Urbanization and the Emerging Water Crisis: Identifying Water Scarcity and Environmental Risk with Multiple Applications in Urban Agglomerations in Western China

Round 1

Reviewer 1 Report

This is a very interesting paper discussing the urbanization and emerging water crisis: Identifying water scarcity and environmental risk with multiple applications in urban agglomerations in Western China.

Minor comments that require authors' attention are mentioned below and others are highlighted on the softcopy attached. 

Some paragraphs lack supporting references. Please refer to the file attached

Figure 1. please add figure caption and references if they are not the authors' own work

Comments for author File: Comments.pdf

The paper is well-written

Author Response

• General Comments.

This is a very interesting paper discussing the urbanization and emerging water crisis: Identifying water scarcity and environmental risk with multiple applications in urban agglomerations in Western China. Minor comments that require authors' attention are mentioned below and others are highlighted on the softcopy attached.

Response: Thank you for your comments on our manuscript. We have revised the manuscript according to your suggestions.

• Specific Comments
• 1- Some paragraphs lack supporting references. Please refer to the file attached.

Response: Thank you for your comments on our manuscript. We have added the supporting references.

Added references:

On the one hand, the overall water situation in the western region is very complex. In 2018, the water resources of the 12 provinces and municipalities in the western region were 1,615.28 billion m3, accounting for 58.8 % of China’s total water resources [5]. However, the water resource endowment of each province and urban area in the region is quite different. Although the total amount of water resources in northwestern China is large, the amount of water resources per capita is small, and a large amount of ecological water is polluted [6, 7]. Therefore, there is a severe water deficit in the local area. In addition, the southwest is relatively rich in water resources, but the develop-ment and utilization conditions are relatively difficult because the spatiotemporal distribution does not match the demand [8, 9]. Regional and seasonal water shortages are equally severe.

On the other hand, the western region has started to experience a rapid growth stage with an urbanization rate of 30-70% [10]. The urbanization rate in most areas has maintained an average yearly growth rate of 1% or more. The problem of disharmony between urbanization construction and water resources carrying capacity is becoming more and more prominent [11]. Many cities and towns face water shortage problems regarding water quantity, quality, resources, and engineering [12]. In this context, the risk of water shortage has attracted significant attention from all walks of life in Western China’s urbanization process [13-15]. How can the water shortage risk be ef-ficiently measured in Western China’s urbanization process? What is the status of wa-ter shortage risk in Western China’s urbanization process? Does this water shortage risk have obvious regional heterogeneity in different regions? The answers to these questions will help to fully estimate and deal with the severe water shortage situation in western China as soon as possible.

• 2- Figure 1. please add figure caption and references if they are not the author’s own work.

Response: Thank you for your comments on our manuscript. We have added the figure caption in Figure 1 and the explanation about the source of the figure 1.

Added the figure caption:

Fig. 1. The overall framework of water scarcity and environmental risk assessment in Western China.

(Source: The figure is drawn by the author himself.)

Author Response File: Author Response.docx

Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

• General Comments.

**The manuscript is well written and the results seem interesting. However, there is a need to improve the English language used in this manuscript. I would recommend that you seek help in this regard from either a native English speaker or a commercial entity that provides that service.

Use of “a"，"an"，“the"，etc.

• Misspelled words
• Improper formatting

Response: Thank you for your comments on our manuscript. We have revised the manuscript according to your suggestions. We have carefully checked the English quality of the full text. According to your advice, this manuscript was edited for proper English language, grammar, punctuation, spelling, and overall style by one or more highly qualified native English speakers.

• Specific Comments
• 1-**Please explain your novelty more clearly, and added a few sentence in the abstract and in last in the introduction section for major results.

Response: Thank you for your comments on our manuscript. We have revised the abstract and added a few sentences in the introduction.

