Optimization of Pressure Management in Water Distribution Systems Based on Pressure-Reducing Valve Control: Evaluation and Case Study

Round 1

Reviewer 1 Report

the topic although remaining very attractive through the years has not been treated properly

The approach seems quite hasty. The literature review is too weak. Extensive editing is absolutely necessary

The abstract is quite bad. And just imagine that the abstract is the frontline of a paper determining many times its fate as many readers decide to read a paper base don how attractive its abstract is. This one is a disaster.

The literature review is far too weak. References of highly-distinguised scholars (e.g. Giugni, Franchini, Giustolisi, Savic, Kapelan, Kanakoudis etc.) are misiisng.

Comments for author File: Comments.pdf

Author Response

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Reviewer 2 Report

1. Existing abstracts fail to attract readers. The innovativeness and relevant research results of this study cannot be made available to readers.

2, The literature quoted in the introduction is too old. I can't get the necessity and innovation of this research from the introduction.

3. Not enough discussion. The discussion should be based on the mechanism of the research results, not a simple description of the results.

4. The conclusion should be further sublimated to get deeper content on the basis of highly summarizing the research results.

5. The references are few and old, and the existing literatures are insufficient to support the research content and innovation of this paper.

Author Response

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Reviewer 3 Report

Brief summary

This paper is interesting for those interested in water distribution network management.

It presents a methodology to assess the results from pressure management projects, using different Pressure Reduction Valve controls. The assessment is based on five indicators: daily flow, daily leakage, unevenness of pressure, median daily pressure at nodes, and water age.

The paper follows a traditional structure, and it has a good set of references, but the journal names are missing.

However, the writing is not perfect, and some sentences are difficult to understand their meaning. The methodology should be better explained, as well as the examples presented.

Although I think this can be an interesting paper, in my opinion authors should be encouraged to rewrite the paper, taking into consideration the comments, perhaps with the help of a native English speaker, and resubmit it.

Specific comments

Authors should avoid using “we” (Line 99) and “our” (Line 101).

Some technical words don’t seem to be the most common, like:

- “pipe updates” (Line 54) and “pipeline updates” (Line 68) (perhaps “pipe replacement”);

- “fixed post-valve pressure regulation” (perhaps “fixed outlet PRV”);

- “time-based regulation” (perhaps “time-modulated PRV”);

- “flow-based regulation” (perhaps “flow-modulated PRV”);

- “pressure regulation based on the most unfavorable pressure point” (perhaps “pressure-modulated PRV”).

Lines 50-51: What is the idea of the sentence “The measures focusing on minimizing the level of economic physical loss”?

Line 53: The reference “mentioned in the figure” refers to which figure?

Section “2.1. Construction of WDS model”: The networks should be better characterized (number of pipes, extension, diameters, number of nodes, demand, elevations, averaged daily demand, average daily losses, peak flow, …). For example, readers don’t know which are the pressures or the water losses levels in these networks. So, when looking at the results from pressure management it is difficult to understand if they are good or not.

Lines 127-128: From the sentence “The relationship between pressure and nodal water demand was described using a segmentation function in an equation [25].” the reader can conclude that authors were using the “Wagner, U. Shamir, D.H. Marks, Water distribution reliability - Simulation methods, J. Water Resources Planning and Management, 114(1988), 276-294.” model for the pressure-demand relationship. But nothing is mentioned about the pressure-leakage relationship.

Line 221: shouldn’t “qj” be expressed in m3 instead of m3/h, like “Qday” and “Qday-leak”?

Lines 245-247: The way it is presented, it seems that each of references 26, 27, 28 and 29 refer to each of the different pressure control systems. But I don’t think it is the case.

Line 284: “Hmin: Minimum service head at the most unfavorable point (10 m)”. Is it really “Head” or is “Pressure”? Is it always “10m” or it depends on the network?

Figure 5: There is a horizontal line from “t=t+1” to the right. Shouldn’t it start at “t<24?”?

Line 314: “Hmin: Minimum service pressure (m)”. Is this the same as in Line 284?

Figure 7: The flows from the ZJ urban pipe network are so small? The peak flow is less than 2 m3/h. The reader should know the original network conditions (pressure and flow before the introduction of PRVs).

Table 3: Perhaps it would be better to keep “a, b, c, d and f” like in Figure 7. The reader doesn’t have enough data to assess if the numbers from this table are correct or if they represent a great evolution regarding the original network working conditions.

Lines 347-349: “The flow performance according to the flow-based regulation was close to the average of time controls of the 2 and 3 segments, but its performance in terms of Pequ, which was close to the 4 segments time control, was superior.” I don’t see such a significant difference to deserve these conclusions.

Figure 8: The flows from the KL urban pipe network are so small? The peak flow is less than 1 m3/h. The reader should know the original network conditions (pressure and flow before the introduction of PRVs). If the pressure is below 20m why does the vertical axis scale is up to 40m? If the flow is below 1 m3/h why does the vertical axis scale is up to 2 m3/h?

Table 4: Perhaps it would be better to keep “a, b, c, d and f” like in Figure 7. The reader doesn’t have enough data to assess if the numbers from this table are correct or if they represent a great evolution regarding the original network working conditions.

Lines 377-378: “At the same time, this method had no discernible advantage over fixed post-valve pressure control;” I just don’t see how this can be possible. I would say that time-based pressure control should be, at least, as good as the fixed-pressure control.

Lines 399-400: “It should be noted that excessive water age is often caused by the unreasonable network topology.” Is it really “topology” or should it be “design” (overdesigned networks lead to high water age values).

