Review Reports - A Dynamic Calculation Method for Water Supply Benefits of Water Diversion Projects Incorporating Ecological Benefits

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article lacks innovation and its core contributions need to be redefined and refined.
The author claims to have established a dynamic water supply benefit evaluation system that takes ecological benefits into account. However, from a methodological perspective, there is already a considerable research foundation for emergy analysis, water resource value calculation, ecosystem service value accounting, and water supply benefit calculation. The truly novel aspect of this article is mainly the separate inclusion of ecological water supply in the water supply benefits of water diversion projects and the use of a fixed growth coefficient to predict the benefits during the service period. This innovation is relatively limited.
It is suggested that the author provide clearer answers to three questions in the introduction: First, what exactly is lacking in the existing research; second, what new elements does this article add compared to the existing emergy analysis studies; third, whether the method proposed in this article is transferable or only applicable to the Henan section of the South-to-North Water Diversion Project. The current research objective is merely summarized as establishing a model and proposing a dynamic quantification method, which is still rather broad in expression.
2. The "dynamic calculation method" lacks scientific rigor, and the linear extrapolation with fixed coefficients is overly simplistic.
The so-called dynamic prediction in this article mainly relies on the fixed growth coefficient method, that is, using the trend of water resource value changes in 2010 and 2021 to extrapolate to 2070. This approach is very rough because the value of water resources in the next 50 years will be affected by multiple factors such as industrial structure, population changes, water use efficiency, ecological policies, water price systems, climate change, and regional development speeds. The author himself also admits in the discussion that the fixed growth coefficient is essentially only a long-term trend extrapolation based on time as a single variable, and has insufficient adaptability to an uncertain environment.
It is suggested that the author at least add scenario analysis, such as low growth, medium growth, and high growth scenarios; or incorporate sensitivity analysis to illustrate how the total benefit results change when the fixed growth coefficient varies by ±10% and ±20%. Otherwise, the title "dynamic calculation method" and the abstract description seem overly strong.
3. The data in the case area is not representative enough, and the data of Shangqiu City cannot simply represent all the water-receiving areas.
In the case, the water supply range of the Henan section includes Zhoukou City and Shangqiu City. However, the author claims that since the economic development levels of the two places are similar, the original data of Shangqiu City is used to calculate the value of water resources and the benefits of water supply. This treatment lacks sufficient justification.
The population structure, industrial structure, agricultural water use, groundwater extraction pressure, and ecological restoration needs of Zhoukou and Shangqiu may not be exactly the same. It is suggested that the author supplement the comparison of indicators such as GDP, industrial structure, population, water use structure, degree of groundwater over-exploitation, and ecological water replenishment targets of the two cities to prove that Shangqiu can represent the entire water-receiving area of the project. Otherwise, the calculations should be made separately for Zhoukou and Shangqiu and then weighted and summarized.
4. The indicator system for ecological water supply benefits is too narrow, and there is a lack of explanation of the ecological response mechanism.
The article classifies the value of ecological water supply services into four categories: biodiversity conservation, groundwater protection, water quality purification, and climate regulation. This classification is somewhat reasonable, but it is still not comprehensive enough. The ecological benefits of water diversion projects may also include river-lake connectivity, wetland restoration, landscape recreation, improvement of aquatic habitats, guarantee of ecological base flow, and alleviation of soil salinization, among others.
More importantly, the author did not explain how the increase in ecological water replenishment could be quantitatively converted into these ecological service values. For instance, how does the value of biodiversity conservation change with the amount of water replenishment? Is there a threshold for the value of groundwater protection? Does the benefit of water quality purification depend on pollutant concentration, flow rate, and water exchange cycle? Currently, it seems that the existing ecological service value indicators are directly applied to the emergy framework, with insufficient explanation of the ecological process mechanisms.
5. The conversion rate of emergy and the emergy/currency ratio parameters are outdated, and there is a lack of sensitivity analysis.
