the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Nov 2021
Soil water sources in permafrost active layer of Three-River Headwater Region, China
Abstract. Water in permafrost soil is an important factor affecting the ecology of cold environments, climate change, hydrological cycle, engineering, and construction. To explore the variations in soil water in the active layer due to permafrost degradation, the soil water sources in the Three-River Headwater Region were quantified based on the stable isotope data (δ2H and δ18O) of 1140 samples. The results showed that the evaporation equation was δ2H = 7.46 δ18O - 0.37 for entire soil water. The stable isotope data exhibited a spatial pattern, which varied over the soil profile under the influence of altitude, soil moisture, soil temperature, vegetation, precipitation infiltration, soil water movement, ground ice, and evaporation. Based on the stable isotope tracer model, precipitation and ground ice accounted for approximately 88 % and 12 % of soil water, respectively. High precipitation contributed to the soil water in the 3900–4100 m, 4300–4500 m, and 4700–4900 m zones, whereas ground ice contributed to the soil water in the 4500–4700 m and 4900–5100 m zones. Precipitation contributed approximately 84 % and 80 % to the soil water in grasslands and meadows, respectively, whereas ground ice contributed approximately 16 % and 20 %, respectively. Precipitation; evapotranspiration; physical and chemical properties of soil; and the distribution of ground ice, vegetation, and permafrost degradation were the major factors affecting the soil water sources in the active layer. Therefore, establishing an observation network and developing technologies for ecosystem restoration and conservation is critical to effectively mitigate ecological problems caused by future permafrost degradation in the study region.
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RC1: 'Review on hess-2021-558', Anonymous Referee #1, 12 Dec 2021
General comments
In this manuscript, the authors analyzed the spatial variability of the isotopic composition of soil water at different depths in the Three-River Headwater Region (China). The isotopic composition of soil water was compared to the isotopic signatures of precipitation and ground ice, and it was related to elevation, soil moisture and soil temperature. In addition, the authors quantified the contribution of precipitation and ground ice to soil water.
The topic of this manuscript is potentially interesting for the readers of Hydrology and Earth System Sciences. I think the authors presented a valuable and interesting dataset that it is difficult to collect at high-elevation catchments. Nonetheless, several important methodological details were not presented in the manuscript, and I have major concerns about the approach adopted for the data analyses.
Firstly, it seems that the authors have not considered how the likely heterogeneous soil properties, the local topography, the climate and other characteristics could have affected the main results of the study. Indeed, the authors carried out their study in a very wide study area, but besides grouping the data based on soil depth, main land use or aspect, they have not analyzed the dataset based on other characteristics (e.g., data could have been grouped by subcatchment, homogeneous soil properties, presence of permafrost etc.).
Secondly, the authors have not described the soil type and in general, the main soil properties in the study area, as well as the spatial distribution of permafrost and the ground ice (details about how the presence of permafrost was determined and thickness of these layers should be added). Furthermore, given the large study area, I recommend a better characterization of the climate and estimates of potential evapotranspiration, as well as an analysis of the temporal variability of the meteorological variables and the isotopic composition of the water sources.
Thirdly, in the quantification of the contribution of precipitation and ground ice to soil water, the authors should estimate the uncertainty due to the measurement errors and the high spatial and temporal variability in the isotopic composition of the various water sources. In addition, I think these contributions should be related to the specific subcatchment and sampling period (particularly, if the samples were collected during different sampling times, from June 2019 to July 2020).
Finally, I think some parts of the results and the discussions should be revised to avoid a mixture of the two sections (please see my technical corrections).
Specific comments
- In section 2.1, the authors should present (by also using a table) quantitatively the land use in the study region, as well as information about the main soil types, their average depths, and other available details on soil properties. Furthermore, details about the spatial distribution of discontinuous permafrost and how the presence of permafrost was assessed should be added in this section.
- Lines 148-152: I suggest providing mean annual precipitation and temperature data here, and adding a table with the monthly characteristics of the meteorological variables during the sampling period.
- In sections 3.1 and 3.2, the isotopic composition of soil water is not presented in relation to the isotopic signature of precipitation determined in the same sampling period.
- Lines 581-592: Figure 8 alone cannot support this discussion because the dual isotope plot depicts the isotopic composition of various water sources, from very distinct sampling sites distributed in a very large study area. My suggestion is providing an analysis based on small subcatchments where there are homogeneous soil characteristics.
- Lines 629-631: This sentence needs to be supported by the results of a statistical test.
- Lines 632-635: Figure 9 is not meaningful because it presents a regression line fitted to only three data points.
- Lines 637-647: Uncertainty should be added when presenting the contribution of precipitation and ground ice to soil water.
- Lines 692-693: Based on Figure 11, I disagree with this sentence because all regressions seem to have very low coefficients of determination. Are the regressions significant?
- Lines 698-703: The regressions should be tested to assess whether they are statistically significant or not.
- Lines 698-736: Most of the sentences report results, which should be moved to the previous sections.
- Lines 766-770: The relations shown in Figure 12 are very weak, and thus they cannot support the statement that the isotopic composition is related to the soil moisture.
- Lines 805-812: The soil temperatures reported in Figure 12 and Table 3 are very high for soils where there is a permafrost layer. Are there soil temperature data measured very close to the permafrost layer? I suggest providing clear details about the spatial distribution of permafrost (and its depth) for the sampling sites where soil water was collected.
- Tables 1, 2 and 3: Sample size per each group of data should be provided in the tables. Furthermore, information about the sampling times should be added in the captions of the tables.
- Figure 1: I suggest adding the spatial distribution of permafrost in the study area, and showing the land use. The size of the labels is too small.
- Figures 5 and 6: I suggest using the same colour scale for all depths, and showing where bare rocks and glaciers are located (it does not make sense having interpolated isotopic values where there is no soil). Furthermore, details about how the interpolated maps were obtained are not present in the Data and methods section.
- Figure 9: Error bars representing the spatio-temporal variability should be added but, given that the figure is not meaningful, I suggest removing the figure.
- Figure 11: The figure is unreadable because the labels are too small, there are too many regression lines (probably the regressions are not significant), and the legend is missing. I suggest moving the equations in a new table.
Technical corrections
- Lines 167-171: Please add a reference to support this sentence.
- Line 183: It is unclear whether it is snowmelt water, glacier melt water or snowmelt from a glacierized area. I suggest rewording.
- Line 236: Based on the description this seems to be glacier melt water, but it cannot be assessed whether it consists more of snowmelt or ice melt water.
- Lines 315-327: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 338-345: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 348-354: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
- Line 526: I suggest replacing ‘there were high variations’ with ‘there was a high variability’.
- Lines 560-568: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Line 579: It should be ‘indicating’.
- Lines 582-594: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 832-838: These results should be moved to the previous sections.
- Lines 647:655: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 685-687: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Line 692: The citation should be (Sprenger et al., 2017).
