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.

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.

The Bohai Bay is encircled by the Bohai Sea economic zone and faces high pressure of environmental protection due to its high pollution load. Water exchange capacity is a key factor of environmental capacity, and in the bay it is dominated by tides and winds. This study develops a water age model using an Eulerian approach, and simulates the role of winds in water exchange in this bay, focusing on comparison of the water age and its temporal and spatial distribution characteristics between two cases ? under the combined effects of tides and winds, and under the effect of tides only. The results show wind action is a crucial factor of water exchange that greatly accelerates the exchange between the bay and the Yellow Sea. Seasonal variations in water age reveal that the exchange between the bay and the central Bohai Sea is strong in winter and weak in summer.

Driven by the carbon peaking and carbon neutrality goals, new forms of energy generation such as wind power and solar power have developed rapidly. To solve the problems of intermittency and volatility in the power system, it is necessary to build matched energy storage facilities. In this paper, the gravity energy storage type of taking water as the medium is defined as Water Energy Storage. A comprehensive comparison is made between different forms of energy storage available at present and in the future, from the aspects of technical principle, economy, environmental impact, and operation safety. The results show Water Energy Storage is the best form of energy storage for supporting new energy development and New Power Systems in the next period of time. This paper also explores the planning idea, regulation calculation, evaluation method, development modes, and other key technologies and relevant policies for pumped storage, hydropower expansion and cascade reservoir energy storage, and takes an outlook for their development in the future. The study would help to plan and design new energy development and New Power Systems.

When the Mann-Kendall (MK) method is used to detect the trend in serially correlated hydrological series, it is often difficult to obtain an accurate result, due to the influences by significant higher-order autocorrelation components or the trend damage in removing the lag-1 autocorrelation in the series. Aiming at this difficulty, this paper presents a hybrid MK test model combining a modified over-whitening (MOW) process and assembling the change point tests in regression and variance and the detrended methods to segment the original series and provide a set of suitable sub-series to over-whitening. In this model, the over-whitening is calculated in sections to remove the high-order autocorrelation while destroying the original trend component as little as possible. The test results of the runoff series at Linjiacun, Shenmu, Zhaoshiyao and Hengshan hydrologic stations indicate that the segmental over-whitening process can retain the trend change in the original series when eliminating its significant lag-high autocorrelation and ensure more accurate results in the MK trend test on over-whitened series.

When the general segmentation model is applied to the apparent cracks in the dam face concrete, the network suffers the problem of depth increasing that leads to excessive model parameters and certain loss of effective crack features. To reduce network memory occupation and feature loss, this paper develops a lightweight crack segmentation method based on a convolutional neural network. The network adopts an encoding-decoding structure, and uses a depth-separable convolution module and a lightweight feature extraction module to construct a cascade encoder; it is equipped with a decoder to fuse cross-scale information in the second stage of the encoder and to reconstruct the pixel-level geometric information lost in feature extraction to improve the accuracy of network segmentation. The experimental results show the model size of the network trained on the crack dataset of dam face concrete is 10.8 MB or a size reduction of 90.8% from U-Net, with its PA of 73.3% and IoU of 85.4%. The results verify the network is feasible in dam face crack segmentation and useful for improving the efficiency of dam face detection and maintenance.

Spatial heterogeneity is an essential property of precipitation and water resources. Based on the results of the second integrated assessment to water resources in China, the Lorenz curve is used to calculate Gini coefficients and Lorenz asymmetric coefficients, which represent the degree and source of spatial heterogeneity respectively. Results indicate that different types of water resources in China show considerable or strong spatial heterogeneity. And the heterogeneity across different water resources divisions increases from east and south coasts to northwest, depending on the area, average precipitation, and other natural conditions. For each division, the heterogeneity in precipitation is the smallest, followed by groundwater resource, total water resources, and surface water resource; and water resources heterogeneity is featured with asymmetry dominated by those sub-divisions with less amount of water resources, or relative symmetry.

To alleviate energy crisis and environmental degradation and enhance the development and use of renewable energy, this study develops a numerical model of a semi-submersible multi-floating body wave power plant through combining wave energy conversion technologies of point absorption and raft type. The device is mainly composed of a central floating platform, an array of oscillating floats, a hydraulic system, and structure connecting floats to the platform, and collects wave energy from the oscillating floats on the sea surface. To improve its collecting efficiency, we numerically simulate and examine its energy conversion using AQWA hydrodynamic simulations, and analyze the frequency domain responses of a single float with different values of parameters such as the mass, size, and structure of the floats. And a detailed analysis is made on the time domain responses of a single float and the whole device under sea conditions of wave height of 1 m and wave periods of 5 s and 3 s. The results show that the geometry of the underwater part of the float has a great influence on its added mass and wave excitation force, and that a cylindrical float of 2 m in diameter features larger amplitude of vertical oscillations. This suggests that in the condition of low wave frequencies, the floats with such a design can capture wave energy closer to the maximum extent, thereby improving overall efficiency. For the floats working at high wave frequencies, they should have a conical shape, the diameter increased appropriately, and the weight reduced so as to capture more wave energy. By optimizing float structure, the energy collection efficiency of the device is raised by about 95%, indicating the importance of float structure in efficiency improvement.

