Interactions Between SDG 6 and Sustainable Development Goals: A Case Study from Chenzhou City, China’s Sustainable Development Agenda Innovation Demonstration Area

Abstract

Achieving the United Nations 2030 Sustainable Development Goals (SDGs) is a critical global challenge. Ensuring the sustainable utilization of water resources has long been a key policy priority for the Chinese government, balancing economic growth with ecological conservation and advancing ecological civilization. Taking China’s sustainable development agenda innovation demonstration area Chenzhou as the object, this work focuses on SDG6 and examines the progress in sustainable water resource utilization from 2015 to 2022, evaluating three dimensions—water quantity, water environment, and water ecology. A comprehensive evaluation index system closely related to SDG6 was constructed to assess the sustainable development progress. Furthermore, the interactions between SDG6 and related SDGs were analyzed. The results show that (1) from 2015 to 2022, the SDG6 composite index has significantly increased over time, with the establishment of the demonstration area (2019–2022) more than twice compared to before (2015–2018), particularly in water environment and water quantity; (2) the SDG composite index and individual SDG indexes have shown a fluctuating upward trend, with an increase of about 89.74% after the establishment of the demonstration area (2019–2022) compared to before (2015–2018), with the most significant progress in the society dimension; and (3) there were significant synergy effects between the improvements in SDG6 and related SDGs. For each unit increase in SDG6, the overall level of related SDGs increased by 0.73 units, specifically, with particularly strong synergies between SDG2, SDG7, SDG9, and SDG11. This study not only provides scientific guidance for water resource management and policy optimization in Chenzhou and similar water resource-based cities but also offers valuable localized case studies, methodologies, and data to support the monitoring of urban sustainable development at a global scale.

1. Introduction

The United Nations 2030 Agenda for Sustainable Development has established 17 Sustainable Development Goals (SDGs) and 169 specific targets to monitor global progress in sustainable development in terms of the economy, society, and the environment, with SDG6 “clean water and sanitation” being a core goal [1]. Water resources are fundamental natural assets and strategic economic resources that underpin socioeconomic development. They play an essential role in food production, energy supply, health security, ecosystem service supply, and environmental sustainability [2]. However, under the combined pressures of global climate change and human activities, water security challenges, such as shortages, pollution, and ecological damage, have become critical barriers to sustainable development [3]. Currently, 26% of the global population struggles to access safe drinking water. Furthermore, the number of urban residents affected by water shortages is expected to rise from 930 million in 2016 to 1.7–2.4 billion in 2050. As a sustainability framework for interconnected social–ecological systems, achieving the SDGs encompasses more than merely accomplishing individual targets. Complex interactions exist among the SDGs, manifesting as synergies (where two SDGs improve or decline together) or trade-offs (where one SDG improves, while the other undermines) [4]. These interactions significantly influence the feasibility and effectiveness of achieving the SDGs. Therefore, a comprehensive understanding of synergies and trade-offs is essential for setting priorities, assessing goal feasibility, enhancing policy coherence, optimizing resource allocation, and promoting systematic progress toward sustainability [5].

The interactions between SDGs are key to achieving global sustainable development strategies. Understanding these interactions is crucial to prioritizing SDGs and accelerating overall progress. Numerous studies have explored SDG interactions [5]. Methodologically, these studies are typically based on qualitative evaluations using expert knowledge or official documents [6,7] and quantitative analyses based on SDG indicator data [8,9]. Common quantitative methods include Pearson correlation coefficients [10], Spearman correlation analysis [11], linear mixed-effects models [12], multivariate analysis [13], and network analysis [10]. Among these, Pearson and Spearman correlation coefficients, as two classical statistical methods for analyzing the interaction between variables, are widely used to reveal interactions among in SDGs research. In terms of content, existing studies on SDG synergies and trade-offs focus on various aspects, such as relationships across all SDGs, multi-goal interactions [14], and connections between specific indicators within a single goal [15]. These analyses span multiple scales, including global, national, and regional levels [13]. Research findings suggest that SDG interactions vary depending on factors such as a country’s economic development level, geographical location, and demographic characteristics, including gender, age, and residence [16]. In most countries/regions (e.g., 16 countries in the Asian water tower region, European Union countries, etc.), there are significant interactions among most indicators, with synergies generally outweighing trade-offs [17,18]. To maximize progress across the SDGs by 2030, priority should be given to SDG3 (good health and well-being), SDG4 (quality education), SDG6 (clean water and sanitation), SDG11 (sustainable cities and communities), and SDG13 (climate action) [19]. Moreover, SDG interactions exhibit significant variations across provinces within the same country. For instance, trade-offs between SDG13 (climate action) and SDG5 (gender equality) observed in 19 Chinese provinces align with national-level trends. Meanwhile, in SDG1 (no poverty) and SDG6 (clean water and sanitation), 24 provinces show the strongest synergies, consistent with the national perspective [5,13].

Current research on the Sustainable Development Goals (SDGs) primarily focuses on global and national scales. While these studies provide insights into overall SDG progress, they often fail to capture the complexity and specificity of SDG interactions at the urban scale. As key intersections of economic, social, and environmental systems, cities exhibit significant variations in their SDG implementation pathways due to differences in resource endowments and development types [20]. Therefore, an in-depth investigation of SDG interactions at the urban scale is essential for formulating more targeted and effective sustainable development policies [21]. Existing studies have explored the SDG implementation practices of economic hub cities [22] and arid-region energy cities [23]. However, a systematic analysis of the sustainable development pathways for water resource-based cities remains lacking. In addition, the temporal evolution of SDG interactions has received relatively little attention. City socioeconomic conditions, technological advancements, and public awareness of sustainable development are dynamic and change over time. These changes may significantly influence the interactions among SDGs. Therefore, continuous monitoring is critical for capturing the dynamic progress of SDGs and informing macro policy adjustments [13].

