[Objective] Focusing on the Yingwen River Basin in Shandong Province, this study aims to explore the extraction, division, naming methods for small watersheds in mixed terrains, and to analyze spatial distribution characteristics of small watershed areas and river network densities. [Methods] This study utilized high-precision SRTM-DEM data, combined with hydrological analysis modules, to extract micro-watersheds, river networks, and watershed boundaries. The optimal catchment threshold was determined using the river network density method. Micro-watersheds were merged into small watershed units based on natural catchment relationships, and named according to Specification SL 653—2013. In complex terrain areas, local corrections were made by referencing high-resolution remote sensing images and field survey results to ensure the accuracy of the division. Meanwhile, the main stream, first-order tributaries, and second-order tributaries of the Yingwen River Basin were extracted, and the characteristics such as the area of small watersheds and the density of river networks were statistically analyzed. [Results](1) This study successfully extracted 1 main stream (the main stream of Yingwen River), 22 first-order tributaries, 48 second-order tributaries, and 1 large reservoir, establishing a complete water system network. (2) A total of 28 small watersheds were merged. Small watershed areas in upstream mountains were generally smaller, while those in downstream hilly plains were relatively larger. This was mainly caused by terrain limitations combined with human activities. (3) All 28 small watersheds were named based on the proposed naming process, providing strong support for watershed management and water resource protection. (4) The river network density in Yingwen River Basin exceeded 0.2 km/km², indicating abundant water system resources. Areas with river network densities of 0.4-0.6 km/km² accounted for 60.71% of the total area, mainly concentrated in the middle and lower reaches. Areas with densities of 0.6-0.8 km/km² accounted for 28.57%, distributed in the upper, middle, and lower reaches. [Conclusion] (1) The analytical framework for division, naming, and spatial distribution characteristics of small watersheds in mixed terrains proposed in this paper provides scientific methods and practical cases for similar studies. (2) Complete-type small watersheds are dominant, indicating relatively intact water systems with limited human disturbance. The spatial distribution characteristics of small watershed areas and river network densities reveal the combined influence of terrains and human activities on water system development. (3) The number of first-order tributaries in the Yingwen River Basin exhibits a significant increasing trend from upstream to downstream, reflecting the complexity of river network systems in middle and lower reaches and the promoting effect of human activities on water system development. The distribution characteristics of the length of tributaries per unit area and the density of river networks further reveal the abundance and spatial differences of water system resources within the basin.

[Objective] The "Three Lines and One Permit" (TLOP) eco-environmental zoning management system plays a crucial role in the development of ecological civilization in China. However, its in-depth integration with Environmental Impact Assessment (EIA) for integrated river basin planning remains underdeveloped. To address the prominent conflict between ecological conservation and development in strategic EIA of river basin planning, this study proposes a TLOP-based EIA design framework to ensure the implementation of zoning management requirements. [Methods] A comprehensive EIA framework integrating “planning analysis, environmental assessment, and admittance list” was established. TLOP-based formulation methods for river basins were proposed, including four-category ecological zoning, quantifiable environmental quality baselines, and dynamic control of resource utilization ceilings, which were validated through a case study of the Ganjiang River Basin. [Results] In Ganjiang River Basin, priority conservation waters spanning 200.46 km and key conservation waters covering 592.99 km were delineated. 36 cross-sections for water quality monitoring were established with a Chemical Oxygen Demand (COD) emission limit set at 201 800 t/a. Five conflicting projects, including the Maodian Cascade, were rejected. The ecological flow management was optimized to ensure that the total planned water use (12.94 billion m³) did not exceed the upper limit indicator. [Conclusion] The study achieves innovative dynamic coupling between TLOP and strategic EIA. The developed eco-environmental admittance list for river basins provides precise control of development intensity, offering a replicable paradigm for cross-scale environmental management and facilitating the coordination between high-quality basin development and ecological conservation.

To investigate the coordinated and sustainable development of the water resources-food-energy-ecosystem (WFEE) in the Shiyang River Basin and mitigate the negative impacts from the development of a single resource sector on other resource domains, we established a coupling and coordination evaluation index system for the WFEE system of the northwest inland Shiyang River Basin as a case study. The CRITIC method was employed for the weighting of subsystem indicators, and the coupling coordination degree model was adopted to analyze the spatiotemporal evolution characteristics and the coordination degree of Shiyang River Basin’s WFEE from 2020 to 2030. Results demonstrate that the comprehensive development index of the Shiyang River Basin’s WFEE system from 2000 to 2020 was at a moderate level, with the energy subsystem showing a negative growth trend. The WFEE system of Shiyang River Basin has undergone six stages, from mildly disordered to well coordinated, displaying an upward trend. The prediction results suggest that the basin will remain a well-coordinated growth trend during the forecast period from 2020 to 2030. These findings provide a scientific basis for the sustainable management and efficient development and utilization of the Shiyang River Basin.