Citation: https://doi.org/10.5194/hess-2021-558-RC1 -
AC1: 'Reply on RC1', Li Zongxing, 22 Jan 2022
General comments
Comment 1:
In this manuscript, the authors analyzed the spatial variability of the isotopic composition of soil water at different depths in the Three-River Headwater Region (China). The isotopic composition of soil water was compared to the isotopic signatures of precipitation and ground ice, and it was related to elevation, soil moisture and soil temperature. In addition, the authors quantified the contribution of precipitation and ground ice to soil water. The topic of this manuscript is potentially interesting for the readers of Hydrology and Earth System Sciences. I think the authors presented a valuable and interesting dataset that it is difficult to collect at high-elevation catchments. Nonetheless, several important methodological details were not presented in the manuscript, and I have major concerns about the approach adopted for the data analyses.
Response 1:
Thank you very much for your guidance and advice. We will revise the manuscript thoroughly according to your comments. Frankly speaking, this is the first time that a systematic study of the sources of soil water on the Tibetan plateau has been carried out. As you say, the authors presented a valuable and interesting dataset that it is difficult to collect at high-elevation catchments.
Comment 2:
Firstly, it seems that the authors have not considered how the likely heterogeneous soil properties, the local topography, the climate and other characteristics could have affected the main results of the study. Indeed, the authors carried out their study in a very wide study area, but besides grouping the data based on soil depth, main land use or aspect, they have not analyzed the dataset based on other characteristics (e.g., data could have been grouped by subcatchment, homogeneous soil properties, presence of permafrost etc.).
Response 2:
Thanks for your comment. We will analyze the influence from the heterogeneous soil properties, the local topography, the climate, the main land use or aspect and the presence of permafrost on stable isotope of soil water in study region, and we have the data for it.
Comment 3:
Secondly, the authors have not described the soil type and in general, the main soil properties in the study area, as well as the spatial distribution of permafrost and the ground ice (details about how the presence of permafrost was determined and thickness of these layers should be added). Furthermore, given the large study area, I recommend a better characterization of the climate and estimates of potential evapotranspiration, as well as an analysis of the temporal variability of the meteorological variables and the isotopic composition of the water sources.
Response 3:
Thanks for your comment. On the one hand, we will add the introduction of the soil type, the main soil properties, as well as the spatial distribution of permafrost and the ground ice, and we have the data for it. On the other hand, we will analyse the climatic characteristics and its changes in the study region, including potential evapotranspiration. In addition, we will briefly introduce the isotopic composition of the water sources.
Comment 4:
Thirdly, in the quantification of the contribution of precipitation and ground ice to soil water, the authors should estimate the uncertainty due to the measurement errors and the high spatial and temporal variability in the isotopic composition of the various water sources. In addition, I think these contributions should be related to the specific subcatchment and sampling period (particularly, if the samples were collected during different sampling times, from June 2019 to July 2020).
Response 4:
Thanks for your comment. On the one hand, the uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013). On the other hand, precipitation samples were collected during from June 2019 to July 2020, whereas other samples for Ground ice, River water, Supra-permafrost water and Glacier snow meltwater in July 2019. In addition, The Three-River Headwater Region covers 363,000 km2 (31°39'–36°12'E, 89°45'–102°23'E), accounting for 50.4% of the total area of Qinghai Province with Very large number of subcatchments. so it is Achievable and reasonable for the quantification of the contribution of precipitation and ground ice to soil water in July 2019.
Genereux, D.P., (1998). Quantifying uncertainty in tracer-based hydrograph separations. Water Resources Research, 34(4), 915-919.
Klaus, J., McDonnell, J.J., (2013). Hydrograph separation using stable isotopes: Review and evaluation. Journal of Hydrology, 505, 47-64.
Comment 5:
Finally, I think some parts of the results and the discussions should be revised to avoid a mixture of the two sections (please see my technical corrections).
Response 5:
Thanks for your comment. We will double check and revise some parts of the results and the discussions in order to avoid a mixture of the two sections based on technical corrections.
Specific comments
Comment 6:
In section 2.1, the authors should present (by also using a table) quantitatively the land use in the study region, as well as information about the main soil types, their average depths, and other available details on soil properties. Furthermore, details about the spatial distribution of discontinuous permafrost and how the presence of permafrost was assessed should be added in this section.
Response 6:
Thanks for your comment. Based on our data and field observations, we will add the analysis on the land use, the main soil types, the average soil depths and other available details on soil properties. Furthermore, details about the spatial distribution of discontinuous permafrost and how the presence of permafrost was assessed will also be added in this section.
Comment 7:
Lines 148-152: I suggest providing mean annual precipitation and temperature data here, and adding a table with the monthly characteristics of the meteorological variables during the sampling period.
Response 7:
Thanks for your comment. Based on our previous studies (Li et al,2021) and data, we will add a table with the monthly characteristics of the meteorological variables during the sampling period.
Li Zongjie, Li Zongxing*, Feng Qi*, Wang Xufeng, Mu Yanhu, Xin Huijuan, Song Lingling, Gui Juan, Zhang Baijuan. (2021). Hydrological effects of multiphase water transformation in Three-River Headwaters Region, China. Journal of Hydrology, 601, 126662: 1-16.
Comment 8:
In sections 3.1 and 3.2, the isotopic composition of soil water is not presented in relation to the isotopic signature of precipitation determined in the same sampling period.
Response 8:
Thanks for your comment. Based on the spatial distribution of national meteorological observation stations, A total of 375 precipitation (event scale) samples were collected from five stations at different altitudes from June 2019 to July 2020: Zhimenda (92.26° E, 34.14° N, 3540 m), Tuotuohe (34.22° N, 92.24° E, 4533 m), Zaduo (32.53° N, 95.17° E, 4066.4 m), Dari (33.45° N, 99.39° E, 3967 m), and Maduo (34.55° N, 98.13° E, 4272.3 m) In study region, which is because these five meteorological stations are staffed by observers, while the others are all automatic stations. Meanwhile , soil profiles of 1 m were excavated at 90 sampling sites In July 2019. So it is reasonable to analyze the stable isotope in soil water. In addition, the The spatial and temporal patterns of precipitation stable isotopes and their environmental significance have been analysed in previous studies (Li et al,2022, under review), so the basic information on stable isotopes of precipitation will be added in the revision.
Li Zongxing*, Feng Qi*, Wang Xufeng, Mu Yanhu, Xin Huijuan, Song Lingling, Gui Juan, Zhang Baijuan. (2022). Spatial and temporal patterns of precipitation stable isotopes and their environmental significance in the Three-River Headwater Region. Journal of Hydrology, under review.
Comment 9:
Lines 581-592: Figure 8 alone cannot support this discussion because the dual isotope plot depicts the isotopic composition of various water sources, from very distinct sampling sites distributed in a very large study area. My suggestion is providing an analysis based on small subcatchments where there are homogeneous soil characteristics.
