the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 May 2024
Spectral Induced Polarization survey for the estimation of hydrogeological parameters in an active rock glacier
Abstract. Degrading permafrost in rock glaciers has been reported from several sites in the European Alps. Changes in ground temperature and ice content are expected to affect the hydrogeological properties of the rock glacier and in turn modify the runoff regime and groundwater recharge in high-mountain environments. In this study, we investigate the use of an emerging geophysical method to understand the hydrogeological properties of the active Gran Sometta rock glacier, which consists of a two lobe-tongue (a white and a black) differing in their geologies. We present the application of the spectral induced polarization (SIP) imaging, a method that provides continuous spatial information about the electrical conductivity and polarization of the subsurface, which are linked to hydrogeological properties. To quantify the water content and the hydraulic conductivity from SIP imaging results, we used the petrophysical dynamic stern layer model. The SIP results show a continuously frozen layer at 4−6 m depth along both lobes which hinders the infiltration of water leading to a quick flow through the active layer. To evaluate our results, we conducted tracer experiments monitored with a time-lapse electrical conductivity imaging which confirms the hydraulic barrier associated with the frozen layer and allows to quantify the pore water velocity (~10-2 m/s). Below the frozen layer, both lobes have distinct water content and hydraulic conductivity. We observed a higher water content in the black lobe, which moves faster than the white lobe supporting the hypothesis that the water content at the shear horizon dominates rock glacier velocity. Our study demonstrates that the SIP method is able to provide valuable information for the hydrogeological characterization of rock glaciers.
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RC1: 'Comment on egusphere-2024-1444', Anonymous Referee #1, 24 Jun 2024
This study presents the results of using Spectral Induced Polarization (SIP) surveys for estimating hydrogeological parameters in an active rock glacier. In addition to SIP, the authors use tracer experiments and photogrammetry to compare various findings regarding rock glacier hydrology and movement. I believe this study is of strong interest to the community and provides an excellent field study to guide future improvements in understanding hydrological processes in such environments. The paper is very well organized and written, and I enjoyed reading it.
My only main concern is regarding the discussion on the estimation of hydraulic conductivity. While the electrical approach seems to provide interesting results for delineating features and tracking the plume during the tracer experiment, I believe the discussion on how SIP is used to estimate hydraulic conductivity (K) lacks depth. I would appreciate it if the authors included more discussion on the various assumptions and sources of uncertainty. I suggest improving the discussion and possibly adding some rough uncertainty bounds to the various parameters used to parameterize the equations and evaluating the impact of those (e.g., using ko on line 233) on the estimated values.
Other comments:
- L.65: "not suited". To my knowledge, drilling boreholes for monitoring temperature is still the most reliable approach to monitor thermal dynamics. Consider rephrasing this sentence.
- L.117: Including a philosophical tone in Latin is a nice touch, but it may be unclear for the reader… and accidental.
- L.185: Consider splitting this sentence into two.
- L.189: "improves" is vague. I suggest "showed some promise to estimate..." and adding more details under specific conditions.
- L.225 to 242: There are many values used from the literature to parameterize these equations. A more thorough discussion of these choices would be appreciated. For example, on line 223, more information on the ko value and the material it was defined for would be appreciated. ko likely has a significant impact on the k and K value and is a considerable source of uncertainty. Discussing these limitations more thoroughly, either here or in the discussion section, would be fair. Another point is the hydraulic gradient, which assumes the groundwater hydraulic gradient but is taken as the topography gradient here. Same for the porosity (0.4, on L. 238) and the implication on the estimates.
- Figure 3: Consider showing the relationship between chargeability and the real part of conductivity (supplementary material would be fine).
- L.437: Please provide an explanation for why you used >20% for the black lobe, or consider stating the maximum increase in white vs. black lobe.
- Figure 6 and associated text: It is unclear if the discussion is about the white lobe only or both lobes. Please clarify in the figure caption and associated text.
- L.626: Please clarify your thoughts on the order of importance in parameter impact. The terrain slope (please provide an estimate and discuss) seems much steeper in the black lobe and would be expected to be a strong control. Does that not complicate and maybe compromise the interpretation of another control using the current data set ? Please consider adding some discussion of the impact of the slope gradient alone.
Citation: https://doi.org/10.5194/egusphere-2024-1444-RC1 - AC1: 'Reply on RC1', Clemens Moser, 15 Aug 2024
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RC2: 'Comment on egusphere-2024-1444', Anonymous Referee #2, 15 Jul 2024
The manuscript "Spectral Induced Polarization survey for the estimation of hydrogeological parameters in an active rock glacier" by Moser et al. describes a very interesting experiment on an active rock glacier. The authors used a suite of electrical measurements (SIP, ERT) to study the structure and hydrological properties of the glacier. The manuscript makes a good argument for the use of geophysical methods in glacier studies and should be published after the authors address the comments discussed below.
First, the good news. The results are really encouraging for the use of electrical methods in such studies. The discussion is mostly well written, adequately discuss the data and the interpretation is very logical, with the proper caution that geophysical methods deserve.. This section really highlights the benefits of such methods for glacier studies.
My main concert is not with the results and the discussion, rather with the presentation and the flow of the manuscript, For example the terminology used is inconsistent and can be confusing, especially to the non expert; acronyms / full terms are used interchangeably, while multiple names are used for the same term (can be introduced, but should use one for consistency).
The authors provide a lot of information, and use multiple results (and past studies), while this is good and needed, results in a manuscript with flow issues. I find the introduction confusing and difficult to follow; the authors introduce new terms, without fully addressing them and discuss some of the methods in not needed detail; I would suggest the authors use the introduction to just introduce the problem (as they do), discuss the need of a solution, and the approach and then introduce the methods only at high level; the details of the methods, including past studies, can go to a 'theory' part of the methods. Same for the results section - results are a mix of theory, results and interpretation making difficult to read / follow.
