the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Aug 2024
Dynamics of snow melt infiltration into mountain soils: an instrumental approach in the Nant Valley, Swiss Alps
Abstract. To gain a deeper understanding of the dynamics of the contribution of snow melt to mountainous water cycles, it is necessary to better grasp the parameters controlling the infiltration of snow melt into mountainous soils. This research uniquely combines snow melt rate data with soil moisture dynamics, providing a comprehensive, three-year dataset. The integration of multiple measurement techniques and the estimation of the snow melt rate through the measurement of snow resistivity offer a new perspective on snow melt infiltration processes. The study area is located in the Nant Valley, Swiss Alps. Measurement points are distributed in mid to high elevations in various alpine environments. Besides demonstrating the instrumental setup, we also investigated the snowmelt-infiltration dynamics in the study area. Results indicate that, even though melt rates are considerably lower than soil saturated hydraulic conductivity values (with a ratio of 3.1x10-3 on average), the response times of shallow soil moisture and stream discharge to melt events is fast (from 2 to 5 hours). At the point measurement, snowmelt hardly infiltrates below 30 cm. These findings emphasize the potential vulnerability of mountain areas to dry periods in the future, particularly in the context of the expected shortening of the melt period due to climate change.
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CC1: 'Comment on egusphere-2024-1832', Giacomo Medici, 27 Aug 2024
General comments
Novel monitoring and excellent research in the field of hydrology. Please, follow my specific comments that can improve the manuscript.
Specific comments
Lines 13-14. “Since snowmelt infiltration toward the subsurface can contribute...mountainous regions”. Please, insert recent and relevant literature on snowmelt and infiltration in the subsurface in other mountainous regions:
- Lorenzi, V., Banzato, F., Barberio, M.D., Goeppert, N., Goldscheider, N., Gori, F., Lacchini, A., Manetta, M., Medici, G., Rusi, S. and Petitta, M., 2024. Tracking flowpaths in a complex karst system through tracer test and hydrogeochemical monitoring: Implications for groundwater protection (Gran Sasso, Italy). Heliyon, 10(2)
- Carroll, R.W., Deems, J.S., Niswonger, R., Schumer, R. and Williams, K.H., 2019. The importance of interflow to groundwater recharge in a snowmelt‐dominated headwater basin. Geophyisical Research Letters, 46(11), 5899-5908 .
Line 20. “illusive”, better unknown? This term is difficult to understand. Maybe try using more words instead of only one
Lines 64-78. Topography highs just above 2900. Have you got a bit of ice/glacier or just moraine?
Line 71. Please, provide age of the limestones. Mesozoic? Triassic and Jurassic?
Line 321. Lots of recent studies show that the snowmelt plays a key role on aquifer recharge. Above 1500 mASL the snowmelt can be the principal component of the groundwater replenishment. There are preferential flow pathways (e.g., roots or surfaces that devide soil zones with different porosities?) in the first centimetres of soil that have not been analysed here?
Lines 338-348. I can see 4 bulletin points in the conclusions, but 3 scientific questions in the introduction. Are the scientific questions actually 4? I suggest to revise the introduction.
Figures and tables
Figure 2. The white lines are unclear in the image / output. Revise the caption?
Figure 5. Numbers in the vertical axes are very difficult to read.
Citation: https://doi.org/10.5194/egusphere-2024-1832-CC1 -
RC1: 'Comment on egusphere-2024-1832', Steven Fassnacht, 01 Oct 2024
review of “Dynamics of snow melt infiltration into mountain soils: an instrumental approach in the Nant Valley,” Swiss Alps by Eeckman et al. https://doi.org/10.5194/egusphere-2024-1832
General comments:
This paper investigates the important physical process of how snowmelt gets into soils. The heterogeneity of soil and snowpack properties, plus melt rates, makes snowmelt infiltration modeling difficult. This paper attempts to better these quantify processes by address the research questions are: 1) melt rates versus soil infiltration capacity for partitioning of surface runoff and infiltration of the melt water, 2) vertical percolation process of melt water into soil layers, and 3) lateral flow of snow melt in the soil layers and response of the streamflow to melt. This paper uses snow electric resistivity to “directly” measure liquid water content in the snowpack.