Response 9:
Thanks for your comment. In addition to the average conditions in the study region, we will further analyse the sources of soil moisture in the permafrost and seasonal frozen zones of the Yangtze River, Yellow River and Lancang River sources region. It should be emphasised that this study mainly explores soil water sources from a large regional scale, while further systematic observations are needed for micro-scale studies, such as subcatchments.
Comment 10:
Lines 629-631: This sentence needs to be supported by the results of a statistical test.
Response 10:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 11:
Lines 632-635: Figure 9 is not meaningful because it presents a regression line fitted to only three data points.
Response 11:
Thanks for your comment. This is not the regression line fitted to only three data points, whereas The straight lines have been artificially added only to reflect the relationship between the three end elements when the soil water source is determined.
Comment 12:
Lines 637-647: Uncertainty should be added when presenting the contribution of precipitation and ground ice to soil water.
Response 12:
Thanks for your comment. the uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013).
Comment 13:
Lines 692-693: Based on Figure 11, I disagree with this sentence because all regressions seem to have very low coefficients of determination. Are the regressions significant?
Response 13:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 14:
Lines 698-703: The regressions should be tested to assess whether they are statistically significant or not.
Response 14:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 15:
Lines 698-736: Most of the sentences report results, which should be moved to the previous sections.
Response 15:
Thanks for your comment. These sentences reported the altitude effect of stable isotopes in soil water, which is different and Non-repetitive from the previous sections.
Comment 16:
Lines 766-770: The relations shown in Figure 12 are very weak, and thus they cannot support the statement that the isotopic composition is related to the soil moisture.
Response 16:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 17:
Lines 805-812: The soil temperatures reported in Figure 12 and Table 3 are very high for soils where there is a permafrost layer. Are there soil temperature data measured very close to the permafrost layer? I suggest providing clear details about the spatial distribution of permafrost (and its depth) for the sampling sites where soil water was collected.
Response 17:
Thanks for your comment. Soil water and temperature were simultaneously measured at intervals of 20 cm in the soil profile during sampling using a portable soil water measurement instrument (TZS-IW) (Fig. 1). Soil temperature ranged from -40 ºC to 100 °C with an accuracy of ± 0.5 ºC. Soil moisture (% (m3/m3)) ranged between 0–100% with a response time of < 2 s. also, we will provide the clear details about the spatial distribution of permafrost (and its depth) for the sampling sites where soil water was collected.
Comment 18:
Tables 1, 2 and 3: Sample size per each group of data should be provided in the tables. Furthermore, information about the sampling times should be added in the captions of the tables.
Response 18:
Thanks for your comment. The average values of stable isotope, Sample size and sampling times will be added in the captions of the tables.
Comment 19:
Figure 1: I suggest adding the spatial distribution of permafrost in the study area, and showing the land use. The size of the labels is too small.
Response 19:
Thanks for your comment. Figure 1 will be revised based on our data.
Comment 20:
Figures 5 and 6: I suggest using the same colour scale for all depths, and showing where bare rocks and glaciers are located (it does not make sense having interpolated isotopic values where there is no soil). Furthermore, details about how the interpolated maps were obtained are not present in the Data and methods section.
Response 20:
Thanks for your comment. Figures 5 and 6 will be revised based this suggestions, and the spline function method with altitude effect of stable isotope will be presented in the Data and methods section.
Comment 21:
Figure 9: Error bars representing the spatio-temporal variability should be added but, given that the figure is not meaningful, I suggest removing the figure.
Response 21:
Thanks for your comment. This is not the regression line fitted to only three data points, whereas The straight lines have been artificially added only to reflect the relationship between the three end elements when the soil water source is determined.
Comment 22:
Figure 11: The figure is unreadable because the labels are too small, there are too many regression lines (probably the regressions are not significant), and the legend is missing. I suggest moving the equations in a new table.
Response 22:
Thanks for your comment. Figure 11 will be revised, and We will analyze the results of a statistical test in the revision. In addition, the equations will be moved in a new table.
Comment 23:
TECHNICAL CORRECTIONS
Lines 167-171: Please add a reference to support this sentence.
Line 183: It is unclear whether it is snowmelt water, glacier melt water or snowmelt from a glacierized area. I suggest rewording.
Line 236: Based on the description this seems to be glacier melt water, but it cannot be assessed whether it consists more of snowmelt or ice melt water.
Lines 315-327: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 338-345: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 348-354: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
Line 526: I suggest replacing ‘there were high variations’ with ‘there was a high variability’.
Lines 560-568: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Line 579: It should be ‘indicating’.
Lines 582-594: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 832-838: These results should be moved to the previous sections.
Lines 647:655: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 685-687: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Line 692: The citation should be (Sprenger et al., 2017).
Response23:
Thanks for your corrections, and we will revise these in the newest version of paper.
Citation: https://doi.org/10.5194/hess-2021-558-AC1
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RC2: 'Comment on hess-2021-558', Anonymous Referee #2, 08 Jan 2022
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2021-558/hess-2021-558-RC2-supplement.pdf
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AC2: 'Reply on RC2', Li Zongxing, 22 Jan 2022
Overall comments:
Comment 1:
The manuscript presented huge field works of soil water/ice sampling in the permafrost area of the Headwater region of Three Rivers, obtaining 1140 samples. The isotope data collection in the Three-Rivers headwater region is a meaningful work. The manuscript elucidated the soil isotopic characteristics of different soil layers under different topographic gradients, vegetation and soil characteristics, estimated the contribution of different water sources in the soil water, and discussed influence factors on soil water sources. This work provides data support for the ecological restoration and maintenance of the Headwater region of the Three Rivers. Nonetheless, many results in the article are too repetitive and the discussion provides many new results but no real discussion on what was learned in this study. There are still many issues that need to be carefully modified.
Response 1:
Thank you very much for your guidance and advice. We will revise the manuscript thoroughly according to your comments, especially the sections of Result and Discussion. Frankly speaking, this is the first time that a systematic study of the sources of soil water on the Tibetan plateau has been carried out. As you say, this work provides data support for the ecological restoration and maintenance of the Headwater region of the Three Rivers.
Featured comments:
Comment 2:
The contribution of precipitation and ground ice to soil water was quantified. But the soil water mixing process was very complex, processes of glacier/snow melting, permafrost freezing and thawing, as well as the water exchange between the surface and subsurface were not well considered and discussed.
Response 2:
Thanks for your comment. Indeed, soil moisture processes are extremely complex, especially in permafrost areas. Studies on the sources of soil moisture are minimal due to the difficulty and cost of direct observational studies in Tibetan Plateau. Due to freeze-thaw processes, soil hydrological processes in the study area in fact only occur during the ablation period (May-October), while in July the snowpack has all melted away and all the glacial meltwater has flowed into the rivers, and the active layer of permafrost has largely melted, so that the main sources of soil water are precipitation and ground ice. Of course, the mechanisms influencing the source of soil water need further study, and the main objective of this study was to determine the source of soil water during the sampling period.
