Brief Communication: A new drought monitoring network in the state of Brandenburg (Germany) using cosmic-ray neutron sensing

Altdorff, Daniel; Heistermann, Maik; Francke, Till; Schrön, Martin; Attinger, Sabine; Bauriegel, Albrecht; Beyrich, Frank; Biró, Peter; Dietrich, Peter; Eichstädt, Rebekka; Grosse, Peter Martin; Markert, Arvid; Terschlüsen, Jakob; Walz, Ariane; Zacharias, Steffen; Oswald, Sascha E.

doi:10.5194/egusphere-2024-3848

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https://doi.org/10.5194/egusphere-2024-3848

Preprints

12 Dec 2024

| 12 Dec 2024

Brief Communication: A new drought monitoring network in the state of Brandenburg (Germany) using cosmic-ray neutron sensing

Daniel Altdorff, Maik Heistermann, Till Francke, Martin Schrön, Sabine Attinger, Albrecht Bauriegel, Frank Beyrich, Peter Biró, Peter Dietrich, Rebekka Eichstädt, Peter Martin Grosse, Arvid Markert, Jakob Terschlüsen, Ariane Walz, Steffen Zacharias, and Sascha E. Oswald

Abstract. In the recent years, the German federal state of Brandenburg has been particularly impacted by soil moisture droughts. To support the timely and informed management of such water-related risks, we introduce a novel soil moisture and drought monitoring network based on cosmic-ray neutron sensing technology. This initiative is driven by a joint collaboration of research institutions and federal state agencies, and it is the first of its kind in Germany to have started operation. By mid 2024, eight sites were instrumented across Brandenburg; four more are planned for 2025. The data will be openly accessible to foster applications and collaboration right from the start.

Received: 06 Dec 2024 – Discussion started: 12 Dec 2024

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

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Journal article(s) based on this preprint

23 Jan 2026

Soil moisture monitoring with cosmogenic neutrons: an asset for the development and assessment of soil moisture products in the state of Brandenburg (Germany)

Maik Heistermann, Daniel Altdorff, Till Francke, Martin Schrön, Peter M. Grosse, Arvid Markert, Albrecht Bauriegel, Peter Biró, Sabine Attinger, Frank Beyrich, Peter Dietrich, Rebekka Eichstädt, Jakob Terschlüsen, Ariane Walz, Steffen Zacharias, and Sascha E. Oswald

Nat. Hazards Earth Syst. Sci., 26, 465–486, https://doi.org/10.5194/nhess-26-465-2026,https://doi.org/10.5194/nhess-26-465-2026, 2026

Short summary

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-3848', Anonymous Referee #1, 20 Jan 2025

