the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 May 2021
Diagnosing the impacts of permafrost on catchment hydrology: field measurements and model experiments in a mountainous catchment in western China
Abstract. Increased attention directed at permafrost hydrology has been prompted by climate change. In spite of an increasing number of field measurements and modeling studies, the impacts of permafrost on hydrological processes at the catchment scale are still unclear. Permafrost hydrology models at the catchment scale were mostly developed based on a “bottom-up” approach, hence by aggregating prior knowledge at the spot/field scales. In this study, we followed a “top-down” approach to learn from field measurement data to understand permafrost hydrology at the catchment scale. In particular, we used a stepwise model development approach to examine the impact of permafrost on streamflow response in the Hulu catchment in western China. We started from a simple lumped model (FLEX-L), and step-wisely included additional complexity by accounting for topography (i.e. FLEX-D) and landscape heterogeneity (i.e. FLEX-Topo). The final FLEX-Topo model, was then analyzed using a dynamic identifiability analysis (DYNIA) to investigate parameters’ temporal variation. By enabling temporal dynamics on several parameters, we diagnosed the physical relationships between parameter variation and permafrost impacts. We found that in the Hulu catchment: 1) the improvement associated to the model modifications suggest that topography and landscape heterogeneity are dominant controls on catchment response; 2) baseflow recession in permafrost regions is the result of a linear reservoir, and slower than non-permafrost regions; 3) parameters variation infers seasonally non-stationary precipitation-runoff relationships in permafrost catchment; 4) permafrost impacts on streamflow response mostly at the beginning of the melting season; 5) allowing the temporal variations of frozen soil related parameters, i.e. the unsaturated storage capacity and the splitter of fast and slow streamflow, improved model performance. Our findings provide new insights on the impact of permafrost on catchment hydrology in vast mountain regions of western China. More generally, they help to understand the effect of climate change on permafrost hydrology.
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RC1: 'Comment on hess-2021-264', Anonymous Referee #1, 15 Jul 2021
This manuscript attempts to understand the impact of permafrost on catchment hydrology in a small mountain catchment in west China. The topic is important. However, I feel there are some major problems of the manuscript need to be addressed. My comments are shown below:
- The conclusions of exp1-4 is that it is important to consider landscape heterogeneity in models to accurately simulate the hydrological processes in permafrost regions. This finding is not novel because the study area is mountain regions with high elevation gradient, similar conclusion may be found at many previous studies using distributed models. I suggest the author should further analyzed how the landscape heterogeneity influence the permafrost distribution and the impact of permafrost change on runoff, soil moisture and groundwater depth. Another problem is that not all the regions in the study area are covered by permafrost, some are seasonally frozen ground. The vegetation on permafrost and seasonally frozen ground may be different. How about these effects influenced the runoff? I suggest the author further explain them.
- It is not clear what is the physical meaning of parameter D in exp 8. It seems to represent the water flux from surface to subsurface. If so, it should be calculated in the model with time and it obviously can not be set as time-invariant. The parameters in the model need to be better physically explained.
- Figure 7, It seems that the red line is not the best fit for the data points. Why?
- The author found that a linear recession can well describe the flow recession processes, and a fixed parameter Ks = 80 d is identified. That may be related to the short study period (4 years) in this study. If a long period (30-40 years) is analyzed, Ks may be changed.
- Figure 10 seems important. Can the frozen depth simulation be involved in the model to improve the hydrological simulation?
Citation: https://doi.org/10.5194/hess-2021-264-RC1 -
AC1: 'Reply on RC1', Hongkai Gao, 16 Aug 2021
Reviewer#1
This manuscript attempts to understand the impact of permafrost on catchment hydrology in a small mountain catchment in west China. The topic is important. However, I feel there are some major problems of the manuscript need to be addressed. My comments are shown below:
Response: We thank Reviewer#1 for his/her positive comments on the importance of this research topic. Please find our replies to your detailed comments below.