China is one of the 13 most water-scarce countries in the world, where issues related to water quantity, water environment, and water ecology are emerging as critical constraints on economic and social development as well as ecological and environmental protection. Conducting sustainability assessments of water resources is of practical significance [24]. Existing research shows that SDG2, SDG1, and SDG6 have the highest priority at the global and regional levels [25]. Numerous studies have explored the interactions between SDGs [26,27,28], revealing strong synergies between SDG6 and other SDGs, including SDG1 (no poverty), SDG2 (zero hunger), SDG3 (good health and well-being), SDG7 (affordable and clean energy), SDG14 (life below water), and SDG15 (life on land) [14,29]. The World Water Assessment Program further emphasizes the fundamental role of water resources in sustainable development, highlighting the critical importance of achieving SDG6. However, such studies did not involve SDG6 and SDG6’s specific indicators’ interaction with other SDGs in a single target system, and the interaction was not fully revealed. SDG6 comprises eight targets and 11 indicators, which can be categorized into the following four dimensions: water quantity (SDG6.1, SDG6.4), water environment (SDG6.2, SDG6.3), water ecology (SDG6.6), and water management (SDG6.5, SDG6.a, SDG6.b). Socioeconomic losses due to inadequate access to drinking water and sanitation services remain substantial [30], making SDG6.1 (drinking water), SDG6.2 (sanitation), and SDG6.6 (water-related ecosystems) particularly critical [31,32,33]. Although UN Water organizes the global monitoring of SDG6 progress, national-scale data collection is often hindered by infrastructure limitations and inadequate data management systems, resulting in insufficient data for subnational-level policymaking and planning [34]. Consequently, comprehensive assessments of SDG6 remain relatively scarce. Therefore, systematic and comprehensive evaluations of SDG6 progress, with a focus on SDG6 as a core goal, and detailed analyses of the interactions between specific SDG6 indicators and related SDGs are still worth further attention. Therefore, this study takes the national sustainable development innovation demonstration area in Chenzhou city as the research object, focuses on the sustainable utilization of water resources (SDG6), and attempts to answer the following questions: (1) Will the development of a single SDG affect the progress of other related SDGs? (2) Can improving the sustainable utilization of water resources promote the sustainable socioeconomic development of a region?

The Chinese government has established 11 sustainable development innovation demonstration areas to take the lead in promoting the implementation of the United Nations 2030 sustainable development agenda. Among these, Chenzhou, a typical water resource-based city, once faced significant challenges in water resource utilization and water ecological environment protection. However, in recent years, the city has made notable progress in the sustainable use of water resources, contributing to its economic and social transformation. This study takes the national sustainable development innovation demonstration area in Chenzhou city as the research object. It aims to explore the progress made by the city in the sustainable utilization of water resources from 2015 to 2022. Furthermore, it compares the effectiveness before and after the establishment of the demonstration area. Finally, the study analyzes the trade-off and synergistic effects with the multiple SDGs.

The main contributions of this study are as follows: (1) This study systematically assesses the progress of SDG6 in Chenzhou city from 2015 to 2022 across three dimensions: water quantity, water environment, and water ecology. (2) It analyzes the evolution trends of SDG6 and its closely related SDGs before and after the establishment of the demonstration area, highlighting the impacts of policy interventions. (3) It explores the trade-offs and synergies between SDG6 and related SDGs, providing a quantitative analytical framework for the sustainable development of water resource-based cities. This study not only offers scientific guidance for water resource management and policy optimization in Chenzhou and similar cities but also serves as a practical reference for the localization, monitoring, and evaluation of SDGs in urban contexts. The proposed research framework, data, and methodology can provide valuable insights for other cities, facilitating multi-objective synergies and advancing the achievement of global sustainable development goals.

2. Materials and Methods

2.1. Overview of the Study Area

Chenzhou city is located in the southeast of Hunan Province, China (Figure 1), with a regional area of 19,317 km². The city is home to three major river systems, the Xiangjiang River, the Ganjiang River, and the Beijiang River, which belong to the Yangtze and Pearl River Basins, with a total water resource of 16.44 billion m³. Dongjiang Lake, one of the largest and most strategic drinking water sources in Hunan Province, is also situated in this region. However, due to the lack of surface water resources in the early urban areas, insufficient groundwater recharge, and the uncontrolled exploitation of mineral resources over the years, the region’s water quality and ecological environment have suffered significant damage. With the rapid pace of urbanization, the city’s water supply capacity became severely inadequate, making Chenzhou a typical example of a water-scarce city in China. In 2019, Chenzhou was designated as a national sustainable development agenda innovation demonstration area with the theme “Sustainable Utilization and Green Development of Water Resources”. It focuses on addressing issues such as low water resource utilization efficiency and heavy metal pollution and has formulated and implemented a series of protection policies and governance measures around “water protection, water treatment, water use, and water conservation”, promoting the coordinated development of a water-ecological environment, economy, and society. It provides practical experience for implementing the United Nation 2030 sustainable development agenda mainly based on SDG6 and is a typical city for promoting economic and social transformation and development through the sustainable utilization of water resources.

2.2. Data Source

The data used in this study include statistical data, geoscience big data, and network data, covering the period from 2015 to 2022. The remote sensing data we utilized were primarily derived from Landsat5-TM and Landsat8-OLI satellite data, encompassing Chenzhou city from 1987 to 2022 with a temporal resolution of 16 days. Shoreline monitoring data of Dongjiang Lake were collected in the years 2015, 2017, 2020, and 2022. The resolution of the digital elevation model (DEM) and land use data are 250 m and 30 m, respectively. During the data preprocessing stage, we conducted atmospheric correction, geometric correction, missing data processing (using time-series interpolation), data smoothing (moving average method), and data resampling (to 30 m), among other steps. The main information is shown in

Table 1. Main data information.

