Evaluation of sustainable development capacity of water sources: a case study of China

Currently, most of the research on water sources focuses on the control of pollution, innovative management models, and adjustment of incentives (Xu et al. 2022). For the study of the sustainability of water sources, a perfect evaluation system has not been established. The current methods for determining the index weights are subjective assignment method, objective assignment method, and combined assignment method. However, the weight of the subjective assignment method is given by experts based on their own experience. The results of the calculation are limited by human experience. The objective assignment method does not take into account the subjective consciousness of people, and the determined weight may not be consistent with the subjective desires of people. Therefore, in order to improve the accuracy and credibility of the evaluation results, this paper will use the combined assignment method to determine the weight coefficients. Based on the extensive analysis of previous studies, this paper adopts the hierarchical analysis method and the entropy method of variation coefficient improvement to assign weights. A coupled coordination degree evaluation model of water source sustainable development ability is established. The research significance of this paper is as follows.

• In this paper, a coupled coordination degree evaluation model for the sustainability of water sources is proposed. It is an innovation and expansion of the traditional evaluation method. Through this model, we can understand the sustainable development status of water sources in a more comprehensive and in-depth way and provide a scientific basis for formulating corresponding protection and management strategies.

• Since the index weights obtained by the entropy method are too equalized, this paper introduces the coefficient of variation method to improve it. It can weaken the influence of outliers and make the evaluation results more accurate and reasonable. In order to make the evaluation results more scientific and objective, this paper adopts the combination assignment method to determine the weights of each evaluation index. It enables to reflect more accurately the importance of each index in the evaluation and improves the accuracy and credibility of the evaluation.

• There is no complete evaluation index system for the study of the sustainable development capacity of water sources. From three aspects, ecological, economic, and social, this paper assesses the sustainable development capacity of water sources with a view to providing useful references for the sustainable development of water sources.

The rest of this study is organized as follows. Section 2 introduces the current status of research on water sources and the evaluation method of water source sustainability. The third section discusses the research methodology of this paper. Results and discussion are in the fourth part. Finally, conclusions and further work are given in Section 5.

The environmental conditions of water sources have an important impact on regional water supply security and sustainable economic development and are also closely related to people's life and health safety. Wu et al. (2019) concluded that organic micropollutants in the water environment have potential impacts on ecological safety and human health. By analyzing four drinking water sources in Henan Province, China, water contaminants were found to be of high risk to algae and invertebrates (Wu et al. 2019). Cao et al. (2019) collected long-term monitoring data of conventional physicochemical parameters and metal elements in water bodies from 2005 to 2017. Multivariate statistical techniques were also used to evaluate the elements' sources. It was discovered that the presence of trace elements was significantly impacted by both endogenous releases and human activity (Cao et al. 2019). Yang et al. (2020) analyzed the current status of ecological compensation in the Yellow River Basin in China and discussed the types and key areas of ecological compensation in the Yellow River Basin. After a series of analyses, it was suggested to strengthen basic research and key case studies on ecological compensation mechanisms in the Yellow River basin (Yang et al. 2020). Sun et al. (2020) realized that the main cause of nonpoint source pollution in drinking water sources is unreasonable management of commercial forests in upstream areas. The relationship between soil factors and surface runoff pollutants was studied using redundancy analysis. It was concluded that effective measures were to increase vegetation cover and improve the soil environment (Sun et al. 2020). Yu et al. (2021) used a questionnaire survey method to statistically analyze the sustainable development of the Sun Moon Lake Reservoir in Taiwan. The study found that the development of the reservoir has brought a large amount of waste. This caused the disappearance of culture and architecture (Yu et al. 2021). Wang et al. (2021) found that the main cause of water source pollution is eutrophication of water bodies. Realizing the importance of implementing clean agricultural production to protect the environment of water sources, a series of feasible measures were proposed (Wang et al. 2021). Leya et al. (2022) used key information interviews to assess the status of water source security in six areas with urban fringe characteristics in Bangladesh. The study showed that partnership among key stakeholders can enhance water source security in similar urban peripheral environments (Leya et al. 2022). In summary, scholars have conducted a large number of studies on contaminants and environmental safety of water sources. A foundation has been laid for the study of the sustainability of water sources.

