the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 May 2025
High-resolution monitoring of the Günz River: Assessing water quality risks for managed aquifer recharge
Abstract. Adapting to hydrological extremes through managed aquifer recharge using river water as a source requires a profound understanding of the quantity and quality dynamics of the river. While quantitative data with high temporal resolution is available at numerous gauging stations, qualitative data for many catchment areas is generally sparse or not available at all. In this work, a combination of risk-based watershed screening, continuous on-site monitoring, and laboratory analyses was carried out to improve this understanding of river quality dynamics. For on-site monitoring, a cost-efficient and reliable monitoring kit was developed to generate time-resolved data, which proved essential for capturing hydrochemical dynamics and can serve as a decision-support tool, reducing the parameter set required for quality control. It was installed at the Günz River in the southwest of Bavaria, Germany. The water quality measurements were combined with the risks arising from this rural watershed, where wastewater treatment plants and agriculture were the primary pollution sources. The contamination state was improving during events with high water levels due to dilution except for very few trace substances washed out from the top-soil. From a technical point of view, turbidity was defined as the most urgent parameter to consider in the water treatment before reuse due to particle-associated contaminant transport and the risk of clogging. The results demonstrated that the Günz River would be a suitable source for managed aquifer recharge with particle removal as pre-treatment step. By linking identified watershed risks to river water quality, this study highlights the importance of understanding catchment processes for effective water management. The insights of this study contribute to optimizing high-resolution monitoring, advancing MAR implementation, and enhancing water resource resilience in similar catchments.
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RC1: 'Comment on egusphere-2025-740', Anonymous Referee #1, 03 Jun 2025
This manuscript presents a comprehensive, well-executed study on high-resolution monitoring of the Günz River in Bavaria, Germany, aimed at evaluating its suitability for Managed Aquifer Recharge (MAR). The combination of watershed risk screening, continuous monitoring using a custom-built kit, and detailed chemical analysis is innovative and well documented. The paper is timely, relevant, and provides new insights into real-time water quality assessment and risk-based management for MAR.
The methodology is robust and transparent. All instruments, calibration methods, and sampling protocols are clearly described. The description of data, methods, and analytical approaches is sufficiently detailed to ensure reproducibility. The availability of code and data as well as the plan for building the monitoring station is commendable.
Suggestions:
1) While the transferability of methods to other rural watersheds is noted, it would help to more explicitly compare the Günz catchment characteristics with other European or international contexts.
2) The abbreviation MAR appears in the abstract without introduction (which follows in the intro). Better state the full term it in the abstract.
3) Spaces before % seem uncommon to me but are apparently sometimes used in articles. I would not use a space before % and I think it's rather international norm to do so.
4) In the conclusion "MAR with river water is -essential- to adapt to the imbalance of the landscape water regime” seems to be a bit if an overreach. While MAR is valuable, calling it essential suggests it's the only viable adaptation, which might not be universally agreed upon.
5) The conclusion could mention how this work supports future MAR implementations or research. Future work could explore microbiological risks and the applicability of this framework in more urbanized regions.
Recommendation: Minor Revisions
The paper is well-suited for publication in NHESS after addressing the minor suggestions above. It provides a valuable case study and a replicable framework for river monitoring in the context of MAR.
Citation: https://doi.org/10.5194/egusphere-2025-740-RC1 -
AC1: 'Reply on RC1', Lea Augustin, 16 Jul 2025
We sincerely thank the reviewer for the thoughtful, constructive feedback and for the positive evaluation of our manuscript. In the following, we respond to each of the reviewer’s suggestions in detail:
- We agree that a direct comparison of the Günz watershed to other watersheds would provide easy access to the suitability of catchments for this type of MAR. In general, we have to distinguish between the transferability of the methodology and the applicability of the site-specific results. The methodology itself is site-independent and can be applied to regions with different hydrological and hydrogeological conditions. Here, we consider the rural–urban distinction and the size of the watershed to be the primary factors influencing transferability. We have clarified this more explicitly in the corresponding discussion section to support a broader comparison with other catchments. However, site-specific results rely on actual measurements and field observations, so direct, quantitative comparisons are limited unless similar data are available.
- We agree and have revised the abstract accordingly.
- Thank you for pointing this out. We have revised the manuscript to remove spaces before all % symbols.
- We appreciate this observation and have adjusted the sentence to “MAR with river water presents a highly valuable strategy to adapt to the imbalance of the landscape water regime.”
- Thank you for this suggestion. We have added a sentence in the conclusion pointing to these potential next steps.
We hope that these additions strengthen the manuscript and address the reviewer’s insightful comments.