The authors provide a concise, yet thorough overview of the problem and the existing literature. They work in an area that has much of the existing infrastructure and necessary data already available.
The big problem with this paper is that 1) it needs to be reorganized using the research questions to guide the flow and presentation of the paper, 2) the variables need to be better explained and consistent (according to “standard protocols”), and 3) the figures and their captions need to be improved. More detail is provided in the sections below. I read the paper and starting in the Results section I get confused.
I would recommend a list of variables, in part because non-common variable letters are used (PR = precipitation) and these at times do not match between figures and captions (e.g., Figure 4 where is HU?). It is easy to get lost in this paper, as some of the variables are not consistent, or not explained.
Some of the Discussion is mixed with the Results. For example, the paragraph on lines 216 to 223 reads much more like Discussion, and thus should be moved there. It seems like the second paragraph in each Results section is Discussion. As such, the Discussion section is limited to four short paragraphs (some of them are too short to be a paragraph). The Discussion does not obviously revisit the research questions; moving the Discussion paragraphs currently in the Results section to the Discussion itself would make it clearer how the research questions were addressed. The current Discussion gives us no understanding of why the Results are as they are. The Conclusions do not circle back to the research questions.
The Conclusions state that an “uncommon” method was tested to assess snow depth.” This method has been used various times before. I do not have the literature at my fingertips. I recommend search for this approach, and rewording “uncommon.”
The Introduction (lines 47-49) states that “estimate[ing] melt rate through variation in snow depth or SWE” does not consider “vertical heterogeneity of the snowpack nor surface effects such as snow sublimation or wind depletion.” Do you mean redistribution with wind depletion? This can be moving snow to a location (adding) or moving snow away from a location (depleting), plus sublimation of the blowing snow. From a How does vertical heterogeneity affect melt rate estimation? This statement does not seem correct. The work concluded that “measurement of the total snow water content through a cosmic ray sensor.” Yes, it does but this does not consider the vertical heterogeneity, so the CRS is not a second method. The SMA does consider heterogeneity at the bottom of the snowpack. Precipitation during snow melt is not considered and is very important. Further, how do you estimate “sublimation or wind depletion?”
Other Considerations
The work partially relies on the Sommer Snow Melt Analyzer (SMA). While this is not a fault of the authors, this instrument has not been independently assessed by anyone other than the manufacturer, so it is uncertain how well it works. The other hardware (visual snow depth, SnowTree, Cosmic Ray Sensor) have all been evaluated and peer-reviewed.
The visual scale does not seem very useful at the Auberge site, as the precision is in the range of 10 cm and the maximum snow depth is less than 50 cm. It seems better suited to be used for snow presence (no, partial, complete/full).
Specific comments:
There are a number of formatting, style, and related issues that will help make the paper more readable. Some of these may be a difference between European and other approaches, but I hope the authors consider my comments (below).
- page 1, line 2: I think you mean variables, and not parameters?
- Figure 1: D is not described in the caption
- line 135-136: why is it S subscript WE for snow water equivalent (SWE)? It is SWE, all uppercase, no subscript
- line 148: delete “snow profiles were dug, and snow samples were collected” as it is repeated.
- line 148: Technically, a horizontal measurement of density with a cylinder biases the sample to the middle of the sample. What is the diameter of the cylinder?
- Results: the authors use the format “The … are presented in Fig. X.” This is not necessary. The reader knows what is in Figure X from the caption. Tell us what is in the figure and then cite the figure. For example, start the first paragraph of the results with “The dynamics of the snow depths are consistent between the temperature based and visual methods (Fig. 2).”
- line 221: I assume that you are using δ (lowercase delta) to represent density? For snow hydrology, lowercase rho is used (ρ). What are the units (g.dm-3)? SI uses kg.m-3. Also, you do not need to report density to four significant figures (1 decimal place) as the precision of the measurement is ~2 kg.m-3 (550 cm3 sample).
- Figure 3: since there are no sub-figure lettering (a, b, c, d), and then no details about each sub-figure, it is not clear what each figure presents. Further, there are points in the second and third figure, but then lines in the legend, so it is difficult to match up the variable (meaning) of each point. Finally, precipitation (as a hyetograph) is by convention a bar chart rather than line.
