Abstract:The number, height, and scale of existing concrete dams in China rank high in the world. Long-term service of dam engineering has a significant influence on dam safety as well as economic construction, social stability, and ecological safety. Based on an analysis of the current status of concrete dam construction and safety in China, the current status of long-term service of concrete dams and theories, methods, and techniques for the risk assessment of concrete dams are summarized from the aspects of concrete material performance evolution, concrete dam disease monitoring, construction quality control, and risk management and assessment. The law of concrete material performance evolution under the coupling effect of multiple factors, the intelligent monitoring of hidden dangers and diseases of concrete dams as well as dam construction quality, the standards and practical methods for dam risk assessment, and the probability calculation and consequence evaluation of dam breaks should be emphasized in future studies, so as to ensure dam safety during long-term service and improve the theories and methods of concrete dam risk assessment.

Abstract:Based on construction and operation of a series of super-high arch dams in China, such as the Ertan Arch Dam, Xiluodu Arch Dam, Jinping-I Arch Dam, Dagangshan Arch Dam, and Xiaowan Arch Dam, construction achievements of super-high arch dams are summarized, and advances in key technologies for super-high arch dam construction are described, including determination of arch dam foundation, shape optimization design, stress analysis and strength design, techniques for stability of dam foundation against sliding, techniques for dam body stability, anti-seismic design, concrete material study, and temperature control and crack prevention of concrete, foundation treatment, and construction technology. It is suggested that construction technology of concrete arch dams in China has reached an internationally leading level. It is pointed out that four issues in construction of super-high arch dams should be further studied: construction of dam safety evaluation systems, dam risk design, anti-seismic measures, and dam health diagnosis technology.

Abstract:The development processes of geomembrane barriers for seepage prevention in reservoirs and dams in China are reviewed, and the advantages of geomembranes are summarized, including good performance in seepage prevention, high adaptability to deformation, convenience in construction and quality control, and low cost. It is pointed out that, although geomembranes have been normally operating in some existing large- and medium-scale projects, they have been only widely used in medium- and small-scale projects in China. An comparative analysis of the development status of geomembrane barriers for seepage prevention in reservoirs and dams shows a large gap between the developments in geomembranes in China and abroad, which is attributed to the lack of an external environment for international communication, the lack of domestic motivation for research and development of techniques, and the lack of timely acceptance of professional specifications in China. It is suggested that, with the accumulation of construction experience and techniques, rapid spread of scientific and technical achievements, and in-depth understanding of related techniques, geomembrane barriers for seepage prevention in reservoirs and dams will have potential advantages and generate significant economic and social benefits.

Abstract:Seepage control techniques for earth-rockfill dams built on a thick overburden layer are reviewed from the perspectives of the vertical cutoff technique, horizontal anti-seepage technique, and joint seepage control. Innovations and breakthroughs in the seepage control of earth-rockfill dams on a deep alluvion foundation using the concrete anti-seepage wall, the grout curtain, a wall and curtain combination, and horizontal coverage techniques are described. And the applications of the FEM and BEM methods in numerical simulation of seepage control for earth dams are introduced. As applied to three typical engineering projects, reasonable seepage control measures and their optimization for earth-rockfill dams on a thick overburden layer were studied. Some suggestions and key issues for seepage control of earth-rockfill dams on a thick overburden layer are described.

Abstract:In this paper, the application of smoothed particle hydrodynamics (SPH) in hydraulic and ocean engineering is divided into four categories: wave and current simulation, fluid-solid coupling simulation, sediment transport simulation, and water-air two-phase flow simulation. The paper describes the research status and corresponding technical treatments of SPH application, especially with regard to the difficulties of non-reflection wave generation, inflow and outflow boundaries, fluid-solid interface movement, and bed scour; elaborates on the advantages and disadvantages of different SPH models; summarizes the development characteristics of SPH over the past decade; and proposes that the future work on SPH application in the hydraulics field focus on developing a high-accuracy and efficient algorithm model, mature turbulence model, and parallel computing model.

