In the manuscript titled “SERGHEI v2.0: introducing a performance-portable, high-performance three-dimensional variably-saturated subsurface flow solver (SERGHEI-RE)”, the authors develop the Richards Equation-based variably-saturated subsurface flow module of SERGHEI. The characteristics of the framework are accuracy, robustness, scalability, and portability, which preserves the parallel performance and scalability across different HPC hardware. There are still certain changes and clarifications that the authors should address prior to publication. For these reasons, I believe that the manuscript can be accepted for publication by the GMD after minor revision. Below, I have some general comments for the authors.

General comments:

1. Line #48 – 49, it would be better provide further explanation on how parallel performance depends on HPC hardware. For example, are the differences in the parallel computing scripts caused by the different HPC compilers, scheduler, or are the differences due to the storage methods (e.g. HPSS, GPFS file system) used by the HPC? This would help readers quickly understand the practical problems that this study aims to solve. If only the compilation issues related to CPU parallelization and GPU parallelization are addressed (line #59-60), please appropriately discuss the limitations of this study.
2. Line #124-129, it would be necessary to provide specific examples of the use of PC and MP schemes in SERGHEI-RE. This would make it more intuitive and help better understand the advanced nature of this research plan.
3. Equation 8 could be illustrated with a diagram like Fig.2.
4. The comparison figures of PC and MP show that, except for the 4 days simulation in Fig. 4, they almost completely overlap. The introduction section regarding these two different types of introductions cannot fully explain the outcome. Therefore, it is best to provide further explanation.
5. Figure 11, almost all evaporation points are zero after 50 days, this seems to be caused by a model code error. If not, please explain briefly.

Specific comments:

1. Figure 1, in this diagram, what is the difference between the dashed lines, solid lines, and those without borders?
2. Line #100, what do α and represent?

The paper presents the development of a high-performance three-dimensional variably-saturated subsurface flow slover (SERGEI-RE). The contents is clear and shows good results. Likewise, the level of high performance computing is quite high.  One last comment might be even the highest level model, the reproducibility of the experimental results is not perfect. There could be some deficiencies in the experiment but also since the initial and boundary conditions always have uncertainty, you may need always kind of sensiticvity analysis or ensemble simulations. At any rate, I think the paper is acceptable for the publication.