The article adopts the common substance energy value conversion rate of Lan et al. and uses the total energy value and annual growth rate of China in 1980 to calculate the energy value/currency ratio. These parameters have a significant impact on the final water resource value, but the article does not explain whether the parameters are applicable to the long-term predictions of 2010, 2021 and 2070.
It is suggested that the author add a table of parameter sources, listing all transformity, emergy/currency ratio, engineering investment allocation ratio, and ecological service value conversion parameters, and conduct a sensitivity analysis. Otherwise, readers will find it difficult to judge the reliability of the final results such as 5.844 billion yuan and 12.349 billion yuan.
There is a risk of conceptual confusion in the calculation of the value of water supply for production, daily life and ecology.
The article multiplies the "value of water resources" by the "water supply volume" to obtain the water supply benefit. However, the value of water resources does not necessarily equal the marginal benefit added by the project. The true benefit of water diversion projects should be based on the comparison between "with the project" and "without the project", such as substituting groundwater extraction, alleviating water shortage losses, enhancing industrial output, and improving residents' welfare. The current model is prone to attributing part of the existing economic output in the water-receiving area to the project's water supply, posing a risk of overestimation.
Especially in the production water supply section, the relationship between industrial output and water input is not linear. Water is just one of many production factors. Although the author introduced the water contribution rate, this rate is calculated based on the proportion of water energy value to the total input energy value. Whether it can represent the contribution to economic growth needs further verification.
7. There are obvious problems with the formula expression and symbol definition.
There are multiple formulas and symbols in the manuscript that need to be modified. For instance, in the formula for the value of ecological water resources, the symbol V is used. E
Please provide the text you would like translated.

However, the formula description was written as V. B
Please provide the text you would like translated.

The symbols are inconsistent. The formula for the value of production water resources includes both industrial and agricultural expressions, but the subsequent cases mainly use "industrial production", and it is unclear how to handle the agricultural production part. Equation (8) only mentions production, living, and ecological categories, but the result table divides living water supply into urban and rural areas. The formula should be expanded accordingly.
Furthermore, in Equation (7), it is given that m = b - a, but later it is written that "a > b > 0", which mathematically would result in m being negative. This clearly needs to be checked. These issues will affect the rigor of the method and must be systematically reviewed.
8. There is an issue of inconsistent time frames in the table and result sections.
The text states that the calculation is based on the official statistics of Shangqiu City in 2011 and 2022, but the table shows the emergy results of 2010 and 2021. This time frame needs to be clarified: is it 2010/2021 or 2011/2022? Is it because the statistical yearbook lags by one year? If so, it needs to be clearly stated.
In addition, Table 1 only provides the water supply volume for 2030 and 2040, but Table 6 presents the benefits for 2021, 2030, 2040, 2050, 2060, and 2070. How were the water supply volumes for 2021, 2050, 2060, and 2070 obtained? Were they derived through linear interpolation, planned values, or a fixed proportion extrapolation? The current explanation is insufficient.
9. "Rationality analysis" cannot fully verify the reliability of the model.
The author compared the apportionment coefficient method with the emergy analysis method and found that the error between the two was only 3.94%, thus verifying the rationality of the emergy method. This verification logic is rather weak. The apportionment coefficient method itself also relies on empirical parameters, such as the industrial water contribution rate of 0.2, the industrial added value rate of 25.85%, the living apportionment coefficient of 0.1, and the water diversion utilization rate of 35.9%. If the two methods share similar basic data or parameter assumptions, the closeness of the results cannot prove the correctness of the model.
It is suggested to enhance external validation, for instance, by comparing the water supply benefits per unit, regional water prices, shadow prices, ecological compensation standards, and the cost of groundwater substitution with those of similar water diversion projects. Uncertainty intervals can also be provided instead of merely reporting a definite value.
The discussion section lacks depth and merely repeats the results.
The Discussion section mainly reiterates that this paper has established an emergy index system, calculated the value of water resources and the benefits during the service period, and then proposed that in the future, it can be combined with eco-hydrological models, system dynamics and machine learning. However, it does not fully discuss the similarities and differences between the results of this paper and existing studies, nor does it explain key phenomena such as why the proportion of industrial water supply benefits has remained above 60% for a long time, why the ecological benefits are only 1%–2%, and why the value of ecological water resources has grown the fastest but still has a low proportion.