Review/comments on Brief Communication: A new drought monitoring network in the state of Brandenburg (Germany) using cosmic-ray neutron sensing by Altdorff et al.
General comments
The Authors present a very relevant and interesting initiative to establish an operational ground-based long-term soil moisture monitoring based on cosmic-ray neutron sensors (CRNS). Nine locations and around six months of data are presented. Comparisons with the soil moisture simulated by the agro-hydrological model SWAP are also reported. The manuscript reads well and clear. The preliminary results are meaningful and the discussion fair.
Personally, I believe that the main contribution of this initiative is (L39) to bring together a consortium of research institutions and state agencies for establishing a long-term monitoring. And I would congratulate with the Authors for such an effort in moving CRNS research activities towards long term operational monitoring. But back to the manuscript, it reads like an internal report of current status of the initiative and I’m not convinced that is worth a publication.
I admit that this bold statement starts from the wish to read novelty in scientific papers and to not consider pure tech-transfer project innovative. In questioning my self-position, I made two actions. First, I look at the description of Brief communications, as it could have provided me with the right angle for judging the manuscript. The description is reported below. In addition, I looked at other published papers with similar vision (to my knowledge). Some of the papers are listed below.
Brief communications are timely, peer-reviewed, and short (2–4 journal pages). These may be used to (a) report new developments, significant advances, and novel aspects of experimental and theoretical methods and techniques which are relevant for scientific investigations within the journal scope; (b) report/discuss significant matters of policy and perspective related to the science of the journal, including "personal" commentary; (c) disseminate information and data on topical events of significant scientific and/or social interest within the scope of the journal. Brief communications have a maximum of three figures and/or tables, maximum 20 references, and an abstract length not exceeding 100 words. The manuscript title must start with "Brief communication:".
Benninga, Harm-Jan F., Coleen D. U. Carranza, Michiel Pezij, Pim van Santen, Martine J. van der Ploeg, Denie C. M. Augustijn, and Rogier van der Velde. ‘The Raam Regional Soil Moisture Monitoring Network in the Netherlands’. Earth System Science Data 10, no. 1 (11 January 2018): 61–79. https://doi.org/10.5194/essd-10-61-2018.
Cosh, Michael H., Todd G. Caldwell, C. Bruce Baker, John D. Bolten, Nathan Edwards, Peter Goble, Heather Hofman, et al. ‘Developing a Strategy for the National Coordinated Soil Moisture Monitoring Network’. Vadose Zone Journal 20, no. 4 (July 2021): e20139. https://doi.org/10.1002/vzj2.20139.
Well, as for the Brief Communications, I leave to the Handling Editor to decide. Anyway, I highlight how the number of pages of the manuscript is way too much. Moreover, its scope might be (c) even if information and data do not seem to be properly disseminated.
By looking at other published papers on similar topic (examples above), I have seen much more information in describing the issues and the effort, e.g., to establish such a network, to standardize the observations, to integrate the new data in current platforms, in defining accessibility to end users.
Overall, while I’m currently not in favour of the publication of the present manuscript, by considering previous published papers, it might be considered if the Authors put much more effort and they succeed in improving the manuscript, e.g., by sharing their experiences in establishing, maintaining, and managing a fixed environmental sensor network that could be of utility to the community for avoiding mistakes and reproducing good practices. Improving metadata (e.g., how was the calibration performed?), transparency (how data have been processed) and data accessibility (e.g., by API-type) should also justify the publication.

Citation: https://doi.org/10.5194/egusphere-2024-3848-RC1
- AC1: 'Reply on RC1', Maik Heistermann, 23 Jan 2025
  
  Please see reply as pdf in the supplement.
  
  Citation: https://doi.org/10.5194/egusphere-2024-3848-AC1
RC2:
'Comment on egusphere-2024-3848', Anonymous Referee #2, 22 Jan 2025

In this Brief Communication, the authors present a new initiative in Germany to establish an operational, long-term soil moisture monitoring system based on cosmic-ray neutron sensors (CRNS) for the state of Brandenburg. In general, this is a very positive development, as CRNS has established itself as a new standard method for the continuous determination of soil moisture at the field scale and the widespread deployment of these sensors is very helpful and highly welcome both for environmental research and for the support of water management.
In terms of content, this article presents the status of the project as well as a comparison of the measured soil moisture with simulations of the agrohydrological model SWAP.
The manuscript is well written; however, I have to agree with reviewer #1 that the paper reads more like a project report and does not fulfil the NHESS requirements for short communications, especially in terms of the length of the paper.
Also, it may be beneficial to complete the installation and subsequently measure soil moisture over a longer period of time. Once this has been achieved, the authors could publish the results as a data paper. Finally, we don’t learn much from the case study and the context of the comparison of CRNS data with simulation is unclear (see also specific comment further below).
Specific comments:
L38: Why mention only national networks?
L44: Such an initiative is not unique in Germany, see e.g. Ney et al. (2021).
Figure 1: The small maps are hardly recognizable and the situation at the measuring stations is not readable. Also, this this information is already available in table 1. Therefore, I suggest removing the small maps.
L54-71: This sounds very much like an interim report.
L116-119: It is not clear to me how this comparison is to be analysed in this project. What are the consequences if there are discrepancies? Do you then not trust the measurement data, even though the model certainly may have a much higher uncertainty?
L126-129: Describing commitments should not be part of a scientific publication. It would make more sense to present the concrete implementation of a real-time data platform.
L139-140: Formulations such as “some validity” and “some transferability” are too vague.
L142-145: This seems to be rather an alternative measurement approach instead of an upscaling approach for the presented CRNS network.
References
Ney, P., Köhli, M., Bogena, H., & Goergen, K. (2021). CRNS-based monitoring technologies for a weather and climate-resilient agriculture: Realization by the ADAPTER project. In 2021 IEEE International Workshop on Metrology for Agriculture and Forestry (MetroAgriFor) (pp. 203-208). IEEE.

