Dear Referee (#1), 

Thank you very much for your comments and suggestions on the manuscript. We will respond to all the raised points and will revise accordingly in the final version of this paper. 

For the time being, concerning some of the points you raised, here is the information to facilitate the interactive discussions on this platform.

-    Your point (d) about the ECTS and how the academic recognition is done by the involved universities. 

Response: 

Typically the workload is equivalent to 3-5 ECTS. 3ECTS were granted for the first three editions in Belgium, and 5ECTS were granted for the 4th(at Bologna)and the 5th(at Bolzano)editions in Italy.  

Briefly, the academic recognition is realized in accordance with the education and other relevant regulations defined by the respective host university. 

-    Your point (e) about the teaching materials

Response: 

The teaching materials are prepared in advance and distributed to the participants during the event. 

-    Your point (f) about how other institutions/IAHR members can benefit from this activity

Response: 

Based on our recent experience, other institutions/IAHR members can benefit directly by, for instance: 

•     Sending their members for training. 

•     Participating by presenting state-of-the-art techniques (e.g. UBERTONE, ILA5150).

•    Proposing a request to organize a W.A.T.E.R. event.

-    Your point (g) about reasonable costs, and Figure 9. 

Response: 

We will re-make Figure 9. Regarding costs, the W.A.T.E.R. initiative aims to be financially neutral. It is typically a 5-day event, and the fees are used to cover the major expenses including the travel costs of invited lecturers, catering, facilities, assurance, etc. The registration fees of the first 2 editions included the accommodation costs for the participants. Due to increasing costs of accommodation and diverse preferences from the participants, it was decided to drop this option and to exclude the accommodation costs from the registration fees from the third edition onward. The registration fee from the last edition was 450eur. This fee is quite competitive compared to the fees defined by other training events nowadays, for instance, an example can be found from (https://www.vki.ac.be/index.php/events-ls/events/eventdetail/522/-/on-site-lecture-series-introduction-to-ground-testing-facilities).

On behalf of all co-authors. 

Thank you very much for your comments and suggestions on our manuscript (MS). We will take into account all the comments and revise accordingly in the final version of this paper. 

For now, we will clarify some of the points you raised.

• Your comment: Please provide links wherever websites are mentioned (e.g. lines 73 and 75).

Response:  The links to the websites will be added in the revised MS.

• Your comment:

Line 80: referring to acousting and imaging velocity measurements the authors state:  "This choice stems from the fact that these families of techniques are almost ubiquitous in many laboratories and field monitoring stations." I am not sure if the statement is valid for experimental facilities on pressurized flows, maybe the challenges of applying such techniques in pressurized closed conduits could be mentioned.

Response:

W.A.T.E.R. benefits from the expertise and setups of the organizing institutions. There is an emphasis on open surface flows that stems from this fact so far. Yet, we will include a remark on this observation and pressurized flows in the revised MS.

• Your comment:

Lines 85 to 97: acquisition frequency is mentioned for ADVP measurements but not for PIV, PTV or LDV, which is relevant and useful information. Would be nice if this could be included as well as accuracy thresholds.

Response:

Several measurement techniques were presented and hands-on training of each technique was provided at the W.A.T.E.R. Summer School. The measurement frequency was achieved at 100 Hz for ADVP, 50 Hz for PIV, 50 Hz for PTV, 130 Hz (short time series) and 350 Hz (long time series) for LDV. The detailed description will be added in the revised MS.

• Your comment:

Line 136: "from edition to edition..." Fig.8 does not provide the progress of participants' perception, trends could be depicted if possible.

Response:  We will re-make Figure 8 and include the trends in the revised MS.

• Your comment:

Conclusions: as the workshop is already in its 6th edition, some reflection could be done in terms of impact on the career development of former participants.

Response:

For the moment, though we do not have the structured and comprehensive data to respond to this pertinent suggestion, we do have ongoing collaborations with some former participants and we are aware that some have pursued research careers. Our intention is to prepare a survey and to gather feedback from the W.A.T.E.R. alumni after the completion of the 6^th edition. That will help us to assess the short and long term impact of W.A.T.E.R. on the career development of the W.A.T.E.R. alumni.

On behalf of all co-authors.