Hydrogeology of Reclaimed Floodplain in A Permafrost Area, Yakutsk, Russia

Round 1

Reviewer 1 Report

General comment

The article entitled "Hydrogeology of reclaimed floodplain in a permafrost area, Yakutsk, Russia» presented by Pavlova et al. presents original data concerning the links between the Lena River, permafrost distribution and groundwater dynamics in a complex area of the reclaimed floodplain of Lena. Creating new land from riverbeds and lake beds of the Lena floodplain was necessary to extend residential and commercial areas in the Yakutsk eastern part from late 70s/early 80s. The materials of the paper consist on hydrogeological, geochemical and thermal data obtained spatially and temporally in two areas of the reclaimed floodplain (namely districts 202 and 203), both submitted to the hydrological regime of the Lena River and regional groundwater system.

First, I would like to indicate that, as a non-native English reviewer, I don't have the skills to assess the quality of the English of the paper.

Even if there are new, interesting data concerning groundwater and permafrost, both domains for which we miss data for Siberia, I would recommand major revisions of the paper. First, a reorganization of the article will help to better identify new interpretations (part « results and discussion ») from that wasalready  existing from past data since numerous data and information are already given in the introduction and the part 3. Secondly, the authors must clearly separate past data (already published) from the new ones (never published). Moreover, all published past data / observation/interpretation must have a reference, which is not always the case.Thirdly, the section « materials and methods » announces a large dataset that is never presented or used in the following sections, e.g. thermal data, several time series, hydrochemical measurements. This suggests that the available dataset is very rich and the discussion does not benefit from it.  Finally, in my opinion, the results are too summurized and are not enough discussed. The conclusions are brought without any real discussions based on the available data. The paper do not present the data in a Table, except for the Lena River and the precipitation between 1992-95 and 2014-2019. I encourage the authors to produce new figures and tables to highlight the processes invoked in the discussion.

In addition to the general comment, hereafter some questions or suggestions:

• The article deals with the question of groundwater dynamics and permafrost in a reworked sedimentary formation. In a context of marked climate change, especially in Arctic / subarctic zones, it is astonishes to have nothing in this paper about the impact of climate even on climate change on the dynamics observed, e.g. that of the permafrost top. I am surprised that the positioning of the permafrost is more influenced by the nature of the sediments, the position of the Lena riverwater than by the climate itself over the investigated timespan (26 years) ?
• 1. Do the authors have to hydrogeological /hydrogeochemical data under Yakutsk in order to expand further west the study area ? A regional potentiometric cross-section or map will be helpul to discuss the groundwater flow direction ?
• Lines 222-228: Hydrogeochemical results seem really important to discuss the direction of the flows and the origin of groundwater below the studied floodplains. I would suggest to detail those results in order to be more convincing. Comparing TDS data are not enough to establishing links between water bodies.
• In several sentences of the paper, different complement of « Talik » are used: suprapermafrost subaerial, relict sub-lake, suprapermafrost permeable, water-bearing, suprapermafrost water-bearing, relict lakebed, etc. It is not always easy to know exactly what this represents. Do these designations come from a published nomenclature, in Russian? If not, these terms have to be defined.
• The paper mentions « buried sandbars ». These sedimentary bodies are not indicated neither
• on Fig. 2 or in Fig. 3. Where are they ? Why these sandbars may have different hydrogeological properties from other sediments of the reclaimed floodplain ?

Detailed remarks:

Abstract  (L9-22)

• L9: « state in the permafrost… »: reconsider « state » since it is not precise enough. What kind of state
• Not enough numerical data in the abstract

Introduction (L26-57)

• - From L. 37 (district 202...] to L. 53, the authors give detailed information about the studied sites that must be displaced in a section « site description » below. This information has no place in the introduction which has to be devoted to a state of the art. When removing these lines, the introduction becomes too short. Anyway, it does not contains sufficient bibliographic references, e.g.  concerning the Siberian permafrost, taliks, groundwater, climate change, impact of urbanization in (Central) Siberia.
• 46-L47: « field observations, laboratory experiments and full-scale testing was carried out prior to construction ». Explain what it was all about in a new section « site description ».

Materials and methods (L.58-106).

