Systematic Modeling and Policy Analysis on the Urban Water–Energy Nexus for Sustainable Resources Management
Round 1
Reviewer 1 Report
2. paragraph: please consider also the aspects of renewable energies; your view here is oriented on fossil energy sources
4. Results: spelling error international city
Figure 2:
Please indicate in the figures which is the energy used for water supply and which for water demand
Figure 3: Please indicate which graph is for energy production and which for energy demand
Author Response
Point 1: paragraph: please consider also the aspects of renewable energies; your view here is oriented on fossil energy sources
Response 1: The authors agree that reviewer’s statement is correct and appropriate. Due to the proportion of renewable energies (e.g., solar and wind power) accounts for less than 5% in total energy supply of Shenzhen city. Meanwhile, the amount of water consumed by renewable energies generation is much less than the water consumed by nuclear & thermal power generation. In this condition, the renewable energies are classified as other sources.
Point 2: Results: spelling error international city
Response 2: The authors agree that reviewer’s statement is correct and appropriate. The spelling error has been corrected in the revised manuscript.
Point 3: Figure 2:Please indicate in the figures which is the energy used for water supply and which for water demand. Figure 3: Please indicate which graph is for energy production and which for energy demand.
Response 3: In the revised manuscript, we have seperated the figures from Figure 3 to Figure 6.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The theme as described in the title and abstarct sounds interesting, but the manuscript is something else.
The subject is in some ways treated with superficiality, starting with formula 2 applied to something that is not known in geometry therms. To this end, the authors should revise the text and some small errors, such as ". m is the slope coefficient." with a full stop and not a comma.
The assumptions of the study are weak in my opinion.
Also, where is the novelty?
Author Response
The authors agree that reviewer’s statement is correct and appropriate. We have checked the whole text carefully and corrected some small errors. By the way, the novelty of this paper consist of two aspects. On the one hand, we provide an integrated nexus framework to assess the interdependence between water and energy from both supply and demand sides in urban scale. On the other hand, we further apply policy analysis to understand urban WE nexus systems by identifying stakeholders and their stakes.
Author Response File: Author Response.pdf
Reviewer 3 Report
Systematic modeling and policy analysis on the urban water-energy nexus in Shenzhen city, China by Y. Wang, C. Kou and X. Zhai
The work investigates the efficiency of different scenario for filling the gap between supply and demand with regard to water and energy. The topic is potentially interesting, nevertheless I got lost along the paper. I think that in this work some steps are missing concerning methodological aspects and the methodological rigor is missing (not shown). Some examples in the following:
I think that the balance between supply and demand is done considering a year, nevertheless this is not clearly stated. For instance, in figure 1 there is a link between rate and amount that is not explained.
At section 3.1.2. is stated that “the water for energy equals the energy for water”: it is not clear the comparison between water (m3) and energy (joule).
Section 3.1.3 what is a “GDP”?
Section 3.2 what do you mean by “transformation between water and energy”? what do you mean by “at different stages”? may be “for different years”
Section 3.2 I don’t know what is reservoir water and extracting reservoir water.
Eq.(1) doesn’t include energy used for pumping at higher levels, but just that use for head loss: why?
The weight of water is a force (newton) and gravity acceleration is m/s2…, these errors are major.
In eq. 2 Q is a discharge not a velocity, this error is major. Do you have canals or pipes for bringing water to Shenzhen? Usually water supply systems are built with pipes and pressured flow not free surface flow.
Based on the above mentioned errors, results are questionable.
In the Policy scenario design it is not clear what happens to the not listed variables. For instance, in Scenario 1 the rate of both diversion WS and import ES increased by 50%: 50% every year? What does it happen to ED and WD in scenario 1?
In the Policy simulation section, results are not adequately presented. I don’t understand the reason by the which some data in 2020 are below zero. It is not explained the meaning of the zero value in figures 5 and 6. Figure captions should be accurate.