Comment 3:
The spatial and temporal differences of isotope data in different water sources are significant, and the uncertainty should be estimated in the quantification of the contribution of different water sources in the soil water. How to consider the heterogeneity of soil properties across such a huge study area? How did the sampling process distinguish the soil water or ice?
Response 3:
Thanks for your comment. The uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013).
Based on the systematic collection of samples, the central objective of this study is to quantify the sources of soil water. Samples were collected regardless of the soil type, which provided the basis for analysing the influence of soil heterogeneity on soil water sources, so in the revised manuscript we will further analyse soil water sources in different soil type zones. For the analysis of δ2H and δ18O, water was extracted from soil using a cryogenic freezing vacuum extraction system (LI-2000, Beijing Liga United Technology Co., Ltd., China), which can achieve complete extraction with high precision (details in the section of Collection and preparation of samples). ground ice has frozen in the soil and is collected directly in the soil profile as showing in fig.2.
Comment 4:
The influence of various factors on the soil water is difficult to distinguish by simple correlation analysis. What’s the meaning of those correlation analysis in the discussion with very low correlation coefficients? How to identify the mutual influence from several factors on the soil water and also the interrelationship among various factors?
Response 4:
Thanks for your comment. The factors influencing soil water are complex and diverse, and require systematic observation if they are to be understood clearly. However, current observational studies in the study region are almost non-existent. Therefore, in this study, systematic sampling was carried out in July, along with observations of soil moisture, temperature and its vegetation, and thus the relationship between these factors and soil moisture was analyzed.
Comment 5:
The authors should carry out a comprehensive language edit of the paper to make it concise and clear.
Response 5:
Thanks for your comment. a comprehensive language has been edited before submission.
Comment 6:
The formatting needs to be carefully laid out, including the formatting of references, etc.
Response 6:
Thanks for your comment. The formatting will be revised again in the revision.
Major issues:
Study Area:
Comment 7:
It is suggested to introduce the types of frozen soil and soil properties in the study area. The introduction of the study area is not specific enough and a little broad.
Response 7:
Thanks for your comment. We will revise the section of Study region, and add the introduction of the types of frozen soil and soil properties.
Sampling methods:
Comment 8:
Repeated sampling methods are not recommended.
Response 8:
Thanks for your comment. The Repeated sampling methods will be removed from the revision.
Results:
Comment 9:
The result part is a little long and the style of writing is not recommended in this part.
Response 9:
Thanks for your comment. The section of Result will be revised again.
Comment 10:
There are too many speculative descriptions, and it would be better to show more definite conclusions.
Response 10:
Thanks for your comment. many speculative descriptions will be changed to the definite conclusions.
Comment 11:
About point 6, please confirm that the runoff segmentation result only refers to July in the study area? The sampling time described is from June 2019 to July 2020. Why does the author only analyse the water source in a single month? Is it the average value of the whole basin? More discoveries may be made according to watershed zoning.
Response 11:
Thanks for your comment. precipitation samples were collected during from June 2019 to July 2020, whereas other samples for Ground ice, River water, Supra-permafrost water and Glacier snow meltwater in July 2019. So the soil water sources in July 2019 have been analyzed. In the revision, In addition to the average conditions in the study region, we will further analyse the sources of soil moisture in the permafrost and seasonal frozen zones of the Yangtze River, Yellow River and Lancang River sources region.
Discussion:
Comment 12:
Some contents of the discussion part and the results are repeated, and it is not recommended to put too much data.
Response 12:
Thanks for your comment. The sections of Result and Discussion will be revised again, and the repeated part will be removed.
Comment 13:
It is suggested to compare and discuss the research results of other scholars in this regard, and it is not recommended to put the research views of others behind the findings of the article.
Response 13:
Thanks for your comment. The sections of Discussion will be revised again, and we will compare and discuss the research results of other scholars in this regard.
Conclusion:
Comment 14:
The conclusion is repeated with the summary. It is not recommended to put too much data and refine it again.
Response 14:
Thanks for your comment. The sections of Conclusion will berefined again.
Figures and Tables:
Comment 15:
Please note the format of the table. You can see the requirements of submission.
The correlation information on the figure has been discussed in the article, so it is recommended not to repeat it.
Response 15:
Thanks for your comment. These figures and tables will be revised again.
References:
Comment 16:
References are repeated and check if there is a problem with the format.
Please check that the DOI and title of some references do not correspond.
Response 16:
Thanks for your comment. These references will be revised again.
Minor issues:
Comment 17:
Line229 Please explain the relationship between supra-permafrost water and soil water.
Line 224, Line235, Line243 repeat the narration.
Line 344 The relationship with the previous logical reasoning is unclear.
Line 410 Please explain what the same pattern is.
Response 17:
Thanks for your comment. These minor issues will be revised again.
TECHNICAL CORRECTIONS
Comment 18:
Pay attention to the format of the article, the upper and lower symbols of the text should be unified, and there are small details such as punctuation.
Response 18:
Thanks for your comment. The format will be revised again.
Comment 19:
It may be necessary to explain the definition of soil water in this paper, the relationship between soil water and supra-permafrost water, and the relationship between the depth of soil water research section and the depth of active layer.
Response 19:
Thanks for your comment. Based on our data, we will explain the definition of soil water in this paper, the relationship between soil water and supra-permafrost water, and the relationship between the depth of soil water research section and the depth of active layer in the revision.
Comment 20:
It is suggested to put forward the dominant influencing factors affecting the soil water content of different soil layers in permafrost according to different regions. There are many influencing factors mentioned in the article, but there is no focus.
Response 20:
Thanks for your comment. Based on our data, we will put forward the dominant influencing factors affecting the soil water content of different soil layers in permafrost according to different regions in the revision.
Comment 21:
This paper repeatedly mentioned the effects of evaporation and soil water migration on soil water isotopes, and there are few explanations for the isotopic characteristics of the soil layer near the underground ice.
Response 21:
Thanks for your comment. Based on our data, we will explanations for the isotopic characteristics of the soil layer near the underground ice.
Comment 22:
Please explain that only two end elements are considered in the runoff division, whether the contribution of snow and ice meltwater is considered, or why snow and ice meltwater is not considered.
Response 22:
Thanks for your comment. Based on our data, we will study the isotopic characteristics of the soil layer near the underground ice.
Comment 23:
The part of runoff segmentation need to add uncertainty analysis.
Response 23:
Thanks for your comment. The uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013).
Comment 24:
At present, the distribution of water content in each soil layer under different conditions reflected by isotope monitoring is beneficial or harmful to the ecological environment. It is suggested to supplement it, so as to promote the goal of better maintaining the ecological environment.
