Dear Editor,

I'm glad to have reviewed the manuscript. My opinion is that major revisions are necessary. Lack of references about important topics that authors discussed in the introduction is present. I have raised to the authors some conceptual questions, especially about the real goal of this study and the related methodology, which is still confused in the statement, from the abstract above all. Moreover, even if I appreciate the great efforts in the pretreatment and management of such amount of data with innovative methods, I think that at the local scale authors should accept the difficulty of the method in providing reliable information (and state it clearly in the text). Despite this, I believe that this work can be an excellent starting point for a computerized and indexed database of groundwater hydrographs on a global scale, useful for the first steps of groundwater resources management in coastal areas.

Dear Editor,

thank you for giving me the opportunity to review this article.

The study is quite well structured and the approach used modern and innovative although it requires further bibliographical references with respect to the topics involved. I believe major revisions are needed to emphasise the real purpose of this study and the limitations it has in dealing with a global-scale dataset. This approach is valid in attempting to categorise groundwater level patterns, but it cannot be a tool for coastal aquifer management planning at the local scale, where geological, hydrogeological, structural and resource exploitation characteristics as well as climatic conditions influence the hydrogeological behaviour of the aquifers. I believe that by revising the article in this sense, it can be a valid starting point for the categorisation of GWLs at a global scale.