It is written “for the energy scenario, S1 and S2 has almost the identical policy effects and either of them cannot satisfy the growing energy demand.” In which figure can I see this result?
In figure 6 right, why do I see increasing energy demand curve for scenarios D1 and D2 in which some reduction for both WD and ED is considered?
It is written “when we combine above four scenarios(D5), it merely exerts positive effect in short period and cannot control the resource gap eventually”: how do you support this statement?
Author Response
Point 1: I think that the balance between supply and demand is done considering a year, nevertheless this is not clearly stated. For instance, in figure 1 there is a link between rate and amount that is not explained.
Response 1: The authors agree that reviewer’s statement is correct and appropriate. The supply and demand of water & energy must be balanced for a specific year. But as the demand increase due to the expansion of pupulation and urbanization, the gap between supply and demand is expect to expanded. In this condition, the city will become rely more on the resource outside boundary. For example, the energy introduced from outside city has accounted for 20% of total energy supply. As for figure 1, the relations between rate and amount are calculated by correlation coefficient based on the historical data.
Point 2: At section 3.1.2. is stated that “the water for energy equals the energy for water”: it is not clear the comparison between water (m3) and energy (joule).
Response 2: We gave a new statement in the revised manuscript that the amount of water for energy equals to the energy-related water consumption in most cases.
Point 3: Section 3.1.3 what is a “GDP”?
Response 3: GDP is an abbreviation for Gross Domestic Product.
Point 4: Section 3.2 what do you mean by “transformation between water and energy”? what do you mean by “at different stages”? may be “for different years”
Response 4: Section 3.2 mianly discussed the the transformations (interdependence) between water and energy at different stages. For example, water extraction, convey, recycling and treatment need energy, energy production need water as well. So there is a transformation coefficient between water and energy.
Point 5: Section 3.2 I don’t know what is reservoir water and extracting reservoir water.
Response 5: the amount of energy consumed by extracting reservoir water refers to the amount of energy used to extract water from reservoirs
Point 6: Eq.(1) doesn’t include energy used for pumping at higher levels, but just that use for head loss: why? The weight of water is a force (newton) and gravity acceleration is m/s2…, these errors are major.
Response 6: We have checked the whole equations carefully and corrected some errors. In Eq.(1), g is the gravitational acceleration (gravity), hf is the lifting height (m).
Point 7: In eq. 2 Q is a discharge not a velocity, this error is major. Do you have canals or pipes for bringing water to Shenzhen? Usually water supply systems are built with pipes and pressured flow not free surface flow.
Response 7: The author agrees with the reviewer. In Eq.(2), Q is the amount of water transportation (m3/s). This equation refers to the dissertation of The Nexus of Water Resource and Electricity Production in China.
Point 8: In the Policy scenario design it is not clear what happens to the not listed variables. For instance, in Scenario 1 the rate of both diversion WS and import ES increased by 50%: 50% every year? What does it happen to ED and WD in scenario 1?
Response 8: In Scenario 1, we just consider the import expansion policy, with the rate of diversion WS and import ES increased by 50% simultaneously. ED and WD in Scenario 1 will changes according to the historical trends, with no additional policy assumptions.
Point 9: In the Policy simulation section, results are not adequately presented. I don’t understand the reason by the which some data in 2020 are below zero. It is not explained the meaning of the zero value in figures 5 and 6. Figure captions should be accurate.
Response 9: Due to the Y-axis refers to the resources gap, the data that below zero means resources supply higher than demand.
Point 10: It is written “for the energy scenario, S1 and S2 has almost the identical policy effects and either of them cannot satisfy the growing energy demand.” In which figure can I see this result?
Response 10: We can see this result for Figure 5. (b) Scenarios simulation in energy supply side from 2020 to 2035.
Point 11: In figure 6 right, why do I see increasing energy demand curve for scenarios D1 and D2 in which some reduction for both WD and ED is considered?
Response 11: It might be the reduction rates for residential & agricultural WD and ED are not enough or the faster demand from industrial & other sectors.