1. The conclusions of exp1-4 is that it is important to consider landscape heterogeneity in models to accurately simulate the hydrological processes in permafrost regions. This finding is not novel because the study area is mountain regions with high elevation gradient, similar conclusion may be found at many previous studies using distributed models. I suggest the author should further analyzed how the landscape heterogeneity influence the permafrost distribution and the impact of permafrost change on runoff, soil moisture and groundwater depth. Another problem is that not all the regions in the study area are covered by permafrost, some are seasonally frozen ground. The vegetation on permafrost and seasonally frozen ground may be different. How about these effects influenced the runoff? I suggest the author further explain them.
Response: We thank Reviewer#1, for pointing out this important issue. Following Reviewer#1’s suggestion, we did further distinguish this study catchment into permafrost and seasonally frozen soil regions. We found that permafrost mostly distributes in the higher elevation regions, covered with alpine desert. As Reviewer#1 expected, permafrost and seasonally frozen ground have different vegetation cover. To avoid any confusion, in the revised manuscript, we will make three changes. Firstly, we will change “permafrost” to “frozen soil” throughout the manuscript. Secondly, we will add a map of the study site, showing permafrost and seasonally frozen soil regions. Thirdly, to further investigate the impact of seasonally frozen soil and permafrost on plot scale, we will add one more soil observation in permafrost area, with profile measurements of soil moisture and soil temperature.
2. It is not clear what is the physical meaning of parameter D in exp 8. It seems to represent the water flux from surface to subsurface. If so, it should be calculated in the model with time and it obviously can not be set as time-invariant. The parameters in the model need to be better physically explained.
Response: Yes, D represents the splitter between water flux from surface (fast response) to subsurface (slow response). I agree that it is an intuitive judgement to take account of a time-variant D while modeling. But as we discussed in the introduction, due to the scaling issue and the complexity of permafrost regions, many intuitive judgements in permafrost hydrology need to be tested and diagnosed, e.g. this parameter D. In this study, we used field measurements and DYNIA method to identify the timing and magnitude of D variation, which we believe is helpful to understand permafrost hydrology from top-down point of view.
3. Figure 7, It seems that the red line is not the best fit for the data points. Why?
Response: The red line is not for fitting the dots. It represents Ks = 80d, which is the bottom envelope of baseflow. The detailed equation derivation can be found in Section 4.2 and (Brutsaerts and Sugita, 2008; Fenicia et al., 2006).
4. The author found that a linear recession can well describe the flow recession processes, and a fixed parameter Ks = 80 d is identified. That may be related to the short study period (4 years) in this study. If a long period (30-40 years) is analyzed, Ks may be changed.
Response: We agree that Ks=80d is not a fixed or time-invariant value. Many previous studies (Ye et al., 2009; StJacques and Sauchyn 2009; Walvoord and Striegl 2007; Rennermalm et al. 2010; Niu et al., 2010) found the increasing trend of baseflow, and decreasing trend of intra-annual streamflow variability (Qmax/Qmin), because of climate change. This means the Ks, in the long term, is likely to change with permafrost degradation. But in this study, we focused on understanding the impacts of existing frozen soil on daily and event scale hydrological processes, of which the climate change effect could be negligible in such a short time scale. We have discussed this issue in Section 6.2. And in the revised manuscript, more relevant discussion will be added.
5. Figure 10 seems important. Can the frozen depth simulation be involved in the model to improve the hydrological simulation?
Response: Yes, Figure 10 is very important in this study. We highly appreciate your very constructive suggestion. Firstly, we would like to clarify that the frozen depth in Figure 10 is measured and not simulated. Secondly, in this study, our initial idea is to diagnose the impacts of permafrost on hydrological processes. Thus involving frozen depth to improve model performance is somehow outside the scope of this study. But anyway, during revision, we will seriously consider this suggestion, to involve the frozen-thawing process to improve hydrological simulation.
