Thank you for your well-considered and detailed comments – these will certainly improve the communication of our work and the quality of the article overall. Replying to each comment in-turn:

1. Clarify the Framing Around Data Scarcity

We agree this can be framed more clearly. We intend to communicate that the issue of scarcity relates in most cases to locally-collected, in-situ or high resolution hydrological datasets and will add that clarification. And indeed for existing datasets (such as remotely-sensed data), issues of data access, sharing and use remain barriers despite greater availability. We will make this clearer in the introduction.

1. Relate More Clearly to Existing Research Infrastructures

We agree that the article will benefit from this. We will add to the introduction to provide reader context on how FDRI fits in with broader research infrastructures and observatories. Then (relating to your Comment 6), we will offer more reflection in the discussion on the implications of FDRI’s design recommendations for its future role and relationships with other infrastructures (in sub-section ‘Considerations for Operational Sustainability’). We especially agree that there is a need to relate to those that have broader ecological/environmental focuses such as eLTER in these sections, as the systematic review procedure maintained a narrower focus on hydrological research and data infrastructures.

1. Improve Transparency and Justification of Stakeholder Sampling

We will expand the explanation in Section 2.2 to provide clearer details about respondent selection, including roles, sectors, and levels of seniority. We will also add detail of how preliminary workshops guided the selection of key informants through purposive and snowball sampling of FDRI’s major expected user groups. Through FDRI’s large project network, we were able to purposively sample key informants from expected major user groups, whilst specifically targeting individuals recognised by others to be knowledgeable about data and research infrastructures like FDRI. Sampling participants with prior experience and understanding of such infrastructures enabled deeper reflections on design elements and priorities.

We emphasise for transparency in the methods that the sample size (n=20) was intended for breadth and depth in a formative design phase and that further rounds of stakeholder engagement are planned. On reflection, we can better clarify this in the conclusion (such as after Line 587) to ensure the reader is aware of sample size limitations and will add this to the revised manuscript.

1. Refine Terminology and Conceptual Framing

Thank you for this observation. The terms used, such as those you highlight, reflect the language commonly used by our interviewees, and we chose to retain them to stay closer to the original expressions of stakeholder perspectives. Also, where they are used, these terms are supported by more specific sub-themes in the tables and are discussed in more detail throughout the text. We hope this helps clarify their meaning. That said, we will keep this point in mind when reviewing the full manuscript in light of all reviewer feedback and consider whether any further clarification or rewording could be helpful to the reader.

1. Clarify the Manuscript Structure: Results vs. Discussion

Thank you for this thoughtful comment. We agree this raises an important point about what constitutes “results” in interpretative qualitative research, and we could improve the article by adding clarifications/modifications to the manuscript.

Firstly, to address the comment on normative claims, we agree there are occasions when interviewee perspectives on FDRI are combined with literature references, then language is used that presents interviewee perspectives more normatively (such as Line 269). We will revise phrasing throughout the results to make it clear when stakeholder recommendations made are specific to FDRI. Then, where there is broader support from the literature, that will be noted additionally. This should help distinguish FDRI-specific observations from generalised recommendations in the results.

Secondly, regarding restructuring, we recognise that Section 3.3 of the results in particular seems more interpretive than descriptive, as the priorities presented are interpretative syntheses based on themes that emerged across the full interview set - not from a single question as in Sections 3.1 and 3.2. We believe this section still belongs in the results. It is common when conducting interviews and inductive analysis for ‘emergent’ points of emphasis (or themes) such as these to arise that span across different questions. In more structured approaches to qualitative research these might be omitted from the results. Here we feel that, pragmatically, and given the semi-structured nature of these interviews, the level of emphasis and evidence supporting these structural design priorities warrants their reporting as an important, relevant result from the semi-structured interview and literature review procedure.