Modified abstract:

Urbanization and climate change have combined to exacerbate water shortages in cities worldwide. While rapid urbanization is faced with the risk of water resource shortage, there are few studies on the impact of water resource shortage and the ecological environment in mega-regions. Taking the three major urban agglomerations in western China as an example, the spatial-temporal agglomeration pattern and driving force for the risk of water shortage are analyzed. First, a new comprehensive index system for environmental risks of water resources has been established, which can be used to assess spatial changes in water resource shortage risks. Secondly, the relationship between water resource shortage and the urban agglomeration effect is discussed from water resource vulnerability, exposure, and recoverability. The results showed:(1) From 2000 to 2018, the risk of total water shortage in 12 provinces (cities) in western China decreased from 3.42 to 2.59; The risk of total water shortage in the GuanZhong Plain urban agglomeration dropped the fastest, with an average annual decline rate of 10.57%. (2) Water resource shortage in different cities of the three major urban agglomerations is out of sync in time and space; The risk level of water shortage is high in the north and low in the south. (3) Geological environment change is an important influencing factor of water resource shortage; The negative impact of industrial water use on the risk of water shortage is the largest, with a contribution of 24.9%. In addition, it also puts forward policy suggestions to alleviate the risks of water shortage in the urbanization process in the western region. This research can provide a scientific basis for the sustainable development of urban water resources.

Modified sentence:

Currently, although some progress has been made in the study of water scarcity risk [34-36], there are still some aspects that deserve further research. Firstly, previous studies have mainly focused on the assessment of water scarcity risk in single or mul-tiple regions and their internal water scarcity risk[34, 37-39], but less on the assessment of water scarcity risk in the western region, especially in the representative western urban agglomerations. Therefore, there is an urgent need to carry out a comprehensive analysis of water scarcity risk and its environment in the western region of China, and to reveal the actual situation of domestic, industrial and agricultural water use risk and its environmental management in the process of urbanization. Secondly, the obstacles to water scarcity risk in the western urban agglomerations should be further examined, and locally adapted policies and guidelines for sustainable water supply should be proposed. The Chengdu-Chongqing urban agglomeration, the Lanxi urban agglomer-ation, and the Guanzhong urban agglomeration are the main typical areas in the west where urban water use is intensive, and they are important ecological logistic barriers that provide a variety of ecological services in China. In addition, although the total amount of water resources in the western region is large, the per capita water resources are small.

• 2-**The Introduction and the Discussion should be improved to better show what is new in your work if compared with similar investigations, also performed in other regions. In your work, well-

known methods are just applied to another case study, and the results are not properly discussed. Also the data details are not enough to guarantee the study reproducibility.

Response: Thank you for your comments on our manuscript. We have revise the introduction and the discussion.

Modified introduction:

Currently, although some progress has been made in the study of water scarcity risk [34-36], there are still some aspects that deserve further research. Firstly, previous studies have mainly focused on the assessment of water scarcity risk in single or multiple regions and their internal water scarcity risk [34, 37-39], but less on the assessment of water scarcity risk in the western region, especially in the representative western urban agglomerations. Therefore, there is an urgent need to carry out a comprehensive analysis of water scarcity risk and its environment in the western region of China, and to reveal the actual situation of domestic, industrial and agricultural water use risk and its environmental management in the process of urbanization. Secondly, the obstacles to water scarcity risk in the western urban agglomerations should be further examined, and locally adapted policies and guidelines for sustainable water supply should be proposed. The Chengdu-Chongqing urban agglomeration, the Lanxi urban agglomeration, and the Guanzhong urban agglomeration are the main typical areas in the west where urban water use is intensive, and they are important ecological logistic barriers that provide a variety of ecological services in China. In addition, although the total amount of water resources in the western region is large, the per capita water resources are small.

In recent years, with the accelerated urbanization and industrialization in the western region, the consumption of water resources has increased, and the water environment has suffered serious pollution [15]. Water resources are one of the key elements to maintain the health of human life and socio-economic development [40]. Therefore, it is of great significance and urgency to explore the risk of water shortage and its environmental impacts in the western region.