Data Type	Main Content	Data Information and Purpose	Source
Statistical Data	2015–2022 Industry Sector Statistical Data	For industry sector analysis	Various Functional Departments of Chenzhou City
	2015–2022 “Chenzhou Statistical Yearbook”	Provides socioeconomic data of Chenzhou city	Chenzhou Municipal Bureau of Statistics
Geoscience Big Data	2015, 2017, 2020, 2022 Monitoring Data of River and Lake Shorelines in Chenzhou City	Used for extracting river and lake shorelines of Chenzhou city	Gaofen-1 and Gaofen-6 Satellite Imagery
	250 m Resolution Digital Elevation Data (DEM)	Used for obtaining terrain data of Chenzhou city	Geospatial Data Cloud
	30 m Resolution Land Use Data	Used for obtaining land use data of Chenzhou city	Geospatial Data Cloud
	Landsat5-TM and Landsat8-OLI Satellite Remote Sensing Data of Chenzhou City from 1987 to 2022	Monitoring the spatial and temporal distribution of Dongjiang Lake transparency	Geospatial Data Cloud
Network Data	37 Policy Documents on Water-Related Issues in Chenzhou City from 2015 to 2022, including notices, measures, work plans, opinions, decisions, etc.	Analyzing the orientation of policy documents	Official Website of Chenzhou Municipal Government

.

2.3. Methods

2.3.1. The Relationship Between SDG6 and Other SDGs

The sustainable utilization of water resources is central to achieving sustainable economic, social, and ecological development. SDG6 plays a pivotal role in all three dimensions, fostering synergies, while also presenting potential trade-offs (Figure 2). In the economy dimension, SDG6 promotes economic growth by ensuring clean water resources and stable water supplies, which are fundamental for agricultural cultivation (SDG2) and industrial production (SDG9). Additionally, water resource management, such as water infrastructure construction, water supply, and sewage treatment services, contributes to the development of the clean energy industry (SDG7) and creates employment opportunities (SDG8). The research and application of water-saving and recycling technologies further enhance resource utilization efficiency (SDG12) and drive industrial transformation and innovation development (SDG9). However, increased investment in achieving SDG6 may strain local government budgets (SDG17), potentially limiting investment in other SDG areas. In the society dimension, improving SDG6 is critical to preventing the spread of diseases, safeguarding public health (SDG3), and promoting water equity between urban and rural areas (SDG10). Nevertheless, achieving SDG6 could lead to disparities in resource allocation among regions and social groups, exacerbating regional development imbalances (SDG10). Furthermore, cultural tradition concepts and community lifestyles (SDG11) may hinder the effective implementation of SDG6. In the ecology dimension, SDG6 serves as a foundation for maintaining ecosystem stability and balance, supporting ecosystem service functions, and promoting ecological restoration (SDG15). However, human activities, such as agricultural excessive reclamation (SDG2), industrial pollution emissions (SDG11, SDG12), disorderly expansion of urbanization (SDG11), and climate change (SDG13), place significant pressure on water resources and the ecological environment (SDG6). At the same time, ensuring ecological water use may also affect regional energy production (SDG7) and economic development (SDG2, SDG9), highlighting the need to balance protection and development.

2.3.2. Analysis Process

Analysis of the sustainable utilization of water resources from the dimensions of water quantity, water environment, water ecology, and water management provides more valuable insights [35]. Similarly, SDG6 also evaluates water resource systems across these four dimensions. The SDGs cover various aspects of sustainable development, including economy, society, and ecology dimensions [36], and effectively characterize the level of sustainable development in cities. Using multi-source data, this study calculates the composite index of SDG6 and eight related SDGs in Chenzhou city through a comprehensive weighted index method to evaluate the progress of these SDGs. Spearman correlation analysis is employed to explore the interactions between SDGs. Based on this analysis, the study further investigates the impact of policy guidance and protective measures on SDG progress and their synergies (Figure 3).

2.3.3. Construction of the Evaluation Index System

In order to comprehensively evaluate the achievements of Chenzhou city in the sustainable utilization of water resources, a multi-dimensional SDG6 index system was built from the following three aspects: water quantity, water environment and water ecology, including 9 indicators (

Table 2. SDG6 progress evaluation index system for sustainable utilization of water resources.

Dimension	Indicator	Indicator Description	Units	Weight	Attribute
Water quantity (0.4815)	SDG6.1.1 (0.11140)	Rural drinking water safety guarantee rate	%	0.4039	+
		Public water penetration rate	%	0.5961	+
	SDG6.4.1 (0.4354)	Water consumption efficiency	m3/CNY 10,000	0.4354	-
	SDG6.4.2 (0.4532)	Comprehensive water consumption per capita	m3	0.4532	-
Water environment (0.2541)	SDG6.2.1 (0.3945)	Density of public toilets	Seats/km2	0.3945	+
	SDG6.3.1 (0.1465)	Urban domestic sewage treatment rate	%	0.5095	+
		Industrial wastewater discharge intensity per CNY 10,000 of industrial added value	Tons/CNY 10,000	0.4905	-
	SDG6.3.2 (0.4590)	Proportion of surface water meeting or better than Class III water bodies	%	0.4590	+
Water ecology (0.2644)	SDG6.6.1 (1.000)	Water-related ecosystem area	ha	1.0000	+

Note: “+” represents a positive indicator, “-” represents a negative indicator.

). Additionally, considering the strong interconnections between water resources and multiple SDGs, 19 specific indicators of 8 SDGs closely related to water resources were selected (

Table 3. Index system of SDGs related to water resources.