Environmental judicial cooperation is a powerful tool for ecological environmental governance in the Yangtze River Basin. As a giant ecological system, the Yangtze River Basin needs to emphasize the special characteristics of the Basin in judicial protection concepts and measures. The construction of a beautiful China has put forward higher requirements for ecological and environmental governance. The Yangtze River Basin has seen its provinces and cities actively exploring judicial coordination practices with notable results. However, an analysis of these practices reveals disparities in the pace and focus of reforms, along with issues such as inadequate legislative supply, incomplete judgment mechanism construction, and poor coordination among collaborative entities. Given the holistic and systematic nature of the Yangtze River Basin, advancing common legislation within the basin, establishing specialized environmental judicial institutions, and enhancing the long-term mechanisms for the interface between judicial and enforcement activities can effectively innovate the judicial collaboration mechanisms for environmental governance. These measures will contribute judicial insights to balancing ecological and environmental protection with joint governance, ensuring sustainable economic and social development in the Yangtze River Basin.

To address the ambiguity surrounding the ecological benefits of hydropower projects and the challenges in quantifying these benefits, we take the Three Gorges Project as a case study to review existing research and define the ecological benefits in hydropower projects. In line with the river ecosystem service functions, we propose an evaluation framework for the ecological benefits of hydropower project from four dimensions: supply service function, support service function, regulation service function, and cultural service function. We further construct an evaluation index system for ecological benefit, and collect relevant data for quantitative analysis. Methods such as the shadow price method are used to convert these benefits into quantifiable economic values. The results indicate that the supply service value of the Three Gorges Project reaches 104.783 billion yuan, the support service value 20.074 billion yuan, the regulation service value 83.38 billion yuan, and the cultural service value 19.556 billion yuan, totaling 227.793 billion yuan. The findings offer technical support for establishing a mechanism for valuing ecological products in the Yangtze River Basin, and enhancing market-oriented and diversified ecological compensation.

Ecological compensation is an economic means to improve, maintain and restore the ecosystem service function, and is also an important measure to implement the scientific outlook on development and promote the coordinated development among regions. In recent years, Hubei Province has made a lot of explorations in establishing a horizontal ecological compensation mechanism with prominent characteristics. This study comprehensively summarizes the construction and practice of basin ecological compensation system in Hubei Province, detailing its evolution, practical applications, and benefits. It also identifies current challenges and proposes solutions, including advancing inter-provincial basin ecological compensation, refining mechanisms for water source areas of the South-North Water Transfer Project, optimizing management coordination, securing funding, and developing robust assessment standards.

The Ministry of Water Resources in 2022 issued the List of Major Drinking Water Sources in the Yangtze Basin,laying a crucial foundation for water resource protection and management in the region.Guiding the protection of these vital drinking water sources is a legal responsibility assigned to water administration departments by the Water Law of the People’s Republic of China and the Yangtze River Protection Law.This duty is essential for ensuring the safety of water supply in the basin.By examining the current state of protecting and managing major drinking water sources in the Yangtze River Basin,we aim to address existing issues such as the inadequate access and withdrawal mechanisms for the water source list,the deficiencies in the safety assessment system,and the insufficient funding mechanisms.Proposed long-term strategies include enhancing the water source security planning system,standardizing the management of the water source list,improving water source security assessments and protections,and implementing rigorous evaluations of water source protection measures.The findings of this research hold significant importance for fulfilling the protection mandates outlined in the Water Law and the Yangtze River Protection Law,adhering to the principles of green development in the Yangtze River Economic Belt,ensuring the Great Protection of the Yangtze River,as well as advancing the establishment of a robust,long-term supervision and management mechanism for major drinking water sources in the Yangtze River Basin.