Citation: https://doi.org/10.5194/egusphere-2024-3848-RC2
- AC2: 'Reply on RC2', Maik Heistermann, 24 Jan 2025
  
  Please see reply as pdf in the supplement.
  
  Citation: https://doi.org/10.5194/egusphere-2024-3848-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2024-3848', Anonymous Referee #1, 20 Jan 2025

Review/comments on Brief Communication: A new drought monitoring network in the state of Brandenburg (Germany) using cosmic-ray neutron sensing by Altdorff et al.
General comments
The Authors present a very relevant and interesting initiative to establish an operational ground-based long-term soil moisture monitoring based on cosmic-ray neutron sensors (CRNS). Nine locations and around six months of data are presented. Comparisons with the soil moisture simulated by the agro-hydrological model SWAP are also reported. The manuscript reads well and clear. The preliminary results are meaningful and the discussion fair.
Personally, I believe that the main contribution of this initiative is (L39) to bring together a consortium of research institutions and state agencies for establishing a long-term monitoring. And I would congratulate with the Authors for such an effort in moving CRNS research activities towards long term operational monitoring. But back to the manuscript, it reads like an internal report of current status of the initiative and I’m not convinced that is worth a publication.
I admit that this bold statement starts from the wish to read novelty in scientific papers and to not consider pure tech-transfer project innovative. In questioning my self-position, I made two actions. First, I look at the description of Brief communications, as it could have provided me with the right angle for judging the manuscript. The description is reported below. In addition, I looked at other published papers with similar vision (to my knowledge). Some of the papers are listed below.
Brief communications are timely, peer-reviewed, and short (2–4 journal pages). These may be used to (a) report new developments, significant advances, and novel aspects of experimental and theoretical methods and techniques which are relevant for scientific investigations within the journal scope; (b) report/discuss significant matters of policy and perspective related to the science of the journal, including "personal" commentary; (c) disseminate information and data on topical events of significant scientific and/or social interest within the scope of the journal. Brief communications have a maximum of three figures and/or tables, maximum 20 references, and an abstract length not exceeding 100 words. The manuscript title must start with "Brief communication:".
Benninga, Harm-Jan F., Coleen D. U. Carranza, Michiel Pezij, Pim van Santen, Martine J. van der Ploeg, Denie C. M. Augustijn, and Rogier van der Velde. ‘The Raam Regional Soil Moisture Monitoring Network in the Netherlands’. Earth System Science Data 10, no. 1 (11 January 2018): 61–79. https://doi.org/10.5194/essd-10-61-2018.
Cosh, Michael H., Todd G. Caldwell, C. Bruce Baker, John D. Bolten, Nathan Edwards, Peter Goble, Heather Hofman, et al. ‘Developing a Strategy for the National Coordinated Soil Moisture Monitoring Network’. Vadose Zone Journal 20, no. 4 (July 2021): e20139. https://doi.org/10.1002/vzj2.20139.
Well, as for the Brief Communications, I leave to the Handling Editor to decide. Anyway, I highlight how the number of pages of the manuscript is way too much. Moreover, its scope might be (c) even if information and data do not seem to be properly disseminated.
By looking at other published papers on similar topic (examples above), I have seen much more information in describing the issues and the effort, e.g., to establish such a network, to standardize the observations, to integrate the new data in current platforms, in defining accessibility to end users.
Overall, while I’m currently not in favour of the publication of the present manuscript, by considering previous published papers, it might be considered if the Authors put much more effort and they succeed in improving the manuscript, e.g., by sharing their experiences in establishing, maintaining, and managing a fixed environmental sensor network that could be of utility to the community for avoiding mistakes and reproducing good practices. Improving metadata (e.g., how was the calibration performed?), transparency (how data have been processed) and data accessibility (e.g., by API-type) should also justify the publication.

