A system dynamics model to simulate the water-energy-food nexus of resource-based regions: A case study in Daqing City, China

Accelerating urban energy transitions: Harnessing EEET framework dynamics for sustainable development in resource-based cities of Sichuan Basin, China

This study examines managing urban energy systems in the Sichuan Basin, considering natural gas production. An integrated approach assessed the economy, energy, ecology, and technology (EEET) connections. The study identifies systemic issues and significant differences across locations and emphasizes the interdependent nature of economic expansion, energy innovations, and environmental commitment. Findings offer valuable insights for policymakers, providing strategic directions for overcoming barriers to sustainable city and energy advancements, and nurturing resilient urban environments. The EEET framework sheds light on the complex interactions of urban development, enabling officials to focus on areas for improvement. Addressing conflicts can create more cohesive and sustainable urban landscapes, uncovering serious environmental and energy-use issues in cities with dense industrial zones. Decision-makers could prioritize solutions like enforcing pollution controls and encouraging green energy use. Addressing disputes among urban development participants can craft strategies to encourage cooperation, finding win-win outcomes for sustainable city growth.

Predictive simulation of the water-energy-food nexus for the City of Cape Town

The City of Cape Town (CoCT), South Africa faced a critical situation between 2015 and 2018 in which the municipal water supply was almost completely exhausted. This situation, commonly referred to as Day Zero in South Africa emanated from a decline in rainfall, resulting in one of the most severe droughts in history. The crisis was also aggravated by rapid population growth and urbanization. CoCT was on the verge of becoming the first city in the past decade to experience a complete cessation of water supply for urban and agricultural purposes. In addition to the effects of low rainfall and population surge, urban energy consumption and increased food demand impacted directly the available water resources. To evaluate the interlinkages between water utilization, water production, energy supply and demand, and food production and demand, this study employed a system dynamics modeling (SDM) approach. The model was developed as a stock and flow diagram utilizing Stella Architect and encompassed five interconnected nodes: water, energy, food, land, and population. The findings revealed that by the end of the 20-year modeling period, the volume of accessible and stored water in all the major dams will be approximately 459 million cubic meters, with residential use accounting for about 85 % of urban water use and agriculture accounting for approximately30.37 % of total water demand. The model illustrates the impacts of precipitation rate, runoff, and evaporation on variables such as land-use change and population dynamics. It is anticipated that the outcomes of this study will serve as valuable inputs for decision-making processes, not only within the CoCT as it aims to mitigate or prevent the recurrence of Day Zero, but also for other cities facing similar challenges.

Forecasting and advancing water carrying capacity in Henan Province in China: Application of 'four determinations with water' in AHP and SD modeling

Water resources carrying capacity (WRCC) is indispensable for sustainable development, acting as a crucial determinant for harmonizing ecological preservation with socio-economic advancement. This research delineates an advanced evaluation index system for WRCC, focusing on Henan Province, China, a region straddling the Yangtze, Huaihe, Yellow, and Haihe river basins. Leveraging the analytic hierarchy process (AHP) with a system dynamics (SD) model, our analysis dissects the nonlinear interplays among demographic expansion, economic activities, land use patterns, water resources, and water environment. We introduce a novel integration of the "Four Determinations with Water" principle with sustainable development tenets, thereby sculpting six exploratory scenarios that chart Henan's potential paths from 2022 to 2035. Through these scenarios, we forecast and scrutinize the evolution of population dynamics, GDP, water supply, and sewage discharge volumes, employing rigorous quantitative analyses for a holistic evaluation. The results show that: WRCC in Henan Province becomes larger gradually, and, in Scenario 6, the WRCC indicator is the largest (0.643 in 2035) and the prediction effect is the best, while in Scenario 1, the WRCC indicator is the smallest (0.472 in 2035) and the prediction effect is the worst. Based on the prediction results, suggestions were made to adjust the industrial structure and strengthen the awareness of water conservation to improve the regional water resources carrying capacity.