Citation: https://doi.org/10.5194/hess-2021-264-AC1
-
RC2: 'Comment on hess-2021-264', Anonymous Referee #2, 16 Jul 2021
Based on the measured data and model experiments, the authors analyzed the influence of different meteorological forcing and terrain distribution on the hydrological process in alpine mountainous areas, which is of great significance for the future development of frozen soil hydrological forecast. However, the story is not clear. Permafrost hydrology is a very complex process. This study only selects the data of one observation station to optimize the model, which I think is unreliable. Moreover, one of the results is that the permafrost impacts on streamflow response mostly at the beginning of the melting season, but I can't find any definite data and scientific insight in the manuscript. As another example, in the manuscript, the descriptions of the topography and landscape heterogeneity are dominant controls on catchment response, what we can learn. Therefore, it is not clear what scientific insight the manuscript provides.Â
Â
Other comments:
- In introduction,the achievements and shortcomings of the present research should be added, and the research significance of this paper should be explained.
- In the Study site and data section, the introduction to the use of data is somewhat simple, please add basic information.
- In the Study site and data section, how do you handle gaps in data? Please give a supplementary explanation.
- In the Modelling approach section, the authors recommend that the model be appropriately simplified by introducing too much space.
- The author sets all parameters to dynamic in Ex9, and explains how this pattern reflects the difference from other patterns.
- It is suggested that the authors increase the applicability of stepwise modeling in alpine mountains in the discussion section. To verify the feasibility of this paper.
- In the discussion section, the authors can compare and discuss the relevant similar studies in alpine mountains at home and abroad, and analyze the similarities and differences.
- What factors lead to the base flow recession in permafrost regions ?
- The author introduces that the study area is located in the northeast of the Qinghai-Tibet Plateau. It is suggested that the study area should be added to Fig. 1 to increase the overall readability of the article.
10.The conclusion of the manuscript is just a summary of the results. This section should include the main findings and outcomes of your work and describes how your research will impact the current state of science in the field.
- References have some format errors, please modify them carefully.
Citation: https://doi.org/10.5194/hess-2021-264-RC2 -
AC2: 'Reply on RC2', Hongkai Gao, 16 Aug 2021
Reviewer#2
Based on the measured data and model experiments, the authors analyzed the influence of different meteorological forcing and terrain distribution on the hydrological process in alpine mountainous areas, which is of great significance for the future development of frozen soil hydrological forecast. However, the story is not clear. Permafrost hydrology is a very complex process. This study only selects the data of one observation station to optimize the model, which I think is unreliable. Moreover, one of the results is that the permafrost impacts on streamflow response mostly at the beginning of the melting season, but I can't find any definite data and scientific insight in the manuscript. As another example, in the manuscript, the descriptions of the topography and landscape heterogeneity are dominant controls on catchment response, what we can learn. Therefore, it is not clear what scientific insight the manuscript provides.
Response: We thank Reviewer#2 for endorsing the importance of this study. We fully agree that permafrost hydrology is very complex. Among the complexities, we attempted to use the hydrological model as a tool to identify which processes play a more important role than others. We found that meteorological forcing and terrain distribution are important. Also landscape heterogeneity is essential to increase model performance. About what we have learned from this study, we summarized as five points: 1) the improvement associated to the model modifications suggest that topography and landscape heterogeneity are dominant controls on catchment response; 2) baseflow recession in permafrost regions is the result of a linear reservoir, and slower than non-permafrost regions; 3) parameter variation infers seasonally non-stationary precipitation-runoff relationships in permafrost catchment; 4) permafrost impacts on streamflow response mostly at the beginning of the melting season; 5) allowing the temporal variation of frozen soil related parameters, i.e. the unsaturated storage capacity and the splitter of fast and slow streamflow, improved model performance. For your detailed comments, we made point-by-point replies in below.
