Decrease in the Water Level of Lake Prespa (North Macedonia) Studied by Remote Sensing Methodology: Relation with Hydrology and Agriculture

Round 1

Reviewer 1 Report

Dear Editor.

I have finished my review on the proposed paper “Decrease water level in Lake Prespa (North Macedonia) studied by remote sensing methodology: relation with the hydrology and agriculture in Pelagonia county” hydrology-1717885-peer-review-v1.

Summary of the manuscript:

In the proposed paper, the authors’ goal is to investigate the factors that caused the Lake Prespa level decline. They used remote sensing data to estimate the land use changes during the period of 1984-2020 and to access the surface decrease of the Lake. They found that vegetation cover was increased mainly due to the change of crop species and the increase of forest aeras.

General review:

1. Generally, the manuscript presents a very interesting topic and the specific research seems to include some significant points for the research community of this field.
2. The proposed paper is very well written with good use of English language. Except some minor grammatical mistakes and word errors, this paper is written with a very good scientific style. However, the authors used too much: “We analyzed….”, “We did… “, “We used…”. In my opinion, passive voice should be used in scientific papers. The authors should check again the paper to correct these minor mistakes.
3. The proposed paper is well structured. It begins with the Introduction with some limited references that helps the reader to get into the subject. In Introduction there is an effort to provide previous studies with similar scientific content, which took place in the research area and in other countries. Authors describe and set very well the scientific problem. At the end of Introduction, authors clearly state the goals of the research. However, the authors didn’t manage to provide adequate number of relative studies that recently published, which deal with almost the same subject. Below, I gave some examples.
4. The methodology is generally very simple, interesting, and well explained, so other researchers could easily repeat it. However, some parts need to be clearer. See below specific comments.
5. The results should be clearer.
6. The quality of the work in Discussion is adequate. See below specific comments.
7. Conclusions are appropriate for this paper.

Additional points for revision:

In my opinion, the proposed paper could be characterized as a good research work, complies with aims of Hydrology. 

INTRODUCTION: This part of the study is weak. More literature should be added, especially from the country that have parts of Lake Prespa watershed, from previous studies and programs that deal with Prespa’s hydrology, using satellite products, field observations, hydrological and hydraulic simulations. You used only 29 references. For the specific subject less than 50 references is not adequate. You should find these studies, add them in Introduction and define what is new/novel in your research. Below I give some of these studies, that you could add in your paper.

Lines 39-43: Here, you used the term “clogging” to describe lake sedimentation (?) process. I am not very familiar with this term. Are you sure that “clogging” is scientifically correct?

Lines 54-56: Please, add some literature for these national and international legislative means

Lines 56-59: Please, add literature for each of treatments from the evolved countries.

Lines 61-63: Please, add literature.

Lines 63-65: Please, add literature.

GENERALLY, IN INTRODUCTION: You give a lot of information without supporting with literature.

Lines 60-72: Here, you say about the political and economic alternation of North Macedonia and this affect the land uses. The same political and economic alternation happened in Albania. However, you did not mention anything about the other countries that have parts of Prespa’s watershed. I believe that you should add a paragraph about Greece and Albania.

Lines 76-78: Here, for the enrichment of your introduction, add one more study which was conducted in similar area very close to Prespa (Kastridis and Stathis 2015).

Line 88: “….maximum depths were reported….”. By whom “were reported”? Add literature.

Figure1a: You should add the watershed area of Prespa.

Line 100: “These two lakes…”. Which lakes?

Lines 116-121: Here you inform that you used one meteorological station to evaluate the climate impact. I think that one station is not adequate to describe the climate for Prespa watershed area of 4950 km².

Lines 139-141: You forgot these lines from authors’ template!!!

Line 142: Subsection 3.1 do not have title!

Lines 152-162: It is not possible and it is not acceptable to draw any conclusion about the climate of Prespa using only one meteorological station. The watershed is huge (4950 km²) and more meteorological data are needed to evaluate the climate effect on the lake. Further, the station is located on the shore of the lake and is not representative of the mean altitude of the watershed. The generation of water runoff is taking place in higher altitudes where the orographic effect in more intense and the rainfall amounts higher.

