It is extremely difficult to carry out fine management and control of the full life cycle of water conservancy objects due to their large quantites, a wide range of types, a wide spatial distribution, complex operation environments, and many interrelated factors. To solve this problem, a fundamental approach is to combine a certain water conservancy big data technology characterized by association analysis with a professional mechanism model characterized by causality, integration and fusion, and efficient process; to analyze the massive and multi-source data intelligently; and to proactivily present useful highly-visualized results to management decision-makers. This paper provides a review on the concept of water conservancy big data and its technology system, along with an overview on the research status quo of natural law analysis, situation research and judgment, trend prediction, and decision optimization for water conservancy. We find that the future trend in big data technology development is toward scenario-based demands, management integration, analysis intelligence, service platforms, and guarantee systems. In water conservancy big data application, data are fundamental, analysis is the core, and the ultimate goal is to improve the efficiency of water treatment by using big data technology. Thus, we should deeply tap the real demands of water conservancy business management; integrate the panoramic data in the fields of water disasters, water resources, water environment, water ecology, and water engineering; comprehensively lay out the research on basic theories and core technologies, so as to accelerate the deep integration of big data technology with water conservancy and support the complete transformation and upgrade of water governance in China.

To implement the dual-carbon strategy, energy is the main battlefield and electricity the main force; developing a new power system with new energy resources as the main body is the only feasible path to achieving carbon neutrality. This paper examines the emission reduction targets, electricity composition, and structure of the power industry under the dual-carbon strategy, and demonstrates that accelerating the construction of conventional hydropower stations and pumped storage power stations is an important basis for solving problems and challenges such as the reliability and long-term regulation capabilities of the new system. Based on the hydropower resources endowment and the development status, we present a strategic idea of strengthening the coordinated development of hydroelectric power and new energy, and redefine the development path of building clean energy bases and energy storage plants and accelerating the construction of pumped-storage power stations and cascaded conventional hydropower reservoirs. This new positioning of hydroelectric power in the new system not only provides basic electricity but plays its capacity function. Thus, we suggest certain policy should be formulated to speed up the construction of clean energy bases and energy storage plants. Our findings could help the revision and compilation of the planning schemes and regulations.

With popularization and application of the project general contracting model in the water conservancy and hydropower industry, the integrated design and construction model led by design has become an effective means of reducing costs and increasing efficiency, unified management, and scientific decision-making. This paper reviews the recent advances in the research of general contracting models, design models, construction models, and design and construction collaboration models for the water conservancy and hydropower industry in China and overseas; and clarifies the current pain points of this industry and its major bottlenecks in developing and implementing such integrated models. We investigate the key roles and concept of applying the informatization technology forefront, deepening technological innovation and practice, and adopting the top-down design and lean construction models in solving the existing problems of low design optimization efficiency in design and construction integration, cumbersome mutual feedback of design and construction information, and low level of intelligent construction. To further develop this concept, taking the digital twin technology as a basic application framework for the future, we expound key research directions for further research, and suggest how to promote the integrated design and construction in hydropower development and overcome the shortcomings in water conservancy informatization.

This paper presents a concrete crack detection method based on cascaded neural networks in complex environments, aiming at the problems of the traditional deep learning crack detection method in complex environments: low robustness, poor edge area identification accuracy, and large errors in damage quantification results. In this three-step method, first it uses the improved semantic segmentation model to preliminarily identify cracks in complex environments, and determines roughly a cracking area of interest in the image. Then, it optimizes the rough segmentation image using the mask based on pyramid pooling to accurately capture the context information of the crack edge. Finally, it calculates crack width using the image pixel resolution with the QR code targets and a crack width parameter acquisition algorithm. The test results show that compared with the traditional crack identification, this method improves significantly in the five evaluation indicators－precision rate, recall rate, accuracy rate, F1 score and intersection ratio－and achieves an overall detection accuracy of higher than 95%, thereby realizing the detection and quantitative analysis of concrete cracks in complex environments.

The fusion of mechanism and data is crucial to accurate and efficient assessment of the dam life cycle state and reservoir regulation. This paper discusses the major problems in dam construction and the development of fusion models, and suggests three types of structure for a mechanism-data-driven model－series, parallel and hybrid－along with a brief description of its basic characteristics and applicability. Then, the application and applicability are demonstrated in detail through an example of temperature field analysis for a concrete arch dam. Results show that this fusion model is more accurate and stronger in analysis, prediction and generalization of dam construction and operation, and it is applicable to complicated dynamical-evolving data. Compared with the traditional model, all the three model structures are advantageous. The mechanism-data-driven model provides a new perspective and paradigm for solving the problems of parameter inversion, monitoring and analysis, and strategy optimization in the stages of dam construction, operation and maintenance.