Abstract:The amount of global fluvial sediment discharge to the oceans is an important and sensitive indicator, reflecting changes in the operation of the Earth, and has a significant influence on global socio-economic and environmental problems. Global river-to-ocean sediment flux has attracted the attention of many scholars around the world. Due to the lack of reliable and complete fluvial sediment load data, it is difficult to estimate the amount and variation of global fluvial sediment discharge to the oceans. There are large differences and inconsistencies between the values estimated by previous studies. In this paper, typical results obtained from 27 recently published papers in regards to the estimations of the global fluvial sediment discharge to the oceans are reviewed. The investigation shows that there have been large differences between estimates of the amount of global fluvial sediment discharge to the oceans in the early stages of such research, but, with increasingly in-depth examination, the estimated results in recent years have tended to be reasonable, with the amount mostly ranging from 12 to 20 billion tons per year. It is concluded that the amount of fluvial sediment discharge to the oceans before and after human activities can be considered 19 billion tons per year and 13 billion tons per year, respectively.

Abstract:In this paper, the origin and development of mechanics of sediment transport are introduced, and different theories and methods with regard to the mechanics of sediment transport are reviewed. The kinetic theory of sediment transport, including the basic equations and their applications in the interaction between the sediment particles and bed surface, erosion rate of bed sediment, transport rate of bed load, and kinetic characteristics of suspended sediment transport, is examined. The results show that the kinetic theory can precisely describe the dynamic characteristics of sediment particles. In addition, the future development trend of sediment research is predicted with the bibliometrical method. The number of papers in which the key word is “bedload or suspended load” continues to increase, implying that sediment research still maintains strong vitality. Furthermore, through analysis of changes in the number of papers in different journals and on different subjects, it is found that study of the combined subject of sediment movement and geomorphology has displayed a trend of rapid development.

Abstract:This paper reviews the formation time, sediment foundation, and sediment sources of radial sand ridges (RSR). Based on some recent outcomes of the sources and transport process of sediment in RSR obtained from the National Science-Technology Support Plan Projects during the Twelve Five-Year Plan period, it is pointed out that research on sediment exchange between the Yangtze Estuary and coastal areas of Jiangsu Province, as well as orders of magnitude of sediment flowing into and out of RSR in the north, east, and south directions, should be carried out.

Abstract:Durability enhancement of reinforced concrete structures can be considered from three aspects: protection, resistance, and rehabilitation. From the aspect of rehabilitation, this paper reviews the research of the traditional repair and electrochemical methods for rehabilitation of reinforced concrete structures. The principles and current research status of cathodic protection, realkalization of reinforced concrete, electrodeposition, electrochemical chloride extraction (ECE), and inhibitor electromigration anticorrosion technology are introduced, and their effects and factors are also discussed, with emphasis placed on bidirectional electromigration rehabilitation (BIEM), which combines the advantages of ECE and inhibitor electromigration anticorrosion technology, as well as its key technical problems. Moreover, based on the research on nanomaterials, the new method of using nanomaterials in BIEM is proposed.

Abstract:In consideration of the significant influence of thethreshold chloride concentration of reinforcing steel corrosion on the service lift of reinforced concrete structures, developments in research of threshold chloride concentration around the world are reviewed from the aspects of its expression, testing methods, and factors. Chloride threshold levels from previous research are presented, and the maximum allowable concentrations of chloride ions set as national standards in China are also provided. Some issues related to threshold chloride concentration are put forward for further research, including the influence mechanisms, testing methods, multi-factor coupling effect, and optimization of calculation models.