Therefore, the aim of this paper is to analyze the water scarcity footprint and its environmental impacts in the western region and its three major urban agglomerations, and to reveal the risk of water scarcity and its impediments in the western region. Based on these results, policy recommendations are made on the need for subregional management of water resources in western cities in accordance with the urbanization process and actual water consumption. This study can provide policy recommendations for western urban agglomerations to reduce environmental pollution of water resources and promote regional ecological protection and sustainable development of water resources.

Added discussion:

    In order to guarantee the sustainability of water resources and water environment pollution prevention in Northwest China, we need to strengthen the planning of eco-logical spatial patterns within Northwest China's urban agglomeration, and create a Yellow River ecological corridor based on the skeleton of mountains and water and green color [58]. In addition, the construction of ecological corridors improves down-stream ecological conditions, realizes the filtering function of water pollutants, pro-motes soil and water conservation and pollution prevention in Northwest China, accelerates the construction of green cities with ecological livability and water resources recycling, and encourages public participation in water resources ecological and environmental protection [55, 58].

    The Chengdu-Chongqing region is an essential strategic region in China to accel-erate the development of the western region, enhance the level of inland openness, and strengthen the country's comprehensive strength [59]. In 2022, the GDP of the Chengdu-Chongqing region accounted for 7.3% of the national GDP [60]. The rapid development of the economy has brought great pressure on the supply of water re-sources. In particular, the accelerated urbanization has led to a continuous increase in domestic water consumption. The primary source of water supply in Chengdu is the Minjiang River, which is a single source of water supply [61].

In recent years, the massive exploitation of water resources in the upper reaches of the Minjiang River has led to the drying up of some of the river's tributaries, resulting in a tight water supply for the city of Chengdu. Chongqing Municipality also faces the same problem, with water scarcity putting tremendous pressure on the city's sustainable development and hindering socio-economic development [61]. However, the Chengdu-Chongqing regional government has adopted a new quality-oriented urban water planning and management, which alleviates the risk of water shortage in Chengdu-Chongqing cities [62]. The bearing status has also been effectively improved. However, seasonal, regional, engineering, and water shortage problems remain prominent, making the situation grim.

The following are the causes of this phenomenon: First, the economic development and urbanization degree of the nine cities in the Lanxi urban agglomeration is rela-tively low [63]. Second, compared with the western region of the urban agglomeration, the eastern region of the urban agglomeration is mainly located in the Loess Plateau region of Gansu Province [64]. The terrain in the area is winding and undulating, the soil is loose, and soil erosion is severe. And mainly for the continental climate, less rainfall, water reserves are relatively insufficient. Thirdly, the level of economic de-velopment and urbanization in the eastern part of the urban agglomeration is higher than that in the western part, resulting in greater population, industry, and social pressure on its water resources system [65]. 

The main water resources of the Guanzhong Plain urban agglomeration are dis-tributed in the Qinling Mountains, and the distribution pattern of water resources shows a trend of high in the south and low in the north, decreasing from south to north [66]. Rainfall in the Guanzhong Plain urban agglomeration is mainly concentrated in the east, with relative water shortages in the country's northwestern part and the Longdong region of Gansu Province [66]. In addition, the urbanization process of population and industrial aggregation is accompanied by severe ecological and environmental problems [65]. In particular, the Guanzhong Plain urban major reliance on coal-based energy consumption has led to serious water pollution problems, making the contradiction between socio-economic development and ecological protection in the Guanzhong Plain urban agglomeration prominent [67]. Therefore, to reduce the risk of water shortage in the Guanzhong Plain urban agglomeration in the future, it is necessary to promote the recycling of urban water resources on the one hand, and on the other hand, it is necessary to encourage the change of the energy consumption structure of the cities in the Guanzhong Plain, to reduce the pollution of the water en-vironment, and to promote the sustainable development of water resources.

• 3-**The conclusion is somewhat vague and need improvement；it should include values and should in summary reflect the outcome of your work.

Response: Thank you for your comments on our manuscript. We have revised the conclusion on your request.