Point 12: It is written “when we combine above four scenarios(D5), it merely exerts positive effect in short period and cannot control the resource gap eventually”: how do you support this statement?
Response 12: We can get support information in Figure 6,with both two prediction lines of D5 are over zero value until 2035, which means the resource demand exceeds supply.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I have read the authors' comment but I remain convinced of my doubts. I do not see any "real" aspect of novelty and the succinct answer of the authors does not make me change my mind.
Author Response
Point 1: I have read the authors' comment but I remain convinced of my doubts. I do not see any "real" aspect of novelty and the succinct answer of the authors does not make me change my mind.
Response 1: The authors have made great efforts to revise the manuscript, especially for the part of 3.2. In this revised version, we adopt a new approach to quantify the transformations between water and energy in different conditions. We collected new statistical data released by municipal government of Shenzhen, as well as obtained some transformation coefficient from relevant literature. In this way, the results of this study will be more convince.
Reviewer 3 Report
I have read the revised version of the manuscript and the answers to my questions. In my opinion the paper cannot be published in the present form.
For for future revisions it would be useful to have both the text with the visible revisions and the text with the changes accepted. Furthermore, it would be better to add the line number for easier references to the text.
In eq. 1 , m is not the weight but the mass (the product mg is the weight).
If you say that hf is the lifting height, then hf cannot be the head loss of eq. 2. I think that hf in eq. 1 is the sum of the geodetic term and the head loss. Is it correct?
About eq. 2, the Authors have not answered to my question: for water transportation, do you have a free surface flow or pipelines?
A brief technical description of the water supply system is useful. What is the elevation of the reservoirs? Do you need pumping systems or do you have mainly gravity systems?
After eq. 2: Q is a discharge, not the amount of water. The amount of water is for a volume and not for a discharge.
Dealing with m: the Authors should use a different symbol because you used m in eq. 1 and it has a different meaning. In eq. 2 m is the slope. What is the slope of? Is the slope of the banks of the canals?
Why in the manuscript are not present the numerical values for hf and L?
In eq. (4), I don’t think that L is a percentage, it has to range between 0 and 1, not from 0 to 100. Again L in eq. (4) is not L of eq.(2). It is not good to assign two meanings to the same letter
The responses given to some of my answers of precedent review should be inserted in the text. I mean, specially, as it concerns points: 8, 9, 11 of my precedent review.
Author Response
Response: We are very grateful to your comments for the manuscript. According with your advice, we amended the relevant part of 3.2. The transformation of the WE nexus in Shenzhen city in new manuscript. Especially for the issue of eq. 1 to eq. 4, we adopt a new approach to quantify the transformations between water and energy in different stages. We collected new statistical data released by municipal government of Shenzhen, as well as obtained some transformation coefficient from relevant literature. In this way, the results of this study will be more convince. The details can be founded in line 4-15 of first paragraph and line 5-8 of second paragraph of part 3.2.1.
Besides, for Point 8: In the Policy scenario design it is not clear what happens to the not listed variables. We added the explanation of while other variables remain the same in line 6 of first paragraph of part 4.3.
For Point 9: In the Policy simulation section, results are not adequately presented. We added the explanation to the title of Figure 5 and Figure 6 that If the value is greater than zero, it means the resources supply lower than demand. Otherwise, the resources supply higher than demand.
For Point 11: In figure 6 right, why do I see increasing energy demand curve for scenarios D1 and D2 in which some reduction for both WD and ED is considered?
We added the explanation of It means the reduction rates for residential & agricultural WD and ED are not enough or the demand from industrial & other sectors sustain the faster growth rates in line 7-9 of second paragraph of part 4.4.
Round 3
Reviewer 2 Report
Despite my misgivings, I see that the authors have done a thorough work in revising the manuscript. In my opinion, the paper can be accepted in its current form.
Reviewer 3 Report
In the last revision the manuscript has improved as I expected.