It is suggested that the author enhance the discussion in three aspects: first, compare the water supply benefits results with those of other water diversion projects; second, explain whether the relatively low ecological water supply benefits result from the small amount of ecological water replenishment, a narrow indicator system or a conservative valuation method; third, clarify the practical significance of this method for water price determination, ecological compensation, post-project evaluation and investment decision-making.
11. The conclusion is stated too strongly. The wording of "accuracy" and "comprehensiveness" should be toned down.
The conclusion states that the model in this paper can "comprehensively evaluate" economic and environmental impacts and enhance the completeness and accuracy of water supply benefit calculations. However, from the current approach, ecological benefits only select four types of indicators, the prediction method is a simple fixed coefficient extrapolation, and there is no uncertainty analysis. Therefore, the expression of "accuracy" lacks support.
It is suggested to adopt a more cautious expression: This paper provides a framework for incorporating the ecological water supply benefits into the water supply benefit assessment of water diversion projects, which can serve as a reference for long-term comprehensive benefit evaluation. However, it still needs to be further improved by integrating multi-scenario predictions, ecological process simulations, and more detailed-scale data.
12. The quality of language, format and charts needs to be comprehensively revised.
There are quite a few issues with English expressions and formats in the manuscript. For instance, the title of Table 1 still retains the template text "This is a table. Tables should be placed...", which is an obvious submission format error. Additionally, there are unnatural or grammatically incorrect expressions such as "Similarity economic development level", "Enhance economic returns", and "The coefficients adopted by the distribution coefficient method are derived..."
The flowchart in Figure 1 has truncated text, with "Calculation of w" not fully displayed. The circular proportion chart in Figure 5 is rather dense in information, and the years, categories, and proportions are not intuitive enough. It is suggested to change it to a stacked bar chart or a line area chart. The overall English needs professional polishing.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Overall Evaluation: Major Revision
This manuscript addresses a topic of considerable practical relevance and theoretical significance. By focusing on the long-standing neglect of ecological benefits and their dynamic evolution in the evaluation of inter-basin water transfer projects, the study innovatively introduces emergy analysis to construct an integrated assessment framework. The case study of the Yangtze-to-Huaihe Water Diversion Project provides an empirical application of the proposed approach. The research design is generally coherent, and the overall structure is well-organized, offering a novel perspective for the comprehensive evaluation of water conservancy project benefits.
However, several substantial issues remain, particularly concerning the rigor of the empirical methodology (notably the 50-year linear projection), the theoretical foundation of key concepts (e.g., emergy accounting of ecological water use), the transparency of data processing, and the precision of terminology. These limitations directly affect the reliability and scientific validity of the study’s conclusions.
Therefore, it is recommended that the manuscript be reconsidered after major revision. The authors are expected to carefully and comprehensively address the concerns raised below, especially those related to the validity of the “fixed coefficient method,” the theoretical justification of ecological emergy accounting, and the detailed documentation of key data sources and computational procedures. Only after these issues have been adequately resolved can the publication value of the manuscript be properly assessed.
Specific Comments
1. Rigor of the “Fixed Coefficient Method”
The manuscript employs a “fixed coefficient method” (i.e., linear extrapolation) to project water resource value over a 50-year period (2021–2070). This approach is overly simplistic and entails significant risks. The value of water resources is influenced by multiple complex factors, including economic structural transformation, technological progress, water pricing policies, and climate change, making a linear trajectory highly implausible in the long run. This methodological choice substantially undermines the credibility of the dynamic benefit assessment. It is recommended that the authors conduct at least sensitivity analyses or explore the feasibility of more sophisticated econometric approaches (e.g., time series models), and explicitly discuss the limitations of this method in the manuscript.