Dimension	Goal	Target	Indicator	Indicator Description	Units	Weight	Attribute
Economy	SDG8	SDG8.1 (0.4342)	SDG8.1.1	GDP growth rate per capita	/	0.4342	+
		SDG8.4 (0.5658)	SDG8.4.2	Per capita domestic material consumption	CNY/person	0.5658	+
	SDG9	SDG9.2 (0.5371)	SDG9.2.2	Industrial added value above designated size	CNY 100 million	0.5371	+
		SDG9.4 (0.4629)	SDG9.4.1	CO2 emissions per unit of GDP	Kg/10,000	0.4629	-
	SDG12	SDG12.2 (0.5686)	SDG12.2.2	Total consumer goods	CNY 100 million	0.5686	+
		SDG12.4 (0.4314)	SDG12.4.2	Comprehensive utilization rate of general industrial solid waste	%	0.4314	+
Society	SDG2	SDG2.1 (0.3666)	SDG2.1.1	Annual grain output	15 kg/ha	0.3666	+
		SDG2.4 (0.3103)	SDG2.4.1	Grain sown area	666.67 ha	0.3103	+
		SDG2.a (0.3231)	SDG2.a.1	Investment in primary industry	CNY 100 million	0.3231	+
	SDG3	SDG3.2 (0.6412)	SDG3.2.1	Mortality rate for children under age 5	/	0.6412	-
		SDG3.8 (0.3588)	SDG3.8.1	Participation rate of basic medical insurance for urban and rural residents	%	0.3588	+
	SDG7	SDG7.1 (0.5252)	SDG7.1.1	Percentage of renewable energy power generation	%	0.6004	+
			SDG7.1.2	Gas penetration rate	%	0.3996	+
		SDG7.2 (0.4748)	SDG7.2.1	Energy consumption per CNY 10,000 of GDP	Tons of standard coal/CNY 10,000	0.4748	-
	SDG11	SDG11.6 (0.3102)	SDG11.6.1	Harmless treatment rate of domestic garbage	%	0.5086	+
			SDG11.6.2	City fine particulate matter PM2.5 concentration	μg/m3	0.4914	-
		SDG11.7 (0.6898)	SDG11.7.1	Per capita green area	m2/person	0.6898	+
Ecology	SDG15	SDG15.1 (1.0000)	SDG15.1.1	Forest coverage	%	0.6317	+
			SDG15.1.2	Area of protected areas as percentage of land area	%	0.3683	+

Note: “+” represents a positive indicator, “-” represents a negative indicator.

). These goals are interdependent on the sustainable development of water resources and together constitute a comprehensive evaluation framework, which can comprehensively reflect the progress of the sustainable development of water resources and related fields in Chenzhou city. The weights for dimensions, targets, and indicators presented in Table 2 and Table 3 were all calculated using the method described in Section 2.3.4, ensuring an objective and systematic weighting process. The calculation follows a bottom-up hierarchical aggregation approach, where weights are progressively aggregated from smaller dimensions to broader dimensions, ensuring consistency and logical coherence in the evaluation framework. Based on the impact of indicators on sustainable development, indicators are divided into the following two types: “+” and “-”. “+” indicates that higher indicator values have a positive contribution to sustainable development, while “-” indicates that higher indicator values have a negative impact on sustainable development.

2.3.4. SDGs Composite Index

The entropy method is employed to objectively determine the weights of evaluation indicators, reflecting the relative importance of each indicator in the comprehensive evaluation system. Subsequently, the weighted comprehensive index method is applied to calculate the composite index for each target. The process consists of the following steps:

First, the data are standardized using the following Formulas (1) and (2):

$$\mathrm{For}\mathrm{positive}\mathrm{indicators}:X_{it}={\displaystyle \frac{x_{it}-\min x_i}{\max x_i-\min x_i}}$$

(1)

$$\mathrm{For}\mathrm{negative}\mathrm{indicators}:X_{it}={\displaystyle \frac{\max x_i-x_{it}}{\max x_i-\min x_i}}$$

(2)

where X_it represents the standardized value of the indicator year t, with i ranging from 1 to n and t ranging from 2015 to 2022; x_it represents the original value of the indicator year t; and minx_i and maxx_i represent the minimum and maximum values of the indicator year.

Secondly, to determine the index weight, the steps are as follows:

(1)

Calculate the characteristic proportion of the index in year t:

$$P_{it}={\displaystyle \frac{X_{it}}{{\displaystyle \sum X_{\mathit{it}}}}}$$

(3)

(2)

Calculate the entropy value of the indicator in year t:

$$E_i=-{\displaystyle \frac{1}{\ln (m)}}\ast {\displaystyle \sum _{i=1}^m{P}_{it}\ln (P_{it})}$$

(4)

(3)

Calculation of difference coefficient:

$$g_i=1-E_i$$

(5)

(4)

Determine the entropy weight:

$$W_i={\displaystyle \frac{g_i}{{\displaystyle \sum _{i=1}^n(1-g_i)}}}$$

(6)

where P_it represents the characteristic proportion of the indicator i in year t; E_i represents the entropy value of the indicator i; m represents the total number of indicators; g_i represents the difference coefficient of the indicator i; W_i represents the weight of the indicator i; and a larger W_i indicates that the indicator i is more important.

Finally, the scores of each target are calculated by the comprehensive weighted index method:

$$I={\displaystyle \sum _{i=1}^n{X}_{it}{W}_i}$$

(7)

where I represents the comprehensive index of SDGs.

2.3.5. Interactions Between SDGs

The Spearman correlation coefficient method is used to measure the interactions between SDG6 and related SDGs. The positive value represents synergy, and the negative value represents trade-off. The absolute value of the correlation coefficient represents the interaction strength. Based on the correlation values, synergies and trade-offs are classified as follows: weak synergy effect (0.6 < p < 0.7), general synergy effect (0.7 < p < 0.8), and strong synergy effect (p > 0.8). The trade-off effects were subdivided into weak trade-offs (−0.7 < p < −0.6), general trade-offs (−0.8 < p < −0.7), and strong trade-offs (p < −0.8).

$$P(x,y)={\displaystyle \frac{n{\displaystyle \sum x_i{y}_i}-{\displaystyle \sum x_i{y}_i}}{\sqrt{n{\displaystyle \sum x_i^2-({\displaystyle \sum x_i^2{)}^2}}}\times \sqrt{n{\displaystyle \sum y_i^2-({\displaystyle \sum y_i^2{)}^2}}}}}$$

(8)

Here, P (x, y) represents the correlation coefficient between indicator x and indicator y.