So, here, I see two options. Or you will remove this section with the climate analysis, or you will add more meteorological station. There are numerous studies that provide meteorological data (SOCIETY FOR THE PROTECTION OF PRESPA 2009, SOCIETY FOR THE PROTECTION OF PRESPA 2021). You can use these studies to find more literature for the study area.

I believe that you can find more meteorological data if you search.

Lines 183-184: Yes, in summer season the forest retain the rainfall water and the increased forest are will retain more water. However, the lake filling with water mainly taking place in autumn and winter and the forest plays crucial role to the rainfall/snow interception and to the enrichment of the groundwater and surface water amounts. You should underline this, because from the text I understand that the increase of forest is a problem for the lake.

Line 186: Where is mount Baba? Show it in figure 1a.

Generally, in the text: Where is Pelagonia county? Show it in figure 1a.

Line 258: This is a speculation. With one meteorological station you can not make such conclusion. More stations are needed.

References

Kastridis A. and Stathis D. 2015. The effect of small earth dams and reservoirs on water management in North Greece (Kerkini municipality). Silva Balcanica, 16(2), pp. 71-84.

SOCIETY FOR THE PROTECTION OF PRESPA 2009. https://www.spp.gr/fullstudy_vol1.pdf

SOCIETY FOR THE PROTECTION OF PRESPA 2021. https://www.prespawaterbirds.gr/img/a9ff3d6e030b898f91cbe163c5ae68fcA6.HabitatVulnerability_ClimateChange_AssesmentReport_incl.summary.pdf

Author Response

Reviewer 1

General review:

1. Generally, the manuscript presents a very interesting topic and the specific research seems to include some significant points for the research community of this field.

Authors: We appreciate this referee´s comment that the MS present a very interesting topic.

1. The proposed paper is very well written with good use of English language. Except some minor grammatical mistakes and word errors, this paper is written with a very good scientific style. However, the authors used too much: “We analyzed….”, “We did… “, “We used…”. In my opinion, passive voice should be used in scientific papers. The authors should check again the paper to correct these minor mistakes.

Authors: We have checked the MS for grammatical mistakes and have amended several sentences to improve the language and style including the point raised by the reviewer.

1. The proposed paper is well structured. It begins with the Introduction with some limited references that helps the reader to get into the subject. In Introduction there is an effort to provide previous studies with similar scientific content, which took place in the research area and in other countries. Authors describe and set very well the scientific problem. At the end of Introduction, authors clearly state the goals of the research. However, the authors didn’t manage to provide adequate number of relative studies that recently published, which deal with almost the same subject. Below, I gave some examples.

Authors: We have added several additional references as suggested by the referee.

1. The methodology is generally very simple, interesting, and well explained, so other researchers could easily repeat it. However, some parts need to be clearer. See below specific comments.
2. The results should be clearer.
3. The quality of the work in Discussion is adequate. See below specific comments.
4. Conclusions are appropriate for this paper.

Authors for comments 4,5,6,7: We have taken into consideration the reviewer´s criticism and suggestions and amended  

Additional points for revision:

In my opinion, the proposed paper could be characterized as a good research work, complies with aims of Hydrology. 

INTRODUCTION: This part of the study is weak. More literature should be added, especially from the country that have parts of Lake Prespa watershed, from previous studies and programs that deal with Prespa’s hydrology, using satellite products, field observations, hydrological and hydraulic simulations. You used only 29 references. For the specific subject less than 50 references is not adequate. You should find these studies, add them in Introduction and define what is new/novel in your research. Below I give some of these studies, that you could add in your paper.

Lines 39-43: Here, you used the term “clogging” to describe lake sedimentation (?) process. I am not very familiar with this term. Are you sure that “clogging” is scientifically correct?

Authors: Yes, the term is correct, and it is employed in literature on hydrology and geology and refers to the accumulation in the bottom layer of various products from the basin..

Lines 54-56: Please, add some literature for these national and international legislative means.

Lines 56-59: Please, add literature for each of treatments from the evolved countries.

Lines 61-63: Please, add literature.

Lines 63-65: Please, add literature.

Authors: In agreement with the referee, we have added several references.