Synergistic evolution of water-energy-food system resilience and efficiency in urban agglomerations

With increasing internal and external risks to the WEF system, a single emphasis on efficiency or a lopsided pursuit of resilience can lead to difficulties in adapting to complex changes and resource redundancy. Revealing the synergistic evolutionary characteristics between efficiency and resilience of the WEF system is an effective method to deal with systemic internal and external risks. However, the current study of the WEF system lacks a synergistic perspective on resilience and efficiency. Thus, taking Chengdu-Chongqing Economic Circle (CCEC) as the research object and its geospatial boundary as the system boundary, this paper adopted the entropy-topsis model to evaluate the WEF resilience, and applied the super-efficient SBM model to measure the WEF efficiency accurately, which fully considered the non-expected outputs in the process of resource utilization. Then, applying the development coordination degree model, the synergistic relationship between the two was measured. The results indicated that: the average value of WEF resilience in CCEC increased from 0.414 to 0.485 and showed spatial characteristics of west＞east＞central. The WEF efficiency interval was 0.79-0.93, and cities with average WEF efficiency reaching the effective production frontier accounted for only 37.5%. The clustered distribution of the synergy levels intensified. The number of cities with primary, medium, more advanced, and advanced levels was 6, 6, 1, and 3, respectively, with primary and medium synergy levels dominating. The findings suggest that cities should strengthen regional exchanges and formulate targeted measures based on their own situations. In addition, CCEC should possess a comprehensive understanding of the interdependencies and conflicts that arise between resilience and efficiency throughout the decision-making procedure.

A simulation and risk assessment framework for water-energy-environment nexus: A case study in the city cluster along the middle reach of the Yangtze River, China

In the Anthropocene, there is a strong interlinkage among water, energy, and the environment. The water-energy-environment nexus (WEEN) has been vigorously advocated as an emerging development paradigm and a global research agenda. Based on the nexus concept, a framework for the WEEN complex system simulation and risk assessment is developed. The three metropolitan areas of the city cluster along the middle reaches of the Yangtze River (CCMRYR) are taken as the objects. Regional policies are combined with generic shared socio-economic pathways (SSPs) to form a localized SSPs suitable for the research region. The dynamic simulation of the WEEN complex system and the risk analysis are carried out with the combination of system dynamics models and copula functions. Results show that: There are obvious differences in water utilization, energy consumption, air pollutant emissions, and water pollutant emissions among the three metropolitan areas. The issue of high carbon intensity in the Wuhan Metropolitan Coordinating Region needs to be emphasized and solved from the perspective of optimizing the industrial structure. Adhering to current development patterns, there will be successive peaks in water utilization, energy consumption, and carbon emissions in Wuhan, Dongting Lake, and Poyang Lake Metropolitan Coordinating Region by 2030, leading to high synergy risks at the systemic level, with maximum values of 0.84, 0.85, 0.62, respectively. A development path based on conservation priorities indicates that future policymaking needs to prioritize a resource-saving and pollution-control development pattern directed by technological upgrading against the backdrop of scarce natural resource endowments. The localized SSPs are a beneficial extension that enriches the narrative of regional-scale SSPs. The evolutionary trajectories and risk assessments of WEEN complex systems under different localized SSPs provide a sweeping insight into the consequences of policy decisions, thus enabling policymakers to appraise policy rationality and implement appropriate corrective measures.

Dynamic simulation of the water-energy-food nexus (WEFN) based on a new nexus in arid zone: A case study in Ningxia, China

'Quantity-type' water shortages and 'quality-type' water shortages are important factors that constrain the security and coordinated development of regional water-energy-food nexus (WEFN) system, especially in arid areas where water is scarce. Therefore, it is of great significance to accurately identify the coupling and mutual feedback effects of the WEFN on different types of water resources demand. This information can be used to understand the regional WEFN and alleviate pressure on regional water resources. In this study, a new relationship diagram of the WEFN system was formed with the incorporation of the water footprint (WF), which can characterize a system's water demand, water source type, water pollution amount and pollution type. Based on this nexus, a WEFN system feedback model suitable for arid regions was established using the system dynamics approach. Taking Ningxia, China, as a case study, six future scenarios were designed, and the development trends of the WEFN system under different development scenarios were simulated to explore the impact of different policies on the WEFN. Finally, practical suggestions to promote the synergistic development of WEFN systems were proposed. The results indicate that the rational distinction between 'quantity-type' and 'quality-type' water resources can effectively alleviate the regional water stress and promote the coordinated development of water, energy and food. And the water security is the main factor that constrains the coordinated development of the WEFN system in Ningxia. Incorporating water environmental pollution policies into the water subsystem is necessary. Furthermore, the resource saving scenario and energy production restructuring adjustment scenario can effectively alleviate the energy security problems that has resulted from rapid economic development. In addition, Ningxia urgently needs to optimize its food production structure to address a continuous reduction in the food security index.