- Figure 4: same comments as Figure 3. Further, some of these figures are so narrow that it is difficult to determine what is what. Also, make the lines in the soil sensor depth legend thicker, as it is difficult to distinguish the different colors. They can be left as the same thickness as presented in the figure itself. I just can’t tell Wr 10 cm from Wr 20 cm? Are HU and W the same variable?
- are the plots in Figure 5 just shorter time periods from Figure 4? Also, the plots in Figure 5 are so narrow, that I cannot see what is going on. Consider post-processing of the figures and adding the letter e.g., “(a) Example 1: Early winter 2021” onto the figure or removing some of the space between the figures. Also, the grey font for axis labels makes those labels difficult to read.
- Figure 6: is SCA greater than 100% at the grey station? Which ones is the grey station? Is it MODIS SCA? I cannot tell the colors apart from chalet and lachaux.
- I see no issue with language or grammar themselves. But the text and figures are confusing (see above).
Citation: https://doi.org/10.5194/egusphere-2024-1832-RC1 -
RC2: 'Comment on egusphere-2024-1832', Anonymous Referee #2, 30 Oct 2024
The paper presents an instrumentation approach to study snowmelt infiltration dynamics in mountain environments, implemented in the Nant Valley, Swiss Alps. Two approaches were implemented to estimate the snowmelt rate: i) the measurement of the dielectric constant at the bottom of the snowpack, and ii) the measurement of the total snow water content through cosmic ray sensors. These are complemented by meteorological (precipitation and temperature) and fluviometric records in the catchment, as well as snow depth estimates. In addition, a characterization of the infiltration capacity of the soil is performed by soil sampling, granulometric analysis, and infiltration tests. Then, based on the assumption that the liquid water content in the bottom snow layer is a proxy for the snowmelt rate, they analyzed and compared the snowmelt rate against hydrometeorological data and soil characteristics to establish relationships oriented to study i) the partitioning between infiltration and surface runoff, ii) vertical percolation, and iii) the dynamics of lateral flow of the melt flow.
Based on my review, to strengthen the paper's clarity, depth, and contribution, I think several essential comments need to be addressed before the manuscript can be considered for publication. My main comments are presented below, followed by the major and minor revisions.
Main comments:
First, it is unclear whether the primary focus is the proposed instrumentation approach or the processes occurring in the study area. The state of the art and how this research aims to address existing knowledge gaps are also not sufficiently explained. Additionally, the research questions lack clarity, and the presented results do not provide a strong foundation for conclusive statements. To assess the broader applicability of the proposed instrumentation methodology in other mountainous regions worldwide, it is crucial to include a discussion about its potential scope and limitations. The extent to which the assumptions made condition the results being presented and opportunities for improvement should be included in the analysis and discussion. Revising figures for clarity, adding quantitative evidence for statements, and analyzing lag times between precipitation, streamflow, and soil moisture would enhance interpretability. Finally, the discussion should align more closely with supported findings, emphasizing the study’s unique contributions over literature-based insights, and rephrasing conclusions to highlight original findings.
Major revisions:
- The first statement (L13:L14) forces the introduction of the concept of snowmelt infiltration. Is the important role of the snow due to snow infiltration or due to its contribution to surface runoff? Is the role of infiltration clear enough to make this statement? I suggest you rephrase the first sentences to emphasize the well-known role of snow (e.g., natural reservoir of fresh water), then the processes involved in snowpack changes, and conclude with the idea of the partitioning of surface runoff and infiltration and its importance in water availability.
- When you mention “... changing the snowmelt infiltration dynamics” (L16:L17) you are hiding all the impacts that an earlier melting would have. What about seasonality, peaks, among others? Logically many things will change, but highlighting the dynamics does not seem intuitive to me because, according to what has been mentioned up to the point of this sentence, there is also no information regarding the role of this process, or is there? I suggest you rewrite the paragraph to give more support to this idea (if there is evidence).
- When citing studies that have been applied in different regions and/or catchments, provide some examples and, perhaps, some of the important findings of such research. This will allow you to establish a certain relationship between your results and those obtained in similar areas. This could be useful to include in the discussion which, currently, is more focused on hypothesizing than discussing the findings obtained and their impact in terms of contribution to the community.