Modified conclusion:

The study analyzes the influencing factors of water resources shortage risk in three major urban agglomerations in Western China from 2000 to 2018 and establishes a new comprehensive evaluation index system of water resources environmental risk from the aspects of water resources vulnerability, exposure, and recoverability. Secondly, the entropy and fuzzy comprehensive evaluation methods are utilized to measure the risk value of water resources shortage in the 12 western provinces (municipalities) as well as the three major urban agglomerations and classify them into grades. Finally, on this basis, the temporal and spatial aggregation characteristics and environmental impact factors of water shortage risk in the western provinces (cities) and the three major urban agglomerations were investigated. The results show that from 2000 to 2018, the risk of water shortage in 12 provinces (cities) in western China has been mitigated to a certain extent, with the overall risk value decreasing from 3.42 to 2.59; among the three major urban agglomerations, the Guanzhong Plain urban agglomeration has the fastest decrease in the total water shortage risk, with an average annual decrease rate of 10.57%, followed by the Chengdu-Chongqing urban agglomeration with an average yearly decline rate of 8.03%. In terms of risk level, the overall water shortage risk of the western urban agglomeration is still at the medium or below the level in the country, and water shortage is still very serious along with the process of urbanization and industrialization in the western part of the country. Secondly, the water shortage of different cities in the three major urban agglomerations is not synchronized in time and space, and the risk level of water shortage shows a situation of "high in the north and low in the south". Finally, due to the special geographic environment and the complexity of water shortage risk in the West, the geological environment change is an important influence factor of water shortage; industrial water use has the biggest negative impact on water shortage risk, with a contribution of 24.9%. Therefore, in order to systematically mitigate the risk of water shortage in the urbanization process in the West in the future, in addition to focusing on the overall management of the Western region, it is also necessary to take targeted measures around the level of each urban agglomeration and carry out differentiated management. In addition, environmental changes in water resources are also a key concern for the sustainable development of urban water resources in the future.

Author Response File: Author Response.docx

Reviewer 3 Report

**The manuscript is well written and the results seem interesting. However, there is a need to improve the English language used in this manuscript.  I would recommend that you seek help in this regard from either a native English speaker or a commercial entity that provides that service.

• Use of “a”, “an”, “the”, etc.
• Misspelled words
• Improper formatting

**Please explain your novelty more clearly, and added a few sentence in the abstract and in last in the introduction section for major results.
**The Introduction and the Discussion should be improved to better show what is new in your work if compared with similar investigations, also performed in other regions. In your work, well-known methods are just applied to another case study, and the results are not properly discussed. Also the data details are not enough to guarantee the study reproducibility.

**The conclusion is somewhat vague and need improvement; it should include values and should in summary reflect the outcome of your work.

See above

Author Response

• General Comments.

The article utilizes the water resources risk assessment index system to reveal the water shortage risk in Western China's urbanization process. It contributes to addressing the water challenges associated with rapid urbanization and supports the long-term availability and sustainability of water resources in the region. To further enhance the article, a few minor revisions can be made.

Response: Thank you for your comments on our manuscript. We have revised the manuscript according to your suggestions.

• Specific Comments
• 1- In the introduction, explicitly state the unique contribution or innovation of the research. It is advised to compare the work with previous studies.

Response: Thank you for your comments on our manuscript. We have revised the introduction and added the contribution and innovation of the research, and also added the previous studies.

Modified introduction:

Currently, although some progress has been made in the study of water scarcity risk [34-36], there are still some aspects that deserve further research. Firstly, previous studies have mainly focused on the assessment of water scarcity risk in single or multiple regions and their internal water scarcity risk [34, 37-39], but less on the assessment of water scarcity risk in the western region, especially in the representative western urban agglomerations. Therefore, there is an urgent need to carry out a comprehensive analysis of water scarcity risk and its environment in the western region of China, and to reveal the actual situation of domestic, industrial and agricultural water use risk and its environmental management in the process of urbanization. Secondly, the obstacles to water scarcity risk in the western urban agglomerations should be further examined, and locally adapted policies and guidelines for sustainable water supply should be proposed. The Chengdu-Chongqing urban agglomeration, the Lanxi urban agglomeration, and the Guanzhong urban agglomeration are the main typical areas in the west where urban water use is intensive, and they are important ecological logistic barriers that provide a variety of ecological services in China. In addition, although the total amount of water resources in the western region is large, the per capita water resources are small.