Ecological challenges in the economic recovery of resource-depleted cities in China

The depletion of resource reserves will cause stagnation of socio-economic development in resource-based cities. The formation of new sources of economic growth in resource-depleted cities can profoundly change the structure of human activities and affect the environment. The Chinese government has established a list of resource-depleted cities in three batches since 2008 to support these cities in finding new sources of economic growth. The article analyzes the impact of the regeneration process of resource-based cities on ecosystem quality. The paper constructs an inter-city panel dataset covering 281 cities from 2003 to 2018. The article valued the habitat quality of Chinese cities. Habitat quality index and normalized vegetation index were used to measure the long-term and short-term ecological impacts of economic recovery in resource-based cities. Using a difference-in-difference technique, the results show that the central government's economic support for resource-based cities significantly improves the condition of urban ecosystems. However, the long-term ecological effects are still smaller than the short-term changes in ecosystems. The transmission path of support policies affecting the ecological quality of cities depends on the shift in industrial structure and economic scale at the provincial level. In addition, urban-rural differences, regional distribution, and resource endowment also significantly affect the ecological effects of supportive policies.

A Comprehensive Evaluation Framework of Water-Energy-Food System Coupling Coordination in the Yellow River Basin, China

For mankind's survival and development, water, energy, and food (WEF) are essential material guarantees. In China, however, the spatial distribution of WEF is seriously unbalanced and mismatched. Here, a collaborative governance mechanism that aims at nexus security needs to be urgently established. In this paper, the Yellow River Basin in China with a representative WEF system, was selected as a case. Firstly, a comprehensive framework for WEF coupling coordination was constructed, and the relationship and mechanism between them were analyzed theoretically. Then, we investigated the spatiotemporal characteristics and driving mechanisms of the coupling coordination degree (CCD) with a composite evaluation method, coupling coordination degree model, spatial statistical analysis, and multiscale geographic weighted regression. Finally, policy implications were discussed to promote the coordinated development of the WEF system. The results showed that: 1) WEF subsystems showed a significant imbalance of spatial pattern and diversity in temporal changes; 2) the CCD for the WEF system varied little and remained at moderate coordination. Areas with moderate coordination have increased, while areas with superior coordination and mild disorder have decreased. In addition, the spatial clustering phenomenon of the CCD was significant and showed obvious characteristics of polarization; and 3) the action of each factor is self-differentiated and regionally variable. For different factors, GDP per capita was of particular importance, which contributed most to the regional development's coupling coordination. For different regions, GDP per capita, average yearly precipitation, population density, and urbanization rate exhibited differences in geographical gradients in an east-west direction. The conclusion can provide references for regional resource allocation and sustainable development by enhancing WEF system utilization efficiency.

System dynamics modelling to simulate regional water-energy-food nexus combined with the society-economy-environment system in Hunan Province, China

Nexus approaches provide an efficient way to analyze the dynamic evolution of the water-energy-food nexus (WEFN), yet there is a need to close the science-policy divide by making simulation models more practically relevant. This study incorporates society, economy and environment systems (SEE) into the WEFN, simulating a broad environmental system. A system dynamics model is constructed to simulate and dynamically track the development of the WEF-SEE system in Hunan Province, China. The developed model is applied to assess WEF-SEE system trajectories from 2021 to 2035 against nine policy goals formulated by the Hunan Provincial Government. Baseline results suggest that Hunan Province will have a surplus of grain production and will be in a state of "self-sufficiency" in water resources. The energy security situation is not as optimistic, with imports being required to meet demand. The sustainable development of the WEF Nexus will be constrained by resource shortages. As the future development of Hunan Province outpaces environmental protection policies, water pollution and CO₂ emissions and are expected to increase. Intra-system trade-offs and synergies under the impacts of different policies indicate that the implementation of an indicative policy has the intended impact within its particular subsystem, but may lead to trade-offs in other subsystems. Due to system interconnectedness, the simultaneous implementation of multiple policies may increase or hinder progress towards certain goals. For example, expanding planting area increases food production, but increase agricultural water demand and water pollutant discharge, counter to water security goal and environmental protection goals. Cross-system impacts must be considered when choosing policies. This study advances environmental system analysis and evaluation, and contributes to practical policy recommendations, providing useful insights for Hunan Province, especially considering potential trade-offs and synergies. Such information could lead to more effective, holistic environmental policy formulation.