3. Results

3.1. Evaluate the Progress of SDG6 in Three Dimensions

From 2015 to 2022, the SDG6 composite index for Chenzhou city increased significantly, rising from 0.06 to 0.64 (Figure 4 and Figure 5). Specifically, the index improved from 0.35 before the establishment of the demonstration area (2015–2018) to 0.72 after the establishment (2019–2022), representing an increase of over 100%. The water quantity index showed a fluctuating upward trend, increasing by more than 1.8 times after the establishment of the demonstration area compared to the period prior. The rural drinking water safety assurance rate (SDG6.1.1) reached 100%, while the public water penetration rate (SDG6.1.1) rose to 97.24%. Water consumption efficiency (SDG6.4.1) decreased by 45.56%, and comprehensive water consumption per capita (SDG6.4.2) exhibited a notable fluctuating downward trend. These results indicate that Chenzhou city has achieved significant progress in optimizing water resource allocation and promoting efficient utilization. The water environment index also experienced considerable improvement, increasing by approximately 67% after the establishment of the demonstration area compared to the period prior. The density of urban public toilets (SDG6.2.1) increased by 162.02%, reflecting the significant effectiveness of the “toilet revolution” policy implemented in the region. Water quality (SDG6.3) showed marked improvement, particularly through the reduction in industrial wastewater discharge intensity per CNY 10,000 of industrial added value, which decreased by 68.89%. In terms of water ecology, the water-related ecosystems area (SDG6.6.1) exhibited a fluctuating upward trend, increasing by approximately 70.59% after the establishment of the demonstration area compared to the period prior. In summary, the Chenzhou city has made substantial progress in the sustainable utilization of water resources, demonstrating significant advancements across water quantity, water environment, and water ecology dimensions.

3.2. Evaluate the Progress of Related SDGs

From 2015 to 2022, the annual average scores of 19 SDG indicators related to SDG6 in Chenzhou city ranged from 0.41 to 0.79, and 9 indicators were higher than the overall average score (0.57), accounting for about half of the total indicators. The distribution of scores across the indicators was relatively balanced (Figure 6). After the establishment of the demonstration area (2019–2022), the average score for each indicator (0.75) is about twice compared to the period before the area’s establishment (2015–2018), which had an average score of 0.38. Specifically, the scores of indicators in the society dimension are slightly higher than those in the economy and ecology dimensions. Among these, indicators such as the harmless treatment rate of domestic garbage (SDG11.6.1), the comprehensive utilization rate of general industrial solid waste (SDG12.4.2), and the per capita green area (SDG11.7.1) score higher. In comparison, the percentage of renewable energy power generation (SDG7.1.1) and the mortality rate for children under the age of five (SDG3.2.1) score lower.

From 2015 to 2022, the SDG composite index and individual SDG indexes showed a fluctuating upward trend, and the composite index increased from 0.30 to 0.84. Following the establishment of the demonstration area in 2019, the composite index increased by approximately 89.74% compared to the pre-establishment period (Figure 7). The linear regression analysis of the composite index reveals a distinct shift before and after the establishment of the demonstration area. From 2015 to 2018, the steeper slope indicates a period of rapid growth. After 2019, the slope is relatively gentle, reflecting a stabilization in progress. This shift suggests that initial policy implementation drove quick progress, while the later phase marks the consolidation of the effectiveness of policy measures. The trend highlights the transition from rapid advancement to steady development in SDG implementation. During this period, significant improvements were observed in the indexes for SDG7, SDG9, and SDG12, which increased by 551.25%, 406.50%, and 354.16%, respectively. These results indicate that the Chenzhou city has made substantial progress in energy efficiency, industrial production, sustainable production, and consumption. However, the COVID-19 pandemic in 2020 caused a notable decline in the SDG composite index. Over time, the score gap between the various SDGs has gradually narrowed, with a trend accelerating significantly after the establishment of the demonstration area in 2019. This indicates that, under the comprehensive management policies for sustainable development in the demonstration area, the level of coordinated development among the SDGs in Chenzhou city is improving.

3.3. A Graded Evaluation of SDG6 and Related SDG Progress

To assess the sustainable development of SDG6 before and after the establishment of the demonstration areas, the SDG6 indicators are classified into three levels based on their scores using the equal interval method: level 1 [0, 0.33], level 2 (0.33, 0.67], and level 3 (0.67, 1] (Figure 8). Policy measures have a significant impact on the sustainable utilization of water resources (SDG6), demonstrating differential effects across different dimensions. Specifically, from 2015 to 2018, level 2 indicators dominated (77.78%), while from 2019 to 2022, level 3 indicators predominated (77.78%), reflecting a substantial improvement in the overall level of sustainable development. Before and after the establishment of the demonstration area, the water quantity indicators improved from levels 1 and 2 to levels 2 and 3, with an increasing proportion of indicators in higher levels, reflecting the sustainability of improvements in water quantity. The water environment indicators have been raised from level 2 to level 3, indicating significant effectiveness in water environment governance. Although water ecology indicators remained at level 2, their overall values have improved. The policy measures in the demonstration area have yielded significant results in enhancing the sustainable utilization of water resources, particularly in water environment governance and water quantity improvement. However, due to limitations related to urbanization expansion, the water ecosystem indicators have remained stable in the region. The effects of policy measures vary across different dimensions of water resources, suggesting the need for optimized governance strategies to achieve more comprehensive sustainable development.

