The Water Balance of Wet Grassland Sites with Shallow Water Table Conditions in the North-Eastern German Lowlands in Extreme Dry and Wet Years
Round 1
Reviewer 1 Report
The manuscript describes in detail an experiment measuring the water balance in shallow water tables conditions. The experiment is well designed and the results support the manuscript conclusions. The manuscript is also well organized and well written.
The discussion on the variation of Kc at both sites and its relationship with water table levels and the vegetation development stage could be improved with a better set of figures presenting the results. Figure 6 is hard to read.
A few other details are also worth revision:
Lines 34-36: The sentence is not clear.
Lines 144-148: Why these specific threshold values?
Fig 4 - This figure can be removed, with its accompanying text.
Fig. 6: This is the most important figure and it is hard to read. Authors should try to explore other ways to present the results, highlighting the relationship of Kc with water table levels and the vegetation development stage.
Fig. 7: As Kc varies significantly over the year, a box-whisker graph of the whole year provides little information.
Author Response
Response to Reviewer #1
Dear Reviewer,
We first of all thank you very much for your review and your detailed hints. They helped us a lot to improve our manuscript. We have taken up the comments and made appropriate changes in the text. The changes have been made in tracking mode. In this letter, we have provided additional explanations directly below the concerned comments where we felt it necessary. Your comments are marked as italic text.
The manuscript describes in detail an experiment measuring the water balance in shallow water tables conditions. The experiment is well designed and the results support the manuscript conclusions. The manuscript is also well organized and well written.
The discussion on the variation of Kc at both sites and its relationship with water table levels and the vegetation development stage could be improved with a better set of figures presenting the results. Figure 6 is hard to read.
Answer: We have simplified Fig 6 by presenting weekly averages. This makes the figure clearer. We have supplemented the illustration with a figure showing the cumulative frequencies of the Kc values and the water levels in the vegetation periods of the individual years. They illustrate how both parameters deviate from the mean years in the wet and dry years as well as the differences between the two study sites. We delete Fig 4 as suggested.
A few other details are also worth revision:
Lines 34-36: The sentence is not clear.
Answer: We have rephrased the sentence.
Lines 144-148: Why these specific threshold values?
Answer: Values smaller the two thresholds are very likely to be measurement errors or measurement inaccuracies. ET0 is in the denominator of the equation 3 and must therefore be non-zero. ET0 values smaller 0 would lead to negative Kc values. ETa values smaller 0.2 mm/d are very likely to be measurement errors. With the threshold values we avoid that the Kc values are far outside the usual range of values and we only use resilient Kc values for the analyses.
Fig 4 - This figure can be removed, with its accompanying text.
Answer: see first answer
Fig. 6: This is the most important figure and it is hard to read. Authors should try to explore other ways to present the results, highlighting the relationship of Kc with water table levels and the vegetation development stage.
Answer: see first answer
Fig. 7: As Kc varies significantly over the year, a box-whisker graph of the whole year provides little information.
Answer: We decided not to delete Fig 7 because it summarises and simplifies the hydrograph of the Kc values in Fig 5 and emphasizes the statistical numbers.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper is part of the multitude of scientific papers that analyze the water balance of wet grassland over typical sites who characterize lowland areas in north-eastern part of Germany. The paper is well structured with exception of the part of results and discussion where authors must clearly delimitate the results part and discussion part with relevance for the topic analyzed.
Also the authors must clearly specify the objectives of the paper in the introduction part and take care about reference numbering in row 36 and 38 appear twice the reference number 2.
in row 147 the authors write the two threshold values are introduced. What are these thresholds?
The results are very well presented from a scientific point of view but once again emphasizes the fact that they must be delimited by the discussion part.
Author Response
Response to Reviewer #2
Dear Reviewer,
We first of all thank you very much for your review. It helps us to improve our manuscript. We have taken up the comments and made appropriate changes in the text. The changes have been made in tracking mode. In this letter, we have provided additional explanations directly below the concerned comments where we felt it necessary. Your comments are marked as italic text.
This paper is part of the multitude of scientific papers that analyze the water balance of wet grassland over typical sites who characterize lowland areas in north-eastern part of Germany. The paper is well structured with exception of the part of results and discussion where authors must clearly delimitate the results part and discussion part with relevance for the topic analyzed.
Also the authors must clearly specify the objectives of the paper in the introduction part and take care about reference numbering in row 36 and 38 appear twice the reference number 2.
in row 147 the authors write the two threshold values are introduced. What are these thresholds?
