The manuscript titled “Reinforce Lake Water Balance Component Estimations by Integrating Water Isotope Compositions with a Hydrological Model” has been thoroughly reviewed. It presents an interesting study with valuable practical applications. However, the reviewer has noted the following concerns for the authors' and editor's consideration:

1. In the abstract (lines 13-14), the authors suggest their approach as an alternative method for capturing the dynamic behaviour of the hydrological groundwater/surface water system, yet the study is based on only one year of sampling. Can this work truly represent the hydrological dynamics of the lake system? Additional clarification or rephrasing may be needed.

2. The authors state that an isotope mass-balance model was used to quantify the evapotranspiration rate by accounting for groundwater inflow to offset evaporation losses, in the context of the lake's water balance. However, how is open water evaporation handled? Does the evapotranspiration calculated in this study include ET from groundwater? Further clarification on this point would be beneficial.

3. The authors mention a hydraulic connection between the lake and groundwater system. Additional details on the assumptions made would be valuable. For instance, is there any seepage from the lakebed to the groundwater?

4. The authors used the HydroGeoSphere (HGS) modeling code (Aquanty Inc., 2023) to simulate hydrological processes in the study area. Could the authors clarify why the HGS model was selected over other 3D models, such as MODFLOW, and discuss any comparative advantages?

5. It would be helpful to provide more information about the HGS model setup, including the number of aquifer layers, initial boundary conditions, and model parameters used in this study.

General comment: The manuscript is engaging, though minor grammatical and punctuation errors are present. Addressing these would improve clarity and readability.