Citation: https://doi.org/10.5194/egusphere-2024-3848-RC1
- AC1: 'Reply on RC1', Maik Heistermann, 23 Jan 2025
  
  Please see reply as pdf in the supplement.
  
  Citation: https://doi.org/10.5194/egusphere-2024-3848-AC1
RC2:
'Comment on egusphere-2024-3848', Anonymous Referee #2, 22 Jan 2025

In this Brief Communication, the authors present a new initiative in Germany to establish an operational, long-term soil moisture monitoring system based on cosmic-ray neutron sensors (CRNS) for the state of Brandenburg. In general, this is a very positive development, as CRNS has established itself as a new standard method for the continuous determination of soil moisture at the field scale and the widespread deployment of these sensors is very helpful and highly welcome both for environmental research and for the support of water management.
In terms of content, this article presents the status of the project as well as a comparison of the measured soil moisture with simulations of the agrohydrological model SWAP.
The manuscript is well written; however, I have to agree with reviewer #1 that the paper reads more like a project report and does not fulfil the NHESS requirements for short communications, especially in terms of the length of the paper.
Also, it may be beneficial to complete the installation and subsequently measure soil moisture over a longer period of time. Once this has been achieved, the authors could publish the results as a data paper. Finally, we don’t learn much from the case study and the context of the comparison of CRNS data with simulation is unclear (see also specific comment further below).
Specific comments:
L38: Why mention only national networks?
L44: Such an initiative is not unique in Germany, see e.g. Ney et al. (2021).
Figure 1: The small maps are hardly recognizable and the situation at the measuring stations is not readable. Also, this this information is already available in table 1. Therefore, I suggest removing the small maps.
L54-71: This sounds very much like an interim report.
L116-119: It is not clear to me how this comparison is to be analysed in this project. What are the consequences if there are discrepancies? Do you then not trust the measurement data, even though the model certainly may have a much higher uncertainty?
L126-129: Describing commitments should not be part of a scientific publication. It would make more sense to present the concrete implementation of a real-time data platform.
L139-140: Formulations such as “some validity” and “some transferability” are too vague.
L142-145: This seems to be rather an alternative measurement approach instead of an upscaling approach for the presented CRNS network.
References
Ney, P., Köhli, M., Bogena, H., & Goergen, K. (2021). CRNS-based monitoring technologies for a weather and climate-resilient agriculture: Realization by the ADAPTER project. In 2021 IEEE International Workshop on Metrology for Agriculture and Forestry (MetroAgriFor) (pp. 203-208). IEEE.

Citation: https://doi.org/10.5194/egusphere-2024-3848-RC2
- AC2: 'Reply on RC2', Maik Heistermann, 24 Jan 2025
  
  Please see reply as pdf in the supplement.
  
  Citation: https://doi.org/10.5194/egusphere-2024-3848-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (06 Feb 2025) by Márk Somogyvári

AR by Maik Heistermann on behalf of the Authors (25 Apr 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (26 May 2025) by Márk Somogyvári

RR by Anonymous Referee #3 (11 Jun 2025)

Suggestions for revision or reasons for rejection

General:
- the authors have provided an extended version of the original manuscript, for which they moved from the brief communication format to the research paper scope. However, there are now minor and major shortcomings. The first results which are presented look promising and it is clear that the overall context is substantially larger than the main work shown, however, in the present form it appears still as a patchwork of ideas with a not very well balanced introduction.
What is the main research question behind it?
Does that network mainly serve as a number of reference points for drought monitoring inferred from railroad measurements?
If so, why is there no analysis presented on that?
Or do the authors intend to provide data on hydrologically relevant locations within Brandenburg in order to (later) feed that into a larger scale model?
What role does clustering of sensors have in that context and to which extend is the scale gap discussion relevant?
- the provided data seems to be available only in German (online interface). Please provide an English version.