Abstract:In order to prevent cracks and improve the construction quality of mass concrete, an intelligent monitoring and control system for crack prevention of mass concrete was developed. The system is composed of four parts, including those relating to perception, interconnection, analysis and decision making, and control, and can realize automatic perception, transmission, interconnection, and sharing of temperature control information throughout the processes of raw material precooling, concrete mixing, transportation, placement, spreading, and vibration, water cooling, and concrete surface maintenance, as well as partly intelligent control of these processes. The system has also realized management of all factors and the entire process of temperature control and crack prevention based on network technologies and the internet of things. Applications show that the system can help improve the managment level and prevent cracks during concrete construction through automatic acquisition of information, accurate control, real-time evaluation, intelligent intervention, and decision making support during the implementation of field temperature control.

Abstract:This paper briefly reviews the research and application progress of parallel seismic testing, focusing on the principle of detection of defects in pile shafts. It is considered that for piles under construction with an exposed top shaft, parallel seismic testing can provide a more comprehensive and reliable evaluation of the pile quality as compared with the conventional reflected wave method, because it has a shorter wave propagation path and lower interference, and can provide additional information on the quality of the pile shaft below the defect position and the location of the pile bottom. A case study was performed to show the application process of parallel seismic testing. The results show that measured signals of parallel seismic testing are clear and can reflect information on the quality of the pile part below the defect position.

Abstract:The main frontier problems in hydrology at present are long-term variation of hydrologic time series, spatial distribution and dynamic variation of rainfall, the relationship between a hydrologic phenomenon and the underlying surface, preferential flow, overland flow, scale transformation, equifinality for different parameters, and hydrologic nonlinearity. The scientific content, breakthrough point, and contributions to further development of hydrology are analyzed with regard to these frontier problems in hydrology. These problems should be studied further. More researchers, especially young ones, will be expected to be concerned with, discover, and discuss these frontier problems in hydrology.

Abstract:Based on observed data, substitutive data, and scientific literature, this paper analyzes the main characteristics of precipitation variations over the last 60 years, 130 years, and 280 years and discusses the possible mechanism influencing precipitation variations on multi-decadal scales. Results showed the following: (1) The average annual precipitation anomaly percentage in the Haihe River Basin exhibited a decreasing trend during the period from 1956 to 2013, with a rate of decrease of 2.6％ per 10 years, but the decreasing trend was weak during the period from 1880 to 2012. (2) During the period from 1736 to 2012, the average annual precipitation anomaly percentage in the Haihe River Basin did not show a significant long-term trend. A reduction in the trend of the average annual precipitation anomaly percentage in the Haihe River Basin appears to be a normal, but the fluctuation still existed on decadal and multi-decadal scales. (3) The period from the late 1940s to the early 1960s had the wettest climate conditions of the last 280 years. There have been several periods of persistent drought since the beginning of the 20th century, including the severe one, which has not been rare over the last 280 years, during the period from 1997 to 2003. The longest period of severe drought occurred from 1826 to 1843. (4) The average annual precipitation in the Haihe River Basin showed a characteristic of quasi-periodical fluctuation, and the relatively significant quasi-periods of fluctuation were 2 to 7 years, 11 years, 22 to 23 years, 33 years, and 63 to 65 years. (5) The reduction in the tendency of the precipitation in the Haihe River Basin after 1960s was a component of the natural low-frequency periodical fluctuation over 63 to 65 years in the regional climate. It is predicted that the annual precipitation in the Haihe River basin will increase over the next few decades, and it will probably reach its peak value during the period from 2035 to 2040.

