This manuscript investigates the realtionship between the inside average water depth (H) and outlet water depth (h) in an arbitrary catchment which is assumed to be a conceptual water tank. After evaluating the water storage ratio curve (H/h) sensitivity to the catchment area, the Manning’s coefficient, the slope gradient and the rainfall intensity, they propose the application of this variable within a simplified yet apparently quite effective rainfall-runoff model named distributed runoff model (DRM), and positively compare the results with an already validated diffusion wave (DW) approximation of the shallow water equations by numerical simulations for simulating ground surface runoff.

The paper has some useful elements, but in my opinion it cannot be published in its current format due to the following reasons:

• the abstract starts in medias res, without any introduction regarding the aim and the methodology of the work
• the discussion is basically absent, the authors just sum up the main results with no added comments
• results are presented in terms of comparison between DW and DRM for a real rainfall event, but no real runoff data (not even discharge) is used
• the overall writing needs some improvement (see the attached file)

This study establishes the existence of a nonlinear relationship between the average water depth within the watershed and the outlet water depth (i.e., water storage ratio), and investigates the factors influencing the fluctuations of this ratio. The authors also introduce the Distributed Runoff Model as a means to simplify the hydrodynamic model, with the goal of improving the effectiveness and efficiency of flood forecasting. While the idea presented is valuable and the findings are interesting, the quality of the paper requires improvement before publication.

1. Figure 4 and lines 158 to 170 discussed the effectiveness and efficiency of DRM, yet there is a lack of evidence demonstrating that DRM is computationally more efficient. Should this be addressed by comparing computational time, space requirements, or other relevant aspects?
2. Figure 7 indicates that the simulation results of DRM closely match those of DW. However, can we confidently draw this conclusion (that DRM reproduces the calculation results of the time-consuming hydrodynamic model well) based solely on one rainfall event at one location? Suggesting applying more rainfall events at different site and using metrics to evaluation the performance of DRM compared with DW.
3. Section 6 only included the results. Discussion could include the comparison between your results and previous studies.
4. The last paragraph of the Introduction Section lacks clarity in introducing/summarizing your study and needs to be revised.
5. Does this study assume that the interbasin groundwater flow is not considered as inputs to the watershed? Please clarify and provide a clear statement regarding this assumption in the Methods Section.
6. Minor revision: Lines 134 to 136 should be one sentence, not two.