Comments to the text body:
- The introduction unfortunately suffers from unrepresentative selection of literature with the focus on self-citations. Examples are:
- In the paragraph of soil moisture monitoring and its data sources Oswald et al. 2024, Babaeian et al. 2019 and Schmidt et al. 2024 are cited. With Babaeian et al. 2019 presenting a more fundamental overview, Oswald et al. 2024 seems to be not strongly linked to the respective claims in the text. There is no reference to point scale probes which make up the largest amount of data sources. Schmidt et al. 2024 is not representative for remote sensing.
To make a more specific example: Oswald et al. 2024 is cited for the following claims:
A: "soil moisture monitoring is widely acknowledged",
B: "remote sensing products are limited by shallow penetration depths, low overpass frequencies, and vegetation-related uncertainties",
C: "Hydrological models have the potential to overcome such limitations".
A is not within the scope of Oswald et al. 2024. To the contrary, this topic is covered in literature since 50+ years. C is neither very well covered as Oswald et al. 2024 focuses on ML applications, whereas here land-surface models for example should be cited. Oswald et al. 2024 provides a short overview about remote sensing product and therefore the claim is covered but again, here the authors should focus on primary sources instead of yet again cite their own works.
- In the paragraph for CRNS networks Heistermann et al. (2023), Ney et al. 2021, Zacharias et al. 2024 are cited - all publications with one of the authors or affiliated German groups. The authors mention the larger networks only in one sentence without citation "Only few countries have already established long-term CRNS monitoring networks at the national scale (e.g., the USA, UK).", even leaving out CosmOz Australia.
- The section about CRNS does not cite the relevant literature - neither does Andreasen et al. 2017 explain the method, nor is Schrön et al. 2017 representative for the footprint. Likewise, Altdorff et al. 2023 is neither the first nor the most relevant publication for roving.
To conclude, the introduction is, for a research paper, fragmentary, unrepresentative and too much narrowed down to the publications of the researchers themselves.

-l41: "So far, however, CRNS has mainly been used in experimental contexts" - what does experimental (short-term) contexts mean? If ignoring other literature about CRNS networks, the reader might come to the conclusion that probes would be installed on a short term basis, but as a matter of fact a large number of the probes are used in long-term monitoring contexts, so that claim seems to be not very well supported.
-l47: "The first attempt in Germany to systematically apply CRNS technology at the federal state level was initiated in 2024". The authors previously cited Ney which is definitely an application of "CRNS technology at the federal state level" prior to the authors' initiative.
-l77: "Such a station includes a neutron detector, logger and telemetry, solar power supply, and sensors for barometric pressure, temperature, and humidity, as well as conventional point-scale sensors of soil moisture in various measurement depths as an additional reference" - please name sensor type and manufacturer.
-l85: "Sensor footprint that are homogeneous with regard to these attributes are preferable with regard to the interpretation of
the CRNS signal." - this statement seems to conflict with the approach to collocate sensor with (considerably dry) train lines. Altdorff et al. 2023 shows in Fig. 1 a sensor in a distance of approximately 1 m to trainlines, which would make the sensor potentially susceptible to the road effect. How distant are these sensors to the rail infrastructure and in which way did the authors account for that?
- Table 1: "Land use from OpenStreetMap contributors (2024)" - why do the authors cite the (relatively vague) OSM maps. Did they not characterize the sites themselves in terms of land use and soil texture? That seems to be a minor red flag.
-l111: "The sensitivity of the neutron detector relative to a known reference" - in what way is that procedure a 'general calibration'. If each sensor still has its own normalization factor this procedure seems to be not different than as has been done at other sites.
-l114: "The spatial variation of incoming cosmic radiation was accounted for by using the PARMA model (Sato, 2015)" - what does that mean? Did the authors conduct an own analysis and how do they map the high-altitude site JUNG to their data?
-l122: "we followed the weighting procedure outlined by Schrön et al. (2017)" - did the authors use the sampling scheme as well or the footprint function?
-l211: "At this point, we should reiterate that the focus of this paper is to introduce the new soil moisture monitoring network in Brandenburg" - the introduction of a monitoring network by itself is not a research goal. The authors claimed to try to focus on providing a substantial contribution, not an outlook based on preliminary findings.
-l214: "we maintain that the model is able to reproduce the observed soil moisture dynamics in the upper 30–50 cm of the soil"- The authors previously mentioned that the sites are only capable of measuring the soil water content to a depth of 30 cm. Explain this statement
- Fig. 2: much too small, please enlarge.
-l311: "ware" -> "were"
- in the conclusions section "User-oriented monitoring products" - many research questions are presented which are not covered in the manuscript. Additionally, with only a German data interface most of the potential users face a language barrier.
-l350: "In any case, (...)" - that is a rather colloquial statement and potentially does not contribute in a meaningful way.
- While the contributions statement suggests MH, TF, DA, AB, AM, and SO were the core researchers, the other co-authors may have had minor roles, potentially indicating 'gift' or 'coercive' authorships.