We will address this second point explicitly with more explanation in the final paragraph of the methods. Specifically, this will justify the inclusion of Section 3.3 in the results section and explain how ‘design priorities’ had a dedicated round of thematic coding inclusive of all questions, in contrast to Sections 3.1 and 3.2, where only direct responses to single questions were coded. We will also add clearer explanation at the start of Section 3.3 in the results (Line 390 onward) about how these design priorities were recorded separately in the interview analysis.

1. Strengthen the Discussion and Critical Reflection

This is a very helpful recommendation and links back to Comment 1. We will add a new paragraph in the discussion Section ‘Considerations for Operational Sustainability’ about implications of this study’s findings for FDRI’s (and equivalent infrastructures’) future role and relationships with other research and data infrastructures, drawing on the references that will have been newly introduced to the introduction.

Best wishes from the Authors.

We sincerely thank the reviewer for taking the time to provide thoughtful feedback on our manuscript and for recognising its contribution to user-centred hydrological monitoring system development.

We appreciate the helpful suggestions for improvement. For the first point, we agree this is important. We will add one to two sentences to the final paragraph of the introduction to clarify the specific research questions the study seeks to address. The second observation is also very helpful and highlights a link that didn't make it into the visualisation - we will update Figure 3 to include a connecting line between “cost” and “supporting infrastructure” to better illustrate this relationship. We will also carefully check the reference list and ensure paragraph breaks are correctly formatted.



Best wishes from the authors.

Thank you to the reviewer for their detailed comments that will certainly improve the manuscript. And we agree, the findings on community elements are interesting and should generate interesting lines of research and scientific debate. We reply to each of the detailed comments in-turn.

1/ A general comment: in the manuscript, the use of the word “infrastructure” is ambiguous, as, to my understanding, it is use for things that are different. The word can refer to physical elements in the fields including sensors, a data information system or an organization that provides services, like its use in the context of European Strategic Forum for Research Infrastructures (ESFRI), in particular the eLTER RI (Integrated European Long-Term Ecosystem, critical zone and socio-ecological Research, https://elter-ri.eu/ ). This ambiguity makes the reading of the paper sometimes confusing. Clarification of the meaning or the use of other words within the paper is recommended.

We agree that we use the term infrastructure for different meanings in the paper and this can be confusing. There is some variance in how eLTER and other infrastructures define themselves, owing mostly to slight differences in their objectives. So we will add to the introduction a clearer description of the infrastructure landscape (eLTER included), how they are defined and how FDRI is defined as a monitoring and research infrastructure within that landscape (FDRI has a greater emphasis on in-situ monitoring data than some research infrastructures). This aligns with comments from the other 2 reviewers.



In other parts of the paper, such as when talking about fixed, mobile and digital components of the monitoring infrastructure, it would be clearer to use the word ‘component’ to avoid confusion – we will make those changes too and any other language clarifications where appropriate.

2/ Line 44: the argument about data scarcity in hydrological sciences is not necessarily true now, with the avenue of satellite data products with a spatial and temporal resolution which becomes relevant for hydrological studies and provide high resolution data that can be useful in water resources management and in running or evaluating models.

Thank you. This reinforces the first suggestion made by Reviewer 1 for better framing around data scarcity, to which we responded:



“We agree this can be framed more clearly. We intend to communicate that the issue of scarcity relates in most cases to locally-collected, in-situ or high resolution hydrological datasets and will add that clarification. And indeed for existing datasets (such as remotely-sensed data), issues of data access, sharing and use remain barriers despite a wide and growing availability. We will make this clearer in the introduction.”

3/ Line 69: explicit the acronym WRM

Thanks, will do.

4/ Lines102: is the Water4All European partnership relevant for the UK (https://www.water4all-partnership.eu/ ). This project is also conducting a survey to define the users’needs.

This is indeed relevant, thank you. We will include that in the introduction and seek internally to connect with them.

5/ Lines 119, 125: ensures and note ensure

Thanks

6/ section 2.1: I am surprised not to see the words “information system” in the search query.

We agree this search term would have been appropriate. However, we expect that the inclusion of the terms “monitoring” and “data” has captured most or all of the literature focussed on information systems relevant to the other search terms.