The section from Gaocun (GC) to Taochengpu (TCP) of the lower Yellow River (LYR) is a typical wide-floodplain transitional reach, featured with a complex channel-floodplain system and severe development into a secondary perched channel. This study conducts a detailed investigation of the relationship between spatiotemporal water-sediment variations and geomorphological evolution observed in this reach, using its historical bathymetric data and the cross-section method. The results show that during the operation of Xiaolangdi reservoir, the main channel was continuously scoured, causing narrower and deeper main channels, a decrease in river cross-sectional geomorphic coefficient, and an increase in the bankfull area mostly by more than 200%. In recent years, however, these trends have been significantly weakened－the main channel was slightly widened horizontally and deepened vertically between GC and Sunkou (SK), while mainly deepened vertically between SK and TCP. In the GC-TCP reach, the channel-floodplain system has gradually switched from sedimentation to erosion patterns, with the resulted erosion rate of roughly 0.07 m/a of its main channel and 0.002 - 0.008 m/a of its floodplains; its cumulative erosion volume during 2000 - 2016 was around 2.251×108 m3. The lateral slope of floodplains increased in time, and its spatial distribution was concentrated between 0.5‰ and 2‰.

Large-scale utilization of new energy such as wind and solar is an important way to achieve the goal of dual carbon, but its uncertainties affect the operation stability of power systems and the capability of absorbing new energy. This paper develops a capacity optimization allocation method considering uncertainties for wind-solar pumped storage power generation systems. First, a random distribution function is used to describe the output characteristics and load distributions of wind power and photovoltaic power generation, and a mathematical model of complementary power generation system is developed. Then, we construct a two-layer capacity optimization configuration model based on the information gap decision theory and the entropy weight method. Finally, we use a multiverse optimization algorithm to solve for capacity optimization configuration schemes. Calculations show that investors can adopt different allocation strategies for source-load uncertainty according to their investment intentions, and the operating results obtained can well meet the requirements in different operation modes and multiple operation scenarios. Our method can help reduce the comprehensive cost significantly, improve the capacity of new energy consumption, and maintain the long-term operation of pumped storage power stations.

The intelligent construction of dams, characterized by safety, high quality, efficiency, economy, and environmental friendliness, is a future development trend. Appropriately evaluating the degree of intelligence in dam construction is crucial to achieving organization-level intelligent construction. However, the current stage of dam construction is in transition from digitization to intelligence, and effective evaluation methods for the intelligence degree in engineering systems are lacking. This paper outlines the system characteristics and hierarchical divisions of intelligent dam construction, based on the theory of intelligent dam construction. We discuss the basic principles of evaluating the intelligence degree and develop a new model for evaluating it, based on a general framework of dam construction. A general model application procedure is also constructed. Finally, our method is applied to projects of typical high earth-rockfill dams and concrete arch dams, and their intelligence degrees are evaluated systematically from the perspectives of execution level, coordination level, and organization level, thus lying a basis for the design of intelligent construction systems in large-scale hydro projects.

In this study, we apply the Beijing flood forecast model and both the gauge-measured and radar-monitored rainfall data to reassess the "July 2023" flood event that occurred in the key regions of Beijing. Results reveal that the radar-derived rainfall data closely align with ground observations, offering a more nuanced representation of the rainfall's temporal and spatial variations. Comparative evaluation of the forecasting capabilities based on these rainfall datasets demonstrates their substantial equivalence, affirming the radar data's viability as a credible alternative to ground measurements. Our specialized Beijing flood forecast model, meticulously tailored to the distinctive runoff characteristics of the city’s mountainous areas, consistently exhibits a high accuracy across a wide range of scenarios. The intricate hydrological processes in the city's mountainous terrains are inherently nonlinear; the parameters of its hydrological model, often derived from the historical floods of varying magnitudes, inherently harbor uncertainties. Recognizing the dynamic nature of runoff and flood events, we emphasize the necessity of proactive model parameter optimization. This optimization procedure should integrate real-time conditions and the most current data so as to bolster the reliability of flood predictions.

