In response to the problems of low water resources allocation efficiency and mismatching between water resources utilization and industrial structure in the Dawen River Basin, based on the principle of spatial balance, an analytical framework coupling the input-output model with the system dynamics model was constructed from two dimensions, i.e., the matching between water resources and industrial sectors and the balance of spatiotemporal distribution. The intersectoral virtual water flow patterns were quantitatively identified, and the spatial balance level under multiple objectives was comprehensively evaluated. Through multi-scenario simulation, the water resources spatial balanced development path was revealed. The research shows that from 2012 to 2017, the direct water consumption coefficient and complete water consumption coefficient of all industries in the Dawen River Basin of Jinan City exhibited downward trends. There is room for improvement in the direct and indirect water use efficiencies of industries, including agriculture, forestry, animal husbandry and fishery, mining, and food and tobacco industries. The industrial structure of the basin has shifted from being dominated by agriculture and traditional industries to being led by the tertiary industry. Except for 2014 and 2015 when the water resources balance level was at a generally unbalanced state, the basin as a whole was in a relatively balanced state. The development scheme for new water sources can significantly reduce the water load coefficient and improve the water-soil matching coefficient, and the water-saving level improvement scheme can effectively improve the water use efficiency. The Dawen River Basin should prioritize the reduction of high-water-consuming and low-value-added industries, increase the proportion of services and high-tech industries, jointly achieving ecological protection and green development at the basin scale.

Based on panel data from 30 provinces, municipalities, and autonomous regions in China from 2008 to 2019, considering the pivotal role of energy structure adjustment in carbon emission control, this study utilizes the Kaya identity and its extensions, combined with the SCAD (smoothly clipped absolute deviation) method for index selection, to construct a detailed assessment system and analyze the contribution of various elements to carbon reduction. By further incorporating a semi-parametric model, the dynamic relationship between energy structure adjustments and regional carbon emissions is revealed. The research indicates that controlling power generation and adjusting the energy structure are the two most effective methods for contributing to carbon reduction. Furthermore, optimizing the energy structure by increasing the proportion of hydropower significantly facilitates carbon reduction. The hydropower proportions of 8%, 38%, and 76% are identified as critical thresholds impacting carbon reduction significantly. Additionally, through an analysis of regional heterogeneity, differentiated strategies for adjusting energy structures are proposed.

Biodiversity is the basic support to maintain the balance of the earth’s ecosystem, which is closely related to climate change. The essence of climate crisis is biodiversity crisis. In order to cope with and mitigate the accelerated destructive impact of climate change on the global ecological environment, carbon reduction is the only way to go at this stage. This paper systematically combs the relationship between carbon reduction and biodiversity, then elaborates that there is a positive correlation between biodiversity and carbon reduction. Reducing carbon dioxide emissions can be achieved by taking measures such as energy structure transformation, industrial structure adjustment, energy conservation and emission reduction technology innovation. At the same time, we can also explore the potential of ecosystem carbon sequestration to reduce the content of carbon dioxide in the atmosphere. Controlling the content of carbon dioxide in the atmosphere can alleviate the interference and damage of climate change to the natural ecological environment, and play a positive role in biodiversity protection. When combing the literature on the relationship between carbon sequestration and biodiversity, it is found that there is also a connection between forestry carbon sequestration and biodiversity in afforestation, that is, biodiversity plants will isolate more carbon than trees alone in artificial afforestation, and there is a trade-off between carbon and biodiversity.

Basin runoff is an important response factor to changing environment. Under the influence of climate change and human activities, watershed runoff has undergone profound changes. Studying its evolution and response characteristics is helpful to improve human’s ability to cope with changing environment. Taking the main catchment area of the Beijing municipal area of the North Canal as the study area, the variation trend of rainfall and runoff in the North Canal basin was analyzed by analyzing the hydrological data of hydrometeorological observation stations in the past 40 years, and the flood field was extracted. The global climate model data is introduced, the downscaling model is used for downscaling, and the runoff forecast is analyzed in combination with the hydrological model. The results show that the historical precipitation trend of the basin is not obvious, and the runoff is increasing. In the future, the change of water resources in the North Canal Basin (Tongxian Station) will be more obvious under the influence of climate change. With the increase of temperature and precipitation, the runoff will increase, and the discharge is predicted to reach a new high of 385.1m³/s in the middle of this century. With the continuous increase of radiative forcing, the degree of hydrological response increases correspondingly, and most of the peak runoff in the North Canal basin occurs in the late 2050 and 2090 periods. The research can provide some reference for the future water resource utilization, flood containment and disaster reduction measures and the realization path of dual carbon targets in urban watershed.

Yinchuan City, Xi’an City, and Dongying City were selected as typical areas in the upper, middle, and lower reaches of the Yellow River Basin, respectively. The human-water relationship was deconstructed into five subsystems: water, city, land, human, and production. A comprehensive evaluation index system was constructed, and combined with Tapio decoupling model, LMDI decomposition model, obstacle model, and Liang Kleiman information flow methods, the decoupling situation and driving factors between water resource utilization and economic development in typical areas of the Yellow River Basin were explored. The results indicate that the economic growth in typical areas of the Yellow River Basin has basically decoupled from the growth of water resources, but there are significant differences in the driving factors of total water use in different regions. The water subsystem is the key factor restricting the coordinated development of the Yellow River Basin, especially in terms of water resource management and utilization efficiency, which still needs to be improved. There are significant differences in the contradictions of human-water relationship in different regions. Yinchuan City is highly dependent on the Yellow River water caused by lacks local water resources, and the competition between ecological water security and agricultural water demand is prominent. The agglomeration of population and economy in Xi’an City has exacerbated the problems of water scarcity, overexploitation of groundwater, and ecological water use encroachment. Dongying City is deeply affected by the dual pressure of low matching of water and soil resources and high demand for industrial water, which has a profound impact on local human-water relationship.