Other comments:
1. In introduction,the achievements and shortcomings of the present research should be added, and the research significance of this paper should be explained.
Response: We will further improve the introduction section, to highlight the scientific question we are targeting to.
2. In the Study site and data section, the introduction to the use of data is somewhat simple, please add basic information.
Response: We will improve Study site and data section.
3. In the Study site and data section, how do you handle gaps in data? Please give a supplementary explanation.
Response: Runoff data has a gap period in 2013 due to flooding and equipment malfunction. The meteorological forcing data is continuous, without gaps. While running the hydrological model, the runoff data gap does not impact model functioning, it only influences model evaluation (in calibration and validation). While evaluating the model, we did not include the data gap period.
4. In the Modelling approach section, the authors recommend that the model be appropriately simplified by introducing too much space.
Response: We are not quite sure we fully understand this question. If our understanding is correct, we will further improve Modelling section, and simplify the narratives.
5. The author sets all parameters to dynamic in Ex9, and explains how this pattern reflects the difference from other patterns.
Response: We are not quite sure we fully understand this question. If our understanding is correct, we will further improve our discussion on Ex9.
6. It is suggested that the authors increase the applicability of stepwise modeling in alpine mountains in the discussion section. To verify the feasibility of this paper.
Response: We will improve the discussion on stepwise modeling.
7. In the discussion section, the authors can compare and discuss the relevant similar studies in alpine mountains at home and abroad, and analyze the similarities and differences.
Response: This is a good point. We will add the comparison and discussion of previous studies in other alpine regions.
8. What factors lead to the base flow recession in permafrost regions ?
Response: This is a very important and basic question. For catchment without permafrost, the baseflow recession is influenced by many factors, including topography, geology, and vegetation. In permafrost regions, the existence of underground ice and freeze-thaw process make the baseflow recession more complicated. Interestingly, we found a beautiful linear baseflow recession in this permafrost catchment, similar to other general regions. Since the baseflow recession is the result of groundwater discharge, and the volume of groundwater reservoir is much larger than the topsoil reservoir, even in permafrost catchments, the large amount of groundwater reservoir may not be significantly influenced by topsoil thaw-freeze processes, whereby it still performs as a linear reservoir.
9. The author introduces that the study area is located in the northeast of the Qinghai-Tibet Plateau. It is suggested that the study area should be added to Fig. 1 to increase the overall readability of the article.
Response: This is a good point. We will add a map to show the location of study area on the Qinghai-Tibet Plateau.
10. The conclusion of the manuscript is just a summary of the results. This section should include the main findings and outcomes of your work and describes how your research will impact the current state of science in the field.
Response: We will improve the conclusion section, to include the main findings and outcomes of this work, and highlight the new knowledge we obtained in this study.
11. References have some format errors, please modify them carefully.
Response: We will correct the reference format thoroughly.
Citation: https://doi.org/10.5194/hess-2021-264-AC2
Status: closed
-
RC1: 'Comment on hess-2021-264', Anonymous Referee #1, 15 Jul 2021
This manuscript attempts to understand the impact of permafrost on catchment hydrology in a small mountain catchment in west China. The topic is important. However, I feel there are some major problems of the manuscript need to be addressed. My comments are shown below:
- The conclusions of exp1-4 is that it is important to consider landscape heterogeneity in models to accurately simulate the hydrological processes in permafrost regions. This finding is not novel because the study area is mountain regions with high elevation gradient, similar conclusion may be found at many previous studies using distributed models. I suggest the author should further analyzed how the landscape heterogeneity influence the permafrost distribution and the impact of permafrost change on runoff, soil moisture and groundwater depth. Another problem is that not all the regions in the study area are covered by permafrost, some are seasonally frozen ground. The vegetation on permafrost and seasonally frozen ground may be different. How about these effects influenced the runoff? I suggest the author further explain them.
