The interactions between vegetation and water balance elements play a crucial role in enhancing the compatibility of water resources and forest-grassland conservation, thereby promoting high-quality development. This study employs key indicators, including the Normalized Difference Vegetation Index (NDVI), precipitation, actual evapotranspiration, and water yield, spanning the years 1982 to 2019, with a 1 km × 1 km grid as the fundamental analytical unit. It examines the spatiotemporal evolution patterns and interrelationships between vegetation and water balance elements across various spatial scales, such as climatic zones, vegetation zones, tertiary watersheds, and primary watersheds. It identifies regions and watersheds with pronounced conflicts between vegetation increase and water yield reduction, and reveals the spatial interactions between vegetation and water yield. Based on these findings, the study outlines the key challenges and recommendations for scientifically restoring and conserving forests and grasslands under the principle of "coordinated water and vegetation management". While national averages for precipitation, actual evapotranspiration, and water yield exhibit no significant trends, notable spatial patterns emerge at specific scales. Significant conflicts between vegetation increase and water yield reduction are observed in regions such as the warm temperate semi-humid zone, warm temperate deciduous broadleaf forest zone, temperate desert zone, and temperate grassland zone, as well as in major watersheds such as the Huaihe, Haihe, Liaohe, and Yellow Rivers, and in 35.7% of tertiary watersheds. Additionally, the main implementation areas of major ecological projects like the Three-North Shelterbelt Program and the Grain for Green Program (e.g., Northwest Rivers and the Yellow River basin) overlap significantly with the identified conflict-prone areas, raising concerns about the ecological water needs of vegetation in these areas. The study recommends enhancing decision-making scientificity, accounting for natural runoff reduction risks in target setting, and strengthening ecological water supply assurance for major projects, thereby providing valuable insights for the future scientific conservation of forests and grasslands.

Southwestern China is prone to drought hazards due to rainfall patterns shift, leading to water scarcity for engineering purposes, crop devastation, and ecosystem destruction. The effective management of rainwater resources is crucial for addressing these issues and mitigate agricultural effects induced by drought, which is vital for ensuring national food security. This study reviews the water resource characteristics and agricultural drought patterns across Yunnan, Guizhou, Sichuan, and Chongqing in Southwestern China, and examines the fundamental characteristics, specific technical approaches, and primary measures of an efficient rainwater regulation and control system in this region. Results of the study indicates that the spatiotemporal distribution of water resources is uneven in Southwestern China and the reliability of agricultural water supply urgently needs further improvement. This is due to a lack of integration among natural water systems, artificial water networks, and rainwater harvesting projects on slopes, which hinders the efficient allocation of water resources across different periods and regions. To address these challenges, it is recommended to (1) enhance the construction of large and medium-sized reservoirs and implement "five types of small water conservancy" projects, (2) develop surface runoff control technologies for different regions and environments, (3) promote ecological and clean small-watersheds management, (4) expand the adoption of water-saving irrigation technologies in agriculture, (5) establish models for utilizing rainwater resources, (6) improve sustainable mechanisms for infrastructure construction, management, and operation, and (7) provide technological support for small water conservancy projects in rural areas. These efforts will provide critical technical support to alleviate agricultural drought impacts, increase agricultural water supply, optimize water distribution, and maintain food security in Southwestern China.

Flood is one of the most serious natural disasters, and China's flood control policies have transitioned from reducing disaster losses to mitigating disaster risks. Research on the driving factors and management approaches of flood risks will provide technical support for formulating and implementing flood control strategies, with great significance for adopting diversified measures to improve flood risk management and reduce flood losses. Based on the research progresses relating flood risk management in China and abroad, this study elucidates the major components or driving factors of flood risks, explores the major approaches to reducing flood risks, and analyzes the environment for effectively implementing flood risk management. The results indicate: (1) Flood risks depend not only on the hazardous flood, but also on the exposure and vulnerability of the economy and society threatened by flood; (2) the risk of flood disasters cannot be completely eliminated, but can be regulated to an acceptable level by implementing a series of measures at different stages of prevention, preparedness, emergency response, and post disaster reconstruction; (3) approaches for flood risk management include improving the planning of flood risk management, strengthening spatial plan and management with inclusion of flood risk information, improving the flood control structure system, and enhancing flood emergency preparedness, response, and recovery capabilities; and (4) improving policies and regulations, effective coordination mechanisms, and promoting participation of the whole social can enable the effective implementation of flood risk management. The following suggestions are further proposed: (1) strengthening flood risk assessment, determining the acceptable flood disaster risks, and improving the flood control standards system; (2) diversifying approaches and measures tailored to different conditions to reduce flood risks; and (3) enhancing the whole society's awareness of flood risks and promoting their participation in flood risk management.