As a typical multiphase heterogeneous material, concrete has been widely used in high-rise buildings, bridges, dams, nuclear power stations as well as other industrial and civil structures. The whole process of concrete production, transportation, construction, curing and hardening, and its nonlinear mechanical and deformation response subjected to complex loading environments are generally dominated by the physico-mechanical properties of meso-scale ingredients and fabrics, including aggregates, mortar and their interfaces. This paper presents a literature review on the state-of-the-art concrete meso-scale mechanics, emphasizing the development progress on experimental investigation on meso-scale ingredients, pre-processing modeling approaches, and numerical modeling methods for concrete. An in-depth review is also presented on selected aspects on the forefront of the meso-scale concrete mechanics, including the fracture failure mechanism, size effect, multi-scale coupling and rate effect. Finally, some recommendations for future studies are provided.

Climate change is closely related to energy-power supply and demand. In the summer of 2022, the upper reaches of the Yangtze River experienced three worst cases: the highest temperature, longest continuous hot days, and lowest rainfall in the same period in history. This resulted in a daily power shortage of 17 million kW and 370 million kW?h in Sichuan, a major hydropower province, and imposed a significant impact on its social and economic development and people’s livelihood. To guarantee energy and power safety, it is of great significance to establish power planning mechanism and some countermeasures for power supply guarantee in extreme weather. This paper presents an analysis on the impacts of extreme weather in the 2022 summer on the power supply guarantee in Sichuan, and examines the shortcomings of previous electric power development. We suggest certain countermeasures for the period of power transformation－such as water-wind-solar-thermal energy complementarity, and a coordinated development of power supply and power grid.

Since the Paris Agreement was signed, it has become a broad consensus of the international community to promote global carbon neutrality. Green energy development is the key to achieving carbon neutrality; Hydropower, as a highly flexible renewable energy, will play an important role in the transformation of the global energy structure. The current hydropower development situation is different across the world, due to the difference in economic development levels, hydropower potentials, and the degree of development. And the development of global hydropower faces both opportunities and challenges under the current complex context of global energy transition, climate change, environmental policy impact, and geopolitical conflicts. In recent years, China is leading the development of hydropower and has made remarkable progress. Therefore, the global hydropower industry needs to speak up and take active measures to formulate development strategies from various aspects, deepen the energy revolution, drive the sustainable development of hydropower globally, and push it to continue to play a role as the backbone of tomorrow's novel energy system for a smooth realization of carbon neutrality.

To examine the fish resources in rivers and its protection, this paper develops a fluvial egg drift model in the Eulerian-Langrangian approach coupling a traditional 2D shallow water model to a 3D particle tracking model. This egg drift model is capable of simulating river hydrodynamics, 3D movement of fish eggs and their dispersive patterns in natural rivers under advection and turbulent diffusion. Its performance is verified by comparing our simulations with the previously published measurements on laboratory flumes using particle tracking velocimetry (PTV), and a good agreement is achieved. Then, the model is used to simulate a field experiment of egg release and capture in the Ouchi tributary of the middle Yangtze, focusing on analysis of egg transport dynamics, vertical egg mixing, transverse distribution of egg concentration, and the influence of river geography and hydrodynamics. The inaccuracy of traditional methods using cross-sectional averages in estimating the drifting egg resources due to the non-uniformity of transverse distribution is addressed and improved through certain correction in numerical simulations. The improvement is verified against field egg capture data, showing that after correction the simulation errors are reduced significantly. Moreover, the simulations reveal that average egg drift velocities are considerably lower than those of the mean flows, which must be considered in predicting the locations of fish spawning grounds.

This article reviews the historical development of dam construction, summarizes the developing trend and key technologies of intelligent construction of dams, sorts out the relationship between the key issues in intelligent construction and intelligent control, and presents a basic control theory for intelligent construction of dams. The concept and definition of intelligent control and its characteristics, theoretical structure and elements are elaborated in detail, and "intelligent decision-making plus automatic control" is clearly defined as its two core elements. On this basis, an intelligent control system for dam construction－featured with the functions of autonomous perception and cognitive information, intelligent organization planning and decision-making tasks, and automatic control of executive agencies to accomplish goals－is constructed; its design concept, component elements, module characteristics, and application levels are explained. This intelligent control theory lays a theoretical basis for solving a variety of dam construction problems: structural service state control, full life cycle safety performance evaluation, construction risk prediction, early warning during dam construction, and cost control. It is also essential to realize the intelligent construction goal of high quality, high efficiency, safety, economy and greenness.