- It is not clear what is the physical meaning of parameter D in exp 8. It seems to represent the water flux from surface to subsurface. If so, it should be calculated in the model with time and it obviously can not be set as time-invariant. The parameters in the model need to be better physically explained.
- Figure 7, It seems that the red line is not the best fit for the data points. Why?
- The author found that a linear recession can well describe the flow recession processes, and a fixed parameter Ks = 80 d is identified. That may be related to the short study period (4 years) in this study. If a long period (30-40 years) is analyzed, Ks may be changed.
- Figure 10 seems important. Can the frozen depth simulation be involved in the model to improve the hydrological simulation?
Citation: https://doi.org/10.5194/hess-2021-264-RC1 -
AC1: 'Reply on RC1', Hongkai Gao, 16 Aug 2021
Reviewer#1
This manuscript attempts to understand the impact of permafrost on catchment hydrology in a small mountain catchment in west China. The topic is important. However, I feel there are some major problems of the manuscript need to be addressed. My comments are shown below:
Response: We thank Reviewer#1 for his/her positive comments on the importance of this research topic. Please find our replies to your detailed comments below.
1. The conclusions of exp1-4 is that it is important to consider landscape heterogeneity in models to accurately simulate the hydrological processes in permafrost regions. This finding is not novel because the study area is mountain regions with high elevation gradient, similar conclusion may be found at many previous studies using distributed models. I suggest the author should further analyzed how the landscape heterogeneity influence the permafrost distribution and the impact of permafrost change on runoff, soil moisture and groundwater depth. Another problem is that not all the regions in the study area are covered by permafrost, some are seasonally frozen ground. The vegetation on permafrost and seasonally frozen ground may be different. How about these effects influenced the runoff? I suggest the author further explain them.
Response: We thank Reviewer#1, for pointing out this important issue. Following Reviewer#1’s suggestion, we did further distinguish this study catchment into permafrost and seasonally frozen soil regions. We found that permafrost mostly distributes in the higher elevation regions, covered with alpine desert. As Reviewer#1 expected, permafrost and seasonally frozen ground have different vegetation cover. To avoid any confusion, in the revised manuscript, we will make three changes. Firstly, we will change “permafrost” to “frozen soil” throughout the manuscript. Secondly, we will add a map of the study site, showing permafrost and seasonally frozen soil regions. Thirdly, to further investigate the impact of seasonally frozen soil and permafrost on plot scale, we will add one more soil observation in permafrost area, with profile measurements of soil moisture and soil temperature.
2. It is not clear what is the physical meaning of parameter D in exp 8. It seems to represent the water flux from surface to subsurface. If so, it should be calculated in the model with time and it obviously can not be set as time-invariant. The parameters in the model need to be better physically explained.
Response: Yes, D represents the splitter between water flux from surface (fast response) to subsurface (slow response). I agree that it is an intuitive judgement to take account of a time-variant D while modeling. But as we discussed in the introduction, due to the scaling issue and the complexity of permafrost regions, many intuitive judgements in permafrost hydrology need to be tested and diagnosed, e.g. this parameter D. In this study, we used field measurements and DYNIA method to identify the timing and magnitude of D variation, which we believe is helpful to understand permafrost hydrology from top-down point of view.
3. Figure 7, It seems that the red line is not the best fit for the data points. Why?
Response: The red line is not for fitting the dots. It represents Ks = 80d, which is the bottom envelope of baseflow. The detailed equation derivation can be found in Section 4.2 and (Brutsaerts and Sugita, 2008; Fenicia et al., 2006).
4. The author found that a linear recession can well describe the flow recession processes, and a fixed parameter Ks = 80 d is identified. That may be related to the short study period (4 years) in this study. If a long period (30-40 years) is analyzed, Ks may be changed.