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.

The SWMM model has been widely used in urban rainfall-runoff simulation and design of sponge cities. A quantitative analysis on the parameters of this model is crucial to parameter identification and uncertainty reduction. In this study, a variance-based Sobol method and different accuracy assessment standards are used to quantitatively analyze the sensitivity of the SWMM model parameters in a case study of the Huangtaiqiao catchment under floods of different levels. Results show that (1) the parameters are different in sensitivity when accuracy assessment standard or flood level is varied, indicating a great uncertainty in model parameters. (2) The Nash coefficient depends much on Dstore-Imperv, MinRate, Roughness (rivers), and Roughness (conduits). (3) Interaction between the parameters is frequent in small flood cases, while it diminishes with a trend toward concentration as flood level is raised. (4) The Sobol method, suitable for the sensitivity analysis of urban hydrological models, can provide the sensitivity of each parameter and the interaction between different parameters.

As the core equipment in high-head hydropower harvesting, the impulse turbine has the advantages of higher operating head and wider high-efficiency range compared with reaction turbines. However, features of flow fields within a Pelton turbine are open, unsteady and multi-phase. Complex flow characteristics affected by multiple flow transitions and component-matching of the Pelton turbine may exert influence on its performance and utilizing efficiency of high-head hydropower. Recent advances in impulse turbine technologies have been accelerated by the rapid development of visual test technology, computational fluid dynamics (CFD), finite element method (FEM), and artificial intelligence optimization design algorithm. The technology of impulse turbines developed late but rapid in China, summarizing by three stages from scratch, independent design to optimization, and breakthrough progresses have been accomplished especially in the past 20 years. Based on a comprehensive synthesis of researches from both national and international impulse turbines researching field, this paper focuses on the main progresses of impulse turbine technology in the past 20 years, and reviews the recent advances in the research of internal flow characteristics, sediment abrasion, failure analysis, and optimization design theories. Several issues with performance analysis and optimization design are discussed, and the development trend of impulse turbine technology is summarized and prospected.

The Wudongde and Baihetan hydropower stations on the Jinsha River are the largest hydropower projects under construction with application of the most challenging technologies under complicated environmental conditions. Construction of the 300-meter super high concrete arch dams is faced with multiple key technological obstacles and management challenges in safety and high quality. Based on the principle of intelligent closed-loop control of comprehensive perception, real analysis and real-time control, this paper deeply integrates the modern information technologies with hydropower engineering construction and formulates an intelligent dam construction technology route focusing on the core construction processes and main business processes. To meet the demands of building these two dams in safety and high quality, key technologies ? such as whole-process real-time monitoring of concrete construction, real-time control of concrete temperature, whole life cycle safety and work performance evaluation, performance review of low-heat cement concrete dam, and in-depth research of an intelligent construction platform iDam ? have been explored and applied, and related intelligent control equipment and management systems have been developed. Engineering practice shows that the key technologies and management platforms achieved in the intelligent construction have greatly improved the technology performance and management efficiency of project construction, enhanced the core competitiveness of Chinese hydropower industry, and provided better technical support for the development of hydropower project and infrastructure construction along the Belt and Road.

This paper first reviews the advancements in dam construction and development in hydraulic engineering, and summarizes the conceptualization of digital dam and its related research achievements. Then, we present an interpretation of the difference between the two concepts of digital dam and smart dam, based on a brief discussion on several disadvantages of digital dam, including insufficient depth in intelligent analysis of massive data and relatively low fusing level of site monitoring, simulation analysis and intelligent control. Smart dam is a new concept that is based on the digital dam conceptualization but emphasizes a specific form of dam development, i.e. adoption of new-generation information technologies as a basic means, such as Internet of things, intellectual technology, cloud computing, and big data. This concept also means a specific intelligent system of dam management and operation that is dynamic, refined, and perceivable in analysis and control. Besides, a smart dam often has distinctive features such as integrity, interoperability, fusion-expansibility, autonomy, and robustness. Third, we describe a basic framework of smart dams in detail, including a real-time information perception module, an interconnected real-time transmission module, an intelligent real-time analysis module, and an intelligent real-time management decision system, focusing on analysis of the progress and superiority of smart dams over digital dams in independent information collection, smart reconstruction analysis, intelligent decision, and integrated visualization. Finally, we explore key directions of smart dam research in fundamental theory, key technology, and management and operation system.