2. Theoretical Foundation of Ecological Emergy Accounting
The study decomposes ecological benefits into biodiversity conservation, groundwater protection, water purification, and climate regulation, assigning emergy values to each component. However, the manuscript lacks a clear and widely accepted theoretical basis for translating these abstract ecosystem services into quantifiable emergy flows. For instance, the use of reference values from the Yellow River Old Course Wetland Park to estimate biodiversity conservation raises concerns regarding generalizability. The authors are advised to provide detailed explanations of the theoretical framework, formulas, and parameter sources underlying the emergy accounting of each ecological service, thereby enhancing methodological robustness and reproducibility.
3. Transparency of Data Sources and Computational Procedures
Although the manuscript indicates the use of statistical data from Shangqiu City for 2011 and 2022, the sources and processing steps of many key variables remain insufficiently transparent. Specifically, it is unclear how the numerous emergy input-output items presented in Tables 2, 3, and 4 are derived from the original statistical data. Furthermore, the allocation of total project investment and costs (7.38 billion and 1.42 billion, respectively) across subsystems based on water supply proportions requires further clarification. Given the importance of these procedures for validating the results, detailed documentation should be provided either in the main text or in an appendix.
4. Precision of Terminology
The manuscript frequently uses the term “water resource value.” However, within the emergy analysis framework, the results are essentially economic equivalents converted via the emergy-to-money ratio (EDR). Strictly speaking, this does not correspond to “value” in the conventional economic sense, but rather to a specific form of valuation grounded in emergy theory. The authors are encouraged to standardize and refine the terminology throughout the manuscript, clearly distinguishing between “emergy,” “emergy-based value,” and traditional “economic value” to avoid conceptual ambiguity.
5. Treatment of the Emergy-to-Money Ratio (EDR)
The introduction acknowledges that EDR declines over time with economic growth (e.g., GNP expansion), which is an important observation. However, this dynamic property does not appear to be explicitly incorporated into the subsequent benefit projections. Instead, the analysis implicitly assumes a constant EDR or subsumes its variation within the “fixed coefficient method.” This treatment neglects the potentially significant impact of EDR changes on benefit estimation. The authors should clarify how EDR is handled during the projection period and provide a justification for the chosen approach.
6. Representativeness of the Case Study and Generalizability of Conclusions
The analysis is based on the Henan section of the Yangtze-to-Huaihe Water Diversion Project, whose socio-economic and ecological characteristics are region-specific. The reported benefit shares (e.g., production water accounting for 60–63%) and their temporal trends may not be directly applicable to other water transfer projects with different geographical and socio-economic contexts. It is recommended that the authors explicitly discuss the scope of applicability of their findings and identify key parameters that would require adjustment when applying the model to other regions.
7. Depth of Comparison with Traditional Methods
The manuscript compares its results with those derived from the “allocation coefficient method,” reporting a deviation of 3.94%. While this comparison is informative, it remains limited to aggregate benefit values and does not sufficiently explore the fundamental differences between the two approaches in terms of logic, conceptual underpinnings, and policy implications. The authors are encouraged to deepen this discussion by clarifying what additional system-level information is captured by emergy analysis but overlooked by conventional methods, thereby better highlighting the methodological contribution of the study.
8. Enhancement of Figure Presentation
Figure 5 presents the proportion of different benefit categories but does not illustrate the absolute growth trends. It is suggested that an additional figure be included to depict the temporal evolution of absolute benefit values for the four categories. Such a visualization would make the key finding—namely, that ecological benefits exhibit the largest growth (a 4.5-fold increase)—more intuitive and compelling.
9. Interpretation of the Low Share of Ecological Benefits
The manuscript reports that ecological water use accounts for only 1–2% of total benefits, attributing this primarily to limited water supply and low contribution rates. However, this observation also reflects the broader issue that ecological values are systematically undervalued in existing water resource evaluation frameworks. The authors are encouraged to provide a more in-depth discussion of the institutional, market, and technical factors underlying this phenomenon. Moreover, the study should emphasize the importance of explicitly incorporating and monetizing ecological benefits (even within an emergy-based framework) for advancing ecological civilization and improving integrated water resource management, thereby strengthening its policy relevance.