General comments

The authors provide an overview of the role of river forcing in ocean models, with an emphasis on current status of Operational Ocean Forecasting Systems (OOFS). This offers an accessible introduction and status update. providing a valuable reference to those working on OOFS and to a wider community for whom the inner-workings of OOFS will be less familiar. The review paper provides a fair reflection of the current state.

Specific comments 

1. Paper title: Given the emphasis on OOFS, consider a more specific title e.g. "The Representation of Rivers in Operational Ocean Forecasting Systems". This better represents the paper content in my view. Consider also updating the Abstract to be clear on scope. or example in Line 13, the authors suggest that "This paper provides an overview of recent advances in river modelling" which might suggest a detailed review of hydrological process representation, whereas I think the paper rather more provides "an overview in recent approaches to representing coastal river discharges and processes in ocean models".

2. In general review of freshwater impacts on ocean prediction in opening paragraph, it  would be worth including example references from Bay of Bengal, as an area with significant sensitivity to freshwater influence (e.g. Jana et al 2015 -  https://doi.org/10.1016/j.csr.2015.05.001), and a body of  literature on resulting influence of BoB freshwater and barrier layers effects on TC and broader monsoon development.

3. Paper structure:

• In describing paper contents on line 40, please sign-post later sections more precisely - i.e. "Section 2 reviews...." etc. 
• I would recommend addition of a brief Section 4: Discussion & Conclusions section that highlights some recommendations for the community, and highlights gaps in capabilities and knowledge to address (see also comment below).
• Recommend to move the detailed Tables 1-4 into Appendix materials, but draw out any key themes/similarities/differences in the main manuscript as shorter (more digestible) Section 3.3. 

4. Recommendations and additional commentary

• While the paper compiles a list of various potential data sources and products, I am missing a particular narrative on relative strengths/weaknesses/limitations of the various approaches.
• This could partly be mitigated by slightly more expansion where relevant and available on reference discussions of data quality. As a specific, but not limited, example, GloFAS-ERA5 is highlighted as an operational discharge product in Section 3.3.1, but without discussion of its quality, or recommendation of its value for OOFS.
• While Section 3.3 provides useful reference detail on OceanPredict community approaches, the authors could help synthesise the details from the Table to better reflect in qualitative discussion the various approaches - e.g. numbers using climatologies, river models etc.

4. Authors might also consider referencing Polton et al 2022 (https://doi.org/10.5194/gmd-16-1481-2023) as additional example of practical guide on implementing freshwater OBC inputs to ocean models (see their Section 3.7).

TITLE - The Role of Rivers in Ocean Forecasting

RECOMMENDATION: Major revisions

This paper aims at providing a review of the river release representation in ocean modeling, spannnig from global to coastal scales.

It offers a valuable contribution to ocean modeling developers and practitioners, as it assesses current advancements and offers recommendations for the next generation modeling of the global coastal ocean to more accurately account for riverine inputs.

I encourage the authors to make additional efforts to deliver a comprehensive and detailed overview of the current state of the field, ensuring it serves as a valuable reference for the community.

As it stands, the manuscript is lacking in several key topics. It would greatly benefit from incorporating a broader range of relevant studies and addressing open issues that deserve reporting and discussion.

Major and minor Comments are in the attached pdf

General Comments:

This paper provides a useful review of methods and data available for providing river runoff forcing into operational ocean forecast models (OOFS). The text is clear and accessible to a wide audience. While not an exhaustive list, the summary tables also provide useful reference of different operational configurations. However, my primary concern is that the review is missing a discussion and conclusion. It would greatly benefit from comparison of the different approaches presented, discussion on challenges for operational implementation, and summarising priorities for future work e.g., considering recent R&D that could be brought through to future OOFS.

Further comments relating to specific aspects of the text are listed below.

Specific Comments:

Abstract: Clarify that here you focus on physical river forcing rather than supply of nutrients or other materials.

Line 17: I would not refer to the tables as a “compendium” as this suggests a complete summary. I would instead simply say that you present responses from a survey of existing OOFS providers.

Line 26-27: This suggests upwelling is the only way that productivity is impacted, whereas all the above may impact productivity. Suggest rephrasing. Also, please clarify that input of nutrients and other parameters that would impact productivity are neglected within this review, but are clearly important for consideration in future work.

Line 33: The use of climatology may not always be limited to coarse resolution models (as suggested here)?

Line 87-88: Even where resolution may be higher than estuary width, explicitly resolving the estuary may still be challenging and therefore unlikely in many coastal models, e.g., due to large inward tidal extent and/or complex coastlines or coastal infrastructure.

Section 2.3: This is an active area of research, so worth clarifying where references refer to use in operational systems vs. ongoing R&D configurations? Further discussion on scope for future development here could be useful in an added summary/discussion section (e.g., is computational cost the main barrier for this approach?).

Line 114: Worth acknowledging here that for some countries even larger rivers may lack routine monitoring (for both historical and NRT data).

Section 3.1.2: While the list of possible datasets is useful, a discussion on the various options and pros/cons for different approaches could be useful? For example, could you present similar methods together (e.g., in situ vs remote sensing), and discuss which are static vs. updated?

Line 137-138: I think these two sources should be referred to separately as provide regional rather than global datasets.

Line 170-172: How many of the other products are actually freely available? (For both historical and NRT?)

Section 3.2: I expected this section to have more discussion around the forcing of T/S at river outflow, rather than purely model validation? While it's worth stressing that tuning models based on incorrect data is an issue, it's also worth reiterating that having T/S data within river outflows (e.g., from hydrological runoff models?) could help avoid this issue. The same would apply for outflow of nutrients and other parameters of course.

Section 3.3: This currently feels like an odd way to complete the review. There is a need to provide a summary and discussion section. For example, summarising the current "state of the art" developments, limitations of existing OOFS, and priorities for future work? To help this flow, I feel the table provided should be included as an appendix (and ideally in landscape format, to assist reading columns with more content).

Within each of the tables, for each of the systems it would be useful to understand whether there are references to the data source and/or publications? If this isn’t available from the survey, then noting simply the responding institution or provider for each OOFS would be useful to provide a contact for further information. Please also clarify whether responses to the survey have been summarised/rephrased or provided as given (I presume the latter, but need to clarify).

Section 3.3.3: How did you differentiate between coastal vs regional domains?

Technical Corrections:

Line 40: OOFS acronym introduced without being defined.

Line 111: Suggest rephrasing “freshwater and salinity” to “volume fluxes and salinity” inputs?

Figure 2: Please clarify whether river networks shown come from GloFAS?

Hyperlinks: Throughout the text there appear to be hyperlinks to relevant data sources. However, these links don’t work. Please ensure they do in the revised version, or make sure to reference in an alternative format.

Acronyms: There are multiple within the survey responses. Please define where possible.