Dear Andreas and co-authors,

Thank you for resubmitting your manuscript to GMD. Although one of the original reviewers had requested to see the manuscript corrections for re-review, I was unable to contact him, and I have therefore evaluated your manuscript myself.

Thank you for your attention to the corrections suggested by the reviewers. I appreciate the effort you put in particularly to updating your literature review described in Table 3. However, before accepting the manuscript, I must ask you to make some additional revisions, as described below, in response to particular reviewer comments that I feel were not sufficiently addressed.

Reviewer 2 requests an explanation of the main features of a karst system, to provide a better context for the model equations:

"Referee #2 The reader is rather rushed into the main part of the paper, and detailed comments are provided below on the introduction. However, it is strongly suggested that to provide a proper context for the equations in Section 2.1 then a basic explanation of the main features of a karst system is provided."

No such explanation was added, and the changes to Section 2 largely consist of moving a section of text from Section 2.1, which is insufficient to address this major reviewer comment. Please add a suitable description of the system such that the reader understands the choice of model formulation.

Reviewer 1 also comments on the same section:

"Referee #1 Section 2.1 is a brief summary of equations previously published by the Author and appears to be shown here for the purpose of explaining the four parameters. This could be stated more clearly because it’s not totally clear whether these are new equations or not. Also, the reader would need to read the previous papers to fully understand their meaning. One reason for the confusion is that this is described as being a new version (VarKarst-R), but the equations have not changed (unless I missed something). Therefore, please explain what was modified in the new version."

This comment has not yet been sufficiently addressed. If I am correct in guessing that the model equations (1-9) are copied from a previous paper, please state that explicitly at the top of the section and provide the reference. The referee comment that it is not possible to fully understand their meaning from the current paper has also not been addressed. I found it very difficult to understand the description of these equations, for example in Equation 2, it is unclear whether these three equations are assumptions, definitions or derivations, or how they follow from each other. It is unclear why an integral rather than a sum is taken over a discrete number of model compartments. It is unclear what 'left' and 'right' refer to (line 130), and what is the link with Figure 1.

In summary, I request you to fully consider the review comments and these additional comments, and undertake a more complete review of Sections 2 and 2.1.

Kind regards,
Hilary McMillan

Thanks for doing these corrections; I'm happy to accept the paper now for GMD.