Abstract:According to observed data of runoff and sediment load in the Yellow River from 1919 to 2012, the trend of the runoff and sediment load in the reaches upstream of Tongguan was analyzed with nonlinear statistical methods. The annual runoff and sediment discharge has shown a declining trend in the Yellow River since the mid-1980s, and the relationship between runoff and the sediment load in the upper and middle reaches of the Yellow River abruptly changed before the late 1960s and abruptly changed again in 1986. At the century scale, the runoff and sediment changes of the Yellow River were mainly influenced by climatic and other natural factors before 1960, high and low runoff and sediment loads occurred with changes in rainfall, while the runoff and sediment changes were influenced by human activities and natural factors since 1960. Though rainfall showed significant changes at different times, the runoff and sediment load decreased continuously. Over the last hundred years, the absolute value of the tendency of the annual sediment transport amount has been significantly higher than that of the annual runoff, and the absolute values of the tendency of annual runoff and the sediment transport amount in the middle reach have been significantly higher than those in the upper reach. Over the last 30 years, the runoff and sediment load were at their lowest levels in the Yellow River, and the outstanding characteristics were the continuous decrease of the runoff and sediment load, the uneven spatial distribution of the runoff and sediment load, the decrease of the sediment load mainly occurring in the middle reaches, and the decrease of runoff mainly occurring in the upper reaches. Thus, the annual distribution of the runoff and sediment load tended to be uniform, the incoming sediment coefficient tended to decrease, and the relation between runoff and sediment load tended to be strong.

Abstract:Based on analysis of the variation of grain transportation and virtual water flow between southern and northern China, a number of potential crises that could be created by the North-to-South Water Transfer Project with regard to virtual water of grain are described: exacerbation of water stress in the northern regions, threats to national food security, and a widening economic gap between the southern and northern regions. Based on the technical level of water use during grain production and current status of water-saving agriculture, we put forward two suggestions: (1)strengthening the macro-control function of the government, implementing the policy of compensation for water use during grain production, tapping the potential of water-saving agriculture, and alleviating the pressure of water resources for grain production in northern regions; and (2)developing modern water-saving agriculture by introducing market mechanisms, establishing relevant policies as soon as possible in order to encourage and support the investment and construction of water-saving enterprises as well as the operation and management of water-saving agricultural projects, and mobilizing various resources in order to promote the development of water-saving agriculture and guarantee national food security.

Abstract:Based on major achievements from the national as well as the provincial-and ministerial-level key scientific and technological projects on regional groundwater evolution during the period from China’s Sixth Five-Year Plan to its Twelfth Five-Year Plan (1981 to 2014), a review is conducted of the main advances in such research over the last 30 years in China. The research on this issue is concentrated in Northern China, and the topic selection and project approval are characterized by time features, and driven by significant social requirements. For example, a national key project on research of regional groundwater evolution at the basin-scale in Northern and Northwestern China has been performed to realize the national development objectives and meet the requirements of regional economic development. Related research in China has revealed the key issues in regional groundwater evolution under the influences of human activities and climate change and demonstrated the time features and necessity of such research.

Abstract:Based on the analysis of the precarious status of water resources in China and the formation of a strictest water resources management system, general requirements for implementing the strictest water resources management system are summarized, and the latest advances in implementing the strictest water resources management system is tracked and investigated. According to the current demands of water policy, key next steps toward implementing the strictest water resources management system are proposed: further strengthening of supervision and management; further prioritization of water conservation, and promotion of the construction of a water-saving society; further strengthening of brand characteristics, and promotion of the construction of water ecological civilization; and removal of three major obstacles (measurement and monitoring capabilities, grassroots management capability, and law-based water management capability), and establishment of three safeguard mechanisms (the national water resources monitoring capacity building project, grassroots water resources management capability, and water resources legislation

Abstract:In view of the features of flood disasters, it is pointed out that the dramatic development of urbanization over the last twenty years in the Taihu Lake Basin contributes to the significant changes of the features of flood risk. Therefore, flood control and disaster mitigation are facing significant pressures and challenges in the basin. It is pointed out that actively promoting flood risk management in the Taihu Lake Basin is an inevitable choice and a direction toward improving the safeguard level of water security. The practices of flood risk management in different stages are summarized. New situations that flood risk management is facing in the basin are evaluated. Finally, the thinking and prospects for flood risk management in the Taihu Lake Basin are both provided.

