Revealing the inherent relationship between urban water systems and carbon emissions has important theoretical and practical significance for promoting “water conservation and carbon reduction” in cities. This study utilizes the 2021 social water cycle statistical data of Yiwu City to quantify the carbon emissions of urban water systems. It analyzes the “water–carbon” related characteristics and carbon emission intensities under different water sources and stages and explores the carbon reduction potential of urban water systems under different scenarios. The results show that the operational phase is the main contributor to the carbon emissions of the urban water system in the research area, accounting for approximately 86% of the total carbon emissions. Over the entire process, the carbon emissions from the water supply and drainage stages are the largest, accounting for 39% and 31% of the total carbon emissions, respectively. In terms of carbon emission intensity, the carbon footprint of the water cycling process using reclaimed water as the water source is higher than that of high-quality water and conventional water sources. This is primarily due to the significantly higher carbon emission intensity in the reclaimed water phase compared with the other phases. In terms of influencing factors, the differences in the “water–carbon” correlation characteristics of different links in the water system in the research area are mainly affected by changes in urban water consumption, water treatment methods and processes, and other related factors. For the coordinated development of “water conservation and carbon reduction” in urban areas, future efforts should focus on improving the reuse rate of reclaimed water in urban life and industry, reducing the leakage rate of water distribution networks, and enhancing water treatment processes. These measures aim to increase water efficiency in urban water systems and reduce carbon emissions.

Poyang Lake, the largest freshwater lake in China, is an important regional water resource and a landmark ecosystem. In recent years, it has experienced a period of prolonged drought. Using appropriate drought indices to describe the drought characteristics of the Poyang Lake Basin (PLB) is of great practical significance in the face of severe drought situations. This article explores the applicability of four drought indices (including the precipitation anomaly index (PJP), standardized precipitation index (SPI), China Z-index (CPZI), and standardized precipitation evapotranspiration index (SPEI)) based on historical facts. A systematic study was conducted on the spatiotemporal evolution patterns of meteorological drought in the PLB based on the optimal drought index. The results show that SPI is more suitable for the description of drought characteristics in the PLB. Meteorological droughts occur frequently in the summer and autumn in the PLB, with the frequency of mild drought being 17.29% and 16.88%, respectively. The impact range of severe drought or worse reached 22.19% and 28.33% of the entire basin, respectively. The probability of drought occurrence in the PLB shows an increasing trend in spring, while in most areas, it shows a decreasing trend in other seasons, with only a slight increase in the upper reaches of the Ganjiang River (UGR). One of the important factors influencing drought in the PLB is atmospheric circulation. The abnormal variation of the Western Pacific Subtropical High was one of the key factors contributing to the severe drought in the PLB in 2022. This study is based on a long-term series of meteorological data and selects the drought index for the PLB. It describes the spatiotemporal distribution characteristics and evolution patterns of drought and investigates the developmental path and influencing factors of drought in typical years. This study provides a reliable scientific basis for similar watershed water resource management.

The Yangtze River is the third largest river basin in the world. With the advancement of research methods and data quality, the understanding of extreme climate changes in the Yangtze River Basin is constantly updated. This study used bias corrected climate projections fitted by stationary and nonstationary extreme generalized extreme value models to quantify historical warm, cold, and rainfall extremes in the Yangtze River Basin and their possible future changes. The uncertainty resulting from the intermodel and emission scenario differences was also discussed. The future annual maximum (minimum) temperature will possibly increase by 1.45°C–4.02°C (1.07°C–2.03°C), 1.54°C–4.45°C (0.99°C–1.76°C), and 1.60°C–4.91°C (0.84°C–1.54°C) in 2100 at the 10-, 20-, and 50-year return periods, respectively. The precipitation extremes are expected to increase by 6.4%–11.6%, 6.6%–12.5%, and 7.0%–14.6% at the 10-, 20-, and 50-year return periods, respectively. The warming trend and spatiotemporal distribution are mainly affected by monsoon climate, altitude, and ocean characteristics, and it is more pronounced in the middle and lower reaches of the river for warm extremes, but in plateau and coastal regions for cold extremes. The stationary generalized extreme value (GEV) model may lead to an overestimation of simulated temperature and precipitation extremes, with a deviation of $<1.0°\mathrm{C}$ for temperature extremes and $<10\%$ for precipitation extremes.

Water-draw and utilization assessment is a basic water resources management system. According to the requirements of "running at most once" and "strong supervision of water resources", aiming at the inadaptability of current water-draw and utilization assessment, this paper puts forward the overall design framework of "regional water-draw and utilization assessment + water consumption standard" system, explores and establishes an innovative management system to replace the traditional way. The key links of the system design are also analysed in this paper, and the register and commitment management pattern for water-draw permission and long-term supervision mechanism based on water consumption index are proposed respectively.

In the context of digital reform in Lishui Province, Lishui started the construction of intelligent water conservancy in order to better exert the benefits of water conservancy projects, reduce disasters and improve management and decision-making levels. Therefore, Lishui's comprehensive application platform of water resources, called “Zhe Li Hao Shui”, which means the good water of Lishui City, has been built. This article elaborates on the design concept and composition of the platform architecture, and uses the correction analysis and dynamic statistics of monitoring data to build a calculation and statistical model for multiple water resource elements. It has been well applied on the platform, and the model simulation results and measured data maintain high correlation and accuracy. Finally, based on development experience and technical summary, three suggestions are proposed for the development of relevant smart water conservancy digital platforms to learn from each other.

According to the requirement of the regional water resources demonstration system to clarify the total water consumption control index and water consumption standard, this paper studies and proposes the establishment of water consumption standard index, puts forward the analysis principle and method of water consumption standard index based on the combination of standard reference and typical investigation, and carries out the application research with Haining Economic Development Zone as an example, The research results provide technical support for regional implementation of water resources demonstration system and enterprise water saving evaluation.