Response: We agree that Ks=80d is not a fixed or time-invariant value. Many previous studies (Ye et al., 2009; StJacques and Sauchyn 2009; Walvoord and Striegl 2007; Rennermalm et al. 2010; Niu et al., 2010) found the increasing trend of baseflow, and decreasing trend of intra-annual streamflow variability (Qmax/Qmin), because of climate change. This means the Ks, in the long term, is likely to change with permafrost degradation. But in this study, we focused on understanding the impacts of existing frozen soil on daily and event scale hydrological processes, of which the climate change effect could be negligible in such a short time scale. We have discussed this issue in Section 6.2. And in the revised manuscript, more relevant discussion will be added.
5. Figure 10 seems important. Can the frozen depth simulation be involved in the model to improve the hydrological simulation?
Response: Yes, Figure 10 is very important in this study. We highly appreciate your very constructive suggestion. Firstly, we would like to clarify that the frozen depth in Figure 10 is measured and not simulated. Secondly, in this study, our initial idea is to diagnose the impacts of permafrost on hydrological processes. Thus involving frozen depth to improve model performance is somehow outside the scope of this study. But anyway, during revision, we will seriously consider this suggestion, to involve the frozen-thawing process to improve hydrological simulation.
Citation: https://doi.org/10.5194/hess-2021-264-AC1
-
RC2: 'Comment on hess-2021-264', Anonymous Referee #2, 16 Jul 2021
Based on the measured data and model experiments, the authors analyzed the influence of different meteorological forcing and terrain distribution on the hydrological process in alpine mountainous areas, which is of great significance for the future development of frozen soil hydrological forecast. However, the story is not clear. Permafrost hydrology is a very complex process. This study only selects the data of one observation station to optimize the model, which I think is unreliable. Moreover, one of the results is that the permafrost impacts on streamflow response mostly at the beginning of the melting season, but I can't find any definite data and scientific insight in the manuscript. As another example, in the manuscript, the descriptions of the topography and landscape heterogeneity are dominant controls on catchment response, what we can learn. Therefore, it is not clear what scientific insight the manuscript provides.Â
Â
Other comments:
- In introduction,the achievements and shortcomings of the present research should be added, and the research significance of this paper should be explained.
- In the Study site and data section, the introduction to the use of data is somewhat simple, please add basic information.
- In the Study site and data section, how do you handle gaps in data? Please give a supplementary explanation.
- In the Modelling approach section, the authors recommend that the model be appropriately simplified by introducing too much space.
- The author sets all parameters to dynamic in Ex9, and explains how this pattern reflects the difference from other patterns.
- It is suggested that the authors increase the applicability of stepwise modeling in alpine mountains in the discussion section. To verify the feasibility of this paper.
- In the discussion section, the authors can compare and discuss the relevant similar studies in alpine mountains at home and abroad, and analyze the similarities and differences.
- What factors lead to the base flow recession in permafrost regions ?
- The author introduces that the study area is located in the northeast of the Qinghai-Tibet Plateau. It is suggested that the study area should be added to Fig. 1 to increase the overall readability of the article.
10.The conclusion of the manuscript is just a summary of the results. This section should include the main findings and outcomes of your work and describes how your research will impact the current state of science in the field.
- References have some format errors, please modify them carefully.
Citation: https://doi.org/10.5194/hess-2021-264-RC2 -
AC2: 'Reply on RC2', Hongkai Gao, 16 Aug 2021
Reviewer#2
Based on the measured data and model experiments, the authors analyzed the influence of different meteorological forcing and terrain distribution on the hydrological process in alpine mountainous areas, which is of great significance for the future development of frozen soil hydrological forecast. However, the story is not clear. Permafrost hydrology is a very complex process. This study only selects the data of one observation station to optimize the model, which I think is unreliable. Moreover, one of the results is that the permafrost impacts on streamflow response mostly at the beginning of the melting season, but I can't find any definite data and scientific insight in the manuscript. As another example, in the manuscript, the descriptions of the topography and landscape heterogeneity are dominant controls on catchment response, what we can learn. Therefore, it is not clear what scientific insight the manuscript provides.