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RR by Anonymous Referee #4 (03 Jul 2025)

Suggestions for revision or reasons for rejection

The paper is interesting as it presents a soil moisture network based on CRNS. The data will be valuable for multiple research applications, and thus it is of interest to publish this manuscript. Looking at the previous reviews I agree it is too much for a Brief communication, but for a research paper it is not innovative or comprehensive enough. It is more suitable as a data paper. For a research paper, the manuscript needs significant improvements before publication. In general, the title points towards a drought monitoring network which is installed in Brandenburg. My expectation is then, that there is a detailed description of the network set-up, how locations were chosen, a thorough validation of the network and with a focus on its ability to monitor drought. However, this is not sufficiently represented in the manuscript. The selection of locations is not satisfactorily described, the validation and quality assurance is lacking (a validation based on one observation per station is not sufficient), and there is no mention of drought monitoring. This needs to be improved in the manuscript before this can be published as an introduction to a new monitoring network in the form of a research paper. I realize that the network is only operational since spring 2024, but currently this gives you one year of data. In addition, the current situation in Brandenburg is pressing with a drought warning and high alert levels (European Drought Observatory), whereas spring 2024 was more humid. So my suggestion is to extend the analysis period to include a full year of data including the last months to also observe the onset of drought conditions in Brandenburg in 2025. One option is for example to calculate a drought indicator based on soil parameters,i.e. the Soil Water Deficit Index, which allows you to also showcase the drought monitoring capabilities.

Furthermore, there are many applications of soil moisture data such as reconstruction of water fluxes and enhancing information along the vertical dimension, but these are all described very minimal without proper evaluation of the results. In addition, they are all based on the modeled soil moisture and not CRNS soil moisture. The paper seems to have a hard time balancing between the CRNS data and the model, and the current content of the paper does not reflect the title of the paper.

line 47 - 50: Adjust this, because this statement is not entirely true, CRNS data is available in the International Soil Moisture Network and also available through other sources.
line 94: Are these stations already installed now? Otherwise I would change this to summer.

The Data and Methods section is missing quite some information, and this should be added to the manuscript. Some methods are mentioned but not explained. In detail the following points should be added to increase the quality of the manuscript:

What has been the method for selecting the sites? A representative network is important, as is written in the introduction, but there is no description on how the sites were chosen based on land cover, terrain and soil characteristics. Looking at the maps in Fig 1 it seems that the south of Brandenburg is not represented, which also includes some areas with a low groundwater table. When planning a network usually one takes an approach to make sure you cover all typical landscapes (or hydrotopes as Bircher et al did for the HOBE network).

In addition, please provide an overview how the locations and characteristics of the stations (table 1) correspond to the characteristics of Brandenburg, are you really covering everything? This is especially important for drought monitoring, which is one of the main purposes of this network. In addition, if in the future the ministries or other institutions are going to use this network for drought monitoring, or if this even is going to be used for agricultural applications (i.e. drought impact analysis, insurance purposes) the representativeness of the network is crucial.

Also, I suggest to add the stations that are/will be installed in spring 2025 for completeness to table 1.

line 120: How were the four soil sampling locations within the CRNS footprint chosen? How do they represent the footprint characteristics?

In line 79 it is mentioned that there are conventional point-scale sensors of soil moisture installed at the site. But in line 129-130 you mention that "To evaluate the CRNS-based soil moisture estimates (θCRNS), reference observations within each CRNS footprint were obtained from the aforementioned soil sampling campaigns". From the results it seems only the sampling is used for validation. But why did you not also use the point-scale sensors for validation. Of course, spatial representativeness can be a point of concern, but a validation on a single sampling date is also not representative or a proper validation. I suggest to add also a validation over time, i.e. with the point-scale soil moisture sensor data.