Response 24:
Thanks for your comment. Furthermore, there is an urgent need to develop technologies for fragile ecosystem restoration and improve the water conservation capacity for wetland ecosystem restoration/conservation, soil and water conservation enhancement, and ecological adaptation and regulation of climate change. Based on the above-mentioned aspects, it is necessary to vigorously implement ecological protection and construction projects, natural forest protection projects, and the conversion of cropland to forest and grassland projects. Such strategies could effectively deal with ecological problems, such as decreased water conservation capacity, increased soil erosion, and vegetation degradation, caused by future permafrost degradation.
Citation: https://doi.org/10.5194/hess-2021-558-AC2
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AC2: 'Reply on RC2', Li Zongxing, 22 Jan 2022
Status: closed
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RC1: 'Review on hess-2021-558', Anonymous Referee #1, 12 Dec 2021
General comments
In this manuscript, the authors analyzed the spatial variability of the isotopic composition of soil water at different depths in the Three-River Headwater Region (China). The isotopic composition of soil water was compared to the isotopic signatures of precipitation and ground ice, and it was related to elevation, soil moisture and soil temperature. In addition, the authors quantified the contribution of precipitation and ground ice to soil water.
The topic of this manuscript is potentially interesting for the readers of Hydrology and Earth System Sciences. I think the authors presented a valuable and interesting dataset that it is difficult to collect at high-elevation catchments. Nonetheless, several important methodological details were not presented in the manuscript, and I have major concerns about the approach adopted for the data analyses.
Firstly, it seems that the authors have not considered how the likely heterogeneous soil properties, the local topography, the climate and other characteristics could have affected the main results of the study. Indeed, the authors carried out their study in a very wide study area, but besides grouping the data based on soil depth, main land use or aspect, they have not analyzed the dataset based on other characteristics (e.g., data could have been grouped by subcatchment, homogeneous soil properties, presence of permafrost etc.).
Secondly, the authors have not described the soil type and in general, the main soil properties in the study area, as well as the spatial distribution of permafrost and the ground ice (details about how the presence of permafrost was determined and thickness of these layers should be added). Furthermore, given the large study area, I recommend a better characterization of the climate and estimates of potential evapotranspiration, as well as an analysis of the temporal variability of the meteorological variables and the isotopic composition of the water sources.
Thirdly, in the quantification of the contribution of precipitation and ground ice to soil water, the authors should estimate the uncertainty due to the measurement errors and the high spatial and temporal variability in the isotopic composition of the various water sources. In addition, I think these contributions should be related to the specific subcatchment and sampling period (particularly, if the samples were collected during different sampling times, from June 2019 to July 2020).
Finally, I think some parts of the results and the discussions should be revised to avoid a mixture of the two sections (please see my technical corrections).
Specific comments
- In section 2.1, the authors should present (by also using a table) quantitatively the land use in the study region, as well as information about the main soil types, their average depths, and other available details on soil properties. Furthermore, details about the spatial distribution of discontinuous permafrost and how the presence of permafrost was assessed should be added in this section.
- Lines 148-152: I suggest providing mean annual precipitation and temperature data here, and adding a table with the monthly characteristics of the meteorological variables during the sampling period.
- In sections 3.1 and 3.2, the isotopic composition of soil water is not presented in relation to the isotopic signature of precipitation determined in the same sampling period.
- Lines 581-592: Figure 8 alone cannot support this discussion because the dual isotope plot depicts the isotopic composition of various water sources, from very distinct sampling sites distributed in a very large study area. My suggestion is providing an analysis based on small subcatchments where there are homogeneous soil characteristics.
- Lines 629-631: This sentence needs to be supported by the results of a statistical test.
- Lines 632-635: Figure 9 is not meaningful because it presents a regression line fitted to only three data points.
- Lines 637-647: Uncertainty should be added when presenting the contribution of precipitation and ground ice to soil water.
- Lines 692-693: Based on Figure 11, I disagree with this sentence because all regressions seem to have very low coefficients of determination. Are the regressions significant?
- Lines 698-703: The regressions should be tested to assess whether they are statistically significant or not.
- Lines 698-736: Most of the sentences report results, which should be moved to the previous sections.
- Lines 766-770: The relations shown in Figure 12 are very weak, and thus they cannot support the statement that the isotopic composition is related to the soil moisture.
- Lines 805-812: The soil temperatures reported in Figure 12 and Table 3 are very high for soils where there is a permafrost layer. Are there soil temperature data measured very close to the permafrost layer? I suggest providing clear details about the spatial distribution of permafrost (and its depth) for the sampling sites where soil water was collected.
- Tables 1, 2 and 3: Sample size per each group of data should be provided in the tables. Furthermore, information about the sampling times should be added in the captions of the tables.
- Figure 1: I suggest adding the spatial distribution of permafrost in the study area, and showing the land use. The size of the labels is too small.
- Figures 5 and 6: I suggest using the same colour scale for all depths, and showing where bare rocks and glaciers are located (it does not make sense having interpolated isotopic values where there is no soil). Furthermore, details about how the interpolated maps were obtained are not present in the Data and methods section.
- Figure 9: Error bars representing the spatio-temporal variability should be added but, given that the figure is not meaningful, I suggest removing the figure.
- Figure 11: The figure is unreadable because the labels are too small, there are too many regression lines (probably the regressions are not significant), and the legend is missing. I suggest moving the equations in a new table.
Technical corrections
- Lines 167-171: Please add a reference to support this sentence.
- Line 183: It is unclear whether it is snowmelt water, glacier melt water or snowmelt from a glacierized area. I suggest rewording.
- Line 236: Based on the description this seems to be glacier melt water, but it cannot be assessed whether it consists more of snowmelt or ice melt water.
- Lines 315-327: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 338-345: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 348-354: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
- Line 526: I suggest replacing ‘there were high variations’ with ‘there was a high variability’.
- Lines 560-568: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Line 579: It should be ‘indicating’.
- Lines 582-594: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 832-838: These results should be moved to the previous sections.
- Lines 647:655: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Lines 685-687: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
- Line 692: The citation should be (Sprenger et al., 2017).
Citation: https://doi.org/10.5194/hess-2021-558-RC1 -
AC1: 'Reply on RC1', Li Zongxing, 22 Jan 2022
General comments
Comment 1:
In this manuscript, the authors analyzed the spatial variability of the isotopic composition of soil water at different depths in the Three-River Headwater Region (China). The isotopic composition of soil water was compared to the isotopic signatures of precipitation and ground ice, and it was related to elevation, soil moisture and soil temperature. In addition, the authors quantified the contribution of precipitation and ground ice to soil water. The topic of this manuscript is potentially interesting for the readers of Hydrology and Earth System Sciences. I think the authors presented a valuable and interesting dataset that it is difficult to collect at high-elevation catchments. Nonetheless, several important methodological details were not presented in the manuscript, and I have major concerns about the approach adopted for the data analyses.