In recent years, significant results have been achieved in the application of water source evaluation index weighting, ranking of evaluation objects, and correction of evaluation results. In order to improve the accuracy of water source evaluation and reduce the influence caused by subjective factors, water source evaluation systems are usually combined with statistical methods. Ding et al. (2019) used a two-dimensional water quality detection model to generate a computational network. A safety platform for drinking water sources in the Three Gorges Reservoir area of China was developed (Ding et al. 2019). Wang et al. (2020) realized that identifying the spatial and temporal variability of nonpoint source pollution is a prerequisite for improving water quality. A combined model based on land use types was used to simulate pollution loads. And the spatial and temporal characteristics of pollution sources in typical urbanized areas were identified by assessing the pollution loads in typical urbanized areas (Wang et al. 2020). Zhang et al. (2020) used a cloud model to analyze the ecological environmental vulnerability of water sources. The ecological environmental vulnerability evaluation index system of water sources was constructed by studying the water sources of the South-North Water Diversion Central project in China (Zhang et al. 2020). Qin et al. (2021) combined multiple linear regression models with Bayesian networks to identify and assess contaminants in water sources (Qin et al. 2021). Liu et al. (2021) combined the water quality index (WQI) and entropy weighting method to evaluate the environmental quality of groundwater in the Dawu water source. Full index method, Delphi method, and multivariate statistical analysis were used to analyze the evaluation results. The conclusion of overall good water quality was drawn (Liu et al. 2021). Xiao et al. (2022) proposed a combined assignment method for the comprehensive evaluation of coastal water quality. The study showed that riverine input is the main source of pollutants in the study area (Xiao et al. 2022). Zhang et al. (2022) proposed an evaluation method that combines the intrinsic vulnerability of aquifers with pollution source loads. The contamination risk of groundwater in the Guanzhong Basin, China, was evaluated from a macroscopic perspective (Zhang et al. 2022). Hou et al. (2022) considered that controlling nonpoint source pollution is crucial. It is necessary to estimate the nonpoint source pollution export and identify the pollution sources. After studying rainfall and topography and investigating the characteristics of pollution sources and surface sources, an improved output coefficient model was developed (Hou et al. 2022). From the existing literature, it can be seen that scholars have focused on qualitative studies and a few scholars have conducted quantitative analyses. However, the single evaluation method is too subjective and has poor evaluation results.

In general, there exists a significant disparity between China and developed countries concerning both theoretical research and practical approaches to water source protection. Many efforts fall short in addressing the driving mechanisms behind changes in water quality, and only a few delve into the effective safeguarding of water sources from the perspective of watershed or catchment land use. The rights and interests of various stakeholders in water sources have not received adequate attention. The absence of operational and promotional mechanisms for water source protection hampers the effectiveness of implemented measures. Research on the evaluation of water sources remains limited, and the existing evaluation system cannot be fully applied to assess water sources. Moreover, the current evaluation methods lack scientific rigor, highlighting the need to identify a suitable evaluation approach. These constitute the primary focus areas of this paper.

The significance of each indicator in the evaluation system is gauged through weighting. A judicious distribution of weights is crucial for ensuring the reliability of evaluation results. To attain a balanced weight composition, this paper employs the entropy value method, wherein the utility value of information entropy is utilized to objectively calculate the weights of indicators. Effective information in the original data is fully utilized under the premise of the interference of subjective factors (Liu et al. 2022). However, the shortcoming of the method is the equalization of indicator weight. There is no horizontal comparison of the degree of influence of each indicator on the sustainability of water sources. The variation coefficient method directly uses the valid information in the original data, which can better overcome the disadvantage of weight equalization distribution (Jin et al. 2022). Therefore, this paper proposes an objective portfolio assignment method based on the coefficient of variation method and the entropy value method.

The entropy method calculates the information utility value based on the information entropy provided in the raw data of each indicator. It is an objective weighting method to determine the weight of each index (Lee & Lee 2022). The steps to determine the index weight by using the entropy method are as follows:

Step 1. The evaluation matrix consists of 20 indicators in three main categories. Raw data X = ⁠, where is the value of the j indicator of category i, i = 1,2; j = 1,2,3,⁠,n.

The coefficient of variation method is an objective weighting method that uses the coefficient of variation and standard deviation of the data to calculate the weight coefficient of each indicator (Yosboonruang et al. 2022). The steps for determining the weight of indicators using the coefficient of variation method are as follows:

Step 1. The evaluation indicator raw data matrix B = ⁠, where is the j indicator value;

In this study, the coupled coordination degree model is employed to assess the sustainable development of the ecological–social–economic complex system within the water source region. This model serves to depict the level of coordination among two or more systems in a manner that closely aligns with real-world scenarios. Its application mitigates the influence of subjective human factors, thereby enhancing the objectivity and validity of the evaluation results across diverse complex situations (Li et al. 2022). The coupling degree mainly reflects the strength of interactions and interactions between systems.

Step 2. The coupling coordination degree function is calculated. Compared with the coupling degree model, the coupling coordination degree can better measure the coordination degree of interactive coupling between systems. It is very necessary to go further to evaluate the coupling coordination degree of the region, where D is the coupling coordination degree; T is the integrated coordination index of the three subsystems; α, β, γ are the coefficients to be determined.

In accordance with the index system for assessing the sustainable development capacity of water sources outlined in Part 3, the weights are initially determined using the combination assignment method. Subsequently, the comprehensive development level is computed and applied to assess the coupling coordination degree among the subsystems. The Zhangwei New River Basin encompasses six or five rivers situated on both sides of the Chen Gong Dike, featuring 12 tributaries ranging from 300 to 1,000 km². Beyond these major tributaries, there are an additional 53 tributaries with a watershed area of 100–300 km² and 114 tributaries with a watershed area of 30–100 km². This has essentially formed a network of interconnected dry and branch rivers, facilitating the discharge and transfer of river water throughout the basin. However, recent years have seen a water shortage from the Yellow River, and the rivers within the region primarily rely on rainfall. The water quantity is intricately linked to the climate characteristics of the upstream areas, and the distribution of precipitation in the city is highly uneven. During the rainy season, water levels rise, leading to floods that can escalate into disasters. Conversely, in the dry season, many rivers progressively dry up. The sustainability of water sources has attracted widespread attention from scholars. The data in this paper are from the 2013–2022 Shandong Statistical Yearbook, see S2.

