the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 Jan 2024
Groundwater-Surface water exchanges in an alluvial plain subjected to pumping: a coupled multitracer and modeling approach
Abstract. Alluvial aquifers represent a vital water resource for many regions. However, understanding and characterizing the interactions between rivers and these aquifers is a major challenge for researchers and water managers. This characterization, in terms of flow velocity or water supply, is important to identify the vulnerability of the aquifers. In this study, our goal is to improve the understanding of interactions between rivers and alluvial aquifers by combining a multi-tracer approach with numerical modeling. By integrating these two complementary methods, we aim to accurately quantify the exchanges between groundwater and surface water, and to identify the water sources contributing to aquifer recharge. This combined approach allows a better quantification of river-aquifer interactions at local scale, in the context of groundwater exploitation by pumping along the river. A large drinking water catchment field located on the banks of the Rhône River, in the southeast of France, was chosen as the study site. This site consists of several pumping wells and observation piezometers parallel to the Rhône. As often, with alluvial aquifer exploitation close to a river, the pumping leads to flow from surface water to groundwater.
Groundwater temperature, piezometric levels and river surface water levels were continuously recorded for an 18-month period. During field campaigns, conductivity, stable isotopes of water and radon activity of groundwater and surface water were measured. Radon was applied in a new way to measure the water flow from the river to the aquifer, which reduces the natural radon signal in the aquifer by radon-poor waters from a river. On the site, the radon data clearly delineates groundwater recharge from the river within 50 meters from the banks. The methodology to interpret periodic groundwater temperature signals was extended to the isotopic signal, making it possible to identify the dispersivity in addition to Darcy's velocity.
All the experimental data were accounted for in a synthetic MODFLOW model, taking into account the boundary effect of the Ouvèze and Rhone rivers. Model calibration was made using the piezometric records and the PEST package. Reactive transport of radon was implemented using MT3DMS to ascertain the overall water balance of the study site. In addition to the Rhône as a supply, we have shown that the other river (Ouvèze) also contributes of the site’s supply (around 55%). By improving our understanding of the interactions between rivers and alluvial aquifers, this study offers valuable insights for sustainable water resource management in regions similar to our study site, i.e., the case of a losing river recharging an exploited aquifer and demonstrates the value of natural tracers, such as radon or stable water isotopes, in situations where the application of artificial tracers is impractical. Our results can guide policy decisions regarding groundwater development and river ecosystem protection.
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Status: closed
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RC1: 'Comment on hess-2023-239', Anonymous Referee #1, 29 Feb 2024
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2023-239/hess-2023-239-RC1-supplement.pdf
- AC1: 'Reply on RC1', Jerome Texier, 13 Apr 2024
-
RC2: 'Comment on hess-2023-239', Anonymous Referee #2, 01 Mar 2024
I reviewer the paper titled “Groundwater-Surface water exchanges in an alluvial plain subjected to pumping: a coupled multitracer and modeling approach”. This study proposes a mulitracer approach as well as modelling to understand the stream/groundwater interactions in an alluvial plain. The particularity of the study site is that pumping wells are located near the stream and the water extraction controls the stream/groundwater interactions and the groundwater flow in the alluvial aquifer. The subject of the study is interesting as the groundwater extraction in alluvial aquifers near streams can have major impacts on the stream ecosystem. An other interesting point is that the groundwater extraction is located between two streams, which both contribute to the aquifer recharge imposed through pumping.