• A new table will be useful here to summerize the collected data and eventually the past data (with appropriate reference).
• Lines 58-78 have to be displaced in a new section « site description ».
• 80 What do you mean by adjacent District 203 area ? where is it on the map (Fig. 2) ?
• L82: Aeral meaning spatial ?
• L84: explain what is a cluster ? Does this refer to the numbers in Figure 2. In this case, indicate also these numbers in the text when dealing with clusters.
• L87: explain how the moisture soil determination was made ? Are they volumetric or gravimetric humidities  ?
• 94. Remove «-»  between 0.5 and m.
• 106  How did you collect the water samples ? explain what are the onfield measurements made ? What are the accuracies of the chemical analysis ? Name of device used for these analyses ?

Natural and modified environmental characteristics  (L. 107-187).

This section is a mixture between a site description and  results. For my point of view, this section has to be separate into 2 sections: site description before «Materials and methods » and « results » after « Materials and methods ». 

• 111: Indicate the period corresponding to the given discharge value of the Lena ? Also give the standard deviation ?
• L114-117: What are the years corresponding to these data ? are they internannual values ? one year values ?
• 117: better explain what 94.7m refer to ?
• L124: a reference is missing after « …. Directions ».
• L131-137: indicate the sampling dates corresponding to the given TDS values ? Give a table with chemical analyses. Chemical type, TDS and pH are not enough to discuss the mixing between « deep » groundwater and riverwater and the origin of groundwater. Please consider to write a sub-section dedicated to water chemistry with L. 154 to L.159.
• 135: replace « Acidity… » by « pH value ». Lena water in acidic to neutral.
• 137:what is stem ?
• 143: add a s to clays.
• L 148-149: Please reconsider the sentence « The suprapermafrost groundwaters are confined below by permafrost».
• 150 what is the reference of this value of 320 m. What was it measured ?
  1. 168: Explain what does the contamination come from ? What is the flow pattern for wasterwater to discharge intn the alluvium water table ?
• L181: what is the new land mentionned here ? which districk ?
• Table 1: where is the Lena station ? indicate it on a map (Fig 1 or 2). What is « summer precipitation » ? Dates ? Indicate the units of « duration of water level above 87 m » (days ?) ? one number is a 2-digit decimal number.
• On Fig. 1, why the ancient oxbox lakes are not visible on the 1946 map ?
• Figure 2: Poor quality. Change definition and symbol of 6. And 7. (too close).

Results and discussion  (L.188-267).

• In several parts of this section, we miss the information of the measurement dates.
• Please reconsider this part in and try to separate the results from the discussion. For the latter, I suggest to organize it in several sub-sections with a clear title.
• L194-196: usefulness of water content in the discussion ?
• L 198: you mention that the groundwater in unconfined. Is it true ? even during the winter when the soils freezes up ?
• L204: How do you interprete that at the end of winter (March-early May), the rivel level is 3-4 m lower than the groundwater level ? what is the reason of a  hydrodynamical desequilibrium between the Lena and the water-table ? Could the high level of the water table be explain by a discharge from the unfreeze regional aquifer toward the river ?
• L207-208: « As the flood…. July».  What data support this conclusion ?
• 222-223: To be demonstrated with data.
• 228: what « ultra-fresh water» means ?
• 244-246: A reference is missing here (previous studies….)
• L248 : « transmission by pressure ». How do you demonstrate this ? Better explain.
• L251-252 : better explain here the methods used (maybe add information in section 2 « Materials and methods »)
• 3 : With the same symbol, you draw the potentiometric level of the suprapermafrost water-table for different seasons of 2016. It is confusing.

The shape of potentiometric level of 1990 between wells 10 and 12 shows a little depression. Why ?

Could you extend the cross-section lateraly toward the Lena (indication of level ranges) and/or toward Yakutsk, even further East (indication of the piezometric level of the regional aquifer) ?

• 4: Symbols 4 and 9 are too close. Please consider to change the colors.

How do you interprete that there are no apparent relationship between the rainfall amounts and the Lena level ? Is it because the river discharge is also linked to air temperature conditions (melt/freeze) and/or to rainfall of upstream areas ?  please indicate it in the text.

In 2019, the time-series of Lena level seems discontinuous. In this case, I suggest to remove the continuous blue line that gives the impression of a continuous dataset.

• Fig 5: please enlarged this figure to make it more clear. Indicate in the figure captions that it is a schematic cross-section.

References

• The reference [14] is not cited in the text.