Detailed comments, and suggestions, on the attached annotated pdf.-
AC2: 'Reply on RC2', Clemens Moser, 15 Aug 2024
Dear Reviewer 2,
thank you very much for the constructive comments and the positive feedback! Please find responses on main concerns and answers on detailed comments in the attached file.
Sincerely,
Clemens Moser, Umberto Morra di Cella, Christian Hauck, and Adrián Flores Orozco
-
AC2: 'Reply on RC2', Clemens Moser, 15 Aug 2024
Status: closed
-
RC1: 'Comment on egusphere-2024-1444', Anonymous Referee #1, 24 Jun 2024
This study presents the results of using Spectral Induced Polarization (SIP) surveys for estimating hydrogeological parameters in an active rock glacier. In addition to SIP, the authors use tracer experiments and photogrammetry to compare various findings regarding rock glacier hydrology and movement. I believe this study is of strong interest to the community and provides an excellent field study to guide future improvements in understanding hydrological processes in such environments. The paper is very well organized and written, and I enjoyed reading it.
My only main concern is regarding the discussion on the estimation of hydraulic conductivity. While the electrical approach seems to provide interesting results for delineating features and tracking the plume during the tracer experiment, I believe the discussion on how SIP is used to estimate hydraulic conductivity (K) lacks depth. I would appreciate it if the authors included more discussion on the various assumptions and sources of uncertainty. I suggest improving the discussion and possibly adding some rough uncertainty bounds to the various parameters used to parameterize the equations and evaluating the impact of those (e.g., using ko on line 233) on the estimated values.
Other comments:
- L.65: "not suited". To my knowledge, drilling boreholes for monitoring temperature is still the most reliable approach to monitor thermal dynamics. Consider rephrasing this sentence.
- L.117: Including a philosophical tone in Latin is a nice touch, but it may be unclear for the reader… and accidental.
- L.185: Consider splitting this sentence into two.
- L.189: "improves" is vague. I suggest "showed some promise to estimate..." and adding more details under specific conditions.
- L.225 to 242: There are many values used from the literature to parameterize these equations. A more thorough discussion of these choices would be appreciated. For example, on line 223, more information on the ko value and the material it was defined for would be appreciated. ko likely has a significant impact on the k and K value and is a considerable source of uncertainty. Discussing these limitations more thoroughly, either here or in the discussion section, would be fair. Another point is the hydraulic gradient, which assumes the groundwater hydraulic gradient but is taken as the topography gradient here. Same for the porosity (0.4, on L. 238) and the implication on the estimates.
- Figure 3: Consider showing the relationship between chargeability and the real part of conductivity (supplementary material would be fine).
- L.437: Please provide an explanation for why you used >20% for the black lobe, or consider stating the maximum increase in white vs. black lobe.
- Figure 6 and associated text: It is unclear if the discussion is about the white lobe only or both lobes. Please clarify in the figure caption and associated text.
- L.626: Please clarify your thoughts on the order of importance in parameter impact. The terrain slope (please provide an estimate and discuss) seems much steeper in the black lobe and would be expected to be a strong control. Does that not complicate and maybe compromise the interpretation of another control using the current data set ? Please consider adding some discussion of the impact of the slope gradient alone.
Citation: https://doi.org/10.5194/egusphere-2024-1444-RC1 - AC1: 'Reply on RC1', Clemens Moser, 15 Aug 2024
-
RC2: 'Comment on egusphere-2024-1444', Anonymous Referee #2, 15 Jul 2024
The manuscript "Spectral Induced Polarization survey for the estimation of hydrogeological parameters in an active rock glacier" by Moser et al. describes a very interesting experiment on an active rock glacier. The authors used a suite of electrical measurements (SIP, ERT) to study the structure and hydrological properties of the glacier. The manuscript makes a good argument for the use of geophysical methods in glacier studies and should be published after the authors address the comments discussed below.
First, the good news. The results are really encouraging for the use of electrical methods in such studies. The discussion is mostly well written, adequately discuss the data and the interpretation is very logical, with the proper caution that geophysical methods deserve.. This section really highlights the benefits of such methods for glacier studies.
My main concert is not with the results and the discussion, rather with the presentation and the flow of the manuscript, For example the terminology used is inconsistent and can be confusing, especially to the non expert; acronyms / full terms are used interchangeably, while multiple names are used for the same term (can be introduced, but should use one for consistency).
The authors provide a lot of information, and use multiple results (and past studies), while this is good and needed, results in a manuscript with flow issues. I find the introduction confusing and difficult to follow; the authors introduce new terms, without fully addressing them and discuss some of the methods in not needed detail; I would suggest the authors use the introduction to just introduce the problem (as they do), discuss the need of a solution, and the approach and then introduce the methods only at high level; the details of the methods, including past studies, can go to a 'theory' part of the methods. Same for the results section - results are a mix of theory, results and interpretation making difficult to read / follow.
Detailed comments, and suggestions, on the attached annotated pdf.-
AC2: 'Reply on RC2', Clemens Moser, 15 Aug 2024
Dear Reviewer 2,
thank you very much for the constructive comments and the positive feedback! Please find responses on main concerns and answers on detailed comments in the attached file.
Sincerely,
Clemens Moser, Umberto Morra di Cella, Christian Hauck, and Adrián Flores Orozco
-
AC2: 'Reply on RC2', Clemens Moser, 15 Aug 2024
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