We understand that authors made efforts to collect field data and to use different approaches and methods, which is always worthy. However, I have major issues with the study and the data interpretation. First of all, I really wonder what is the novelty of the study. The methods used in the study have been widely applied in the context of stream/groundwater interactions and the scientific contribution is not clear at all. Then, it can be a good point to use different methods. However, in this case, it does not seem relevant. The fact that the pumping controls the groundwater flow and the stream/groundwater interactions is obvious and can be seen only using piezometric levels. The others methods used (isotope, radon…) lead to the same conclusion and it is not clear how the different methods are complementary. Likewise, the model could be interesting but its potential is not fully used. We have the feeling that the Modflow model only allows reproducing the piezometer levels. It should have been more interesting to discuss the integration of the data collected in a model. In addition, I found that the text is not always clear (and is confusing at some points) and that Figures could be improved for a better understanding. I also have major concerns about the data interpretation of the thermal signals (see details below) and I am not sure that the results are consistent and relevant.
To summarize, I would say that the manuscript could be considerably improved. The methods and the data interpretation could go further. Most importantly, the complementarity of the methods should be strengthen. In this present form, the manuscript seems to be a succession of data that are not fully used and enhanced. I am not sure that the scientific contribution is enough for a publication in HESS and I would recommend to submit it in a journal specialized in regional studies.
In addition to the major issues mentioned above, here are some specific comments that could help improve the manuscript :
- The introduction should be significantly improved. It is not pleasant to read as it is a list of methods that can be used. It would be interesting to better explain the purpose of the use of each method. The last paragraph is way too long and not clear at all. It seems there are some results in it and at the end, we don’t understand the goal of the study.
- I recommend to add a section that clearly explains the goal of each approach, how the data collected will be used and why you have chosen these approaches.
- The section 2.2 is not clear at all.
- 200 the solutions of Goto and Stallman have been adapted … what does this imply ? Are there references ? I am sure that you can find in the literature some authors who used the temperature signal in a purely horizontal case.
- Section 2.3.1 / section 2.3.2 – what is the purpose of these methods ? what parameters will be estimated from these solutions ? At what spatial resolution ?
- 205 . I don’t understand this sentence. Can you explain how thermal properties are defined exactly ?
- Figure 2 . We don’t clearly see the data of Prg7 and Prg1. Please, change the color of Prg1 or Rhône (using blue for both is not practical). In the aquifer, the flow direction don’t vary in time ? The GW level is always : Prg2>Prg1>Prg6>Prg7 ? Also, can you add the stream level in the Ouvèze ?
- Figure 3 should be better presented and discussed (only one sentence about it). In the present form, the figure seems useless. It would be interesting to show one map under pumping and one map without pumping.
- One interesting point to discuss and interpret is the change observed when the pumping stops.
- Figures 4 and 5 are incomprehensible… you speak about three campaigns but we don’t see these results in the Figure (different colors for the different campaigns should be good); The legends do not correspond with the data presented in the Figure (shape and colors); It should be nice to add the name of piezometers to better visualize the position of the measurements; how was estimated the distance from the Rhone ? what is the reference ? From Figure 1 and 3, I don’t see how you can have data between 650 and 750 m ? ; the points at streams seem to be 0. Did you try a log-scale ? Likewise, the text from L. 275 should be revised because, in the present form, the text does not reflect what we see in Figure 4 – for instance, I don’t see the different campaigns…
- Section 3.3 – do you have the same results with and without pumping ?
- For the interpretation of temperature data, there are several critical points.
- You have one equation and several unknown parameters – how did you manage that ?
- The value of the thermal conductivity is a critical point when you interpret thermal curve (see for instance 10.5194/hess-26-1459-2022). How did you whose the value of the thermal conductivity (which is included in the thermal diffusivity) ? it would have be nice to have a sensitivity analysis to see the flux interpretation for different values of thermal diffusivity.
- In understand that under pumping conditions, the hydraulic gradient is quasi-constant. However, during the pumping stop, the GW flux and the flow direction changed. In this case, how is it possible, with only one value of flux, to model the entire period ? This result does not seem consistent to me
- The estimated values of thermal diffusivity don’t seem consistent to me. In the literature, we can find in Stauffer 2013 that values of thermal diffusivity vary between 3.2x10-7 and 1.8e-6 (for all materials – clay, silt, sand, gravel, blocks) (for instance : Stauffer, F., Bayer, P., Blum, P., Molina Giraldo, N., & Kinzelbach, W. (2013). Thermal Use of Shallow Groundwater. https://doi.org/10.1201/b16239), the values of thermal diffusivity very) . This may explain that the value of flux are not consistent with Darcy results.