Citation: https://doi.org/10.5194/egusphere-2025-740-AC1
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AC1: 'Reply on RC1', Lea Augustin, 16 Jul 2025
-
RC2: 'Comment on egusphere-2025-740', Anonymous Referee #2, 03 Jul 2025
The introduction of increased circularity in water management will gain importance in Germany due to declining water availability coupled with growing pressure on water resources. The main reason for this is rising temperatures as a result of climate change, which lead to increased evaporation and higher water consumption, particularly for irrigation purposes. Additionally, some regions are experiencing rising population numbers, as exemplified by the Berlin area. Alongside rainwater management measures (blue-green infrastructure, sponge city principles) and the reuse of treated wastewater, Managed Aquifer Recharge (MAR) represents another fundamentally suitable method for returning water to the cycle. Compared to technical storage systems, a key advantage lies in the activation of naturally existing storage spaces, which offers significant economic as well as planning-related benefits. Against this background, the present work investigates, using the example of the Günz River, whether the quality of runoff is suitable for MAR and how the quality can be effectively monitored.
The study addresses a highly topical issue that is of great relevance in many regions of Germany and certainly also in other countries. Moreover, it is very practice-oriented and even provides a concrete proposal for setting up monitoring stations. The results are presented clearly and are easy to follow.
Suggestions for improvements:
- The manuscript should discuss in more detail the transferability of the results to other river catchments.
- The manuscript should also address the aforementioned alternative or complementary methods. MAR does not necessarily have to be implemented centrally at major rivers but can also be realized in a decentralized manner within the catchment area.
Citation: https://doi.org/10.5194/egusphere-2025-740-RC2 -
AC2: 'Reply on RC2', Lea Augustin, 16 Jul 2025
We would like to thank the reviewer for this valuable, supportive feedback and for highlighting the importance of the discussed topic.
We agree that the manuscript benefits from a clearer discussion of the transferability. Here, we have to distinguish between the transferability of the methodology and the transfer of the site-specific results. The methodology itself is site-independent and transferable to regions with different hydrological and hydrogeological conditions. Nevertheless, we consider the rural–urban distinction and the size of the watershed to be the primary factors influencing the applicability. We clarified this key limitation more explicitly in the discussion. While the study site stands representative of many rural catchments, the actual results are likely site-specific. However, they show the potential of MAR with river water in rural catchments with similar characteristics, as well as the potential of linking watershed risks with quality measurements.
Regarding the implementation of MAR, we fully agree with the reviewer that especially the upper catchments are promising locations. Although MAR is a versatile tool that can be implemented even at longer distances to the river, infiltration near major rivers often faces constraints due to high volumetric flows and elevated groundwater levels. Additionally, coupling MAR with direct flood protection measures is typically not feasible at major rivers. We further clarified in the introduction that we understand the presented potential MAR scheme as decentralized MAR.
We hope that these adjustments are in the reviewer's interest and will further improve our manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-740-AC2
-
RC3: 'Comment on egusphere-2025-740', Anonymous Referee #3, 08 Jul 2025
egusphere-2025-740
The scope of the paper is very unclear and so the reasoning behind the paper and your arguments. Is the focus on MAR and how river water quality and quantity affect its performance or is it on rivers and how MAR affects their quality and quantity. Or is it on something else: eg. Testing monitoring setup? Please clarify and adjust the text accordingly. Particularly, the introduction is confusing, please state clearly your hypotheses and objectives.
The section on Examples of safeguarding water quality can be derived from the drinking water sector should be shortened or even removed from the introduction as far too long.
Discussion should be structured with meaningful headings and address set up in the introduction hypotheses and objectives. At the moment it is rather dense, difficult to follow and spoiled with unnecessary details. Please streamline it.
line 5 grammar
Citation: https://doi.org/10.5194/egusphere-2025-740-RC3 -
AC3: 'Reply on RC3', Lea Augustin, 16 Jul 2025
We thank the reviewer for this critical comment. The aim of this paper is to present a methodology for assessing river water quality with regard to its potential use as a source for MAR. Since laboratory confirmation of water quality typically occurs on a different time scale than flooding events, the quality of the source water must be ensured intrinsically. We propose that this can be achieved through a combination of high-resolution monitoring at strategically selected sites, a limited number of targeted laboratory analyses, and a risk assessment of the catchment. The new methodology was applied exemplarily to a river in southern Germany, which is representative of many rural watersheds of similar size. The methodology itself is site independent and transferable to regions with different hydrological and hydrogeological conditions. In the revised manuscript, we communicated the primary focus and structure of the study more clearly.