Author Response

Point 1: The article deals with the question of groundwater dynamics and permafrost in a reworked sedimentary formation. In a context of marked climate change, especially in Arctic / subarctic zones, it is astonishes to have nothing in this paper about the impact of climate even on climate change on the dynamics observed, e.g. that of the permafrost top. I am surprised that the positioning of the permafrost is more influenced by the nature of the sediments, the position of the Lena riverwater than by the climate itself over the investigated timespan (26 years) ?

Response 1: It is true that the mean annual air temperature shows an increase in central Yakutia starting from the 1980s. This warming trend is mainly due to shorter winter season and warmer winter temperatures. The effect of this warming on permafrost is not uniform. Some locations (especially those containing ice wedges) are experiencing deepening of the active layer. In Yakutsk, ground temperatures have been increasing within the layer of annual temperature fluctuations in recent decades, but they remain well below 0°C. Some locations, on the contrary, show freezing of suprapermafrost taliks. In suburban areas on the low terrace, no significant changes in active layer thickness or temperature have been observed. These findings are reported in [23, 26, 38-40]. The purpose of this study was to investigate the hydrodynamic regime of an anthropogenic aquifer and its interaction with natural hydrological and hydrogeological conditions. Therefore, the impact of climate change on the aquifer is not addressed in the article. However, we have added to sub-section “Soil Saturation Mechanisms” information on air temperature changes during the last 40 years and noted that there is no prerequisite for freezing of suprapermafrost taliks at the study site.

Point 2: Do the authors have to hydrogeological /hydrogeochemical data under Yakutsk in order to expand further west the study area ? A regional potentiometric cross-section or map will be helpul to discuss the groundwater flow direction ?

Response 2: Figure 1 is replaced and Figure 6 is added They illustrate the occurrence of taliks in the reclaimed floodplain area. In the adjacent area (first terrace of the Lena River above the floodplain) the permafrost is vertically continuous (i.e., the active layer which thaws in summer freezes back completely during winter down to the permafrost table). Groundwaters in the terrace area exist from June to December when they freeze. Flow from these aquifers to the study sites is very limited due to their short existence period and low thickness, the flatness of the ground surface (slope angle is one thousandth of unity) and the heavy disruption of natural drainage patterns in the city. Characterization of environmental conditions in the low terrace area is added to Section “Problem Statement and Methods”.

Point 3: Lines 222-228: Hydrogeochemical results seem really important to discuss the direction of the flows and the origin of groundwater below the studied floodplains. I would suggest to detail those results in order to be more convincing. Comparing TDS data are not enough to establishing links between water bodies.

Response 3: Figure 5 is added showing the chemical composition of natural waters in the study area. Table 2 is added which shows seasonal changes in the chemical composition of groundwater and river water.

Point 4: In several sentences of the paper, different complement of « Talik » are used: suprapermafrost subaerial, relict sub-lake, suprapermafrost permeable, water-bearing, suprapermafrost water-bearing, relict lakebed, etc. It is not always easy to know exactly what this represents. Do these designations come from a published nomenclature, in Russian? If not, these terms have to be defined.

Response 4:The terms denoting talik types were used following the classification by N.N. Romanovsky (1983). Reference to this classification is added.

Point 5: The paper mentions « buried sandbars ». These sedimentary bodies are not indicated neithe on Fig. 2 or in Fig. 3. Where are they ? Why these sandbars may have different hydrogeological properties from other sediments of the reclaimed floodplain ?

Response 5:They are shown in Fig. 2. Description the lithology of soils beneath the buried lakes and bars between these lakes is given in Section “Natural and Modified Environmental Conditions in the Floodplain”.

Point 6: Abstract  (L9-22): L9: « state in the permafrost… »: reconsider « state » since it is not precise enough. What kind of state.

Response 6: Rewritten.

Point 7: Introduction (L26-57) From L. 37 (district 202...] to L. 53, the authors give detailed information about the studied sites that must be displaced in a section « site description » below. This information has no place in the introduction which has to be devoted to a state of the art. When removing these lines, the introduction becomes too short. Anyway, it does not contains sufficient bibliographic references, e.g.  concerning the Siberian permafrost, taliks, groundwater, climate change, impact of urbanization in (Central) Siberia.

Response 7: Information about the studied sites is moved to section “Problem Statement and methods”. Introduction is extended.

Point 8: 46-L47: « field observations, laboratory experiments and full-scale testing was carried out prior to construction ». Explain what it was all about in a new section « site description ».