To enhance the rational and efficient utilization of Yangtze River shoreline resources, we examine the current management status of the Jiangsu segment and propose comprehensive management measures tailored to its protection and utilization. Despite notable achievements in the Yangtze River protection strategy in Jiangsu, shortcomings persist, notably insufficient comprehensive management and unified planning along the shoreline. Recommendations include enhancing the joint conference system for comprehensive shoreline management, establishing a provincial-level task force for Yangtze River shoreline protection, and implementing unified management strategies. Considering water area and land area factors along the shoreline, we introduce the shoreline grade coefficient and utilization efficiency coefficient to optimize the paid use method for shoreline resources, exploring a paid-use mechanism for the Jiangsu segment of the Yangtze River's mainstream. This approach aims to effectively promote the rational development and utilization of Yangtze River shoreline resources.

The transfer of water source conservation service value between different regions is the key content to be considered in the horizontal ecological compensation between the upstream and downstream of river basin. This transfer is dependent upon the basin's hydrological cycle path and river water transport. However, the current method for evaluating the transfer of water source conservation service value lacks an account of hydrological characteristics, thus requiring an enhancement of the rationality of evaluation results. Addressing this issue, the present study enhances the fracture point-field intensity model from two perspectives: transfer direction and transfer path. Firstly, the introduction of the river direction coefficient aids in assessing the hydraulic connection between the basin's upstream and downstream, as well as its main and tributary regions. Secondly, the assessment of water source conservation service transfer takes into account the hydrological characteristics of rivers, with particular application to the Yangtze River Basin (YRB), thereby improving the rationality and applicability of assessment outcomes. The findings reveal that the water source conservation capacity of the YRB in 2020 reached 1 153.85 billion m³, with the associated value of water source conservation service amounting to 1 195.38 billion yuan. In contrast to the evaluation results obtained from existing models, the present enhanced fracture point-field intensity model underscores the transfer of water source conservation service value from upstream to downstream, and amplifies the transfer intensity and range. Within the YRB, the water source conservation service value transferred from Sichuan ranks the top, followed by Jiangxi, Hunan, Guizhou, Hubei, Anhui, Chongqing, Yunnan, Zhejiang, Qinghai, Shaanxi, Guangxi, Xizang, and Henan in descending order; the service value received by Yunnan is the largest, followed by Anhui, Hubei, Chongqing, Jiangsu, Hunan, Sichuan, Shanghai,and Xizang in descending order.

To address the time-consuming nature of traditional hydrodynamic model combined with scheduling model, we propose a surrogate model as an approximation to enhance efficiency. The research focuses on the practical scheduling of cascade reservoirs from lower Jinsha River to the Three Gorges. By combining hydrodynamics theory with the Kriging surrogate model, we established a multi-objective dispatching model for a multi-reservoir system, and subsequently solved the model using a multi-objective evolutionary algorithm. Ultimately, we identified the multi-objective Pareto front of the model by adopting the projection pursuit method in decision-making. Research findings demonstrate that the surrogate model exhibits an average simulation error of less than 1.5%, effectively replacing the time-consuming hydrodynamic model while generating a competitive Pareto front and providing reasonable compromise solutions. These outcomes lay a theoretical foundation for advancing the comprehensive benefits of cascade reservoirs.

In recent years, the issue of refilling cascade reservoir group in the upper Yangtze River at the end of flood season has become increasingly prominent. Ensuring flood control safety while raising the reservoir water level and facilitating a smooth connection between flood control and reservoir refill operations is of particular importance. Using power generation and water utilization rate as evaluation criteria, we investigated the strategy of in-advance water refill during flood season (July to August) for cascade reservoirs in lower Jinsha River, namely Wudongde, Baihetan, Xiluodu, and Xiangjiaba. The findings indicate the following: 1) In normal (50%), low (75%), and extremely low (90%) inflow conditions, the reservoir water level for Wudongde and Baihetan should be raised in advance as much as possible, with priority given to Wudongde. Specifically, regardless of whether the inflow in August is normal or low, if the inflow in July is normal, the water level of Wudongde should be raised above 960 m as a priority. On the other hand, if the inflow in July is low, the water level of Wudongde should be raised above 954 m as a priority. 2) For Xiluodu, regardless of the inflow conditions, it is advisable to raise the reservoir water level as much as possible, while ensuring it does not exceed 585 m.