- The introduction does not provide an understanding of the state of the art, or the gaps detected, which motivate this research. Although it is mentioned that it is essential to improve our understanding of the parameters that control the infiltration of melt into the soil, then papers that have addressed this problem are presented.
- Research questions are not research questions but, to my understanding, define the objectives of the work. First, I understood that they could also be gaps, but after finishing reading the paper, the first option makes more sense to me. I suggest you rewrite this paragraph to clarify your questions and, also, to emphasize which are the gaps you are trying to fill with this work. In addition, the defined objective (L33) is also not addressed in the development of the work. Are the results obtained (and the analyses carried out) sufficient to conclude in this respect?
- Modeling approaches are mentioned, and their uncertainties are discussed given the limitations in accurately representing snowmelt infiltration (L41:L42). Why not use a model in this case to evaluate the added value of the experimental setup and how it can change the perception of the processes from the comparison of the obtained results?
- It is emphasized that the experimental approach is novel. What makes it novel? What are the traditional instrumentation approaches? What differences are obtained in terms of process understanding? What is the added value of the proposed new instrumentation approach (cost/benefit)? It is recommended to include a benchmarking case where the proposed experimental setup is not available.
- In L89 you mention the high uncertainty in precipitation records. Is it quantified in any way? I think a good idea (at least to check) would be to relate precipitation amounts under a threshold (e.g., 0°C) with respect to positive SWE differences (i.e. SWE(t) - SWE(t-1) > 0). With this, a relationship could be established to proxy for these biases.
- Is it enough to consider LWC at the bottom of the snowpack as a proxy for snowmelt rate? What does this assumption imply? Are any conditions required for the cold content (I would expect something like CC=0)? Shouldn't we talk about “potential snowmelt”? Is it appropriate to assume that the LWC would immediately leave the bottom snow layer within the evaluated time step?
- For the implementation of the SnowTree, is there any influence of the land cover on the measurements? Some of them are in forest areas.
- Do the empirical thresholds defined in Eq. 1 have any theoretical basis? Are they calibrated? How sensitive are the results to different thresholds? What would be a plausible range for them? Could the same thresholds be applied in other mountain regions?
- When applying the cosmic ray sensor approach, how are the differences between the properties of the snowpack layers interpolated when estimating the mass? Is a single representative value obtained? Is it possible to distinguish fresh and old snow from neutron attenuation? I suggest to discuss this further and comparing it directly with the other approaches presented, otherwise it is not possible to link them.
- It is not clear how the selection of soil sampling points is oriented. How representative are these points with respect to the catchment? One option would be to include something like, for example, SoilGrids to have a proxy.
- The processes identified in L211:L215 are in line with what one would not expect and do not present a finding. Such behavior must be related to the cold content of the snowpack and the solid (liquid) precipitation on days with temperatures lower (higher) than 1°C.
- It is suggested to quantitatively support the statements made. L219 mentions the possible estimation of more precise results for melting rates, but what is the reference?
- It is recommended to analyze how negative SWE changes (i.e., SWE(t) - SWE(t-1) < 0) relate to the infiltration estimates made.
- Why is it important to include parameter estimation as part of the results? Wouldn't it be better to include it in the characterization of the study area? Or is soil parameter estimation also part of the instrumental setup?
- Figure 3 is complex to understand because it combines, in the same panel, variables with different units and without including independent axes. This makes it difficult to analyze. What is the idea of this figure? What message is it trying to communicate?
- In Figures 4 and 5, how are the positive and negative snowmelt rates interpreted? There is a lack of analysis of the results being presented.
- In the analysis of the partitioning between infiltration and runoff associated with snowmelt, the effect of the different soil layers on this process is not discussed. Similarly, it is not possible to visualize what is indicated in the text in the figures referred to (e.g., L249).
- It is suggested to analyze how are the lags between precipitation peaks, flow, soil moisture and, additionally, infiltration estimates and negative SWE changes when such information is available. Currently, the analysis performed is brief and mainly qualitative (e.g., L251:L253).