Response 8: Information is added about the results obtained.

Point 9: Materials and methods (L.58-106). A new table will be useful here to summerize the collected data and eventually the past data (with appropriate reference). Lines 58-78 have to be displaced in a new section « site description ». 80 What do you mean by adjacent District 203 area ? where is it on the map (Fig. 2) ? L82: Aeral meaning spatia

Response 9: is displaced to new section ‘Problem Statement and Methods”

the word adjacent is removed. “Areal changed to “spatial”

Point 10: L84: explain what is a cluster ? Does this refer to the numbers in Figure 2. In this case, indicate also these numbers in the text when dealing with clusters.L87: explain how the moisture soil determination was made ? Are they volumetric or gravimetric humidities  ?94. Remove «-»  between 0.5 and m.

How did you collect the water samples ? explain what are the onfield measurements made ? What are the accuracies of the chemical analysis ? Name of device used for these analyses ?

Response 10: cluster means a group of two boreholes; one is for hydrogeological observation and the other is for ground temperature measurements. This is explained in the text as follows: «It consisted of four clusters of paired hydrogeological and thermal boreholes». The word “gravimetric” added to the text. «-»  between 0.5 and m is removed.

Description added to the methods. Name of device is not given because this may be considered manufacturer advertisement.

Point 11: This section is a mixture between a site description and  results. For my point of view, this section has to be separate into 2 sections: site description before «Materials and methods » and « results » after « Materials and methods ». 

• 111: Indicate the period corresponding to the given discharge value of the Lena ? Also give the standard deviation ?
• L114-117: What are the years corresponding to these data ? are they internannual values ? one year values ?
• 117: better explain what 94.7m refer to ?

L124: a reference is missing after « …. Directions ».

This is replaced to section «Natural and Modified Environmental Characteristics of the Floodplain Area»

Response 11:The discharge data for the Lena River was taken from the literature, a reference is provided.

Long-term data were taken from the literature sources, references are provided.

94.7 m means water level of 5% probability

References [32,33] added.

Point 12: L131-137: indicate the sampling dates corresponding to the given TDS values ? Give a table with chemical analyses. Chemical type, TDS and pH are not enough to discuss the mixing between « deep » groundwater and riverwater and the origin of groundwater. Please consider to write a sub-section dedicated to water chemistry with L. 154 to L.159.

Response 12: Figure 5 added; Table 2 added with sampling dates and results of chemical analysis of water samples

Point 13: 135: replace « Acidity… » by « pH value ». Lena water in acidic to neutral. 137:what is stem ? 143: add a s to clays. •

Point 14: Changed to «the рН value». «stem» changed to «channel» Changed to «clays»

Point 14: 148-149: Please reconsider the sentence « The suprapermafrost groundwaters are confined below by permafrost». 150 what is the reference of this value of 320 m. What was it measured. 168: Explain what does the contamination come from ? What is the flow pattern for wasterwater to discharge intn the alluvium water table. L181: what is the new land mentionned here ? which districk ? •

Response 14: Permafrost is impermeable and acts as a confining unit from below.

«the base of permafrost to lie at 320 m». Drilling showed that the lower limit of permafrost is at a depth of 320 m

The sentence is removed, because it referred to the area located outside the study area.

Changed to «The reclaimed land created in the 1980s acted as a barrier to water flow»

Point 15: where is the Lena station ? indicate it on a map (Fig 1 or 2). What is « summer precipitation » ? Dates ? Indicate the units of « duration of water level above 87 m » (days ?) ? one number is a 2-digit decimal number.

On Fig. 1, why the ancient oxbox lakes are not visible on the 1946 map ?

Figure 2: Poor quality. Change definition and symbol of 6. And 7. (too close).

Response 15: A sentence added to “Problem Statement and Methods” about the station location. Period of precipitation events is given.

In 1946, a side channel (City Channel) of the Lena River flew through the study area. This channel migrated with time leaving behind oxbow lakes. Channel migration was described in «Natural and Modified Environmental Characteristics of the Floodplain Area». Figure 5 changed

Point 16: Results and discussion  (L.188-267). In several parts of this section, we miss the information of the measurement dates.Please reconsider this part in and try to separate the results from the discussion. For the latter, I suggest to organize it in several sub-sections with a clear title. L194-196: usefulness of water content in the discussion ? L 198: you mention that the groundwater in unconfined. Is it true ? even during the winter when the soils freezes up ?