Line 135, please write out the method you used to get the weighted reference soil moisture, not just the publication. And also, which method and metrics did you use to then validate your CRNS soil moisture?

Table 2 contains many acronyms that are not explained, please write them out in full.

Section 2.3 what is the spatial and temporal resolution of your model?

For the inputs to the pedotransfer function, why didn't you use the actual soil information from the soil sampling campaign and instead did a so-called "fine-tuning"? Is soil texture (sand, silt, clay) data not available for the sites from your sampling campaign? It would be beneficial to use this instead of tweaking your model inputs with estimated sand, silt and clay values to a point to get satisfactory results. If it is not available I suggest to at least check your calibrated sand, silt and clay content with the bulk density values from your samples to see if this is comparable.

Results and discussion

Section 3.1 gives a short overview of the soil moisture estimation and validation. First, which in situ soil moisture measurements were now used here, the stations or the samples? I suggest to also use the RMSE as a quality control metric, as this is quite common in soil moisture validation studies (i.e. Gruber et al. 2020 for satellite soil moisture retrievals). Also, I suggest to add some more references to publications that have validated CRNS sensors, to place your network in context to other CRNS networks, i.e. what were the metrics obtained for the TERENO network. Especially, as the soil moisture values are very low at the time of sampling, your MAE and bias might be not representative (i.e. higher errors might occur with a higher variability in soil moisture).

One of my major concerns is that you have calibrated your model parameters on the actual CRNS SM data. Then you use the same datasets, both CRNS and model SM to evaluate your results. This is not a proper way of doing an evaluation, as you have used the same data for calibration and validation, making these results invalid. So, either split your data in training and test (cal/val) data to asses model performance, or use another approach to obtain the model parameters. And, to assess your model performance, why not use the point-scale SM measurements as independent reference?

In section 3.2 please add a paragraph on how your calibrated parameters compare to your soil samples. From Table 4 it can already be observed that for the station OEH your calibrated sand, silt and clay is at the boundary conditions. This means your model had difficulties for this site. Please check this.
Also, in table 4, I assume T it Ton, but change this to C for clay, and also change U.

In section 3.2 you describe the possible impact of vegetation dynamics on the CRNS SM. This is something that needs to be discussed more in detail. There have been studies using a dynamic vegetation parameterization in the CRNS soil moisture estimation. Especially in crop- and grasslands this might improve your estimates.

Figure 2: it may help to add the land cover type in brackets behind the station name.

The section on Increasing temporal coverage is very minimal. I do not see how this is relevant is in context with the introduction of a CRNS network for drought monitoring and what the benefit is of your model. Because what you do not show is, how reliable the SM data is for the other years. Is this better then for example satellite data or other models? Likely you do not have validation data from point-scale sensors, but you could compare it to e.g. ERA5-Land and CGLS Soil Water Index in a triple collocation approach to showcase the quality of your data in comparison to existing data sets.
In addition, the sections on vertical integration and reconstruction of water fluxes is too minimalistic. At least make a comparison to ERA5-land. Your sites are far enough apart to allow for this.

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ED: Reconsider after major revisions (further review by editor and referees) (21 Jul 2025) by Márk Somogyvári

AR by Maik Heistermann on behalf of the Authors (17 Sep 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (07 Oct 2025) by Márk Somogyvári

RR by Anonymous Referee #3 (19 Oct 2025)

Suggestions for revision or reasons for rejection

The reviewer thanks the authors for their extensive work and their well organized answers for the questions brought up during the review. The reviewer specifically thanks the authors for including more/improved context into their manuscript which significantly increased its scientific value and the understanding of the contribution of this network.
There is, however, a final remark on the evaluation of the CRNS data, which is central to the methodology of this manuscript. The authors seem to be surprisingly confident about the results of the soil moisture assessment. The reviewer is thankful for the transparency the authors show with respect to their analysis, it, however, delivers a message of mediocre performance comparing the estimated soil moisture date with the evaluated soil moisture data. Originally, the title of the manuscript referred to a drought monitor and the precision the authors show one can raise questions whether this is approach which would be suitable for such. The CRNS footprint is large and there may be many unknowns of influence (for example the rail tracks or other infrastructure), given the systematic deviation of soil moisture values it may rather required to address the methodology. The Heistermann 2024 et al. approach seems to offer an elegant way to overcome a local calibration, but the manuscript rather seems to confirm that a local calibration as shown by other authors yields better results. At the given stage the reviewer is not having the relevant details to go more deep into the analysis chain of the authors. In good faith the authors may one last time recheck some basic assumptions like the compared count rate or whether the devices would be supplied with a different soil moisture calibration relation in order to potentially get a better alignment with the sample evaluation.
Regardless of that technical detail the reviewer is confident about the improvements and congratulates the authors for their article.