Developing major projects concerning the national water network and shoring up the construction of the national water network has strategic significance in comprehensively improving China's capacity to guarantee its water security and supporting its high-quality economic and social development. This study first discusses the necessity and urgency of constructing national water network projects based on China's water security situation. Consequently, it summarizes the technical achievements and practical experience regarding the construction from the aspects of planning, construction, and operation, drawing from the examples of the first stage of the South-to-North Water Diversion Middle Route Project, the water diversion project from the Three Gorges Reservoir to the Hanjiang River, and the water resource allocation project in the west region of Chongqing. Moreover, it explores the challenges in the high-quality construction of national water network projects and proposes several key technological research directions, including the construction principles and effectiveness evaluation systems, intelligent construction and performance maintenance, and intelligent regulation of the national water network projects. Furthermore, the following suggestions are proposed to promote high-quality construction of national water network projects and to guarantee future water security: (1) accelerating the construction of the follow-up projects of the South-to-North Water Diversion Project to complete the main framework of the national water network, (2) optimizing the regional layout of the water network project to support China's major regional development strategies, (3) promoting the demonstration projects that integrate the development of water network with other networks so as to enhance comprehensive benefits, and (4) promoting the application of digital technologies throughout the entire process of the construction and enhancing the water network's ability to serve social and economic development.

Under the influence of global climate change, hydrological drought events in the Yangtze River have occurred frequently with an increasing intensity, seriously threatening food security and economic development. This study uses the monthly water balance model developed by the Research Center for Climate Change (i.e., the RCCC-WBM model) to analyze the historical evolution and future trends of hydrological features in four hydrological stations (Zhimenda, Zhutuo, Cuntan, and Yichang) in the upper reaches of the Yangtze River and the basins above. Meanwhile, hydrological drought events and their characteristics are identified based on the Standardized Runoff Index (SRI). The results show that: (1) From 1961 to 2020, the runoffs of Zhutuo, Cuntan, and Yichang hydrological stations, along with the SRI of the main stream area in the upper reaches of the Yangtze River and the sub-basins of the Minjiang, Tuojiang, Jialing, and Wujiang River, exhibited a decreasing trend, indicating a slight drying trend, while the runoff of the Zhimenda hydrological station and the SRI of the Jinsha River basin above it showed an increasing trend, suggesting no drought tendency. (2) From 2021 to 2090, the SRI of each hydrological station and its upstream basins all showed an increasing trend, indicating that the upper reaches of the Yangtze River have no drought tendency in the future; this may be closely related to the significant increase in projected precipitation and runoff. The frequency, occurrence rate, duration, and intensity of hydrological droughts will be stronger in the near term and weaker in the long term. Given the increasingly prominent extreme hydrological droughts in the upper reaches of the Yangtze River, drought prevention and disaster reduction becomes urgent. It is recommended to improve the drought combating mechanism and system, strengthen infrastructure construction and emergency management capabilities, promote the digital technology to build a smart drought-prevention and disaster-reduction system, and highlight technological innovation to strengthen the scientific and technological support for drought prevention and mitigation.

Agriculture is an important industry in the Yangtze River Delta. Agricultural non-point source pollution has brought severe challenges to water security, food security, and ecological safety in the Yangtze River Delta; therefore, it is urgent to synergistically manage agricultural non-point source pollution through co-governance of water resource protection, water pollution control, and aquatic ecosystem restoration, thereby safeguarding the high-quality and integrated development of the Yangtze River Delta. This study systematically analyzes the challenges faced in the management of agricultural non-point source pollution in the region: large agricultural water consumption and low recycling rate; complex composition of agricultural non-point source pollution and variable production and transportation process; mutual interaction of regional planting and breeding with superimposed pollution emissions; lack of coordination between water quality improvement, water quantity, and aquatic ecosystem; unclear responsibility of non-point source pollution governance entities; and difficulties in long-term operation and maintenance of engineering projects. The study proposes the following suggestions for the system construction aimed at synergistic governance of agricultural non-point source pollution in the Yangtze River Delta: (1) constructing a regional circular wetland system for farmland to facilitate the recycling of water, fertilizer, and pesticides; (2) leveraging irrigation and drainage systems to realize stepwise interception and purification of farmland pollutants; (3) coordinating the integrated use of water and fertilizer for planting and breeding to achieve near-zero emission of non-point source pollutants; (4) integrating the governance of water resource protection, water pollution control, and aquatic ecosystem restoration to establish technical standards and management paradigms; and (5) establishing a platform for co-governance to enhance the comprehensive control system for water resources, environment, and ecology in the Yangtze River Delta.