Response 1:
Thank you very much for your guidance and advice. We will revise the manuscript thoroughly according to your comments. Frankly speaking, this is the first time that a systematic study of the sources of soil water on the Tibetan plateau has been carried out. As you say, the authors presented a valuable and interesting dataset that it is difficult to collect at high-elevation catchments.
Comment 2:
Firstly, it seems that the authors have not considered how the likely heterogeneous soil properties, the local topography, the climate and other characteristics could have affected the main results of the study. Indeed, the authors carried out their study in a very wide study area, but besides grouping the data based on soil depth, main land use or aspect, they have not analyzed the dataset based on other characteristics (e.g., data could have been grouped by subcatchment, homogeneous soil properties, presence of permafrost etc.).
Response 2:
Thanks for your comment. We will analyze the influence from the heterogeneous soil properties, the local topography, the climate, the main land use or aspect and the presence of permafrost on stable isotope of soil water in study region, and we have the data for it.
Comment 3:
Secondly, the authors have not described the soil type and in general, the main soil properties in the study area, as well as the spatial distribution of permafrost and the ground ice (details about how the presence of permafrost was determined and thickness of these layers should be added). Furthermore, given the large study area, I recommend a better characterization of the climate and estimates of potential evapotranspiration, as well as an analysis of the temporal variability of the meteorological variables and the isotopic composition of the water sources.
Response 3:
Thanks for your comment. On the one hand, we will add the introduction of the soil type, the main soil properties, as well as the spatial distribution of permafrost and the ground ice, and we have the data for it. On the other hand, we will analyse the climatic characteristics and its changes in the study region, including potential evapotranspiration. In addition, we will briefly introduce the isotopic composition of the water sources.
Comment 4:
Thirdly, in the quantification of the contribution of precipitation and ground ice to soil water, the authors should estimate the uncertainty due to the measurement errors and the high spatial and temporal variability in the isotopic composition of the various water sources. In addition, I think these contributions should be related to the specific subcatchment and sampling period (particularly, if the samples were collected during different sampling times, from June 2019 to July 2020).
Response 4:
Thanks for your comment. On the one hand, the uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013). On the other hand, precipitation samples were collected during from June 2019 to July 2020, whereas other samples for Ground ice, River water, Supra-permafrost water and Glacier snow meltwater in July 2019. In addition, The Three-River Headwater Region covers 363,000 km2 (31°39'–36°12'E, 89°45'–102°23'E), accounting for 50.4% of the total area of Qinghai Province with Very large number of subcatchments. so it is Achievable and reasonable for the quantification of the contribution of precipitation and ground ice to soil water in July 2019.
Genereux, D.P., (1998). Quantifying uncertainty in tracer-based hydrograph separations. Water Resources Research, 34(4), 915-919.
Klaus, J., McDonnell, J.J., (2013). Hydrograph separation using stable isotopes: Review and evaluation. Journal of Hydrology, 505, 47-64.
Comment 5:
Finally, I think some parts of the results and the discussions should be revised to avoid a mixture of the two sections (please see my technical corrections).
Response 5:
Thanks for your comment. We will double check and revise some parts of the results and the discussions in order to avoid a mixture of the two sections based on technical corrections.
Specific comments
Comment 6:
In section 2.1, the authors should present (by also using a table) quantitatively the land use in the study region, as well as information about the main soil types, their average depths, and other available details on soil properties. Furthermore, details about the spatial distribution of discontinuous permafrost and how the presence of permafrost was assessed should be added in this section.
Response 6:
Thanks for your comment. Based on our data and field observations, we will add the analysis on the land use, the main soil types, the average soil depths and other available details on soil properties. Furthermore, details about the spatial distribution of discontinuous permafrost and how the presence of permafrost was assessed will also be added in this section.
Comment 7:
Lines 148-152: I suggest providing mean annual precipitation and temperature data here, and adding a table with the monthly characteristics of the meteorological variables during the sampling period.
Response 7:
Thanks for your comment. Based on our previous studies (Li et al,2021) and data, we will add a table with the monthly characteristics of the meteorological variables during the sampling period.
Li Zongjie, Li Zongxing*, Feng Qi*, Wang Xufeng, Mu Yanhu, Xin Huijuan, Song Lingling, Gui Juan, Zhang Baijuan. (2021). Hydrological effects of multiphase water transformation in Three-River Headwaters Region, China. Journal of Hydrology, 601, 126662: 1-16.
Comment 8:
In sections 3.1 and 3.2, the isotopic composition of soil water is not presented in relation to the isotopic signature of precipitation determined in the same sampling period.
Response 8:
Thanks for your comment. Based on the spatial distribution of national meteorological observation stations, A total of 375 precipitation (event scale) samples were collected from five stations at different altitudes from June 2019 to July 2020: Zhimenda (92.26° E, 34.14° N, 3540 m), Tuotuohe (34.22° N, 92.24° E, 4533 m), Zaduo (32.53° N, 95.17° E, 4066.4 m), Dari (33.45° N, 99.39° E, 3967 m), and Maduo (34.55° N, 98.13° E, 4272.3 m) In study region, which is because these five meteorological stations are staffed by observers, while the others are all automatic stations. Meanwhile , soil profiles of 1 m were excavated at 90 sampling sites In July 2019. So it is reasonable to analyze the stable isotope in soil water. In addition, the The spatial and temporal patterns of precipitation stable isotopes and their environmental significance have been analysed in previous studies (Li et al,2022, under review), so the basic information on stable isotopes of precipitation will be added in the revision.
Li Zongxing*, Feng Qi*, Wang Xufeng, Mu Yanhu, Xin Huijuan, Song Lingling, Gui Juan, Zhang Baijuan. (2022). Spatial and temporal patterns of precipitation stable isotopes and their environmental significance in the Three-River Headwater Region. Journal of Hydrology, under review.
Comment 9:
Lines 581-592: Figure 8 alone cannot support this discussion because the dual isotope plot depicts the isotopic composition of various water sources, from very distinct sampling sites distributed in a very large study area. My suggestion is providing an analysis based on small subcatchments where there are homogeneous soil characteristics.
Response 9:
Thanks for your comment. In addition to the average conditions in the study region, we will further analyse the sources of soil moisture in the permafrost and seasonal frozen zones of the Yangtze River, Yellow River and Lancang River sources region. It should be emphasised that this study mainly explores soil water sources from a large regional scale, while further systematic observations are needed for micro-scale studies, such as subcatchments.
Comment 10:
Lines 629-631: This sentence needs to be supported by the results of a statistical test.
Response 10:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 11:
Lines 632-635: Figure 9 is not meaningful because it presents a regression line fitted to only three data points.
Response 11:
Thanks for your comment. This is not the regression line fitted to only three data points, whereas The straight lines have been artificially added only to reflect the relationship between the three end elements when the soil water source is determined.
Comment 12:
Lines 637-647: Uncertainty should be added when presenting the contribution of precipitation and ground ice to soil water.
Response 12:
Thanks for your comment. the uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013).