Response: We thank Reviewer#2 for endorsing the importance of this study. We fully agree that permafrost hydrology is very complex. Among the complexities, we attempted to use the hydrological model as a tool to identify which processes play a more important role than others. We found that meteorological forcing and terrain distribution are important. Also landscape heterogeneity is essential to increase model performance. About what we have learned from this study, we summarized as five points: 1) the improvement associated to the model modifications suggest that topography and landscape heterogeneity are dominant controls on catchment response; 2) baseflow recession in permafrost regions is the result of a linear reservoir, and slower than non-permafrost regions; 3) parameter variation infers seasonally non-stationary precipitation-runoff relationships in permafrost catchment; 4) permafrost impacts on streamflow response mostly at the beginning of the melting season; 5) allowing the temporal variation of frozen soil related parameters, i.e. the unsaturated storage capacity and the splitter of fast and slow streamflow, improved model performance. For your detailed comments, we made point-by-point replies in below.
Other comments:
1. In introduction,the achievements and shortcomings of the present research should be added, and the research significance of this paper should be explained.
Response: We will further improve the introduction section, to highlight the scientific question we are targeting to.
2. In the Study site and data section, the introduction to the use of data is somewhat simple, please add basic information.
Response: We will improve Study site and data section.
3. In the Study site and data section, how do you handle gaps in data? Please give a supplementary explanation.
Response: Runoff data has a gap period in 2013 due to flooding and equipment malfunction. The meteorological forcing data is continuous, without gaps. While running the hydrological model, the runoff data gap does not impact model functioning, it only influences model evaluation (in calibration and validation). While evaluating the model, we did not include the data gap period.
4. In the Modelling approach section, the authors recommend that the model be appropriately simplified by introducing too much space.
Response: We are not quite sure we fully understand this question. If our understanding is correct, we will further improve Modelling section, and simplify the narratives.
5. The author sets all parameters to dynamic in Ex9, and explains how this pattern reflects the difference from other patterns.
Response: We are not quite sure we fully understand this question. If our understanding is correct, we will further improve our discussion on Ex9.
6. It is suggested that the authors increase the applicability of stepwise modeling in alpine mountains in the discussion section. To verify the feasibility of this paper.
Response: We will improve the discussion on stepwise modeling.
7. In the discussion section, the authors can compare and discuss the relevant similar studies in alpine mountains at home and abroad, and analyze the similarities and differences.
Response: This is a good point. We will add the comparison and discussion of previous studies in other alpine regions.
8. What factors lead to the base flow recession in permafrost regions ?
Response: This is a very important and basic question. For catchment without permafrost, the baseflow recession is influenced by many factors, including topography, geology, and vegetation. In permafrost regions, the existence of underground ice and freeze-thaw process make the baseflow recession more complicated. Interestingly, we found a beautiful linear baseflow recession in this permafrost catchment, similar to other general regions. Since the baseflow recession is the result of groundwater discharge, and the volume of groundwater reservoir is much larger than the topsoil reservoir, even in permafrost catchments, the large amount of groundwater reservoir may not be significantly influenced by topsoil thaw-freeze processes, whereby it still performs as a linear reservoir.
9. The author introduces that the study area is located in the northeast of the Qinghai-Tibet Plateau. It is suggested that the study area should be added to Fig. 1 to increase the overall readability of the article.
Response: This is a good point. We will add a map to show the location of study area on the Qinghai-Tibet Plateau.
10. The conclusion of the manuscript is just a summary of the results. This section should include the main findings and outcomes of your work and describes how your research will impact the current state of science in the field.
Response: We will improve the conclusion section, to include the main findings and outcomes of this work, and highlight the new knowledge we obtained in this study.
11. References have some format errors, please modify them carefully.
Response: We will correct the reference format thoroughly.
Citation: https://doi.org/10.5194/hess-2021-264-AC2
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