- At last, I would recommend to interpret the temperature signal with other approachs and tools – for instance using FLUX-BOT http://dx.doi.org/10.1002/hyp.11198 - to compare your results
- The authors should better highlight the limits of the model/approach (there are many unknown parameters…)
- The authors should better explained the interest of the model… Section 3.5.1 What is the interest of the model ? Apart from reproducing the piezometric maps. Fig 9 : what is the interest of the radon transport model ? What are the new results (compared to piezometric levels) ?
Some minors comments/suggestions :
- 51 : The issue with the Darcy method is also that it is integrative in space
- 54 “several orders of magnitude” – in space or time ?
- 56 what are the advantages and disadvantages of this approach ?
- 60 Artifical tracers should be defined here
- 104 . Can you rephrase this ? It is not clear
- 125 – defined ‘thermal parameters of the environment’
- Fig 1 . The name of the streams are not visible. A legend should be used to say what are yellow triangles and red points. I know this is written in the caption but it is not practical for the reader.
- 149 . What do you mean about “extraction site” ? is it relevant ?
- 149 Please make two sentences. What is the flow rate of each stream ?
- 158-166 . this is not clear at all. From L;164 – Do you speak about the same piezometer as above ?
- 172 . One campaign means one sample for each point ?
- 176. Frequency of measurements ?
- 191 please specify the unit of the thermal diffusivity
- Any reference for Equation 4 ? If not, how did you validate the use of this solution ?
- 219. The sentence should be rephrased. The purpose of the model is not to integrate the results obtained with the tracers
- 233 . THE volumetric..
- 237; Can you justify the northern boundary conditions (17 m?)
- 244 – what is the purpose of integrating radon transport in the model?
- 254 – what do you mean by “short time scale” ? idem L. 257 for long time
- 258 – flooding is not a long time scale for me.
- 263 – What about the direction of flow relative to the Ouvèze ?
- 263 – Can you clarify what are the “periods of flooding” – it is difficult to see them in the Figure and to estimate their duration.
- 274 . The title should be changed – there is no interpretation in this section.
- 276 – where is Prg2 on the Figure ?
- 280 – SRV3 id RV3 ?
- 295 – please refer to Figure 6
- 298 – what is GMWL ?
- Figure – there are several points for each piezometer – what is the frequency of measurements?
- 322-323. I don’t understand what you mean here.
- 328 . Is the value of porosity consistent with literature ?
- 331 – 333 – where does the values of hydraulic conductivity come from ?
- 340 – this paragraph should in the discussion section
- 418. 56% is important compared to the size/rate of the stream. Does the infiltration significantly affect the flow rate of the stream ? What is the loss in height ?
Citation: https://doi.org/10.5194/hess-2023-239-RC2 - AC2: 'Reply on RC2', Jerome Texier, 13 Apr 2024
Status: closed
-
RC1: 'Comment on hess-2023-239', Anonymous Referee #1, 29 Feb 2024
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2023-239/hess-2023-239-RC1-supplement.pdf
- AC1: 'Reply on RC1', Jerome Texier, 13 Apr 2024
-
RC2: 'Comment on hess-2023-239', Anonymous Referee #2, 01 Mar 2024
I reviewer the paper titled “Groundwater-Surface water exchanges in an alluvial plain subjected to pumping: a coupled multitracer and modeling approach”. This study proposes a mulitracer approach as well as modelling to understand the stream/groundwater interactions in an alluvial plain. The particularity of the study site is that pumping wells are located near the stream and the water extraction controls the stream/groundwater interactions and the groundwater flow in the alluvial aquifer. The subject of the study is interesting as the groundwater extraction in alluvial aquifers near streams can have major impacts on the stream ecosystem. An other interesting point is that the groundwater extraction is located between two streams, which both contribute to the aquifer recharge imposed through pumping.