We restructured the paragraph starting in line 95 and clarified the presentation of our hypotheses and aims by adding two sentences. The section on examples of safeguarding water quality was indeed detailed, which we tried to tweak by deleting the three sentences on the implementation of the Water Safety Plan concept in Germany. Furthermore, we structured the discussion with subheadings and are now picking up the main research questions and hypotheses from the introduction. We rechecked our abstract with a grammar checker, but found no incorrectness in line 5.
We hope these changes improve the clarity and focus of the manuscript and appreciate further consideration.
Citation: https://doi.org/10.5194/egusphere-2025-740-AC3
-
AC3: 'Reply on RC3', Lea Augustin, 16 Jul 2025
Status: closed
-
RC1: 'Comment on egusphere-2025-740', Anonymous Referee #1, 03 Jun 2025
This manuscript presents a comprehensive, well-executed study on high-resolution monitoring of the Günz River in Bavaria, Germany, aimed at evaluating its suitability for Managed Aquifer Recharge (MAR). The combination of watershed risk screening, continuous monitoring using a custom-built kit, and detailed chemical analysis is innovative and well documented. The paper is timely, relevant, and provides new insights into real-time water quality assessment and risk-based management for MAR.
The methodology is robust and transparent. All instruments, calibration methods, and sampling protocols are clearly described. The description of data, methods, and analytical approaches is sufficiently detailed to ensure reproducibility. The availability of code and data as well as the plan for building the monitoring station is commendable.
Suggestions:
1) While the transferability of methods to other rural watersheds is noted, it would help to more explicitly compare the Günz catchment characteristics with other European or international contexts.
2) The abbreviation MAR appears in the abstract without introduction (which follows in the intro). Better state the full term it in the abstract.
3) Spaces before % seem uncommon to me but are apparently sometimes used in articles. I would not use a space before % and I think it's rather international norm to do so.
4) In the conclusion "MAR with river water is -essential- to adapt to the imbalance of the landscape water regime” seems to be a bit if an overreach. While MAR is valuable, calling it essential suggests it's the only viable adaptation, which might not be universally agreed upon.
5) The conclusion could mention how this work supports future MAR implementations or research. Future work could explore microbiological risks and the applicability of this framework in more urbanized regions.
Recommendation: Minor Revisions
The paper is well-suited for publication in NHESS after addressing the minor suggestions above. It provides a valuable case study and a replicable framework for river monitoring in the context of MAR.
Citation: https://doi.org/10.5194/egusphere-2025-740-RC1 -
AC1: 'Reply on RC1', Lea Augustin, 16 Jul 2025
We sincerely thank the reviewer for the thoughtful, constructive feedback and for the positive evaluation of our manuscript. In the following, we respond to each of the reviewer’s suggestions in detail:
- We agree that a direct comparison of the Günz watershed to other watersheds would provide easy access to the suitability of catchments for this type of MAR. In general, we have to distinguish between the transferability of the methodology and the applicability of the site-specific results. The methodology itself is site-independent and can be applied to regions with different hydrological and hydrogeological conditions. Here, we consider the rural–urban distinction and the size of the watershed to be the primary factors influencing transferability. We have clarified this more explicitly in the corresponding discussion section to support a broader comparison with other catchments. However, site-specific results rely on actual measurements and field observations, so direct, quantitative comparisons are limited unless similar data are available.
- We agree and have revised the abstract accordingly.
- Thank you for pointing this out. We have revised the manuscript to remove spaces before all % symbols.
- We appreciate this observation and have adjusted the sentence to “MAR with river water presents a highly valuable strategy to adapt to the imbalance of the landscape water regime.”
- Thank you for this suggestion. We have added a sentence in the conclusion pointing to these potential next steps.
We hope that these additions strengthen the manuscript and address the reviewer’s insightful comments.
Citation: https://doi.org/10.5194/egusphere-2025-740-AC1
-
AC1: 'Reply on RC1', Lea Augustin, 16 Jul 2025
-
RC2: 'Comment on egusphere-2025-740', Anonymous Referee #2, 03 Jul 2025
The introduction of increased circularity in water management will gain importance in Germany due to declining water availability coupled with growing pressure on water resources. The main reason for this is rising temperatures as a result of climate change, which lead to increased evaporation and higher water consumption, particularly for irrigation purposes. Additionally, some regions are experiencing rising population numbers, as exemplified by the Berlin area. Alongside rainwater management measures (blue-green infrastructure, sponge city principles) and the reuse of treated wastewater, Managed Aquifer Recharge (MAR) represents another fundamentally suitable method for returning water to the cycle. Compared to technical storage systems, a key advantage lies in the activation of naturally existing storage spaces, which offers significant economic as well as planning-related benefits. Against this background, the present work investigates, using the example of the Günz River, whether the quality of runoff is suitable for MAR and how the quality can be effectively monitored.