The Necessity of Maintaining the Resilience of Peri-Urban Forests to Secure Environmental and Ecological Balance: A Case Study of Forest Stands Located on the Romanian Sector of the Pannonian Plain

Climate change’s negative effects, such as rising global temperatures and the disruption of global ecological ecosystems as a direct effect of rising carbon emissions in the atmosphere, are a significant concern for human health, communities, and ecosystems. The condition and presence of forest ecosystems, especially those in peri-urban areas, play an essential role in mitigating the negative effects of climate change on society. They provide direct benefits to the residents of large cities and their surrounding areas, and they must be managed sustainably to protect all their component ecosystems. This research was carried out in the forests of Lunca Muresului Natural Park and Bazos Arboretum, located in the Romanian sector of the Pannonian Plain, near urban agglomerations. The results showed high variability in the stands. Using the height-to-diameter ratio indicator concerning dbh and species, a strong Pearson correlation was registered (between 0.45 and 0.82). These values indicate the high stability of these stands, providing positive human–nature interactions such as recreational or outdoor activities (and a complementary yet indirect use value through attractive landscape views). Protecting these ecosystems offers a so-called insurance policy for the next generations from a climate change standpoint.

Evaluation of the symbiosis level of the water-energy-food complex system based on the improved cloud model: a case study in Heilongjiang Province

As the conflict between the supply and demand of resources intensifies, it is critical to deeply study the important relationships and symbiotic evolution mechanisms among water resource development and utilization, energy production, agriculture, and the socioeconomic system to promote multiresource synergy management. This study introduced symbiosis theory to build a regional water-energy-food complex system in which the water-energy-food nexus was the main body and the social-economic-natural system was the external environment. Then, a symbiosis evaluation index system was established from three dimensions, including the symbiotic unit, symbiotic relationship, and symbiotic environment. Using the improved cloud model, we judged the symbiosis level of the water-energy-food complex system in Heilongjiang Province from 2010 to 2019. The results indicated that (1) the symbiosis level of the provincial water-energy-food complex system, symbiotic unit, and symbiotic environment was on the rise from level II in 2010 to level IV in 2019, and the symbiosis level of the symbiotic unit fluctuated between level III and level IV. The system exhibited an overall strong symbiosis state. (2) The weights of the three criteria were ranked as symbiotic environment > symbiotic unit > symbiotic relationship. The state of the social-economic-natural system could be considered a "monitor" of the symbiosis level, the symbiotic unit was an important basis for the evolution of the complex system, and the symbiotic relationship was the shortcoming of the system symbiosis enhancement. (3) The trade-offs between food production and water savings constrained socioeconomic development in the province. The resource demands of the economic and social systems and the emissions to the natural system that occurred during the resource exploitation and utilization processes were important factors affecting the coordinated development of the studied system. Overall, the experimental results were consistent with the research subjects' actual situations, and the government should promote the regional three-way flow of social, natural, and economic resources to allow the targeted management of multiresource security.

Spatial–temporal distribution measurement of input–output efficiency of the water–energy–food nexus of the Yangtze River Economic Belt, China

Water, energy, and food are important factors affecting people’s lives and socio-economic development, and their production and consumption processes are closely related, so it is necessary to do research on input–output efficiency as a whole. The research is conducive to promoting the effective utilization and rational allocation of relevant resources in the Yangtze River Economic Belt, thereby promoting sustainable development. This study calculates the input–output efficiency of the water–energy–food (WEF) nexus of 11 provincial administrative regions in the Yangtze River Economic Belt utilizing the DEA-BCC model. Then, new indicators called area expansion degree and the subsystem’s influence degree are proposed with the aid of the standard deviation ellipse model to analyze the characteristics and trends of spatial–temporal distribution of input–output efficiency. The standard deviation ellipse model starts from the basic spatial elements, including point, line, and surface, and is used to study the spatial distribution and trend change of efficiency according to the center of gravity and area. The shift of the center of gravity shows the direction of significant improvement in the effect of resource allocation, and the change of area shows the differences in the speed of efficiency improvement between regions and the future development trend. The results mainly indicate that the resource allocation in the middle and lower reaches of the Yangtze River Economic Belt is more reasonable than that in the upper reaches, and the efficiency distribution is obviously concentrated in the northeast direction. It is suggested that the provincial administrative regions in the upper reaches should optimize the industrial structure, the regions in the middle and lower reaches should improve the resource structure, and the flow of talents and technology of regions should be promoted.