We understand that authors made efforts to collect field data and to use different approaches and methods, which is always worthy. However, I have major issues with the study and the data interpretation. First of all, I really wonder what is the novelty of the study. The methods used in the study have been widely applied in the context of stream/groundwater interactions and the scientific contribution is not clear at all. Then, it can be a good point to use different methods. However, in this case, it does not seem relevant. The fact that the pumping controls the groundwater flow and the stream/groundwater interactions is obvious and can be seen only using piezometric levels. The others methods used (isotope, radon…) lead to the same conclusion and it is not clear how the different methods are complementary. Likewise, the model could be interesting but its potential is not fully used. We have the feeling that the Modflow model only allows reproducing the piezometer levels. It should have been more interesting to discuss the integration of the data collected in a model. In addition, I found that the text is not always clear (and is confusing at some points) and that Figures could be improved for a better understanding. I also have major concerns about the data interpretation of the thermal signals (see details below) and I am not sure that the results are consistent and relevant.
To summarize, I would say that the manuscript could be considerably improved. The methods and the data interpretation could go further. Most importantly, the complementarity of the methods should be strengthen. In this present form, the manuscript seems to be a succession of data that are not fully used and enhanced. I am not sure that the scientific contribution is enough for a publication in HESS and I would recommend to submit it in a journal specialized in regional studies.
In addition to the major issues mentioned above, here are some specific comments that could help improve the manuscript :
- The introduction should be significantly improved. It is not pleasant to read as it is a list of methods that can be used. It would be interesting to better explain the purpose of the use of each method. The last paragraph is way too long and not clear at all. It seems there are some results in it and at the end, we don’t understand the goal of the study.
- I recommend to add a section that clearly explains the goal of each approach, how the data collected will be used and why you have chosen these approaches.
- The section 2.2 is not clear at all.
- 200 the solutions of Goto and Stallman have been adapted … what does this imply ? Are there references ? I am sure that you can find in the literature some authors who used the temperature signal in a purely horizontal case.
- Section 2.3.1 / section 2.3.2 – what is the purpose of these methods ? what parameters will be estimated from these solutions ? At what spatial resolution ?
- 205 . I don’t understand this sentence. Can you explain how thermal properties are defined exactly ?
- Figure 2 . We don’t clearly see the data of Prg7 and Prg1. Please, change the color of Prg1 or Rhône (using blue for both is not practical). In the aquifer, the flow direction don’t vary in time ? The GW level is always : Prg2>Prg1>Prg6>Prg7 ? Also, can you add the stream level in the Ouvèze ?
- Figure 3 should be better presented and discussed (only one sentence about it). In the present form, the figure seems useless. It would be interesting to show one map under pumping and one map without pumping.
- One interesting point to discuss and interpret is the change observed when the pumping stops.
- Figures 4 and 5 are incomprehensible… you speak about three campaigns but we don’t see these results in the Figure (different colors for the different campaigns should be good); The legends do not correspond with the data presented in the Figure (shape and colors); It should be nice to add the name of piezometers to better visualize the position of the measurements; how was estimated the distance from the Rhone ? what is the reference ? From Figure 1 and 3, I don’t see how you can have data between 650 and 750 m ? ; the points at streams seem to be 0. Did you try a log-scale ? Likewise, the text from L. 275 should be revised because, in the present form, the text does not reflect what we see in Figure 4 – for instance, I don’t see the different campaigns…
- Section 3.3 – do you have the same results with and without pumping ?
- For the interpretation of temperature data, there are several critical points.
- You have one equation and several unknown parameters – how did you manage that ?