The low-carbon transformation of electricity has an overall strategic significance for China to achieve the goal of carbon neutrality. This paper presents an analysis and predictions of the power growth process and phased development goals in China in the next 40 years, on the basis of summarizing the developing process of low-carbon electricity in the past 10 years, and taking population, urbanization, economic aggregate, and economic structure as the boundary conditions and driving forces. We examine the influence of a variety of factors on the carbon emission level－such as fossil power proportion, terminal power consumption proportion, nuclear power development scale, and Carbon Capture, Utilization, and Storage (CCUS)－with the constraints of system security and supply-demand balance. We estimate that the total carbon emission from electricity will reach its peak around 2035, 6 - 6.5 billion tons, and then be reduced year by year down to a level below 1 billion tons in 2060. With the help of CCUS technology, zero electricity emissions can be achieved. Finally, in view of the long-term coexistence of demand growth and low-carbon transformation, we suggest that future power development be based on the premise of safe supply, giving priority to the development of renewable energy power, multi-energy development, and a wider range of multi-energy complementary coordinated development and complementary operation.

The performance of hydraulic turbines, as the core mechanical equipment for developing hydropower, determines the development and utilization rate of hydropower. Driven by the progress of modern science and technology, hydraulic turbine technology has made a great progress in China, it has experienced the developing stages of introduction, absorption, digestion and recreation, and now has reached an internationally advanced level after a rapid development over recent two decades. This paper focuses on the key research advances made in the field of turbine technology in the past two decades, based on a comprehensive synthesis of research achievements in this field in China and abroad. The progress is summarized in three parts: hydrodynamic foundation of hydraulic turbines, optimal design theory of hydraulic turbine flow components, and development of new hydraulic turbines. This paper also discuss the problems in some of the research fields and present a prospect for the development trends in hydraulic turbine technology.

Climate change and rapid urbanization have modified the process of urban eco-hydrologic cycle, aggravating urban problems such as water shortage, water environment pollution, water ecology destruction, and rainstorm flood disaster. This paper presents a systematic summary of the core indexes and control points of sponge city construction in new and rebuilt urban areas with different planning objectives, to obtain the spatial optimal allocation scheme and multi-objective cost-benefit optimal curve of a system coupling low impact development (LID) facilities or green infrastructure (GI) with urban gray infrastructures. Aimed at the existing issues in research, a regional optimal allocation pattern of rainwater infrastructure is constructed, comprising three major parts–performance index database of rainwater infrastructure, cost-benefit quantification, and computer aided decision-making. The key parameters and performance indexes of typical LID facilities in numerical calculation and model simulation are discussed. Then, the method of quantifying sponge city construction with cost and benefit indexes is analyzed by applying the theory of environmental economics. Finally, multi-objective intelligent optimization schemes are explored for improving urban water environment, water ecology, water resources, and water security with limited cost input. Meanwhile, model simulations are combined to realize the virtuous cycle and sustainable development of urban ecology and hydrology.

With global warming, extreme rainfall events are increasing, leading to frequent disasters in small watersheds in mountainous regions and threatening severely the safety of people's lives and property. A small watershed can adopt various forms of disaster prevention and reduction, among which the combination of ecological engineering measures and geotechnical engineering measures can not just fully utilize the disaster reduction effects of the two measures at different periods, but also increase the overall disaster reduction effectiveness. At present, the principle of collaborative disaster reduction between ecological and geotechnical engineering measures is unclear, and their evaluation methods are also unclear; so, it is extremely difficult to combine the two organically or conduct a comprehensive disaster reduction benefit assessment. On the basis of natural solutions, this paper establishes a principle of coordinated ecological-geotechnical measures for reducing disasters in small watersheds in mountainous regions. Specifically, a stable step-deep pool structure using ecological and geotechnical engineering measures should be formed through collaboration of both fields, slope protection, and channel regulation, so as to achieve collaborative disaster reduction. Then, we give a quantitative method for evaluating the effectiveness of synergistic disaster reduction by small watershed ecological and geotechnical engineering measures based on energy reduction planning, thus laying a basis for design, species selection, and integration with geotechnical engineering strategies.

This paper presents a new array-type device of wave energy generation and describes its working
principle.A simulation model for this device was developed and its parameters and finite element mesh were
calculated by the method of AQWA. Using this model, we analyzed the RAO parameters of frequency
responses for a single float of different sizes and drafts and the characteristics of whole float array under
different angles of wave incidence. The results show that for a single float, when its draft is in the range
1.2-1.4m and its diameter 2.8m, the RAO parameter is maximized. And for the float array, a greater average
amplitude of relatively higher efficiency in capture of wave energy can be achieved at an incidence angle of
22.5° with a small variation in the amplitudes of different floats.