Comment 13:
Lines 692-693: Based on Figure 11, I disagree with this sentence because all regressions seem to have very low coefficients of determination. Are the regressions significant?
Response 13:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 14:
Lines 698-703: The regressions should be tested to assess whether they are statistically significant or not.
Response 14:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 15:
Lines 698-736: Most of the sentences report results, which should be moved to the previous sections.
Response 15:
Thanks for your comment. These sentences reported the altitude effect of stable isotopes in soil water, which is different and Non-repetitive from the previous sections.
Comment 16:
Lines 766-770: The relations shown in Figure 12 are very weak, and thus they cannot support the statement that the isotopic composition is related to the soil moisture.
Response 16:
Thanks for your comment. We will analyze the results of a statistical test in the revision.
Comment 17:
Lines 805-812: The soil temperatures reported in Figure 12 and Table 3 are very high for soils where there is a permafrost layer. Are there soil temperature data measured very close to the permafrost layer? I suggest providing clear details about the spatial distribution of permafrost (and its depth) for the sampling sites where soil water was collected.
Response 17:
Thanks for your comment. Soil water and temperature were simultaneously measured at intervals of 20 cm in the soil profile during sampling using a portable soil water measurement instrument (TZS-IW) (Fig. 1). Soil temperature ranged from -40 ºC to 100 °C with an accuracy of ± 0.5 ºC. Soil moisture (% (m3/m3)) ranged between 0–100% with a response time of < 2 s. also, we will provide the clear details about the spatial distribution of permafrost (and its depth) for the sampling sites where soil water was collected.
Comment 18:
Tables 1, 2 and 3: Sample size per each group of data should be provided in the tables. Furthermore, information about the sampling times should be added in the captions of the tables.
Response 18:
Thanks for your comment. The average values of stable isotope, Sample size and sampling times will be added in the captions of the tables.
Comment 19:
Figure 1: I suggest adding the spatial distribution of permafrost in the study area, and showing the land use. The size of the labels is too small.
Response 19:
Thanks for your comment. Figure 1 will be revised based on our data.
Comment 20:
Figures 5 and 6: I suggest using the same colour scale for all depths, and showing where bare rocks and glaciers are located (it does not make sense having interpolated isotopic values where there is no soil). Furthermore, details about how the interpolated maps were obtained are not present in the Data and methods section.
Response 20:
Thanks for your comment. Figures 5 and 6 will be revised based this suggestions, and the spline function method with altitude effect of stable isotope will be presented in the Data and methods section.
Comment 21:
Figure 9: Error bars representing the spatio-temporal variability should be added but, given that the figure is not meaningful, I suggest removing the figure.
Response 21:
Thanks for your comment. This is not the regression line fitted to only three data points, whereas The straight lines have been artificially added only to reflect the relationship between the three end elements when the soil water source is determined.
Comment 22:
Figure 11: The figure is unreadable because the labels are too small, there are too many regression lines (probably the regressions are not significant), and the legend is missing. I suggest moving the equations in a new table.
Response 22:
Thanks for your comment. Figure 11 will be revised, and We will analyze the results of a statistical test in the revision. In addition, the equations will be moved in a new table.
Comment 23:
TECHNICAL CORRECTIONS
Lines 167-171: Please add a reference to support this sentence.
Line 183: It is unclear whether it is snowmelt water, glacier melt water or snowmelt from a glacierized area. I suggest rewording.
Line 236: Based on the description this seems to be glacier melt water, but it cannot be assessed whether it consists more of snowmelt or ice melt water.
Lines 315-327: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 338-345: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 348-354: This explanation also belongs to the discussion. I suggest moving the sentences to the proper section.
Line 526: I suggest replacing ‘there were high variations’ with ‘there was a high variability’.
Lines 560-568: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Line 579: It should be ‘indicating’.
Lines 582-594: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 832-838: These results should be moved to the previous sections.
Lines 647:655: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Lines 685-687: This explanation belongs to the discussion. I suggest moving the sentences to the proper section.
Line 692: The citation should be (Sprenger et al., 2017).
Response23:
Thanks for your corrections, and we will revise these in the newest version of paper.
Citation: https://doi.org/10.5194/hess-2021-558-AC1
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RC2: 'Comment on hess-2021-558', Anonymous Referee #2, 08 Jan 2022
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2021-558/hess-2021-558-RC2-supplement.pdf
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AC2: 'Reply on RC2', Li Zongxing, 22 Jan 2022
Overall comments:
Comment 1:
The manuscript presented huge field works of soil water/ice sampling in the permafrost area of the Headwater region of Three Rivers, obtaining 1140 samples. The isotope data collection in the Three-Rivers headwater region is a meaningful work. The manuscript elucidated the soil isotopic characteristics of different soil layers under different topographic gradients, vegetation and soil characteristics, estimated the contribution of different water sources in the soil water, and discussed influence factors on soil water sources. This work provides data support for the ecological restoration and maintenance of the Headwater region of the Three Rivers. Nonetheless, many results in the article are too repetitive and the discussion provides many new results but no real discussion on what was learned in this study. There are still many issues that need to be carefully modified.
Response 1:
Thank you very much for your guidance and advice. We will revise the manuscript thoroughly according to your comments, especially the sections of Result and Discussion. Frankly speaking, this is the first time that a systematic study of the sources of soil water on the Tibetan plateau has been carried out. As you say, this work provides data support for the ecological restoration and maintenance of the Headwater region of the Three Rivers.
Featured comments:
Comment 2:
The contribution of precipitation and ground ice to soil water was quantified. But the soil water mixing process was very complex, processes of glacier/snow melting, permafrost freezing and thawing, as well as the water exchange between the surface and subsurface were not well considered and discussed.
Response 2:
Thanks for your comment. Indeed, soil moisture processes are extremely complex, especially in permafrost areas. Studies on the sources of soil moisture are minimal due to the difficulty and cost of direct observational studies in Tibetan Plateau. Due to freeze-thaw processes, soil hydrological processes in the study area in fact only occur during the ablation period (May-October), while in July the snowpack has all melted away and all the glacial meltwater has flowed into the rivers, and the active layer of permafrost has largely melted, so that the main sources of soil water are precipitation and ground ice. Of course, the mechanisms influencing the source of soil water need further study, and the main objective of this study was to determine the source of soil water during the sampling period.
Comment 3:
The spatial and temporal differences of isotope data in different water sources are significant, and the uncertainty should be estimated in the quantification of the contribution of different water sources in the soil water. How to consider the heterogeneity of soil properties across such a huge study area? How did the sampling process distinguish the soil water or ice?
Response 3:
Thanks for your comment. The uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013).