In recent years, with the accelerated urbanization and industrialization in the western region, the consumption of water resources has increased, and the water environment has suffered serious pollution [15]. Water resources are one of the key elements to maintain the health of human life and socio-economic development [40]. Therefore, it is of great significance and urgency to explore the risk of water shortage and its environmental impacts in the western region.

Therefore, the aim of this paper is to analyze the water scarcity footprint and its environmental impacts in the western region and its three major urban agglomerations, and to reveal the risk of water scarcity and its impediments in the western region. Based on these results, policy recommendations are made on the need for subregional management of water resources in western cities in accordance with the urbanization process and actual water consumption. This study can provide policy recommendations for western urban agglomerations to reduce environmental pollution of water resources and promote regional ecological protection and sustainable development of water resources.

• 2- Regarding the information entropy weight method and fuzzy comprehensive evaluation method, it is necessary to provide a more detailed description of their application as evaluation methods. This would increase the credibility of the article.

Response: Thank you for your comments on our manuscript. We have provided a more detailed description of their application as evaluation methods.

Added description:

Entropy is derived from thermodynamics and can be used to measure system disorder [49]. The entropy weight method is an objective assignment method that determines weights according to the magnitude of indicator variability. Suppose the in-formation entropy value of an indicator is smaller. In that case, it indicates that the greater the degree of variability of the indicator value, the more information is pro-vided, and the greater the weight in the comprehensive evaluation; on the contrary, the greater the entropy value is, the smaller the weight assigned to the indicator [50].

The fuzzy comprehensive evaluation method is a method to make a comprehensive decision on a thing for a certain purpose in a fuzzy environment, considering the influence of multiple factors [51]. The method is characterized by clear and systematic results, and can better solve ambiguous and difficult problems [52]. Therefore, this method is often used to solve various non-deterministic problems.

• 3- Please explain the correlation between the secondary indicators mentioned in Table 2，such as forest cover degree and nature reserve, and the assessment index of recoverability in Table 1.

Response: Thank you for your comments on our manuscript. Due to the availability and representativeness of the data, the tertiary indicators of the recoverability of the water shortage risk in the urban agglomerations of the western region replace the forest cover degree and the nature reserves area. The correlation between them is expressed as follows:

Protecting and increasing forest cover improves the sustainability and quality of ecosystem water use, as forests play an essential role in water quality protection and availability in the water cycle [53]. Higher forest cover implies, on the one hand, that the urban area is rich in water resources and can provide better water conditions for urban ecosystems [54]; on the other hand, higher forest cover indicates better water quality protection and ecosystem services, and more efficient and sustainable urban water recycling [55].

Nature reserves serve to protect water sources and guard against pollution. Nature reserves usually include natural environments with essential water source functions, such as mountain ranges, lakes, and rivers [56]. The establishment and management of these reserves help to maintain the pristine state of water sources and reduce the negative impacts of human activities on water resources, thus improving the water quality of drinking water sources. In addition, the ecosystems of nature reserves can filter and absorb pollutants from urbanization, reducing the risk of contamination of water bodies [57]. Therefore, a larger area of nature reserves may further contribute to a higher compliance rate of drinking water sources.

• 4- Pay attention to certain details, such as the absence of a caption for Figure 1 and ensuring the correct formatting of line 528.

Response: Thank you for your comments on our manuscript. We have added the figure caption in Figure 1 and correct formatting of line 528.

Added the figure caption:

Fig. 1. The overall framework of water scarcity and environmental risk assessment in Western China.

(Source: The figure is drawn by the author himself.)

Author Response File: Author Response.docx