The study addresses a highly topical issue that is of great relevance in many regions of Germany and certainly also in other countries. Moreover, it is very practice-oriented and even provides a concrete proposal for setting up monitoring stations. The results are presented clearly and are easy to follow.
Suggestions for improvements:
- The manuscript should discuss in more detail the transferability of the results to other river catchments.
- The manuscript should also address the aforementioned alternative or complementary methods. MAR does not necessarily have to be implemented centrally at major rivers but can also be realized in a decentralized manner within the catchment area.
Citation: https://doi.org/10.5194/egusphere-2025-740-RC2 -
AC2: 'Reply on RC2', Lea Augustin, 16 Jul 2025
We would like to thank the reviewer for this valuable, supportive feedback and for highlighting the importance of the discussed topic.
We agree that the manuscript benefits from a clearer discussion of the transferability. Here, we have to distinguish between the transferability of the methodology and the transfer of the site-specific results. The methodology itself is site-independent and transferable to regions with different hydrological and hydrogeological conditions. Nevertheless, we consider the rural–urban distinction and the size of the watershed to be the primary factors influencing the applicability. We clarified this key limitation more explicitly in the discussion. While the study site stands representative of many rural catchments, the actual results are likely site-specific. However, they show the potential of MAR with river water in rural catchments with similar characteristics, as well as the potential of linking watershed risks with quality measurements.
Regarding the implementation of MAR, we fully agree with the reviewer that especially the upper catchments are promising locations. Although MAR is a versatile tool that can be implemented even at longer distances to the river, infiltration near major rivers often faces constraints due to high volumetric flows and elevated groundwater levels. Additionally, coupling MAR with direct flood protection measures is typically not feasible at major rivers. We further clarified in the introduction that we understand the presented potential MAR scheme as decentralized MAR.
We hope that these adjustments are in the reviewer's interest and will further improve our manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-740-AC2
-
RC3: 'Comment on egusphere-2025-740', Anonymous Referee #3, 08 Jul 2025
egusphere-2025-740
The scope of the paper is very unclear and so the reasoning behind the paper and your arguments. Is the focus on MAR and how river water quality and quantity affect its performance or is it on rivers and how MAR affects their quality and quantity. Or is it on something else: eg. Testing monitoring setup? Please clarify and adjust the text accordingly. Particularly, the introduction is confusing, please state clearly your hypotheses and objectives.
The section on Examples of safeguarding water quality can be derived from the drinking water sector should be shortened or even removed from the introduction as far too long.
Discussion should be structured with meaningful headings and address set up in the introduction hypotheses and objectives. At the moment it is rather dense, difficult to follow and spoiled with unnecessary details. Please streamline it.
line 5 grammar
Citation: https://doi.org/10.5194/egusphere-2025-740-RC3 -
AC3: 'Reply on RC3', Lea Augustin, 16 Jul 2025
We thank the reviewer for this critical comment. The aim of this paper is to present a methodology for assessing river water quality with regard to its potential use as a source for MAR. Since laboratory confirmation of water quality typically occurs on a different time scale than flooding events, the quality of the source water must be ensured intrinsically. We propose that this can be achieved through a combination of high-resolution monitoring at strategically selected sites, a limited number of targeted laboratory analyses, and a risk assessment of the catchment. The new methodology was applied exemplarily to a river in southern Germany, which is representative of many rural watersheds of similar size. The methodology itself is site independent and transferable to regions with different hydrological and hydrogeological conditions. In the revised manuscript, we communicated the primary focus and structure of the study more clearly.
We restructured the paragraph starting in line 95 and clarified the presentation of our hypotheses and aims by adding two sentences. The section on examples of safeguarding water quality was indeed detailed, which we tried to tweak by deleting the three sentences on the implementation of the Water Safety Plan concept in Germany. Furthermore, we structured the discussion with subheadings and are now picking up the main research questions and hypotheses from the introduction. We rechecked our abstract with a grammar checker, but found no incorrectness in line 5.
We hope these changes improve the clarity and focus of the manuscript and appreciate further consideration.
Citation: https://doi.org/10.5194/egusphere-2025-740-AC3
-
AC3: 'Reply on RC3', Lea Augustin, 16 Jul 2025
Data sets
Video footage of the effects of a thunderstorm on the water level and the turbidity of a small river + hourly data from the monitoring box Thomas Baumann and Lea Augustin https://mediatum.ub.tum.de/1338693
Documentation for building the river water monitoring kit Thomas Baumann and Lea Augustin https://gitlab.lrz.de/smart-sws/riverpi
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