Response 16: The section is divided into sebsections. The suprapermafrost aquifer is ubiquitous, as shown by drilling data and borehole observations. In winter, the penetration depth of subzero temperatures is less than 5 m. Therefore, the aquifer which occurs below 8 m is not subject to seasonal freezing.

Point 17: How do you interprete that at the end of winter (March-early May), the rivel level is 3-4 m lower than the groundwater level ? what is the reason of a  hydrodynamical desequilibrium between the Lena and the water-table ? Could the high level of the water table be explain by a discharge from the unfreeze regional aquifer toward the river ?

Response 17: The hydraulic connection between groundwater and the Lena River is not disrupted. When the flood levels subside, the water edge is displaced 1 km away from the fill mass. This decreases the hydraulic gradient between the floodplain groundwater and the river. Under these conditions, the fill mass is drained slowly until the next flood event. Information added to subsection “Groundwater level regime”

Point 18: L207-208: « As the flood…. July».  What data support this conclusion ? 222-223: To be demonstrated with data. 228: what « ultra-fresh water» means ? 244-246: A reference is missing here (previous studies….) L248 : « transmission by pressure ». How do you demonstrate this ? Better explain. L251-252 : better explain here the methods used (maybe add information in section 2 « Materials and methods »)

Response 18:Supporting data are given in Figure 4. Reference to this figure is added. Table 2 is added. «ultra-fresh” explained  (mineralization 0.06–0.1 g/L)»

References [15,20] are added. Added to section “Problem Statement and Methods”

Point 19: The shape of potentiometric level of 1990 between wells 10 and 12 shows a little depression. Why ? Could you extend the cross-section lateraly toward the Lena (indication of level ranges) and/or toward Yakutsk, even further East (indication of the piezometric level of the regional aquifer) ? Symbols 4 and 9 are too close. Please consider to change the colors.

Response 19: The area between boreholes 10 and 12 had no taliks before fill placement. Taliks developed during the fill placement process.

In the Yakutsk area, there is a regional subpermafrost aquifer. Its level is at depths of 120-140 m. These levels are much deeper than the aquifer described in the article and there is no point in showing them in Figures. Explanation of contribution of suprapermafrost groundwaters is given above. Colors changed.

Point 20: How do you interprete that there are no apparent relationship between the rainfall amounts and the Lena level ? Is it because the river discharge is also linked to air temperature conditions (melt/freeze) and/or to rainfall of upstream areas ?  please indicate it in the text.

In 2019, the time-series of Lena level seems discontinuous. In this case, I suggest to remove the continuous blue line that gives the impression of a continuous dataset.

Fig 5: please enlarged this figure to make it more clear. Indicate in the figure captions that it is a schematic cross-section.

Response 20: The following explanation is added to section “Groundwater level Regime”: “Precipitation accounts for a minor contribution to aquifer recharge because of its low amount (see Table 1 and Fig. 5) and high evaporative loss. This is evidenced by the lack of groundwater level response to rain events and the very low (3–6 %) gravimetric moisture content of the soils in the zone of aeration.” Fig 5: Corrected.

The authors are sincerely grateful to the reviewers for valuable comments and suggestions.

Reviewer 2 Report

Overall, the paper reads well and the subject area is an interesting and relevant contribution to better understand the intersection between permafrost and hydrology in urban areas. There are few modern papers that I know of in this area that address the complications of filling floodplain areas in permafrost regions. This is a mitigation technique that more communities may need to consider in order to provide increased flood protection in a warming climate where in many areas of the Arctic precipitation is expected to rise.

I would suggest minor revisions to Figures 2-4. The numbering of the geotechnical boreholes is fine -- however, it is difficult to easily relate the locations of the groundwater boreholes. I'd suggest renaming the units in Figure 2 and 3 to something that makes it easier to interpret Figure 4. For example, when you carefully compare the stratigraphy in Figure 3, it appears that the buried lake areas are too conservative on the transect itself. Perhaps classes could include 1) last extent lake margins, 2) maximim lake margins, 3) back channel and 4) fore-channel. Boreholes 2 and 8 represent clear margins of lakes, where the second margin should be placed between boreholes 10 and 12. Even if "the site had two large, 100–120 m wide oxbow lakes elongated in the direction of river flow" the stratigraphy indicates that those lakes have been much larger.