To assess the sustainable development of related SDGs before and after the establishment of the demonstration areas, the related SDGs indicators are classified into five levels based on their scores using the equal interval method: level 1 [0, 0.2], level 2 (0.2, 0.4], level 3 (0.4, 0.6], level 4 (0.6, 0.8], and level 5 (0.8, 1] (Figure 9). Policy measures have a significant driving effect on sustainable development, with differentiated impacts across various dimensions. In terms of specific indicators, from 2015 to 2018, levels 1 and 2 were predominant (63.16%), whereas from 2019 to 2022, levels 4 and 5 became the dominant categories (78.94%), indicating a significant improvement in the overall level of sustainable development. From different levels, among the indicators scoring above 0.6 (levels 3 and 4), the proportion of indicators in the economy, society, and ecology dimensions was equal from 2015 to 2018. However, from 2019 to 2022, the proportion of society dimension indicators was 1.8 times that of the economy dimension. Specifically, in the society dimension, the proportion of indicators scoring above 0.6 increased from 9.09% in 2015–2018 to 81.81% in 2019–2022, while those scoring below 0.4 (levels 1 and 2) dropped from 63.63% to 0, indicating a notable improvement in social sustainable development. A similar trend was observed in the economy dimension, where the proportion of indicators above 0.6 increased from 16.67% in 2015–2018 to 83.33% in 2019–2022, and those scoring below 0.4 fell from 66.66% to 0. Across all dimensions, society and economy indicators were mostly at levels 1 to 4 in 2015–2018, while ecology indicators were primarily at levels 1 and 4. By 2019–2022, society and economy indicators had improved to levels 3 to 5, and ecology indicators were at levels 2 and 5. The comprehensive management policy for sustainable development in the demonstration area has effectively promoted the enhancement of various SDGs, particularly achieving breakthrough progress in the society dimension, significant improvements in the economy dimension, and stability in the ecology dimension.

3.4. Interactions Between SDG6 and Related SDGs

The linear fitting method was employed to analyze the comprehensive impact of SDG6 on related SDGs. The results revealed that the impact coefficient of SDG6 on related SDGs was 0.73, with a significant positive correlation at the 1% level. This indicates that improvements in the sustainable utilization of water resources in Chenzhou city had a notable positive influence on the achievement of related SDGs. Specifically, for every one-unit increase in SDG6, the combined level of related SDGs increased by 0.73 units (Figure 10).

The Spearman correlation coefficient method was further utilized to evaluate the synergies and trade-offs between SDG6 and related SDGs. The analysis revealed a synergistic relationship between the SDG6, SDG6 dimensions, SDG6 indicators, and related SDGs (Figure 11). Among these, significant positive relationships were observed between SDG6 and SDG2, SDG7, SDG9, and SDG11, with strong synergies identified between SDG6 and SDG2, SDG9, and SDG11 (Figure 11a). From a dimensional perspective, the strongest synergies were observed between water quantity, water environment, and related SDGs. Water quantity exhibited general synergies with SDG2, SDG3, SDG7, and SDG9 and strong synergy with SDG11, all of which were statistically significant. Water environment showed general synergies with SDG3, SDG7, and SDG8 and significant strong synergies with SDG9, SDG11, and SDG12. Water ecology exhibited a significant strong synergy with SDG12. From the perspective of specific indicators (Figure 11b), substantial synergies were identified between SDG6.1 (drinking water), SDG6.2 (adequate sanitation and hygiene), SDG6.3 (wastewater treatment and water quality), SDG6.4.1 (water-use efficiency), and related SDGs, particularly with SDG11. Overall, these findings indicate that the sustainable utilization of water resources in Chenzhou city has significantly contributed to advancing the sustainable development of clean energy utilization, industrial production, urban air quality improvement, public space enhancement, and sustainable consumption.

4. Discussion

4.1. Water Resources Management Policies and Governance Measures Initiatives as Drivers of SDG6 Progress

“Value is everywhere”. Evaluation, as a systematic and scientific approach, plays a critical role in identifying challenges and guiding governance and management decisions in modern society. Identifying problems through evaluation in various fields serves as the cornerstone of good governance. This study examines the progress of SDG6 in Chenzhou city from 2015 to 2022 and its interactions with related SDGs. While this study provides an in-depth analysis of SDG6 in Chenzhou city, the water management dimension indicators in SDG6 could not be fully evaluated due to data limitations. The findings reveal that the SDG6 composite index increased significantly during this period, with particularly pronounced improvements after the establishment of the demonstration area (2019–2022). This trend underscores the effectiveness of local government policies and measures in water resources management. A text analysis of 37 water resource-related policy documents from 2015 to 2022 highlights the primary focus areas of these policies: water quantity (water conservation and drinking water safety), water environment (urban sewage treatment, water source protection, and water environment quality), and water ecology (ecological protection, mine restoration, and ecological civilization). These policies have yielded substantial improvements in water resources management, enhanced water environment quality, and promoted the transformation of Chenzhou from a resource-based city to an eco-friendly development model. Specifically, the water quantity index exhibited a fluctuating upward trend, with increasing rural drinking water safety assurance rates and public water penetration rates (SDG6.1.1), alongside a notable reduction in water consumption efficiency (SDG6.4.1). These advancements are due to Chenzhou’s development orientation of “sustainable utilization and green development of water resources”, the continuous improvement in the system of total water consumption and quota control, and the comprehensive construction of a water-saving society. Currently, 285 water-saving units at or above the county level have been built, enabling the rational allocation and efficient utilization of water resources across domestic, industrial, and ecological sectors. The water environment index also showed significant improvement. Through measures such as constructing sewage treatment facilities, enhancing sewage collection networks, and regularly monitoring water quality, the urban domestic sewage treatment rate has exceeded 90% in recent years, leading to substantial improvements in water quality. Similarly, the water ecology index demonstrated a general upward trend despite fluctuations. A remote sensing analysis of river and lake shorelines and water transparency in Chenzhou showed that the length and area of river and lake shorelines increased between 2015 and 2022. Notably, Dongjiang Lake’s water transparency, ranging from 1.8 to 3.5 m, has significantly improved over the past 30 years, with an average annual increase of approximately 3 cm. These improvements highlight the success of key initiatives, such as Dongjiang Lake protection, Shisanwan mining area regulation, Yangxi River remediation, and Yangtian Lake grassland restoration. Despite these achievements, combined with the actual investigation, the growth potential of water-related ecosystem area in the water ecology dimension in the future is limited. Therefore, the continuous promotion of water quantity and water environment management policies is essential to safeguard these hard-won achievements after the establishment of the demonstration area. Further efforts are needed to sustain progress in the sustainable utilization of water resources and to drive additional advancements in SDG6.

