This study conducted a detailed analysis on the soil water in the Three-river Headwaters Region, including its spatiotemporal variation, water sources and influence factors. The end member mixing analysis was adopted to determine the contributions of multiple soil water sources, based on the isotope data of different water bodies. The results are based on large amount of field measurement data, and could provide useful information about the soil water in this region, making it worth publishing in HESS. However, there are some issues not clear enough to me, which should be clarified before acceptance. I also recommend to improve the English writing thoroughly with the aid of a native speaker or professional English editing service.

Thank you very much for your comments. We will spend a great deal of time for improving the language and general presentation with the help of professional English editing service.

-Introduction: Please introduce the definition and importance of soil water sources, and reduce the references not related to this topic. It seems that the authors are introducing the research background of soil water (e.g., estimation of soil water, the change of soil water under climate change), but suddenly draw the conclusion that the research on the soil water sources is important. In my opinion, they are two different issues.

Thank you very much for your comments. We will revise the introduction as suggested, focusing on the definition and importance of soil water. On the other hand, we will remove sentences and references that are not relevant to the topic.

-Method: The definition of soil water sources is confusing. The authors collected soil water, precipitation, ground ice, river water, supra-permafrost water and glaciers snow meltwater, but only calculated the contributions of precipitation, ground ice and glaciers snow meltwater in the results section. So was the isotope data of river water and supra-permafrost water used in the calculation? Please clarify.

Thank you very much for your comments. River water and permafrost water are used to help us determine the relationship and transformation of various water bodies in the study region. For example, in Figure 5, through the clustering relationship of various stable isotopes of water bodies, we can better identify the relationship between water bodies and verify the rationality of the research results through this relationship. At the same time, we will also elaborate on the role of such data in the revised manuscript.

Discussion:

- The authors calculated the correlation between soil moisture and meteorological/vegetation variables in this section, which is not clear to me. If I understand correctly, the soil moisture data was obtained by measuring the soil samples. However, the soils were sampled in a spatially distributed way, which means that they were sampled at several sites in a one-time field work, rather than sampled continuously during a long period, so there is only one soil moisture data in each site/grid in one month. It is confusing for me how to calculate the correlation between the one-time soil water data and the continuous meteorological/vegetation data. Please clarify this in the method section.

     Thank you very much for your comments. Although we sampled in a one-time field work, however, our sampling points (2600 samples) cover almost the whole area of the study area. More importantly, we will measure the corresponding soil temperature, soil moisture and other data when collecting each soil sample. In other words, all data, including soil stable isotopes, soil temperature, soil moisture are on points, but we have many of these points, so we put them in one space and did their correlation.

We will clarify this in the method section.

- The authors described the correlation analysis results in details in this section. However, given that this paper focused on the soil water sources, I think there should be discussions about the relations between the isotope-based results and the correlation analysis results. Meanwhile, the connection between the water source results and the implications on vegetation restoration is not clear. I suggest the authors to do some analysis on the influence of soil water sources on vegetation, to combine them together.

Thank you very much for your comments. We will supplement the relations between the isotope-based results and the correlation analysis as you suggested on the one hand. On the other hand, we will do some analysis on the influence of soil water sources on vegetation.

-Conclusions: Please shorten the conclusion section and summarize 3~4 points of most important messages.

Thank you very much for your comments. We will revise the conclusions as suggested.

-Please find the annotation in the attached pdf file for the minor issues, including comments on English writing, Figure and some specific questions.

Thank you very much for your comments. We will revise the manuscript carefully according to your suggestion

In this work, Zongxing et al., has quantified the soil water sources in the Three-River Headwater Region under different ablation periods used two thousand six hundred samples of soil water, precipitation, river water, ground ice meltwater, supra-permafrost water, and glacier snow meltwater samples. The topic of this paper was new and original and the method was reasonable. The analysis of this article also was perfect. In general, the outcome of this work can be interesting for the scientific community. I suggested that this manuscript should be published after moderate modifications.

1. In abstract ：Some sentences are too colloquial, please revise them. For examples the sentence of “So it is crucial to understand the spatial-temporal changes in soil water sources.” and “So there is an urgent need to monitor soil water, warn of vegetation degradation associated with soil moisture loss, and identify reasonable water-soil conservation and vegetation restoration patterns.”

Thank you very much for your comments. We have modified such sentences as suggested.