Answer: The thresholds are ET0 > 0 and ETa >= 0.2 mm/d. Values smaller the two thresholds are very likely to be measurement errors or measurement inaccuracies. ET0 is in the denominator of the equation 3 and must therefore be non-zero. ET0 values smaller 0 would lead to negative Kc values. ETa values smaller 0.2 mm/d are very likely to be measurement errors. With the threshold values we avoid that the Kc values are far outside the usual range of values and we only use resilient Kc values for the analyses.
The results are very well presented from a scientific point of view but once again emphasizes the fact that they must be delimited by the discussion part.
Answer: Thank you very much for your comment. We decided not to separate the results section and the discussion. The journal makes this possible. But you are right, a separate presentation would perhaps improve clarity. Since the other two reviewers did not explicitly note this and we have little time to revise, we have not make a rigorous change. We have added discussion sections in the individual sections. We hope that we can meet their requirements with this.
Author Response File: Author Response.pdf
Reviewer 3 Report
Title can be revised: The water balance of wet grassland sites in the north-eastern German lowlands for extreme dry and wet years.
This paper is easy to read and understand for readers. It evaluates and compares wetland sites under different wetness years. The water usage and distribution among various vegetation is diverse across all wetlands. The management strategies and allocation policies for different stakeholders largely depend on water resource availability and its end use goal specially at catchment and watershed scale. Authors highlighted comparison of water balance of two different wetland sites and can help in large scale hydrological planning.
Major comments:
Abstract: At the beginning, please add couple of line to set the context in abstract to introduce what author is trying to convey.
Introduction: Authors missed to highlight the recent development in water stress (excess and deficit) mitigation measures in Introduction section. Hypothesis is not defined clearly with clear objectives
Methodology: Properly explained. Need to explain about gap filling of missing data.
Discussion: There was lack of recent literature to support and counter the finding, Speciaaly 3.1 and 3.2 section is more of reporting the results but lack of supporting and counter citations. Discussion is superficial without any explanation on the physiological/biophysical attributes of water balance impacts on vegetation. Discussion is good for line 338-341. Similar discussion is needed for each of the section.
Conclusion: Conclusion can be improved with future implications of this work rather than summarizing results.
References: Please double check doi of all references.
Here are specific comments:
Line 10: water and matter. What do authors mean by matter here?
Line 12 and 18 and in entire manuscript: ETa and Kc keep subscript
Line 27 and elsewhere: Why few words are kept bold?
Line 29: sandy sites and used for agricultural purposes.
Line 99: The long-term temporal dynamics of CBW gives a better understanding, usually 30 years
Line 108: Data cleaning and gap filling for eddy data should be explained. A long‐term database for continuous flux measurement will contain a considerable number of data gaps, since flux gaps are unavoidable due to system failures such as power cuts, rain, lighting, wrong calibration, lens/filter/transducer contamination, and data quality filtering, such as steady‐state testing and developed turbulent condition testing. Gap‐filling is typically conducted before analyzing data, such as by quantifying seasonal/annual/decadal time frame.
Line 115: How did it affect the analysis (data gap)?
Line 132: Here authors have explained about data aggregation. A line about gap filling method would be sufficed.
Line 202: What is T here ? av/max/min? (Fig 2)
Line 245-216 (methodological or any citation)
Figure 3: y axis title: m.b.s (period missing after m)
Line 285: hydrograph will differ with wet and dry year, which is normal, please highlight any specific finding and discuss with recent literature
Line 377- 280: Please also discuss importance of vapor pressure deficit for ET and water requirement, and Kc (Please see: Jha PK (2019) ‘Agronomic management of corn using seasonal climate predictions, remote sensing and crop simulation models.’ (Michigan State University: East Lansing, MI, USA).)
Comments for author File: Comments.pdf
Author Response
Response to Reviewer #3
Dear Reviewer,
We first of all thank you very much for your review and your detailed hints. They helped us a lot to improve our manuscript. We have taken up the comments and made appropriate changes in the text. The changes have been made in tracking mode. In this letter, we have provided additional explanations directly below the concerned comments where we felt it necessary. Your comments are marked as italic text.
This paper is easy to read and understand for readers. It evaluates and compares wetland sites under different wetness years. The water usage and distribution among various vegetation is diverse across all wetlands. The management strategies and allocation policies for different stakeholders largely depend on water resource availability and its end use goal specially at catchment and watershed scale. Authors highlighted comparison of water balance of two different wetland sites and can help in large scale hydrological planning.
Major comments:
Abstract: At the beginning, please add couple of line to set the context in abstract to introduce what author is trying to convey.
Answer: We rephrased the abstract. But the abstract is limited to 200 words. So we couldn’t extent it too much.