Similar to Chenzhou city, Chengde city is a national sustainable development innovation demonstration area and a key water source for the Beijing–Tianjin region. In the past, industrialization, agriculture, and urbanization posed significant challenges to its water quantity, environment, and ecology. Recently, Chengde has implemented policies to enhance water security, strengthen environmental protection, and promote ecological restoration. These efforts have led to continuous improvements in water ecology and contributed to sustainable socioeconomic development. Compared with Chenzhou, the experience of Chengde provides a valuable comparative case. The demonstration area policy in Chenzhou mainly focuses on the efficient utilization of water resources, while Chengde emphasizes its ecological protection responsibility as an important water source in the Beijing–Tianjin region [37]. Both cities have made significant progress in sustainable water management, highlighting the impact of policy support on ecological restoration and economic sustainability. However, their distinct regional positioning and development paths have resulted in different policy priorities. This contrast offers useful insights for other regions in designing tailored water resource management strategies.

4.2. The Promotion of SDG6 Has Effectively Promoted the Overall Progress of Related SDGs

In the economy, society, and ecology dimensions, Chenzhou city has achieved significant improvements in the SDG composite index and related SDGs, with SDG7, SDG9, and SDG12 showing the largest increases. This is consistent with the trend of significant SDG progress at the national level reflected in the China’s Progress Report on Implementation of the 2030 Agenda for Sustainable Development (2023) and related studies [38,39]. The growth of SDG7 benefits from advancements in renewable energy and the optimization of the energy consumption structure. Chenzhou has focused on building a renewable energy-based power system, expanding non-fossil energy generation, and promoting green technologies and lifestyles. These efforts have significantly reduced energy costs, while supporting sustainable economic and social development. The improvement in SDG9 is driven by the development of green aquaculture and the modernization of infrastructure. Chenzhou has leveraged its abundant water resources to foster water-related industries, such as cold-water fisheries, hot spring tourism, water supply projects, and bottled water production, thereby contributing to industrial structure optimization. Additionally, the adoption of intelligent and digital water resource management systems has enhanced efficiency and provided strong support for the growth of the SDG9 index. The rise in the SDG12 index is closely tied to the transformation of production and consumption patterns. The strict implementation of dual-control policies on total water consumption and water use intensity has significantly reduced water resource waste and pollution. Furthermore, initiatives such as mine pollution remediation, green mine construction, and advocacy for environmentally friendly production and consumption practices have encouraged efficient resource utilization and recycling, further boosting the SDG12 index. The significant growth in the SDG composite index reflects Chenzhou’s coordinated progress in economic, social, and ecological development, alongside its achievements in advancing SDG6. Water resource management policies in the demonstration area have proven highly effective. Despite a temporary decline in SDG indexes during the COVID-19 pandemic, the rapid subsequent recovery underscores the resilience and adaptability of Chenzhou city to respond to social risks. Through the sustainable utilization and protection of water resources, Chenzhou city has successfully driven economic and social transformation, demonstrating an effective path for valuing water ecological products. This success exemplifies China’s ecological civilization philosophy of “lucid waters and lush mountains are invaluable assets” and provides a valuable reference for other cities and regions seeking to overcome resource and environmental constraints and path dependency in development.

4.3. Significant Synergies Exhibit Between SDG6 and Related SDGs

Water is the source of life, the foundation of ecology, and the key to production. The characteristic of “water benefits all things without contending” reflects the core position of SDG6 among all SDGs [40]. SDG6 has the highest priority globally and regionally, not only ensuring the basic survival needs of human beings but also helping the realization of other SDGs [25]. This study confirms significant synergies between SDG6 and related SDGs, particularly with SDG2, SDG7, SDG9, and SDG11, aligning with previous research findings [14,41]. There are usually more synergies between SDG6 and related SDGs than trade-offs [42], but this does not mean that trade-offs can be underestimated. For example, in some cases, measures taken to achieve SDG6 may have a certain trade-off effect on SDG14 [28]. Therefore, it is essential to carefully consider these potential trade-offs and complexities during policy formulation and implementation to ensure that the overall impact of the policies is optimized. These strong synergies highlight the critical importance of sustainable water resource management in advancing economic, social, and ecological sustainability. Among these, the synergy between SDG6 and SDG2 is the most prominent [43], with the water quantity dimension showing the strongest synergies with SDG2. Scientific and efficient water resource utilization enhances water quality, ensures food security, and improves agricultural productivity [28]. The water environment dimension exhibits strong synergies with most SDGs, with synergy indexes exceeding 0.5. For example, increasing urban sewage treatment rates improves water quality, thereby reducing health risks (SDG3), fostering sustainable cities and communities (SDG11), ensuring irrigation water availability (SDG2), and promoting resource efficiency (SDG12) [44]. Furthermore, the synergy between the water ecological dimension and SDG12 is particularly strong. Improvements in SDG12 reduce the consumption of natural resources, thereby protecting water-related ecosystems from encroachment [28]. Specifically, access to safe drinking water (SDG6.1), enhanced water use efficiency (SDG6.4), and increased water pollution treatment rates (SDG6.3) are critical measures for meeting water needs across life, production, and ecological dimensions. These measures also improve public well-being and support sustainable city development. Therefore, Chenzhou city should fully consider the interactions between different SDGs when designing and implementing policies, explore the potential synergies [25], and amplify the combined effects of policies related to protection and development to achieve more efficient and comprehensive sustainable development.