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RR by Anonymous Referee #5 (08 Dec 2025)

Suggestions for revision or reasons for rejection

The paper presents an interesting new effort to monitor soil moisture in the state of Brandenburg by developing a network of CRNS stations. It addresses the issue of obtaining reliable, precise soil moisture measurements. The authors describe the design, implementation and evaluation of the new CRNS-network and how these measurements can be useful to improve soil moisture products. The manuscript is well written and has no methodological or major technical flaws.

I want to praise the authors and reviewers for the excellent work and great effort put into the manuscript. I agree with the other reviewers that the Brief Communication was not a proper format and that the expanded version better aligns with the authors' intent to publish their technical work. The added analysis and comparison of different datasets also broaden the scope of the papers.

Although the paper does not introduce fundamentally new ideas, the authors give meaningful contributions through the documentation of developing a CRNS-network in the state of Brandenburg and how the measurements can be used to improve indirectly-assessed soil moisture. I do believe it is of interest to the scientific community, being particularly useful for other groups interested in developing similar monitoring systems

Notwithstanding, it is important to address the limitation of the manuscript's scope. Although the authors consider the context of water-related risks in Brandenburg, the manuscript remains focused on soil-moisture monitoring and technical evaluation of the product, adding limited value to natural hazard discussions. The authors do not directly address natural hazards such as droughts and floods, nor impacts, risks, and policy contexts in the region.

Although the paper's focus is on soil moisture monitoring in the State of Brandenburg (Germany), its results and general scope do not tackle natural hazards such as drought and flood risks. It is my opinion that the manuscript should be submitted to a different journal.

Recommendation:
The manuscript is well-executed and well-written, and deals with the issue of regional monitoring of soil moisture. Readers working on soil moisture measurement, hydrological modelling, and water resources planning/management will have great interest in the text. Given the scope and emphasis of the manuscript, I recommend **rejection** and advise the authors to consider submitting to a more specialised journal, rather than one focused on natural hazards.

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ED: Publish subject to technical corrections (22 Dec 2025) by Márk Somogyvári

ED: Publish subject to technical corrections (28 Dec 2025) by Uwe Ulbrich (Executive editor)

AR by Maik Heistermann on behalf of the Authors (07 Jan 2026) Author's response Manuscript

Journal article(s) based on this preprint

23 Jan 2026

Soil moisture monitoring with cosmogenic neutrons: an asset for the development and assessment of soil moisture products in the state of Brandenburg (Germany)

Nat. Hazards Earth Syst. Sci., 26, 465–486, https://doi.org/10.5194/nhess-26-465-2026,https://doi.org/10.5194/nhess-26-465-2026, 2026

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Month	HTML	PDF	XML	Total
Dec 2024	81	18	4	103
Jan 2025	106	22	5	133
Feb 2025	24	13	1	38
Mar 2025	23	6	0	29
Apr 2025	39	9	3	51
May 2025	27	8	1	36
Jun 2025	26	9	7	42
Jul 2025	25	13	2	40
Aug 2025	95	21	3	119
Sep 2025	425	14	1	440
Oct 2025	40	7	0	47
Nov 2025	33	20	3	56
Dec 2025	44	16	4	64
Jan 2026	22	20	2	44

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The German federal state of Brandenburg is particularly prone to soil moisture droughts. To support the management of related risks, we introduce a novel soil moisture and drought monitoring network based on cosmic-ray neutron sensing technology. This initiative is driven by a collaboration of research institutions and federal state agencies, and it is the first of its kind in Germany to have started operation. In this brief communication, we outline the network design and share first results.


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