1. Line 36：Change “Soil water is a vital water resource, a link between precipitation, surface water, soil water, and groundwater” to “Soil water is an important water resource, also a link between precipitation, surface water, soil water, and groundwater”

Thank you very much for your comments. We have Changed “Soil water is a vital water resource, a link between precipitation, surface water, soil water, and groundwater” to “Soil water is an important water resource, also a link between precipitation, surface water, soil water, and groundwater”

1. Line 46: Change “Tetzlaff, & Soulsby” to “Tetzlaff and Soulsby”

Thank you very much for your comments. We have Changed “Tetzlaff, & Soulsby” to “Tetzlaff and Soulsby”

1. Line 107: Change “followed by air temperature and wind speed in the sources region of the Yellow river” to “followed by air temperature and wind speed in the source region of the Yellow River”

Thank you very much for your comments. We have Changed “followed by air temperature and wind speed in the sources region of the Yellow river” to “followed by air temperature and wind speed in the source region of the Yellow River”

1. 4．Line 117-118 Change “The TRHR is undergoing a glacier retreat, permafrost degradation, precipitation increase, snowfall decrease, water conservation decrease” to “The TRHR is undergoing a glacier retreat, permafrost degradation, precipitation increase, snowfall decreases, water conservation decrease”

Thank you very much for your comments. We have Changed “The TRHR is undergoing a glacier retreat, permafrost degradation, precipitation increase, snowfall decrease, water conservation decrease” to “The TRHR is undergoing a glacier retreat, permafrost degradation, precipitation increase, snowfall decreases, water conservation decrease”

1. Line 122-123: Change “So there is an urgent need to quantify the soil water sources to improve the effectiveness of ecological restoration in permafrost regions.” to “Thus there is an urgent need to quantify the soil water sources to improve the effectiveness of ecological restoration in permafrost regions.”

Thank you very much for your comments. We have Changed “So there is an urgent need to quantify the soil water sources to improve the effectiveness of ecological restoration in permafrost regions.” to “Thus there is an urgent need to quantify the soil water sources to improve the effectiveness of ecological restoration in permafrost regions.”

1. Line 241: Change “Glaciers snow meltwater” to “Glacier snow meltwater”

Thank you very much for your comments. We have Changed “Glaciers snow meltwater” to “Glacier snow meltwater”

1. River names in manuscripts should be capitalized. For example “Lancangjiang River”

Thank you very much for your comments. We've capitalized all the river names that appear in the manuscript.

1. Line 298: Change “heavy ablation period” to “strong ablation period”

Thank you very much for your comments. We have Changed “heavy ablation period” to “strong ablation period”

1. Please change all tables to triple table.

Thank you very much for your comments. We have replaced all the tables in the manuscript with three-line tables.

Table.1 The average values of stable isotopes and relationship between δ¹⁸O and d-excess for soil waters in TRHR

Table.2 The LEL for soil waters in study region

1. Line 300-301: Change “Again it becomes higher in September, while it exhibits an opposite trend for d-excess (Table.1).” to “It again becomes higher in September, while it exhibits an opposite trend for d-excess (Table.1).”

Thank you very much for your comments. We have Changed “Again it becomes higher in September, while it exhibits an opposite trend for d-excess (Table.1).” to “It again becomes higher in September, while it exhibits an opposite trend for d-excess (Table.1).”

1. Line 319: Give the terms “LWML” and “LEL” a definition when they first appeared

Thank you very much for your comments. “LWML” and “LEL” were defined on line 291: “In addition, the global meteoric water line (GMWL), local meteoric water lines (LMWLs), and evaporation line (LEL) have been used to analyze the relationship between soil water and other waters in the TRHR.”

1. Line 323-325 Change “The slope and intercept of LEL for the 0‒40 cm layer were the lowest during the heavy ablation period” to “The slope and intercept of LEL for the 0‒40 cm layer was the lowest during the heavy ablation period”

Thank you very much for your comments. We have Changed “The slope and intercept of LEL for the 0‒40 cm layer were the lowest during the heavy ablation period” to “The slope and intercept of LEL for the 0‒40 cm layer was the lowest during the heavy ablation period”

1. Line 354: “snow meltwater” or “glacier snow meltwater”?

Thank you very much for your comments. It is “glacier and snow meltwater”. We have modified it.

1. Line 354: “supra-permafrost” or “supra-permafrost water”?

Thank you very much for your comments. It is supra-permafrost water. We have modified it.

1. Line 437: please change “Based on the calculation, precipitation, ground ice, and snow meltwater account for approximately 72%, 20%, and 8% of soil water, respectively” to “Based on the calculation, precipitation, ground ice water, and glacier snow meltwater account for approximately 72%, 20%, and 8% of soil water, respectively”

Thank you very much for your comments. We have Changed “Based on the calculation, precipitation, ground ice, and snow meltwater account for approximately 72%, 20%, and 8% of soil water, respectively” to “Based on the calculation, precipitation, ground ice water, and glacier snow meltwater account for approximately 72%, 20%, and 8% of soil water, respectively”

1. Please make sure the citation appeared in the article are consistent with those listed in the Reference part.

Thank you very much for your comments. We have checked all the references to make sure that the manuscript is consistent with those listed

1. The conclusion part is too long. I recommend rephrase this paragraph and state the importance of the findings.

Thank you very much for your comments. We will revise the conclusions as suggested.

1. Please refer to the journal requirements to modify the format of the references

Thank you very much for your comments. We will carefully modify the format of the references according to the requirements of the journal.

1. English writing: The English writing of this manuscript should be improved thoroughly. The issues include the choice of word, grammar issue and the structure of sentence.

Thank you very much for your comments. We will spend a great deal of time for improving the language and general presentation again.