Introduction: Authors missed to highlight the recent development in water stress (excess and deficit) mitigation measures in Introduction section. Hypothesis is not defined clearly with clear objectives
Answer: Thank you for the hint. Adaption to climate change is a broad field including many different measures in water management or wetland restauration. Adaption measures were not the focus of our study, that’s why we didn’t address it in the introduction. Our focus is on analysing the effects of extreme weather conditions on the water balance of wetlands. In doing so, we rely on experimental investigations. The results can also be a good validation basis for the many model studies.
We expanded the last paragraph of the introduction with a clearer defined objective.
Methodology: Properly explained. Need to explain about gap filling of missing data.
Answer: we answered your commends in the detailed part.
Discussion: There was lack of recent literature to support and counter the finding, Speciaaly 3.1 and 3.2 section is more of reporting the results but lack of supporting and counter citations. Discussion is superficial without any explanation on the physiological/biophysical attributes of water balance impacts on vegetation. Discussion is good for line 338-341. Similar discussion is needed for each of the section.
Answer: Thank you for the comment. You are right, the results in section 3.1 and 3.2 are rarely discussed. Section 3.1 primarily serves to describe the long-term meteorological conditions in the study regions and their development against the background of climate change. In section 3.2, conditions of the four study years are classified in the long-term conditions. They are important for the overall assessment and classification of the results, but are not discussed in detail. The effects of extreme meteorological conditions on the water balance of wet grassland sites, which is the main objective of the study, are discussed in the following three sections 3.3 to 3.5.
Conclusion: Conclusion can be improved with future implications of this work rather than summarizing results.
Answer: Thank you very much for your hint. We removed the summarising part and expanded the conclusions. But we don’t want to speculate about mitigation or adaptation measures, we do not have investigated.
References: Please double check doi of all references.
Answer: the literature database was updated
Here are specific comments:
Line 10: water and matter. What do authors mean by matter here?
Answer: We changed “matter” by “nutrient”
Line 12 and 18 and in entire manuscript: ETa and Kc keep subscript
Answer: We changed it in the whole manuscript
Line 27 and elsewhere: Why few words are kept bold?
Answer: Sorry, we have overseen it. It was not our intention to write the words bold. We corrected it.
Line 29: sandy sites and used for agricultural purposes.
Answer: Thank you very much. We have added to your suggestion.
Line 99: The long-term temporal dynamics of CBW gives a better understanding, usually 30 years
Answer: You are right. We used the long-term CWB values of the DWD stations for an assessment of the changing climate conditions (s. Table 1). We have just not pointed directly to it again at this point.
Line 108: Data cleaning and gap filling for eddy data should be explained. A long‐term database for continuous flux measurement will contain a considerable number of data gaps, since flux gaps are unavoidable due to system failures such as power cuts, rain, lighting, wrong calibration, lens/filter/transducer contamination, and data quality filtering, such as steady‐state testing and developed turbulent condition testing. Gap‐filling is typically conducted before analyzing data, such as by quantifying seasonal/annual/decadal time frame.
Answer: Thank you for the hints. We described it two paragraphs later.
Line 115: How did it affect the analysis (data gap)?
Answer: The monthly sums of the concerned months are smaller. We have pointed out in the results section.
Line 132: Here authors have explained about data aggregation. A line about gap filling method would be sufficed.
Answer: We have decided not to fill in any data gaps. There are a number of different methods for filling data gaps in eddy covariance measurement series. All have their advantages and disadvantages. Since it was not absolutely necessary for our evaluations to have complete time series, we refrained from using these procedures. We added one sentence in the manuscript that we did not fill data gaps.
Line 202: What is T here ? av/max/min? (Fig 2)
Answer: Thank you very much. We have made it more precise.
Line 245-216 (methodological or any citation)
Answer: Thank you for the hint. We refreshed the first sentences. It should be better understandable now.
Figure 3: y axis title: m.b.s (period missing after m)
Answer: “m” means meter. It is correct without “.”
Line 285: hydrograph will differ with wet and dry year, which is normal, please highlight any specific finding and discuss with recent literature
Answer: We rephrased the paragraph and added additional information for the grading of the measured values.
Line 377- 280: Please also discuss importance of vapor pressure deficit for ET and water requirement, and Kc (Please see: Jha PK (2019) ‘Agronomic management of corn using seasonal climate predictions, remote sensing and crop simulation models.’ (Michigan State University: East Lansing, MI, USA).)
Answer: The vapor pressure deficit is a meteorological parameter, which affects ET. It is part of the FAO-Grass-Reference ET, which summarises the meteorological boundary conditions and reflects the evaporation demand of the atmosphere. Therefore, the vapor pressure deficit influences ETa in the same way. The crop coefficient serves as an aggregation of the physical and physiological differences between crops. It does not depend on meteorological parameters like water vapor deficit. Unfortunately, we do not know what this remark is aimed at.
Author Response File: Author Response.pdf
