The manuscript by Tiwari et al. presents the use of a novel metric, SPAEF, for estimating the spatial variability of hydrological variables during hydrological model calibration. Various calibration strategies, including stepwise calibration and traditional global optimization methods, were employed. To enhance clarity and conciseness, the abstract and introduction should be streamlined to ensure that readers can easily grasp the take-home messages from the study. Some introductory content may be relocated to other sections. Furthermore, it is essential to clearly and succinctly illustrate the novelty of this study.

Lines 3-6: These two sentences appear somewhat unrelated to the main focus of this study. Consider removing them from the abstract.

Line 8: What is SNODAS? It might not be well known (which may not be true). Please provide a complete description of this acronym.

Lines 9-11: This information may not constitute the primary takeaway from the paper and may not be necessary.

Line 21: Consider adding a sentence at the end of the abstract to explicitly emphasize the novelty of this study.

Line 35: Consider specifying "during the snow-melt season."

Line 52: Please provide specific details regarding the fine resolution.

Lines 54-58: Consider relocating these sentences to the discussion or conclusion section to avoid confusion among readers regarding the use of TSMM SWE.

Line 94: Consider using "variable" instead of "parameter" to clearly distinguish between model parameters and hydrological variables.

Lines 115-141: This paragraph could be relocated to the methodology section. Additionally, in the description of the optimization algorithms, please clarify the number of repeated experiments conducted to obtain parameter values.

Line 115: The final paragraph of the introduction should emphasize the novelty of this study, potentially by comparing it to current methodologies or existing approaches for optimizing model parameters.

Line 164: Add "the variation of" before SWE for clarity.

Line 169: Please clarify the time step of the model employed in this study.

Line 177: Please explain the selection of the Thiessen polygon method. Does the elevation change the precipitation (lapse rate)?

Line 205: Specify the nature of the data used for March. Is it the mean value of March or daily values?

Line 223: As mentioned earlier, please specify the time step of the streamflow data.

Line 226: The sentence regarding NSE and similar sentences describing RMSE, KGE, etc., may not be necessary. These details are more suitable for a project report than a science paper.

Lines 266-269: Further elaborate on the rationale for selecting March for SPAEF analysis to avoid appearing arbitrary. Consider testing SWE throughout the year or in other months using a similar approach for model calibration and provide this analysis in the Supplementary material.

Line 275: Consider placing the KGE metric for model validation in a separate section, distinct from the objective functions used for optimization.

Lines 457-459: The support for this result appears insufficient. Please provide additional information or clarification.

Line 530: When drawing the conclusion, be specific and careful about specifying the type of hydrological model and the situations in which this conclusion holds true.

Figures: The figure axes and the labels should be more obvious. Currently, they are too small.

Overall, I think the paper exhibits novelty, especially in introducing a new objective function for SWE in model parameter calibration. However, the writing style of the scientific paper can be further improved. I would recommend accepting this paper after moderate revisions.