCI for drought indices? What is the reason this result came from? How can we overcome this crucial problem?
- It was added 2 more paragraphs to the conclusion section.
“The use of hydrological and meteorological indices should be preferred for the analysis of drought in variable lands. In basins where the land structure does not change much, plant indices can give accurate results in a short time only with satellite data.
Considering that the number of satellites in space has increased recently, it may not be correct to analyze drought with only one plant index. Plant indices, which are compatible with meteorological and hydrological drought indices, can be used in terms of less data and fast results. It may not give accurate results in areas with high terrain variability.”
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
The author revised the manuscript considering my comments.
Final spell checks or reconstruction of some paragraphs (LN 176-190, 369-376) should be reviewed.
Author Response
#Response to Reviewer 2’ Comments (V3)
The author revised the manuscript considering my comments.
Thank you very much for your constructive and guiding comments.
Final spell checks or reconstruction of some paragraphs (LN 176-190, 369-376) should be reviewed.
We have rearranged the relevant sections as follows:
LN 176-190
“If we summarize some advantages and disadvantages of this method below:
Unlike other data collection methods that may take years, the remote sensing method allows extremely rapid analysis. Using this method, comparably large areas can be analyzed using just one satellite image. With remote sensing, the required area works for the selected area can be minimized. Some areas that are easy to reach are selected and the accuracy of the data can be tested.
Also, with this method, it is easier to locate potential floods or forest fires over a large region which makes it easier to plan a rescue mission easily and fast.
On the other hand, this method also has some disadvantages as explained below.
Examining a small area can be costly. The variability of the weather may cause inaccurate measurements during image acquisition. Powerful active remote sensing systems such as radars that emit their own electromagnetic radiation can be intrusive and affect the phenomenon being investigated. A surveying engineering training may be required to correct, digitize, and analyze raw satellite images and check selected test sites.
The two most commonly used vegetation indices of this method were used in this study.”
LN 369-376
“To investigate the accuracy of the vegetation indices that are thought to be used in the basin, it is important to compare them with the meteorological indices.
The SPEI (Standardized Precipitation Evapotranspiration Index), SPI (Standardized Precipitation Index), SRI (Standardized Runoff Index) and DI (Deciles Index) indices were described to analysis the drought in the Asi Basin in a previous study [21].
SPEI12, SPI12, SRI12 and DI (Figure 7) drought indices obtained by meteorological data were compared and it was seen that the values were very close to each other [72].”