Based on the systematic collection of samples, the central objective of this study is to quantify the sources of soil water. Samples were collected regardless of the soil type, which provided the basis for analysing the influence of soil heterogeneity on soil water sources, so in the revised manuscript we will further analyse soil water sources in different soil type zones. For the analysis of δ2H and δ18O, water was extracted from soil using a cryogenic freezing vacuum extraction system (LI-2000, Beijing Liga United Technology Co., Ltd., China), which can achieve complete extraction with high precision (details in the section of Collection and preparation of samples). ground ice has frozen in the soil and is collected directly in the soil profile as showing in fig.2.
Comment 4:
The influence of various factors on the soil water is difficult to distinguish by simple correlation analysis. What’s the meaning of those correlation analysis in the discussion with very low correlation coefficients? How to identify the mutual influence from several factors on the soil water and also the interrelationship among various factors?
Response 4:
Thanks for your comment. The factors influencing soil water are complex and diverse, and require systematic observation if they are to be understood clearly. However, current observational studies in the study region are almost non-existent. Therefore, in this study, systematic sampling was carried out in July, along with observations of soil moisture, temperature and its vegetation, and thus the relationship between these factors and soil moisture was analyzed.
Comment 5:
The authors should carry out a comprehensive language edit of the paper to make it concise and clear.
Response 5:
Thanks for your comment. a comprehensive language has been edited before submission.
Comment 6:
The formatting needs to be carefully laid out, including the formatting of references, etc.
Response 6:
Thanks for your comment. The formatting will be revised again in the revision.
Major issues:
Study Area:
Comment 7:
It is suggested to introduce the types of frozen soil and soil properties in the study area. The introduction of the study area is not specific enough and a little broad.
Response 7:
Thanks for your comment. We will revise the section of Study region, and add the introduction of the types of frozen soil and soil properties.
Sampling methods:
Comment 8:
Repeated sampling methods are not recommended.
Response 8:
Thanks for your comment. The Repeated sampling methods will be removed from the revision.
Results:
Comment 9:
The result part is a little long and the style of writing is not recommended in this part.
Response 9:
Thanks for your comment. The section of Result will be revised again.
Comment 10:
There are too many speculative descriptions, and it would be better to show more definite conclusions.
Response 10:
Thanks for your comment. many speculative descriptions will be changed to the definite conclusions.
Comment 11:
About point 6, please confirm that the runoff segmentation result only refers to July in the study area? The sampling time described is from June 2019 to July 2020. Why does the author only analyse the water source in a single month? Is it the average value of the whole basin? More discoveries may be made according to watershed zoning.
Response 11:
Thanks for your comment. precipitation samples were collected during from June 2019 to July 2020, whereas other samples for Ground ice, River water, Supra-permafrost water and Glacier snow meltwater in July 2019. So the soil water sources in July 2019 have been analyzed. In the revision, In addition to the average conditions in the study region, we will further analyse the sources of soil moisture in the permafrost and seasonal frozen zones of the Yangtze River, Yellow River and Lancang River sources region.
Discussion:
Comment 12:
Some contents of the discussion part and the results are repeated, and it is not recommended to put too much data.
Response 12:
Thanks for your comment. The sections of Result and Discussion will be revised again, and the repeated part will be removed.
Comment 13:
It is suggested to compare and discuss the research results of other scholars in this regard, and it is not recommended to put the research views of others behind the findings of the article.
Response 13:
Thanks for your comment. The sections of Discussion will be revised again, and we will compare and discuss the research results of other scholars in this regard.
Conclusion:
Comment 14:
The conclusion is repeated with the summary. It is not recommended to put too much data and refine it again.
Response 14:
Thanks for your comment. The sections of Conclusion will berefined again.
Figures and Tables:
Comment 15:
Please note the format of the table. You can see the requirements of submission.
The correlation information on the figure has been discussed in the article, so it is recommended not to repeat it.
Response 15:
Thanks for your comment. These figures and tables will be revised again.
References:
Comment 16:
References are repeated and check if there is a problem with the format.
Please check that the DOI and title of some references do not correspond.
Response 16:
Thanks for your comment. These references will be revised again.
Minor issues:
Comment 17:
Line229 Please explain the relationship between supra-permafrost water and soil water.
Line 224, Line235, Line243 repeat the narration.
Line 344 The relationship with the previous logical reasoning is unclear.
Line 410 Please explain what the same pattern is.
Response 17:
Thanks for your comment. These minor issues will be revised again.
TECHNICAL CORRECTIONS
Comment 18:
Pay attention to the format of the article, the upper and lower symbols of the text should be unified, and there are small details such as punctuation.
Response 18:
Thanks for your comment. The format will be revised again.
Comment 19:
It may be necessary to explain the definition of soil water in this paper, the relationship between soil water and supra-permafrost water, and the relationship between the depth of soil water research section and the depth of active layer.
Response 19:
Thanks for your comment. Based on our data, we will explain the definition of soil water in this paper, the relationship between soil water and supra-permafrost water, and the relationship between the depth of soil water research section and the depth of active layer in the revision.
Comment 20:
It is suggested to put forward the dominant influencing factors affecting the soil water content of different soil layers in permafrost according to different regions. There are many influencing factors mentioned in the article, but there is no focus.
Response 20:
Thanks for your comment. Based on our data, we will put forward the dominant influencing factors affecting the soil water content of different soil layers in permafrost according to different regions in the revision.
Comment 21:
This paper repeatedly mentioned the effects of evaporation and soil water migration on soil water isotopes, and there are few explanations for the isotopic characteristics of the soil layer near the underground ice.
Response 21:
Thanks for your comment. Based on our data, we will explanations for the isotopic characteristics of the soil layer near the underground ice.
Comment 22:
Please explain that only two end elements are considered in the runoff division, whether the contribution of snow and ice meltwater is considered, or why snow and ice meltwater is not considered.
Response 22:
Thanks for your comment. Based on our data, we will study the isotopic characteristics of the soil layer near the underground ice.
Comment 23:
The part of runoff segmentation need to add uncertainty analysis.
Response 23:
Thanks for your comment. The uncertainty of tracer--based hydrograph separations can be calculated using the error propagation technique (Genereux, 1998; Klaus and McDonnell, 2013).
Comment 24:
At present, the distribution of water content in each soil layer under different conditions reflected by isotope monitoring is beneficial or harmful to the ecological environment. It is suggested to supplement it, so as to promote the goal of better maintaining the ecological environment.
Response 24:
Thanks for your comment. Furthermore, there is an urgent need to develop technologies for fragile ecosystem restoration and improve the water conservation capacity for wetland ecosystem restoration/conservation, soil and water conservation enhancement, and ecological adaptation and regulation of climate change. Based on the above-mentioned aspects, it is necessary to vigorously implement ecological protection and construction projects, natural forest protection projects, and the conversion of cropland to forest and grassland projects. Such strategies could effectively deal with ecological problems, such as decreased water conservation capacity, increased soil erosion, and vegetation degradation, caused by future permafrost degradation.
Citation: https://doi.org/10.5194/hess-2021-558-AC2
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AC2: 'Reply on RC2', Li Zongxing, 22 Jan 2022
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