To coordinate between flood control and profit promotion and enhance the efficient utilization of flood resources, we proposed a stage-based division of flood season using the improved fuzzy set method, and subsequently established a system coordination degree model to calculate the dynamic control domain of flood limit water level. The limit water levels in Silin Reservoir, as an example, in pre-flood season and post-flood season are directly proportional to the synergetic contribution degree of power generation benefit, but inversely proportional to the synergetic contribution degree of flood control risk. To achieve the maximum degree of system coordination, the dynamic control domain of flood limit water level is recommended to be [435, 437]m and [435, 438]m in pre-flood season and post-flood season, respectively. These recommendations would lead to additional electricity generation of 2 169.907×10⁴ kW·h and 6 509.722×10⁴ kW·h, and an increase in water resources utilization of 0.716×10⁸ m³ and 1.079×10⁸ m³, during the pre- and post-flood seasons, respectively. The findings of this study contribute to improved flood resource utilization and offer valuable insights for the safe and reasonable operation of reservoirs.

Establishing a cross-provincial ecological compensation mechanism for river basins is an important approach to coordinating basin governance and protection. Since the pilot implementation of the first cross-provincial ecological compensation in the Xin’an River basin in 2012, thirteen cross-provincial river basins in China have established ecological compensation mechanisms. Since the implementation of the cross-provincial transverse ecological compensation mechanism in the Yangtze River basin, the level of cross-provincial basin governance has significantly improved. However, the establishment and implementation of cross-provincial transverse ecological compensation mechanisms still face challenges such as limited incentive effects, insufficient basin coordination, and restricted water quality compensation standards. From a management perspective, we analyze the scientific issues related to cross-provincial transverse ecological compensation and clarify the core principles of cross-provincial transverse ecological compensation mechanism. To strengthen incentive effects and promote coordination, we put forward suggestions to promote the necessary incentive functions for cross-provincial transverse ecological compensation, to leverage the coordinating mechanisms in the Yangtze River basin, and to establish a compensation benchmark system that fits the characteristics of the resources in the Yangtze River basin. These recommendations provide a reference for the improvement of a comprehensive cross-provincial ecological compensation mechanism in the Yangtze River basin.

The New York Bay Area, San Francisco Bay Area, and Tokyo Bay Area have experienced rapid development and are recognized as first-class bay areas due to their robust economic and social growth. These regions have enacted a number of laws and regulations and implemented effective engineering measures to address water resources, water supply, flood control, and water ecological conservation. These measures aim to meet the increasing demands of water security while sustaining the rapid growth of bay area economies. In this article we analyze the current water security status of first-class bay areas, focusing on aspects such as water resources allocation, water conservation, flood control, and watershed management. We introduce the methods and successful experiences employed by these bay areas in overcoming resource constraints, coping with extreme weather events, and protecting ecological environment. Drawing on the characteristics of water resources in the Guangdong-Hong Kong-Macao Greater Bay Area, as well as the challenges faced in terms of water resource constraints, extreme weather, and ecological environment protection, we propose several recommendations to enhance water management in the bay area. These include promoting coordinated governance and management of water resources, strengthening the water resources allocation network, advancing research and application of new products and technologies for water-saving in agriculture and households, improving water transmission pipelines, implementing flood insurance systems, and enhancing water ecological environment management systems. These suggestions aim to provide valuable insights for ensuring water security and facilitating high-quality development in the Guangdong-Hong Kong-Macao Greater Bay Area.

Transverse ecological compensation in river basin is an important means to promote high-quality and green development in the Yangtze River Economic Belt. While transverse compensation within provinces of the Yangtze River Economic Belt has made rapid progress, compensation between provinces in the main stream and tributaries of the Yangtze River has lagged behind. In an attempt to promote the construction of transverse ecological compensation and optimize the paths of transverse ecological compensation among provinces in the Yangtze River Economic Belt, we systematically examine the progress, theoretical and practical challenges facing the ecological compensation system in the Yangtze River Economic Belt. Problems include low awareness among residents, limited scope, single compensation methods, ambiguous standards, and an inadequate supervision and evaluation system system. To address these challenges, we propose that measures should be taken to strengthen institutional support, promote policy, deepen interdepartmental collaboration, establish comprehensive compensation frameworks with multi-party participation, explore market-oriented and diversified compensation methods, and improve the monitoring and post-assessment system.

Joint prevention and control for trans-provincial rivers and lakes is the key and difficult problem in river and lake management. Modernizing the system and capacity of river and lake governance requires a coordinated overall planning of river basin and a joint prevention and control for trans-provincial rivers and lakes under the river chief system. The defects of joint prevention and control for trans-provincial rivers and lakes are summarized and analyzed in terms of the institutional system, the capacity of performing duties, the planning for river basin, the unified monitoring, joint law enforcement, and supervision and assessment. In the light of advanced experience of river basin management in China and abroad, some improvement suggestions are put forward based on the river chief system. The research is expected to provide scientific basis and enlightenment to the policy-making for a high-quality development of water conservancy.

