Tracer test modeling for characterizing heterogeneity and local-scale residence time distribution in an artificial recharge site

Valhondo, Cristina; Martínez-Landa, Lurdes; Carrera, Jesús; Hidalgo, Juan J.; Tubau, Isabel; De Pourcq, Katrien; Grau-Martínez, Alba; Ayora, Carlos

doi:https://doi.org/10.5194/hess-20-4209-2016

Articles | Volume 20, issue 10

https://doi.org/10.5194/hess-20-4209-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/hess-20-4209-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 20, issue 10

Research article

|

18 Oct 2016

Research article |

| 18 Oct 2016

Tracer test modeling for characterizing heterogeneity and local-scale residence time distribution in an artificial recharge site

Cristina Valhondo, Lurdes Martínez-Landa, Jesús Carrera, Juan J. Hidalgo, Isabel Tubau, Katrien De Pourcq, Alba Grau-Martínez, and Carlos Ayora

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Final revised paper (published on 18 Oct 2016)
Preprint (discussion started on 10 May 2016)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Referee Comment', Jordan Clark, 14 Jun 2016
- AC1: 'response to reviewer comments', Cristina Valhondo, 14 Jun 2016
RC2: 'Comments on "Tracer test modeling for local scale residence time distribution characterization in an artificial recharge site"', Marc Walther, 29 Jun 2016
- AC2: 'Reply to comments by Prof. Marc Walther', Cristina Valhondo, 07 Jul 2016
RC3: 'Review of Valhondo et al.: Tracer test modeling for local scale residence time distribution characterization in an artificial recharge site', Anonymous Referee #3, 16 Jul 2016
- AC3: 'Reply to comments by Reviewer 3', Cristina Valhondo, 25 Jul 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (26 Jul 2016) by Insa Neuweiler

AR by Cristina Valhondo on behalf of the Authors (10 Aug 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Aug 2016) by Insa Neuweiler

RR by Marc Walther (22 Aug 2016)

Suggestions for revision or reasons for rejection

Reply to answers on the manuscript "Tracer test modeling for local scale residence time distribution characterization in an artificial recharge site" by Valhondo et al.

I would like to thank the authors for their detailed responses and the time they invested to answer my questions. I see that the manuscript has improved significantly (although it has already been in a very good state). There is only a small number of comments I would like to have addressed, which I list in the following; these are mainly related to figures, and transport parameters.

R2.5 and fig. 1: Thank you for clarification.
- Concerning the blue small arrows for text reference: please use them consistently, either pointing from the text to the object or vice versa (compare arrows for "Recharge Basin" and "Quaternary Terrace"); also, not all arrows are clear: on the right, does the arrow show the location of "Aluvial Fan" or the direction of "Lateral Inflow"?
- Concerning the stratigraphical log: I understand your intention to add some more, but not too much, background information for the reader. I think, however, that with the current state of the log figure, it is too less explanation to be valuable: I see a legend for a figure as compulsory, and additionally, the figure is in very low resolution so I cannot identify the texture to guess the character of the layers. I really think it would be better to add more details here. Maybe, you can add text to the layers (as you did with "Clay" at 17m)?

R2.26 Concerning your answer "We used abbreviation "Ly" because it is the same nomenclature displayed in Figure 4." - I could not find an explaination of this abbreviation (although it is clear to me, it may not be for all readers). Maybe, you can simply add this to the caption of figure 4?

R2.34 I still cannot find information about which model setup you show in figure 2 (homogeneous, het1 or het2)? Can you please add this?

R2.35 You write "horizontal and vertical diffusion coefficients" - do you mean dispersion coefficients? I can find information on the dispersivity (P6L6).
Can you please add information on the diffusion coefficient?

R2.36 Thank you for the detailed answer! I suggest that you add your description of the RMSWE value to the manuscript, as it is relatively uncommon how you calculate this (also considering the high value of it). Is there a unit for RMSWE or is it unitless through normalization of the parameters/values? Frankly speaking, an equation or reference would be nice for the RMSWE (to better understand and interpret the value you show in table 1).

R2.38 Your answer "Yes, the white area was colored to grey to make it easier to identify the different layers, but corresponds to value 0mg/l." - so why don't you change the legend to show a grey value for 0mg/l?

R2.40 The phrasing of "because the aquifer transmissivity in the local domain was ultimately the same." is still used. I understand your answer in the reply, but am in doubt that readers may misinterpret this in the first place.

R2.41 Is it right, that you set a molecular diffusion coefficient of 10e-10, 10, and 10000 m2/d, for the domain, 1D near the wells, and at the edge of the local domain??? That would be about 1e-15, 1e-4, and 1e-1 m2/s, which is in any case far from what is reported to be a common value for diffusion of a solute in water ~2e-9 m2/s (not even speaking of an effective diffusion coefficient in porous media (but this is probably not important))! Please, explain your choice of diffusion values here.

P7 L29: "mean weighted residual for head observations" should have a unit (meter?).

P15 L24: "ACWAPUR (XXXXX)" - is there a number/reference missing?

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Finally, the following comment should be considered as a discussion - I would be happy, if you would respond, although I do not see a necessary change in the manuscript: (The comment may be a little naive, though I would still like to give it.) R.36: I like that you discuss already the topic of uniqueness and identifiability (end of section 3.2, 3.3 and 4)! Within the light of my questions and considering your reply (R2.28 and R2.36), I interpret the model setup to be rather "an empirical/characteristical approach" for the study area, but should not be treated as a representation of the real aquifer structure. If I am right with the interpretation, I would be happy if you considered discussing the fact, that your model (although being calibrated and validated in a remarkable way), only represents one characterization, and how you would interpret the possibility to develop a model following hydrogeological conceptualization, maybe also utilizing Monte-Carlo-like methods with different heterogeneous subsurface domains.

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RR by Anonymous Referee #3 (12 Sep 2016)

ED: Publish as is (24 Sep 2016) by Insa Neuweiler

AR by Cristina Valhondo on behalf of the Authors (28 Sep 2016) Author's response Manuscript

Short summary

We performed and evaluated a pulse injection tracer test in an artificial recharge system to understand the fate of potential contaminants. A 2-D multilayer model (under homogeneous and heterogeneous medium hypothesis) was used to evaluate the measured breakthrough curves at six points. Both homogeneous and heterogeneous models reproduce the long tails observed. This implies that the shapes of the breakthrough curves are caused not only by heterogeneity, but also by the mean flow structure.