GENERALLY, IN INTRODUCTION: You give a lot of information without supporting with literature.

Lines 60-72: Here, you say about the political and economic alternation of North Macedonia and this affect the land uses. The same political and economic alternation happened in Albania. However, you did not mention anything about the other countries that have parts of Prespa’s watershed. I believe that you should add a paragraph about Greece and Albania.

Authors: We understand the reviewer´s point but the study is focused on the Macedonian part of the lake (and one of the two authors of this study is Macedonian) and although the economic changes also happened in Albania, we are not so familiar with them as to address in sufficient depth.

Lines 76-78: Here, for the enrichment of your introduction, add one more study which was conducted in similar area very close to Prespa (Kastridis and Stathis 2015).

Authors: we have found some other works related to Prespa Lake and added in the introduction.

Line 88: “….maximum depths were reported….”. By whom “were reported”? Add literature.

Authors: We specified that these values reflect the measurements taken before the major decline in the water level and have added a reference.

Figure1a: You should add the watershed area of Prespa.

Line 186: Where is mount Baba? Show it in figure 1a.

Generally, in the text: Where is Pelagonia county? Show it in figure 1a.

Authors: We have drawn the watershed and made other changes in figure 1a. Pelagonia is the name of an administrative County and a geographical Valley crossed by the Black river (Crna reka in Macedonian). We are referred to the geographical area and stated in the manuscript now.

Line 100: “These two lakes…”. Which lakes?

Authors: Corrected.

Lines 116-121: Here you inform that you used one meteorological station to evaluate the climate impact. I think that one station is not adequate to describe the climate for Prespa watershed area of 4950 km².

Authors: We agree with the referee´s opinion. However, to our knowledge there is no other station in the Macedonian part of the Lake that offers complete temperature and precipitation data. Climatological station in Resen (881 m asl) was established in 1947 but stopped operation in 1993 while meteorological station in Pretor (993 m asl) was established in 1991. Nevertheless, we have modified the text in order to reflect this limitation in the Discussion.

Lines 139-141: You forgot these lines from authors’ template!!!

Authors: We thank the reviewer for spotting this. It has been corrected.

Line 142: Subsection 3.1 do not have title!

Authors: Corrected.

Lines 152-162: It is not possible and it is not acceptable to draw any conclusion about the climate of Prespa using only one meteorological station. The watershed is huge (4950 km²) and more meteorological data are needed to evaluate the climate effect on the lake. Further, the station is located on the shore of the lake and is not representative of the mean altitude of the watershed. The generation of water runoff is taking place in higher altitudes where the orographic effect in more intense and the rainfall amounts higher. So, here, I see two options. Or you will remove this section with the climate analysis, or you will add more meteorological station. There are numerous studies that provide meteorological data (SOCIETY FOR THE PROTECTION OF PRESPA 2009, SOCIETY FOR THE PROTECTION OF PRESPA 2021). You can use these studies to find more literature for the study area. I believe that you can find more meteorological data if you search.

Authors: There are papers that offer some meteorological data and also, we know of the existence of some small automatic recording units that monitor precipitation at least in the territory of N. Macedonia but we are not aware of any complete source of information. In the present, updated version of the MS, we have added data of the automatic station at Stenje however it only offers data about the precipitation.

Lines 183-184: Yes, in summer season the forest retain the rainfall water and the increased forest are will retain more water. However, the lake filling with water mainly taking place in autumn and winter and the forest plays crucial role to the rainfall/snow interception and to the enrichment of the groundwater and surface water amounts. You should underline this, because from the text I understand that the increase of forest is a problem for the lake.

Authors: We have include some comments about the role of the forest in water retention during rainfall.

Line 258: This is a speculation. With one meteorological station you can not make such conclusion. More stations are needed.

Authors: We have clearly stated that this not a firm conclusion. There is limited availability of meteorological data in N. Macedonia and is not easy to obtain the data numbers and are not free; we must pay a tax for the service.