Based on these stratigraphy classes, the groundwater boreholes could then be interpreted. If you include a subset in Figure 3 showing these units and then laying out where the groundwater wells roughly fit that would be very helpful. Then the labeling of Figure 4 can be corrected to understand how to interpret the graphs.

Figure 3 - the phrase "permafrost table in 1990" needs "7 - " added.

Figure 4 - symbol 10 should be the same color as in the graph.

The other area that could be strengthened is the discussion. I would suggest picking out four main findings to discuss in more detail and use heading to draw the reader to pick them out more readily. The first is already identified, as lateral fluxes, which account for the groundwater changes at 110–140 m in distance from the river. Figure 5 could be altered to show a plan view of the distance, where the current figure 5 is inserted from 0 to 140 m to show the influence of the lateral component. Then at 400–600 m the second topic area can be highlighted as sub-channel talik hydraulically connectivity. Then the relationship between hydraulic diffusivity and groundwater table rise could be better illustrated. The third could be something on how this research challenges common engineering design assumptions -- which is already discussed and includes eliminating anthropogenic influences and the absence of continuous groundwater flow at the bottom of the fill. The fourth might include what can be done -- which is also already framed in terms of adequate consideration of groundwater movement in and adjacent to riverine systems and fluvial landforms.

I liked the abstract and conclusions. I thought they were clear and highlighted the approach and findings.

Author Response

Response to Reviewer 2 Comments

Point 1: Overall, the paper reads well and the subject area is an interesting and relevant contribution to better understand the intersection between permafrost and hydrology in urban areas. There are few modern papers that I know of in this area that address the complications of filling floodplain areas in permafrost regions. This is a mitigation technique that more communities may need to consider in order to provide increased flood protection in a warming climate where in many areas of the Arctic precipitation is expected to rise.

I would suggest minor revisions to Figures 2-4. The numbering of the geotechnical boreholes is fine -- however, it is difficult to easily relate the locations of the groundwater boreholes. I'd suggest renaming the units in Figure 2 and 3 to something that makes it easier to interpret Figure 4. For example, when you carefully compare the stratigraphy in Figure 3, it appears that the buried lake areas are too conservative on the transect itself. Perhaps classes could include 1) last extent lake margins, 2) maximim lake margins, 3) back channel and 4) fore-channel. Boreholes 2 and 8 represent clear margins of lakes, where the second margin should be placed between boreholes 10 and 12. Even if "the site had two large, 100–120 m wide oxbow lakes elongated in the direction of river flow" the stratigraphy indicates that those lakes have been much larger.

Based on these stratigraphy classes, the groundwater boreholes could then be interpreted. If you include a subset in Figure 3 showing these units and then laying out where the groundwater wells roughly fit that would be very helpful. Then the labeling of Figure 4 can be corrected to understand how to interpret the graphs.

Figure 3 - the phrase "permafrost table in 1990" needs "7 - " added.

Figure 4 - symbol 10 should be the same color as in the graph

Response 1:

Figure 2 is revised, and Figures 6 and 7 added.

Legend has been changed for clarity.

Point 2: The other area that could be strengthened is the discussion. I would suggest picking out four main findings to discuss in more detail and use heading to draw the reader to pick them out more readily. The first is already identified, as lateral fluxes, which account for the groundwater changes at 110–140 m in distance from the river. Figure 5 could be altered to show a plan view of the distance, where the current figure 5 is inserted from 0 to 140 m to show the influence of the lateral component. Then at 400–600 m the second topic area can be highlighted as sub-channel talik hydraulically connectivity. Then the relationship between hydraulic diffusivity and groundwater table rise could be better illustrated. The third could be something on how this research challenges common engineering design assumptions -- which is already discussed and includes eliminating anthropogenic influences and the absence of continuous groundwater flow at the bottom of the fill. The fourth might include what can be done -- which is also already framed in terms of adequate consideration of groundwater movement in and adjacent to riverine systems and fluvial landforms.

Response 1:

“Results and Discussion” section has been divided into sub-sections (Permafrost conditions, Groundwater levels, Chemistry of surface and subsurface waters, Soil saturation mechanisms).

Figure 6 and Table 2 have been added with detailed characterization of the chemistry of surface and subsurface water.

Figure 5 has been replaced with Figure 7.

The authors are sincerely grateful to the reviewers for valuable comments and suggestions.