Based on the multi-regional input and output table, the water, energy, and food (WEF) resource flow between Guangdong Province and other provinces/autonomous regions/cities in China was calculated, and the amount of risk transferred through WEF resource flow between these provinces/autonomous regions/cities was innovatively quantified. Moreover, the value of risk transfer was explored.The results show that: in the inter-provincial WEF resource trade, the net inflow of embodied water to Guangdong Province is 11.706 billion cubic meters; the net inflow of embodied energy is 2.80×10⁹ GJ, and the net inflow of embodied food is 16.2293 million tons. Most regions have a net inflow of WEF resources to Guangdong Province, with Guangxi Zhuang Autonomous Region, Henan, Anhui, and Hunan provinces exhibiting the highest inflow values.The influence coefficient and induction coefficient of WEF resources in Guangdong Province are low, and the driving and influence effect on other provinces/autonomous regions/cities in the national WEF resource trade is not strong. In addition, the induction ability of resource consumption changes in other provinces/autonomous regions/cities is weak. The risk transfer value of WEF resource flows exhibits an asymmetrical pattern between input and output regions. For most regions, the risk transfer value of WEF resource flow into Guangdong Province is high. On the basis of alleviating the risk of WEF resources in Guangdong Province, the risk in these regions has not significantly improved, especially in Hainan Province, Tianjin City, Shanghai City, Henan Province, and Gansu Province.The risk transfer value of Yunnan Province, Beijing City, Shanxi Province, and Zhejiang Province is relatively low, and the WEF resource risk caused by the resource input of Guangdong Province is relatively large.

In order to realize the spatial equilibrium and dynamic regulation of water resources at different time scales in the future, a complete and rigorous model system for “defining city, land, population, and industry based on water”, suitable for balance measurement and dynamic control of water resources in different provinces and cities, was created. The total regional water consumption was predicted by the support vector machine (SVM) model based on fuzzy information granulation window, the regional sub-water consumption was predicted by the autoregressive-SVM model based on time series similarity analysis, and uncertainty of the two types of data was analyzed. Complex regression functions were constructed to predict various water use indicators in different scenarios, which were used as future water use indicators under current water use pattern after statistical test. Then, a water resources carrying capacity model of “defining city, land, population, and industry based on water” and a water resouces spatial equilibrium model were constructed, and three indicators including the water resources loading coefficient, water consumption efficiency, and matching factor of water and soil resources were selected based on the future total water consumption, future sub-water consumption, and future water use indicators, to quantify the spatial equilibrium degree of water resources in combination with the Gini coefficient and analyze the future equilibrium degree of water resources under current water use pattern. Finally, an optimization model was constructed, with minimization of the Gini coefficient as the objective function, to adjust the future water use pattern and realize dynamic regulation of water resources. The model system can realize the spatial equilibrium and dynamic regulation of water resources at different time scales in the future.

The "defining city, land, population, and industry based on water" (DCLPIW) regulation and control model based on water resources spatial equilibrium constructed in previous research was used to carry out applied research of water resources spatial equilibrium dynamic regulation of Linyi City, Shandong Province. The spatial equilibrium of water resources in different districts (counties) in the future was explored based on the forecast results of water consumption and water use indicators, and dynamic regulation of future water consumption was conducted on different time scales. The results show that the regulation and control model is highly reliable and universally applicable, and future water resources in Linyi City are in an absolute spatial equilibrium state under the current water use pattern, only the water and soil matching coefficient is in a general equilibrium state. The dynamic regulation of future water consumption of different types in various districts (counties) can make the spatial equilibrium indicators of water resources in Linyi City reach the absolute equilibrium state on different time scales. Under the constraints of DCLPIW and spatial equilibrium of water resources, Linyi City is expected to realize dynamic equilibrium of water consumption based on the long- and short-term dynamic regulation of water consumption in the future.

This paper constructed a spatial equilibrium evaluation model of water resources combined with the relationship between supply side and demand side. Based on the quantitative evaluation and analysis of the state and change process of water resources spatial equilibrium level by the five-element connection number, the evaluation model of water resources spatial equilibrium is constructed, and the evaluation system of water resources spatial equilibrium including 12 evaluation indicators of the supply subsystem and the demand subsystem is established. Then, the development trend and influencing factors leading to the change of water resources spatial equilibrium level are diagnosed and analyzed by the subtraction set pairs. Applying the model to 11 counties and districts in Ulanqab City, the study shows that the spatial balance level of water resources has been improved from 2011 to 2020 in 6 counties and 5 counties, among which Jining District has been in a low level of equilibrium. From 2011 to 2020, the overall level of spatial balance of water resources in Ulanqab City has shown a trend of improvement year by year. In the level of supply subsystem in 2020, Jining District is in a counter trend state, while Huade County and Shangdu County are in a counter trend state. At the demand subsystem level, only Jining District is in a negative state. The vulnerability indicators of Ulanqab City are water resources per capita and water demand load of ecological environment.

In allusion to the trend of green development and high-quality development of watershed eco-cities, based on explaining the theoretical origin and development process of green development and high-quality development, the relationship between the two aspects was analyzed from the theoretical and practical perspectives, and the high-quality development path under the carbon peaking and carbon neutrality goals was clarified. From the angle of watershed ecological protection, three major bottleneck factors in the current eco-city construction planning were analyze, and strategies and recommendations for watershed eco-city construction were put forward, including to enhance population quality and develop and utilize natural resources rationally, to observe ecological protection red lines strictly and improve resilience against natural disasters, and to develop green economy and promote economic transformation.