Reviewer 2 Report

I added almost all my suggestions as comments to a copy of the manuscript. However, here are my major concerns:

1. The introduction makes a big jump between the relevance of the topic and what the work is about. It lacks more bibliography about work done in the past, and about what you did.
2. Your methods section does not describe well how you did your work.
3. The results section seems unconnected and I am missing some more analysis.
4. The discussion section goes away from the main topic all the time. And it is not clear how some conclusions are connected to your results. 

Author Response

Reviewer 2

I added almost all my suggestions as comments to a copy of the manuscript. However, here are my major concerns:

1. The introduction makes a big jump between the relevance of the topic and what the work is about. It lacks more bibliography about work done in the past, and about what you did.
2. Your methods section does not describe well how you did your work.
3. The results section seems unconnected and I am missing some more analysis.
4. The discussion section goes away from the main topic all the time. And it is not clear how some conclusions are connected to your results.

Authors for comments 1,2,3,4: We appreciate the referee´s criticism and suggestions to improve the MS. We have amended and added several additional references in all the sections (Introduction, Methods and Discussion), as comment also by reviewer 1; please see the corrected version of the manuscript.

Round 2

Reviewer 1 Report

Dear authors.

Thank you very much for the provided responses. I could say that the paper has significantly improved. I appreciate your time and effort to address my comments. However, I have some concerns about the climate analysis.

You say in the text (and this is correct) that the absence of appropriate climate data is a limitation of the study. But you draw some conclusion about the influence of climate on water levels. Also, you applied Mann-kendal test using fragmented data from two stations. One could say, how you managed to make trend analysis with fragmented data? Generally, I do not agree with your approach, concerning the climate. Maybe, it would better to make the trend analysis to satellite data (GPM-IMERG), which are also FREE of charge. And it is sure that cover your study area.

Also, I believe that you can add in line 90 (in the revised paper, with the reference [16]) the following two studies. One of them is very close to your study area, and deals with the same subject and uses remote sensing data. (https://doi.org/10.17221/174/2014-SWR)

(https://doi.org/10.1016/j.rse.2020.111831)

Author Response

Dear authors.

Thank you very much for the provided responses. I could say that the paper has significantly improved. I appreciate your time and effort to address my comments. However, I have some concerns about the climate analysis.

You say in the text (and this is correct) that the absence of appropriate climate data is a limitation of the study. But you draw some conclusion about the influence of climate on water levels. Also, you applied Mann-Kendal test using fragmented data from two stations. One could say, how you managed to make trend analysis with fragmented data? Generally, I do not agree with your approach, concerning the climate. Maybe, it would better to make the trend analysis to satellite data (GPM-IMERG), which are also FREE of charge. And it is sure that cover your study area.

Authors: According to Hirsch et al. 1982, the Mann-Kendall Test is not affected by missing data other than the fact the number of sample points are reduced and hence might affect the statistical significance adversely. Also, it is not affected by irregular spacing of the time points of measurement or by the length of the time series. In our time series, we have some missing data (not available from the National Hydrometeorological Service for unknown reasons) - some months have missing values which is why we cannot calculate the annual mean value. But these data are in the middle of the series and do not affect to the general trend of the time series.

In order to be more accurate, we have specifically addressed the missing data in the new version of the MS. We have added these sentences in line 178: “About the precipitation data, we collected 840 monthly data, but data about 24 months in the series are missing in the register. Therefore, in order to be able to perform statistical analysis of the trend, we added for the missing data the mean value of the precipitation in the other months”. A similar sentence was added for the seven missing data of temperature.

Hirsch, R.M., J.R. Slack, and R.A. Smith. 1982. Techniques of trend analysis for monthly water quality data. Water Resources Research 18(1):107-121.

In order to study the GPM satellite, the server has only data from 1997 to present, but only available from 2015. This could be an interesting approach to complete the gaps of the time series in future studies.

Also, I believe that you can add in line 90 (in the revised paper, with the reference [16]) the following two studies. One of them is very close to your study area, and deals with the same subject and uses remote sensing data. (https://doi.org/10.17221/174/2014-SWR)

(https://doi.org/10.1016/j.rse.2020.111831)

Authors: Thank you very much for providing these interesting papers. The first one is added in discussion, in line 312, when we expose the consequences of the changes in land use. The second one is added in line 100 about the utility of RS in the bathymetry.