- The value of the thermal conductivity is a critical point when you interpret thermal curve (see for instance 10.5194/hess-26-1459-2022). How did you whose the value of the thermal conductivity (which is included in the thermal diffusivity) ? it would have be nice to have a sensitivity analysis to see the flux interpretation for different values of thermal diffusivity.
- In understand that under pumping conditions, the hydraulic gradient is quasi-constant. However, during the pumping stop, the GW flux and the flow direction changed. In this case, how is it possible, with only one value of flux, to model the entire period ? This result does not seem consistent to me
- The estimated values of thermal diffusivity don’t seem consistent to me. In the literature, we can find in Stauffer 2013 that values of thermal diffusivity vary between 3.2x10-7 and 1.8e-6 (for all materials – clay, silt, sand, gravel, blocks) (for instance : Stauffer, F., Bayer, P., Blum, P., Molina Giraldo, N., & Kinzelbach, W. (2013). Thermal Use of Shallow Groundwater. https://doi.org/10.1201/b16239), the values of thermal diffusivity very) . This may explain that the value of flux are not consistent with Darcy results.
- At last, I would recommend to interpret the temperature signal with other approachs and tools – for instance using FLUX-BOT http://dx.doi.org/10.1002/hyp.11198 - to compare your results
- The authors should better highlight the limits of the model/approach (there are many unknown parameters…)
- The authors should better explained the interest of the model… Section 3.5.1 What is the interest of the model ? Apart from reproducing the piezometric maps. Fig 9 : what is the interest of the radon transport model ? What are the new results (compared to piezometric levels) ?
Some minors comments/suggestions :
- 51 : The issue with the Darcy method is also that it is integrative in space
- 54 “several orders of magnitude” – in space or time ?
- 56 what are the advantages and disadvantages of this approach ?
- 60 Artifical tracers should be defined here
- 104 . Can you rephrase this ? It is not clear
- 125 – defined ‘thermal parameters of the environment’
- Fig 1 . The name of the streams are not visible. A legend should be used to say what are yellow triangles and red points. I know this is written in the caption but it is not practical for the reader.
- 149 . What do you mean about “extraction site” ? is it relevant ?
- 149 Please make two sentences. What is the flow rate of each stream ?
- 158-166 . this is not clear at all. From L;164 – Do you speak about the same piezometer as above ?
- 172 . One campaign means one sample for each point ?
- 176. Frequency of measurements ?
- 191 please specify the unit of the thermal diffusivity
- Any reference for Equation 4 ? If not, how did you validate the use of this solution ?
- 219. The sentence should be rephrased. The purpose of the model is not to integrate the results obtained with the tracers
- 233 . THE volumetric..
- 237; Can you justify the northern boundary conditions (17 m?)
- 244 – what is the purpose of integrating radon transport in the model?
- 254 – what do you mean by “short time scale” ? idem L. 257 for long time
- 258 – flooding is not a long time scale for me.
- 263 – What about the direction of flow relative to the Ouvèze ?
- 263 – Can you clarify what are the “periods of flooding” – it is difficult to see them in the Figure and to estimate their duration.
- 274 . The title should be changed – there is no interpretation in this section.
- 276 – where is Prg2 on the Figure ?
- 280 – SRV3 id RV3 ?
- 295 – please refer to Figure 6
- 298 – what is GMWL ?
- Figure – there are several points for each piezometer – what is the frequency of measurements?
- 322-323. I don’t understand what you mean here.
- 328 . Is the value of porosity consistent with literature ?
- 331 – 333 – where does the values of hydraulic conductivity come from ?
- 340 – this paragraph should in the discussion section
- 418. 56% is important compared to the size/rate of the stream. Does the infiltration significantly affect the flow rate of the stream ? What is the loss in height ?
Citation: https://doi.org/10.5194/hess-2023-239-RC2 - AC2: 'Reply on RC2', Jerome Texier, 13 Apr 2024
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