Lines 436-437: “Thus, the ultimate decision was to regulate the system by fixing the inlet pressure value at 0.315 MPa.” If during the period of 14:00-18:00 the network needs 0.33MPa to meet the water demand, how is it possible that for the period of 18:00-24:00 (peak water usage period) only 0.315 MPa is enough?

Line 443: There is a reference to an “exponential leakage model” but nothing is specified about it (equation, coefficients, …).

Line 444: If “the total leakage volume of the pipeline network within a 30-day period was determined to be 851.21m3”, it means that this network almost doesn’t have water losses (about 1.2 m3/h). Is it so? If it this is correct, what is the goal of implementing pressure management in a network with such conditions?

Lines 481-483: “It may require the deployment of a municipal power supply to maintain the long-term operation of the pressure reducing station. This is also the reason why this method cannot be applied to Case's Networks.” I remind that pressure-based control was used in the period between 5 and 14h.

Author Response

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Reviewer 4 Report

- Research gap is vague, it has to be precise. "However, the majority of the studies focused on the isolated working of the instruments, and there are very limited studies involving" It is important to provided the existing studies to be able to ensure the proposed system is innovative.

- Figure 2 is mentioned twice. 

- justification in the discussion has not been considered. 

- Conclusion needs to be detailed with the enhancement percentages between the different techniques. 

Author Response

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Round 2

Reviewer 1 Report

the revised version of the paper is better compared to the original one

several comments can be found in the annotated manuscript attched

The most important one is that results and conclusions should be discussed more explaining the deeper causes and not just present them as findings. Critisize them. 

Suggested studies are just indicative.

Comments for author File: Comments.pdf

Author Response

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Reviewer 2 Report

Based on the author's modification of the reviewer's opinion, I think it is not fully improved and cannot meet the publication requirements of "Sustainability" in terms of the existing level of the manuscript.

Author Response

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Reviewer 3 Report

Brief summary

Authors took into consideration the reviewer comments, but there are still some issues that should be analysed.

Although I think this new version of the paper is a good improvement, in my opinion authors should be encouraged to rewrite the paper, taking into consideration the comments presented below, and resubmit it.

Specific comments

Authors should avoid using “we” (Line 455) and “our” (Lines 25, 454).

Lines 50-51: The sentence “The measures focusing on minimizing the economic level of leakage” seems completely lost in this paragraph.

Lines 78-81: The sentence “There are four recognized control methods for PRVs based at the critical point and they are in two groups[25], hydraulically-operated (namely Fixed Outle (FO) PM and Critical Node Modulated (CNM)PM) and electronically operated (Time Modulated (TM) PM and Flow Modulated (FM) PM)[17, 26-29].” is not correct. In fact, there are for different controls to implement pressure management, depending on the way the outlet pressure is adjusted:

-          - Fixed

-          - Time modulated

-          - Flow modulated

-          Pressure modulated

And this has nothing to do with being hydraulically or electronically operated (usually, the one that is completely hydraulically operated is the Fixed Outlet pressure, and the others always make use of some kind of electronic device to control the outlet pressure).

If authors change the pressure control names, they need to be corrected along the text.

Line 101: Suggest changing “sThe” to “The”.

Lines 356-357: It seems that something is missing in this sentence.

Figure 7: The flows from the ZJ urban pipe network are so small? The peak flow is less than 2 m3/h. This is not in accordance with the values presented in lines 142-144. The flow unit in these graphs is really m3/h?

Table 4: In line “a” (FOPM) the Qday (m3) value is higher than the one before pressure management and the Qday-leak (m3) value is equal to the one before pressure management. Is this correct? It would be interesting to know the Pmid value before pressure management. Suggest introducing a new line, before “a”, with the values before pressure management.

Lines 347-349: “The flow performance according to the FMPM was close to the average of time controls of the 2 and 3 segments, but its performance in terms of Pequ, which was close to the 4 segments time control, was superior.” What the numbers show is that Qday-leak for FMPM (16,596m3) is lower than those from 2TSC (19,116m3) and 3TSC (17,172m3), so, its performance regarding water loss reduction is superior.

Line 382: Two times “Table 5”.

Figure 8: The flows from the KL urban pipe network are so small? The peak flow is less than 1 m3/h. This is not in accordance with the values presented in lines 145-147. The flow unit in these graphs is really m3/h?

Table 5: The Qday-leak values reduced a lot from the one before pressure management. It would be interesting to know the Pmid value before pressure management. Suggest introducing a new line, before “a”, with the values before pressure management.

Lines 474-475: If “the total leakage volume of the pipeline network within a 30-day period was determined to be 851.21m3”, it means that this network almost doesn’t have water losses (about 1.2 m3/h). This is not in accordance with previous results presented in the paper.

Author Response

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Reviewer 4 Report

This sentence is a bit vague and needs to be more precise "There is little information on which control method is more effective for the network, how to evaluate its application and the basis for objective conclusions."

Also, I suggest that authors add an enhancement percentage in the conclusion as mentioned in the previous reviewing round. 

No further comments on my side

Author Response

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Round 3

Reviewer 1 Report

the paper still needs more work

see annotated manuscript attached

Comments for author File: Comments.pdf

Author Response

We have responded to each of your suggestions in the PDF（Please see the attachment. For specific modifications, please refer to the newly submitted draft.

Author Response File: Author Response.pdf

Reviewer 2 Report

结论太长，文献太陈旧。这是我给作者的最后机会。

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