Cascade hydropower development disrupts the continuity of natural river water temperature, leading to a significant cumulative effect on the temperature and a series of ecological effects. This study examines the water temperature along the lower Jinsha River and in the Three Gorges reservoir area , and reveals its spatial and temporal variations on different scales before and after dam construction and the cumulative effects. The impact of water temperature changes on fish spawning is also discussed. The results show that after the Xiluodu and Xiangjiaba dams were constructed, the annual mean water temperature difference along the lower Jinsha becomes smaller; along the river, the annual highest temperature at the hydrological stations shows a decreasing trend, while the annual lowest is significantly elevated, especially in January and December. After the construction, the annual temperature variation is reduced, and the time period featuring water temperature distribution has a trend of ‘convergence’－the days of water temperature distribution changed from M-type to V-type. An examination on the cumulative effect indicator finds that after dam construction, a significant time crowding effect occurs－a lag time in the extreme water temperature, water temperature delayed up to 1 - 2 months, the fish of 48% and 44% affected to a high degree at the Panzhihua section and the section downstream of Xiangjiaba dam respectively－thereby affecting severely the fish spawning and reproduction in the downstream and the fish protection sections. The study demonstrates the cumulative effects of water temperature impacted by cascade dam construction and its impact on fish spawning, laying a basis to enhance the role of temperature changes caused by large-scale cascade dams and the downstream ecological restoration.

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.

Along with rapid change in global climate and fast development in urbanization, the frequency of urban waterlogging events becomes increasingly higher. Dongguan is located in the Pearl River Delta, a region of high-level economic development that is vulnerable to attacks by storm surges and high level floods in its outer rivers. Hence, waterlogging threat to this city is becoming increasingly higher and its waterlog control requires a storm water model for evaluation of its existing drainage capacity and risks of waterlogging. This study coupled LISFLOOD-FP (a 2D hydrodynamic model) with SWMM (a 1D model for a drainage system) in simulations of rainstorms and waterlogging over a study area covering typical regions of Dongguan and obtained following conclusions. By constructing a SWMM model and coupling SWMM and LISFLOOD-FP for the city, we simulated the inundated area of waterlogging and its water depth. Verification with the measured rainfall data of 13-6-2008 rainstorm shows that this coupling model was effective and satisfactory. Then, the model was used to simulate the design rainfalls with return periods of 0.5, 1, 2, 5, and 20 years. Results indicates that as the return period increases from 0.5 to 20 years, the discharges are increased at outfalls, overflow discharges, and the number of flooding nodes in the study area, and the floods have earlier peak flows and longer durations. And the inundated area increases from 0.92 to 1.93 km2, with a portion of 0.02 to 0.25 km2 subject to flooding deeper than 2m. In the study area, high risk waterlogging covers Dongzong road, Dongchengxi road, Yinshan street, and Donghui road.

To better understand the effect of disturbance in overlying water on nitrogen and phosphorus release from aquaculture pond sediments, we collected sediment samples from aquaculture ponds, designed laboratory experiments of nitrogen and phosphorus release in the condition of overlying water stirred mechanically for seven consecutive days at different stirring speeds, and measured concentrations of ammonia nitrogen, nitrate nitrogen and SRP in the overlying water and sediment pore water. The results showed that faster mechanical stirring increased the concentration of ammonia nitrogen at the early stage but in hydrodynamic conditions it was a short-term effect and a dynamic equilibrium between release and adsorption was gradually reached. A higher stirring speed promoted the release rate of nitrate nitrogen with a higher peak concentration, indicating the release rate of nitrate nitrogen from the pore water in dynamic ponds to be significantly different from that in the static pond case. The release rate of SRP was also increased to a certain degree by increasing the stirring speed. Fitting of pseudo-first-order kinetic equations to the process of SRP release reveals multiple correlation coefficients R2 greater than 0.92 and an extremely significant level (P < 0.01) of the equations fitted, showing a satisfactory representation of the process.

As typical hydraulic machines, pumps play an important role in the national economy, and progress in pump technology attracts concerns from many industries. Driven by various application requirements on the modern pump, significant advances have been achieved in its theory and technology along with the rapid development in the related disciplines such as materials science, mechanics, informatics, and computer science. At present, its internal flow mechanisms and operating characteristics are understood more deeply, information technology is widely used in its design, operation and maintenance, and new pump products are gradually becoming eco-friendly and intelligent. This article focuses on the progress in the technology of various vane pumps achieved over the last two decades, including vortex pumps, centrifugal pumps, mixed flow pumps, axial flow pumps, and tubular pumps. Based on the requirements of product applications, this paper summarize the developing trends in the hydrodynamics, design technology, vibration and noise, and operation and maintenance technology of the modern pumps.

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.

The Yarlung Zangbo River is a river of rich water resources, but its upper reach runoffs are impacted significantly by climate changes, glacier and frozen soil degradation. This paper develops a distributed eco hydrological model (GBEHM) coupled with cryospheric process modeling to simulate the runoff changes in its upper basin, focusing on an analysis of the variation trends of the hydrological elements in the study area and a quantitative assessment of the impact of climate changes. The results show that from 1981 to 2010, the annual runoff and evapotranspiration in this basin experienced a significant increase, and precipitation increase contributed most to the runoff increase. This period saw a 7% decrease in the permafrost area, a 30.6 cm/10a increase in the thickness of the permafrost active layer, and a 7.3 cm/10a decrease in the annual maximum freezing depth of seasonal frozen ground. The water reserves in the glaciers were decreased significantly at a rate of 1 billion m3/a, while their melting runoff increased at 2.7 mm/a.