7/ line 147: if I understood correctly, you launched the project using online questionnaire and online workshops. Could you have a bias in the participation of such events, that tends to attract persons that usually participate in such events. How do you ensure that you have reached all the potential users?

We will add some detail in the methods on the scoping survey (127 completed), 2 workshops (81 total attendees), stakeholder group discussions (20 held) and how they were setup to be inclusive for a representative sample of FDRI’s expected users. This was an iterative process as scoping stage discussions gradually refine the objectives, services and potential users of the infrastructure. More details on the scoping study available here (https://www.ceh.ac.uk/sites/default/files/2022-06/FDRI_Community%20Report_FINAL.pdf).

8/ Line 212: could you explain what an inductive approach is?

Will clarify this better in the paper methods. It is a qualitative research approach whereby questions do not have pre-set answers, and instead ‘codes’ and ‘themes’ are generated and tagged to sections of text by the data analyst based on their interpretation of the qualitative responses.

9/ Line 335: users ask for real-time access to data. This objective is more an operational one and is generally the role of monitoring networks. However, the initial objective of the FDRI network is “to support state-of-the-art research and innovation” (line 72). This seems somehow incompatible.

Thanks, this touches upon a prudent debate on real-time data that we can elaborate more clearly in the text. One of FDRI’s priorities is to support practical research to support better management of floods, droughts and other hydrological issues in the UK. As such, studies such as those involving citizen scientists (e.g. surge monitoring in 24 hours after a flood), and studies evaluating operational or management activities sometimes require real-time data to trigger or inform subsequent data collection efforts. It is also an important additional incentive/reward for engagement with research activities for civil society, community and industrial data user/contributors if their efforts yield real-time data, insights or feedback that is interesting or useful to them. On the other side of the debate, real-time data is more expensive and comes with operational risks such as telemetry failure, so this is a decision to take case-by-case considering the benefit, costs and operational risks of the data being real-time.

10/ Lin 355: FAIR principles are only principles and their practical implementation may lead to different interpretations. Their meaning within the context of the FDRI program should be defined.

Good point, we will do so.

11/ Open Geospatial Consortium (OGC) standards are not only relevant for remote sensing date. They are also relevant for vector data.

Thank you, we will clarify this.

12/ p13: I am surprised not to see the harmonization of protocols to measure the targeted observed properties as an issue. It proves to be a challenge (for instance, in the eLTER RI, it required several years of work (Zacharias et al, 2025)

Thank you, this is a very good point and it is brilliant to see this research by Zacharias et al. (2025). This was raised by respondents T1, A6 and A9 in particular but have been coded to other labels such as standardisation, FAIR principles, quality assurance and control, interoperability etc. We agree this is a major issue and should be addressed explicitly in the text. Harmonisation of protocols can be addressed explicitly the analysis on digital infrastructure requirements in Section 3.2, as well as Section 3.3. in the analysis of required data collection enabling services.

13/ Line 364: “automated by manually verified processes”: could you elaborate on the way you see the implementation of such processes?

We will elaborate on this – respondents advised periodic manual reviews and alerts for QA/QC input when issues are flagged that need review.

14/ Line 371: I am surprised to see that the used of X or Facebook is suggested. With such platforms, how do you ensure the protection of personal data?

We will add a note on this, but this is largely just as a data, insights and research communication & tool where data sharing agreements allow. We will add a note however on personal data considerations of subsequent engagement of users on those platforms.

15/ p.15: would the paper of Brantley et al. (2017) be relevant for your discussion?

Thank you and yes, the common measurements across the CZOs networks in the US are especially interesting here. It is certainly worth raising and including in the introduction as ‘critical zone observatory’ is another definition to define early in this article.

16/ Figure 3: could you add some elements in the caption on how to read this figure?

Yes, thank you for flagging this.

17/ lines 582-591: this paragraph is more discussion than conclusion

Agreed. We will move this into the discussion. Thank you for your review and thoughtful comments.