Researching the spatial accessibility of national nature reserve would offer theoretical support for the construction and comprehensive development of regional national nature reserves. The spatial accessibility of 1 624 national nature reserves in the Yangtze River Economic Belt was estimated by using ArcGIS spatial analysis method, and the influencing factors of spatial accessibility were investigated with GWR (Geographically Weighted Regression) model. Results revealed excellent distance accessibility and time accessibility of the national nature reserves in the Yangtze River Economic Belt . A percentage of 90.14% of the national nature reserves locates within 100 km from prefectural centers, with an average time of accessibility only 24.23 minutes. The accessibility on county level display a strong agglomeration pattern, and a spatial pattern high in the east and low in the west with the line of “Chengdu-Kunming” as the dividing line. The altitude elevation of the county units is negatively correlated with the accessibility of national nature reserves. The abundance of the reserves and the density of road network are positively correlated with the accessibility. The density of road network has the greatest impact on accessibility, followed by the abundance of protected land and the elevation. The per capita GDP of county has no significant impact on accessibility. In addition, the accessibility of national nature reserves in middle and south Guizhou, southeast Yunnan, south Hunan and Anhui, as well as the coastal areas of northern Jiangsu Province is slightly sensitive to altitude elevation; the accessibility in the upper reaches of Yangtze River Economic belt is highly sensitive to road network density; the accessibility of natural reserves to the west of Chengdu-Kunming line is much more sensitive than the east.

The old and new water problems of Yangtze River intertwined as disturbed by intensifying human activities and increasingly frequent climate change. In line with the new requirements posed by the 14^th Five-Year Plan and the Great Protection of the Yangtze River, we analyzed the basic situation of Yangtze River’s four water problems from a macroscopic view: water resources problem involving local water shortage, insufficient management performance and others, water environment problem including excessive total phosphorus emission and unclear characteristics of persistent organic pollutants, water ecology problem such as sharp decline in ecological capacity and biological resources, as well as water-related disaster problem like frequent extreme floods and droughts. We further revealed the external driving influences of climate change factors such as temperature increase and human factors such as hydropower development, shipping, agricultural activities, and urbanization on the development and change of the four water problems. We also expounded the internal connection and feedback mechanism among the four water problems in expectation of enhancing people’s understanding of the coupling relationship among the four water problems and improving the ability of managing the Yangtze River.

To strengthen the overall planning and coordination of river basins and improve the level of joint management and great protection of rivers and lakes are problems to be solved in implementing the river chief system. By summarizing the progresses of river chief system and analyzing the demand for overall planning, we put forward suggestions on enhancing the capacity of overall planning and coordination for major river basins as follows: (1) the current water related management law can be revised, the legislation of large rivers and lakes protection promoted; regulation for river basin protection and guidance for joint prevention and control should be promulgated for trans-provincial rivers and lakes. (2) Inter-ministerial cooperation should be deepened through the inter-ministerial joint meeting platform, and basin cooperation should be facilitated by establishing and improving the “basin management organization in association with provincial river chief office”; regional cooperation can be fostered by employing and assigning personnel among provincial river chief offices in the basin. (3) A unified planning, unified standard and joint implementation mechanism can be built throughout the basin. (4) The inter-ministerial joint meeting office should supervise and inspect the overall planning of major river basins, and the investigation results can be taken as annual comprehensive evaluation basis for provincial leaders. (5) Inter-ministerial cooperation can be carried out for watershed monitoring and information sharing; water-related big data center can be built by basin management organizations; joint monitoring of provincial boundaries can be conducted between provincial river chief offices of adjacent provinces. (6) Ecological compensation should be regraded as the key issue of inter-ministerial cooperation, and basin management organizations should participate in ecological management.

The river chief system is an institutional innovation for river and lake management and protection based on regional management. Insufficient watershed management and a lack of trans-provincial cooperation are the weaknesses in fully implementing the river chief system. Through discussion and communication, data collection and field research, we sort out the progresses of implementing river chief system in Dongjiang River, a typical trans-provincial river in the Pearl River Basin, and systematically summarize the experiences and lessons learned from the joint protection and management practices. We also put forward some suggestions as follows: promoting river basin coordination, accelerating the construction of trans-provincial joint protection and management systems, strengthening joint monitoring, joint law enforcement, and information sharing capabilities, etc.. The study offers reference for basin integrated protection and management for other trans-provincial rivers in China.