Step 3. The coefficient of variation method was used to determine index weights, as shown in Table 2. Table 2 systematically organizes the calculations derived from the coefficient of variation method, providing a transparent and quantitative basis for the determination of index weights. The resulting weights play a pivotal role in shaping the overall evaluation of the sustainability of the water source under consideration.

Step 4. The combined weights are calculated, and the results are shown in Table 3. This table presents the results of the evaluation of various indicators using three different methods: the entropy value method, the coefficient of variation method, and the combination weighting method. Each row corresponds to a specific indicator, and the columns display the weights assigned to each indicator by the respective evaluation method.

Step 7. The coupling coordination degree between the three subsystems is calculated according to the coupling coordination degree model, which is shown in S3.

However, a pivotal shift occurred in 2018 when the coupling coordination degree reached its lowest point. In response, local governance initiatives sought to address this challenge by expediting the transformation and upgrading of the service industry. This strategic move resulted in a significant shift in the industrial structure from the previous ‘two, three, one’ configuration to a more balanced ‘three, two, one’ paradigm (Qiu et al. 2017). This restructuring aimed to alleviate the dissonance and enhance coordination among the social, economic, and ecological dimensions.

Despite these efforts, the coupling coordination degree witnessed a continuous decline after 2019, accompanied by an increase in the absolute deviation of the evaluation index. This trend highlights the intricate relationship between the three subsystems, where inhibiting factors within one subsystem impact the others. The data underscore a crucial insight – the absolute value of the deviation in the comprehensive evaluation index is inversely proportional to the coupling coordination degree. This implies that true harmony can only be achieved through mutual promotion and collective improvement.

The findings reveal that the ecological environment construction and socio-economic development in the Shandong water source area did not achieve synchronized progress. Instead, there is evidence of a reciprocal inhibition and influence between socio-economic development and ecological environment development. This suggests that the rapid socio-economic advancements in the region are intricately linked to the state of the ecological environment, emphasizing the need for a holistic approach to achieve sustainable and coordinated development.

For the sustainable and healthy development of the water source area of six or five rivers, the following aspects should be emphasized when carrying out ecological construction of the water source area: as the origin of six or five rivers in Xiajin County, Shandong Province, the implementation of the water transfer project has undoubtedly intensified the burden of ecological protection for the people of the water source area. For Xiajin County, which provides high-value ecosystem services and is poor and backward, ecological compensation can be provided by the ecological beneficiary area as a way to improve the sustainable development of people in the water source area.

In the social development factor, the urbanization level of the water source area should be improved. Increase the proportion of non-agricultural population in the total population and improve the living conditions of residents in the water source area. In terms of economic development factors, efforts should be made to increase farmers' income and local financial income; in terms of ecological environment factors, environmental pollution control needs to be further strengthened. Reduce the amounts of pesticides and chemical fertilizers used in agriculture and strictly control industrial waste gas and wastewater emissions.

Water source is an important ecological barrier of a region, and it is necessary to provide a scientific method for the evaluation of the sustainability of a water source. It has been proved that the method can effectively solve this problem. It also provides a reference for the sustainability evaluation of other water sources. Second, in view of the shortage of current methods, this paper proposes a method for combining the entropy value method and variation coefficient method, which lay a solid foundation for the determination of weight. Next, to address the shortcomings of the current method, this paper proposes a method that combines the entropy value method and the coefficient of variation method. A solid foundation is laid for the determination of weight. Finally, a study is conducted on the example of the South-North Water Transfer of Six or Five Rivers in Shandong, China, and the coupled coordination degree model is applied to the evaluation of the sustainable development capacity of water sources. The rationality and validity of the evaluation model in the evaluation of the sustainable development capacity of water sources were verified. It provides a new research idea for the evaluation of water sources. The issue of water source development has always been a focus of attention, but there is little literature on the study from the perspective of coupled social–ecological–economic coordination, and this paper attempts to contribute to this part. Despite the valuable insights gained in this study, certain limitations and gaps exist in our evaluation of water source sustainability. The current evaluation index system is hindered by a lack of hands-on experience in water source engineering projects. Additionally, limitations stemming from the researcher's experience and knowledge background are acknowledged.

To address these shortcomings, future research endeavors can focus on innovating the identification method for water source evaluation indexes. This innovation can contribute to a more comprehensive and robust evaluation framework. Furthermore, staying attuned to emerging evaluation methods is crucial, and conducting a comparative study of these methods can enhance the sophistication of our assessments. Improvements in data selection are essential for enhancing the representativeness of our findings. Future studies should aim for more diverse and scientifically rigorous data sources to ensure the accuracy of the evaluation model. As the field evolves, researchers should strive to refine the evaluation process, incorporating new methodologies and ensuring a more holistic understanding of water source sustainability.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.