General comments: Well-developed and written. Clear. Important foundational work, regardless of performance. Novel use of Delft-FEWS, HOOPLA and HEC-RAS.

Specific comments: No specific concerns.

Technical corrects:

line 385: extra space before a period ending the sentence.

line 515: should 2023 be 2022? Line 517 references 100 days, which does not add up with 2023.

line 630: replace 'till date' with 'to date'

line 633: should 'stale' be 'stable'?

Major comments:

I have several concerns about your model evaluation. In your forecasts for the evaluation, the measurement is always available on day 1. Why did you choose to do so? What is the difference if you start the forecast earlier (so that the measurement is available on day 2, 3, …)? Does this help to evaluate the model forecast for different days? Could you perform this analysis?

Unfortunately, the discussion of your work is very limited. What are the implications and limitations of your work? How is your model performing better than models not accounting for ice conditions? Could you discuss the uncertainty in your data and model estimates as well as your system evaluation? How do you estimate the uncertainty of your corrected observed discharge data (corrected with the backwater coefficient)? How does your study compare to others, what are differences and similarities?

You discussed one event in detail, including three figures, and provided both the results of the hydrological and hydraulic modelling. Why have you chosen this period? Is it representative of frequently occurring conditions?

Minor comments:

How can the presented methodology be transferred to another study site? Which conditions and data are required? What may cause problems?

This study strongly relies on Montero et al., 2023. Please clarify the difference between your study and the previous one as well as your advances compared to that study.

L21: system or systems?

L29: Is the hydrological module better including the ice component than without it?

L36: introduce

L50-58: How are measurements of under-ice discharge made in other countries across the world?

L61: What is the HBV model? Can you describe it quickly?

L83: Please provide a reference for HEC-RAS.

Table 1: Please provide a reference for your data.

Figure 1: Please clarify your figure (increase font size, no upside down labels, make clear that the Lower Chaudière is not included into the analysis, use different shapes and easily visible colors for the different measurement stations). You may consider labelling the subcatchments right next to them for simplified identification. Please add also a clearer map of the location of the study area in North America, including readable city names.

L155: The correct name is Environment and Climate Change Canada.

L156: Please provide the reference of these data sets, not of the secondary literature.

L157: Please provide the reference.

L170-186: Please clarify this paragraph, the determination of the backwater factor is not clearly described and easily understandable but has a major impact on the corrected data. How do you make sure that the applied correction is correct and representative of the in-situ conditions?

Figure 2: Please increase the font size of the axis labels and label the subplots as a) and b) instead of using figure titles.

L194-202: Please provide references.

L206-215: Please provide references for the used softwares and models. What is precisely the novel contribution of your study in this methodology and which part of this approach has been used in former studies?

L218: Are only the resulting precipitation values used or also other data?

Figure 3: Is REPS0 the unperturbed control member? Why is it framed? Please write the numbers of the control members elsewhere in each subfigure instead of within the catchment. The color scheme of the legend seems to be different to the one used in the figures.

L240-242: Please clarify. Are all data (open water and ice) used at a 3h resolution for the modelling? If yes, how have you increase the resolution during ice conditions, where only daily data is available?

Figure 4: Please increase the font size of the axis labels and label the subplots as a) and b) instead of using figure titles. The data are hardly visible, so that the measurements and the model are hardly distinguishable. This hinders the evaluation of the model’s performance. Please improve the readability of the results.

Figure 5: Please increase the font size of the axis labels.

L262-265: What do you think is the reason for the lower KGEm in the validation case in the Upper Chaudière?

L267-270: Please explain why you are using the unsteady model.

L483-484: To which water stage does this elevation correspond? How many days per year or measurements are not possible at this site? What is its influence? Can measurements be performed in winter during the ice conditions?

L494: How are the RMSE and Pbias calculated for the average ensemble values for each event? Are they calculated for every ensemble and then averaged to obtain the results in Figure 13?

L500, 508: Please reorder figures or their reference, here Figs. 11 and 12 are referenced before Fig. 10.

L502-504: How was the discharge measured? How is the averaged discharge for the entire day determined?

L524: You mentioned that ice thickness and the under ice roughness are important. Have you performed any measurements of the under ice roughness? If no measurements are available, how is this value chosen in the model?

L504: How was the ice thickness measured? At one cross-section only or several ones?

Figure 10: Please label the subfigures with according the journal guidelines, instead of using figure titles. Please provide the reference for the used data.

Figure 11: Please clarify this figure. Especially in the right part (after Feb 25^th), the different lines and percentiles are difficult to distinguish, you may want to use different line styles and filling styles.

L531-545: Please consider splitting this paragraph. What is the uncertainty in the corrected observed data?

Figure 12: Please also rework this figure.

Figure 13: Please use different colors in the top and bottom plots to represent different locations. What represents the grey shaded areas precisely? Is this performance evaluation for this specific February 2022 event only or averaged values for all events? Please clarify.

L654-655: Are those your future steps or do you generally recommend this to others?