4.4. The Trade-Offs Between SDG6 and Other SDGs

In recent years, Chenzhou city has made significant progress in the sustainable utilization of water resources, especially after the establishment of demonstration area. These efforts have led to improvements in water availability, environmental quality, and ecological health. However, rapid development and stricter water resource management have also posed challenges. While there are many synergies between SDG6 and related SDGs [42], there may also be potential trade-offs and negative interactions in achieving these goals. These trade-offs may have significant impacts on policy formulation and implementation and, therefore, require special attention and management.

Implementing comprehensive water management policies (SDG6) requires substantial financial investment, which can strain local government budgets. Infrastructure upgrades, pollution control, and ecological restoration demand sustained funding, potentially limiting resources for essential public services, such as healthcare (SDG3) and education (SDG4). Prioritizing water sustainability in certain areas may also lead to unequal resource distribution, impacting poverty reduction (SDG1) and food security (SDG2), as well as widening regional disparities (SDG10). Although Chenzhou has made notable progress under the demonstration area policy, cities without similar support may struggle, resulting in uneven national progress toward SDG6. Stricter environmental regulations and water-saving policies may also pose challenges for industries and agriculture. Industry sectors reliant on water, such as manufacturing (SDG9) and large-scale farming (SDG2), could face higher operational costs, affecting economic growth and employment (SDG8).

In order to address the challenges posed by the potential trade-offs between SDG6 and other SDGs, it is recommended to make the following policy adjustments: (1) Implement targeted subsidies and investment mechanisms to ease financial burdens on local governments and vulnerable communities; (2) strengthen regional cooperation frameworks to ensure fair distribution of water resources and funding [45]; and (3) promote cross-sectoral governance to balance water security with economic, social, and environmental priorities. By recognizing and addressing these challenges, policymakers can develop more resilient and inclusive strategies to achieve SDG6, while supporting broader sustainable development objectives.

5. Conclusions

This study focuses on the sustainable development of water resource-based cities, using the Chenzhou sustainable development agenda innovation demonstration area as a case study. It evaluates progress on SDG6 from the following three dimensions: water quantity, water environment, and water ecology. Additionally, it assesses related SDGs and explores the synergies and trade-offs between SDG6 and these SDGs. The main findings are as follows:

(1)

From 2015 to 2022, The Chenzhou city has made significant progress in the sustainable utilization of water resources. The SDG6 composite index has increased significantly over time. The establishment of the demonstration area (2019–2022) led to an improvement in more than one times compared to the period before its establishment (2015–2018). The proportion of indicators in higher levels has increased, particularly in water environment and water quantity improvement. The significant improvement in water quantity, water environment, and water ecology indexes and key indicators all reflect the effectiveness of sustainable water resource management policies in this region. These changes mark the successful transition of Chenzhou city from decentralized management to comprehensive water resource management, in line with the principle of adaptive joint management. Currently, Chenzhou city has implemented a series of policies for sustainable utilization and the management of water resources. However, with the slow improvement in the comprehensive level of sustainable development in the later stage, it is necessary to shift to a comprehensive adaptive joint management policy of water resources, society, ecology, and economy in the future.

(2)

From 2015 to 2022, the SDGs composite index and individual SDG indexes showed a fluctuating upward trend. After the establishment of the demonstration area (2019–2022), it increased by approximately 89.74% compared to before the establishment (2015–2018). The proportion of indicators in higher levels has increased, while the proportion of low-level indicators decreased, with the most significant progress in the society dimension. Among them, the SDG7, SDG9, and SDG12 indexes have the largest increase, and as time goes on, the gap between each SDG indexes has gradually narrowed. The coordinated development of SDGs in Chenzhou city is constantly increasing. The lag in ecosystem restoration could lead to a mismatch between ecosystem service supply and socioeconomic demand, potentially undermining the long-term stability of sustainable development. In the future, Chenzhou must enhance ecosystem resilience, avoid overemphasis on short-term economic gains, and strengthen the monitoring and evaluation of ecosystem services. Timely policy adjustments should be made to ensure the coordinated development of society, economy, and ecology. Moreover, while the expansion potential of water-related ecosystems is limited, improving their quality and stability can support the growth of water-related industries, thereby advancing the integrated progress of relevant SDG targets.

(3)

There is a significant synergy between the improvement in SDG6 and related SDGs in Chenzhou city. For every unit increase in SDG6, the comprehensive level of related SDGs will increase by 0.73 units, with particularly strong synergies observed with SDG2, SDG7, SDG9, and SDG11. Promoting the sustainable utilization and management of water resources and enhancing SDG6 to foster the synergistic development of other SDGs is a viable pathway for water resource-based cities like Chenzhou to comprehensively advance the 2030 Sustainable Development Goals and achieve high-quality economic and social development.

However, data limitations remain a significant constraint on SDG assessments. Approximately, 30% of national-level SDG indicators still lack effective data, and data incompleteness on the city scale are more prominent [35]. On average, United Nations member countries have about 2/3 of the data in the SDG6 indicator system, and 24 member countries have less than half of the indicator data [34]. However, data limitations may affect the comprehensiveness of the assessment and analysis of synergy effects. In the future, earth big data based on earth observation are expected to support further research [46]. In this study, since Chenzhou city is a water resource-based city, the analysis between SDG6 and related SDGs is a synergy effect, the possible trade-off effects are not fully explored, and the interactions between them still need to be comprehensively explored and understood in the following research.