The Impact of Pollution Fee Reform on the Emission of Water Pollutants: Evidence from Manufacturing Enterprises in China

With the development of China's industrial economy and urbanization, water pollution has become serious and gradually exposed to the public. The pollution fee policy is an important tool to force enterprises to reduce pollution. This study used the panel data of manufacturing enterprises during 2006-2013 and the multiperiod difference in differences (DID) method to systematically analyze the impact of water pollution fee reform on emissions of manufacturing enterprises in China. In general, enterprises facing improved pollution fee collection standards reduce COD emissions by approximately 4.1%. However, significant location heterogeneities are captured in China. The rising water pollution fees have promoted the emission reduction of enterprises in northern China and resource-based cities, but the effect is not significant in southern China and nonresource-based cities. Furthermore, the mechanism analysis shows that enterprises mainly reduced emissions through terminal treatment and reducing production. This study provided micro evidence for research on the effect of pollution fee reform and supplied a reference for the improvement of the environmental protection tax system in China.

Distribution, Genesis, and Human Health Risks of Groundwater Heavy Metals Impacted by the Typical Setting of Songnen Plain of NE China

Heavy metals pollution in groundwater and the resulting health risks have always been an environmental research hotspot. However, the available information regarding this topic and associated methods is still limited. This study collected 98 groundwater samples from a typical agricultural area of Songnen Plain in different seasons. The pollution status and sources of ten heavy metals (As, Ba, Cd, Co, Cr (VI), Cu, Fe, Mn, Ni, Pb, and Zn) were then analyzed and compared. In addition, the human health risks assessment (HHRA) model was used to calculate human health risks caused by heavy metals in groundwater. The results revealed that heavy metals were mainly distributed in the northwest of the study area and along the upper reaches of the Lalin river and that the concentrations of heavy metals were higher during the wet season than the dry season. Industrial and agricultural activities and natural leaching are the main sources, and each kind of heavy metal may have different sources. Fe and Mn are the primary pollutants, mainly caused by the native environment and agricultural activities. The exceeding standard rates are 71.74% and 61.54%, respectively based on the Class III of Quality Standard for Groundwater of China (GB/T 14848-2017). The maximum exceeding multiple are 91.45 and 32.05, respectively. The health risks of heavy metals borne by different groups of people were as follows: child > elder > young > adult. Carcinogenic heavy metals contribute to the main risks, and the largest risks sources are Cr and As. Therefore, the government should appropriately restrict the use of pesticides and fertilizers, strictly manage the discharge of enterprises, and control man-made heavy metals from the source. In addition, centralized water supply and treatment facilities shall be established to prevent the harm of native heavy metals.

Simulation and Optimization Strategy of Storm Flood Safety Pattern Based on SCS-CN Model

The contradiction between rapid urbanization’s demand for land resources and the ecological environment is increasing, which has led to large-scale hardening of the underlying surface of the city and reduction of land for storage. In addition, construction land occupies rainwater confluence land, resulting in a significant decline in urban stormwater control capabilities. The increasingly frequent flood disasters in recent years have exposed the contradiction between urban construction and stormwater safety that cannot be ignored. Therefore, this article takes the central city of Harbin as the research object, uses ArcGIS for spatial analysis and SCS (Soil Conservation Service) hydrological model simulation to construct the rain and flood safety pattern in the research area, and proposes targeted optimization suggestions and strategies based on the evaluation results to achieve the purpose of coordinating the water ecosystem service function with social and economic development. The research shows that protecting the original stormwater corridor and strengthening the connection between the stormwater control patches can effectively guarantee the connectivity of the stormwater corridor, build the natural stormwater regulation and storage system, and then increase the ability of the city to resist the risk of rainstorm, reduce the disaster caused by urban waterlogging, and achieve the goal of sponge city construction.