Optimal Near Real-Time Control of Water Distribution System Operations
Round 1
Reviewer 1 Report
This is an interesting advancement of a popular and important topic. I have some comments for the authors to consider before I can recommend acceptance.
The results are for a specific system and do not represent general findings. The authors should avoid conclusions like “The results revealed that real-time control schemes reduce the operational costs of WDS by up to 17.8%” (as in the Abstract, and again in the Conclusions) that imply general findings for all WDS instead of a specific demonstration on one model. The authors must separate specific and general findings.
Similarly, the authors should be careful not to misrepresent a hydraulic model as a real system case study. It is a computational experiment, not a real field test. But obviously it can still provide useful information to learn from.
Rossman (1994) is for an earlier version of EPANET. Its references should be replaced with Rossman (2000) for the 2.0 version of EPANET the authors are using.
Throughout, the authors should clarify “demand” as “water demand” or “energy demand,” as it could mean both.
Integrated water and energy demand forecasting, which the authors are approaching, is highlighted as a priority research area in “Making waves: Research to support water and wastewater utilities in the transition to a clean-energy future,” https://doi.org/10.1016/j.watres.2023.119739.
I see the value of the approach, but I question how it can scale up. The authors have demonstrated optimizing a simple system with one source, two pumps, and two tanks. Optimization is almost trivial for such systems, but real and more complex ones may have dozens or hundreds of such facilities and can really benefit from optimization heuristics. Given the computational effort mentioned, are 15-minute steps really the best general approach, or is that again a system-specific finding? How sensitive are the results to other, more extreme demand patterns that exist in large systems? What about unexpected events like fire flow or the uncertainties about valve settings and flow directions in large networks? The authors must better address these and other issues of scale before acceptance (or at least acknowledge the limitations of their small system study), as they are key to real applications. There is just one sentence on the matter (lines 468–469) and it deserves much more.
Despite much research, real-time control seems to have limited uptake among water systems (https://blog.virtuosity.com/hydraulics-hydrology/is-real-time-control-real). This may be a point worth discussing, as I think the authors’ method has some merit for overcoming some of the challenges.
All units need to be SI instead of USCS.
Operational cost is not strictly energy cost. I get the point, but please word it more carefully.
The exclusion of realistic TOU energy prices and demand charges (mentioned in lines 481–483) is serious. The authors should discuss earlier in the paper why a flat rate was used what effects this can have on the results. Again, this reaffirms my point about the results being case-specific rather than general: the energy savings may be very different when demand charges or other dynamic prices are involved.
Author Response
"Please see the attachment."
Author Response File: 
Author Response.docx
Reviewer 2 Report
In the Introduction part, I suggest discussing the novelty of the analysis and the gap in the knowledge to be addressed by this paper.
It is not specified for which area the method is developed?
The methodology and database part needs to be reworked and explained as it has some gaps.
I recommend a reorganization of the article for easier reading and in journal temeplate.
I recommend a revision of the bibliography, the paper is based on only 24 papers.
I suggest more attention to the way the article is written and to the citations
The same work is cited too many times.
Author Response
"Please see the attachment."
Author Response File: Author Response.docx
Reviewer 3 Report
Hi,
Here are my editorial suggestions:
Line 288:
Table 1. It is noteworthy that the baseline scheme, which is based on pre-determined........
Line 290:
boundaries (as can be seen in Table 1); similarly Similarly, the real-time control......
Author Response
"Please see the attachment."
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have satisfactorily addressed my comments. I recommend the article for acceptance.
Reviewer 2 Report
I agree with the changes made