- The discussion presents a set of new hypotheses that cannot be supported by the results obtained in the research. It is recommended to guide this section looking for common points with other studies, understanding what is the contribution of the proposed methodology in the improvement of the understanding of processes, and evidencing limitations and opportunities for improvement (besides the installation of wells, which is something that is mentioned as in progress).
- Some of the conclusions presented could be derived from a literature review and the contribution of the research is not clear. It is suggested to rephrase them to emphasize own findings.
Minor revisions:
- Modify the title of the paper as it does not reflect what is being presented.
- Include a table with catchment descriptors. Parameters such as area, slope, elevation range, and others are needed to interpret some results (e.g., what is the contributing rainfall area during precipitation events? -> changes in the catchment outflow hydrograph).
- In Table 1, include in brackets the range of variation of the estimated soil parameters. This will give an idea of the heterogeneity of each point.
- In Figure 1, is it accurate to mention geomorphological units instead of "Landforms" units?
- In Figure 1 include the point where the cosmic ray sensor was installed.
- For clarity and readability of the document, it may be useful to combine the granulometric analysis and infiltration tests with the Soil sampling and analysis section.
- In Figure 2, considering that the y-axis depends on the scale of the SnowTree, wouldn't it be more accurate to refer to snow height?
- Adjust size of labels in figures. For example, in Figure 5 the labels are difficult to read or are not complete (cut off by label dimensions).
- Correct labels and maintain consistency in abbreviations. For example, in Figure 4 Soil Moisture (HU) is mentioned in the caption, but in the panels, it is individualized differently (W?).
- Describe the caption in the order in which the panels are presented. For example, in Figure 4 you start with Soil Moisture, then Precipitation, Temperature, among others, and the panels are ordered as precipitation, streamflow, soil moisture.
- Verify that the figures show what is indicated in the panels and captions. For example, Figure 6 shows SCA(%) and snow depth (cm) but the gray lines associated, as I understand, with SCA(%) have values above 100%.
- Use “snow melt” or “snowmelt”, but do not combine both terms.
Citation: https://doi.org/10.5194/egusphere-2024-1832-RC2 -
RC3: 'Comment on egusphere-2024-1832', Anonymous Referee #3, 25 Nov 2024
The primary objective of this paper is to understand the “parameters controlling the infiltration of snow melt into mountainous soils.” The authors combine several methods to accomplish this objective, some quite simple (e.g., snow depth measurements using a snow tree and validation from timelapse cameras) and some more complex (snow melt analyzer and cosmic ray sensor). Though the approach and study design are interesting, the paper lacked a precise presentation of the results and discussion. The conclusions did not follow logically from what was presented in the paper. Below are some general recommendations for improving the paper, and attached is an annotated PDF with line-by-line feedback.
1. The paper needs a unifying parallel structure: describe the methods in the same order as they will be listed in the results and figures. For example, in Figure 3, the caption does not describe the contents of the graph in the order that it is presented. The authors would greatly benefit from choosing a consistent structure and sticking to it (e.g., present all the applicable figures and results as air temperature, precipitation, snow depth measurements, snow water equivalent from cosmic ray sensor, snow moisture analysis, and finally soil moisture – essentially, find a structure that works and stick to it so the reader doesn’t have to work hard to understand what is going on)
2. The results are heavily focused on establishing that the chosen methods were appropriate for determining snowmelt infiltration while not effectively summarizing key data patterns. It is difficult to understand inter-site and temporal dynamics of snowpack and soil metrics given how the results are currently written. The results also contain quite a bit of interpretation and discussion (see lines 278-285 for an example of what I’m referring to). Instead, the results need to focus on accurately summarizing trends in data.
3. The discussion and the conclusions section are extremely sparse and don’t include meaningful interpretation of the data. Without a well-written results section, it is difficult to follow along through the discussion and conclusions.
Please refer to the annotated PDF to view the rest of my line-by-line comments.
Data sets
Liquid water content, ice water content and density measured via the SnowMelt Instrument at Auberge station Judith Eeckman et al. https://doi.org/10.5281/zenodo.11580271
Soil study results at Vallon de Nant: Soil moisture and soil temperature time series and granulometry results Judith Eeckman et al. https://doi.org/10.5281/zenodo.10136586
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