Abstract:In view of the uncertainty of flood and drought disaster systems, a flood and drought disaster risk system, consisting of the disaster hazard, exposure of disaster receptors, damage sensitivity, and disaster resistance capacity, is proposed, and its quantitative characterization is examined. From the methodology point of view, a method system for flood and drought disaster risk assessment, consisting of five methods: disaster hazard analysis, vulnerability analysis, loss risk analysis and assessment, risk evaluation, and risk decision analysis, was established. The results obtained from these methods in empirical research done by the authors are summarized and analyzed. The results indicate that the method system has universality and effectiveness and can provide a reference for risk assessment of different natural disasters, that the physical mechanism of the method system should be further analyzed in the future, and that these risk assessment methods for flood and drought disasters should be enriched, improved, and perfected, especially the loss risk curve assessment method based on the risk process.

Abstract:Groundwater contamination risk assessment is not only an important component of groundwater environmental risk assessment, but also a significant link in prevention and control of groundwater contamination. In order to provide a thorough grasp of the current research status of groundwater contamination risk assessment, this paper summarizes and discusses relevant research achievements in groundwater contamination risk assessment based on many domestic and foreign publications and data. The paper first reviews the concept of groundwater contamination risk and outlines its characteristics and assessment process, then elaborates on the main research contents and specific methods of groundwater contamination risk assessment, and finally analyzes the existing shortcomings and points out that several research fields of groundwater contamination risk assessment should be emphasized in the future, such as the theoretical system of groundwater contamination risk, uncertainty analysis of groundwater contamination risk assessment, contamination risk division, and contamination risk management.

Abstract:Varying degrees of water pollution have been found in lots of reservoirs built between the 1950s and 1960s in China after operation for several decades. Compared with point-source pollution and non-point source pollution, internal pollution is more difficult to find and control. Based on review of worldwide research on internal pollution, the cause of rapid formation of internal pollution of reservoirs is discussed from three aspects: the source, the discharge routes, and the factors of accumulation of pollutants. The impacts of internal pollution on the water quality of reservoirs are analyzed. It is pointed out that adaptive samplers, monitoring of internal pollutant transport in and out of reservoirs, distribution of pollutants, the sink-source mechanism of internal pollution, and internal pollution treatment technology should be further studied.

Abstract:The implications and research focuses of ecological water conservancy are stated. It is considered that eco-hydrology, ecological hydraulics, and assessment of the eco-environmental effect of water conservancy projects are the theoretical basis for the development of ecological water conservancy, that the idea of ecological water conservancy should be first reflected in the planning and design of water conservancy projects, with the health and sustainability of aquatic ecosystems taken into account, and that the negative effects of existing projects can be alleviated through the recovery and re-construction of habitats, aquatic ecology restoration, ecology regulation, water connectivity improvement, and other measures. This paper also analyzes ecological restoration measures for rivers and watershed habitats, summarizes methods of estimating ecological water demand, defines water connectivity, and identifies key research problems relating to ecological water conservancy in China, involving the fundamental research on the relationship between hydrological regime and biological responses and analysis of the scientificity and uniformity of ecological impact assessment of water conservancy projects.

Abstract:Indicators for aquatic ecoregions at levels I and a level Ⅱ are defined according to the driving force-pressure-state-impact-response (DPSIR) framework, and an indicator system is established on the basis of assessment of the relationship between environmental and aquatic ecological components, and the spatial heterogeneity of the environmental components. A combined zoning method moving from top to bottom and from bottom to top is used for zoning of aquatic ecoregions at levels I and Ⅱ in the Liaohe Basin. The Liaohe Basin is divided into four aquatic ecoregions at level I and eight aquatic ecoregions at level Ⅱ. The features of each ecoregions are described. It is pointed out that subjective factors still exist in the zoning process of aquatic ecoregions in the Liaohe Basin, especially in determining the boundary of ecoregions at level Ⅱ.

Abstract:Based on analysis of the concept of virtual water and the water footprint, this paper systematically reviews the latest achievements in the three fields of calculation of virtual water of product, regional virtual water trade assessment, and the changing mechanisms of virtual water. In the section on calculation of virtual water of product, the papers electively analyze the virtual water calculation method of the intermediate product and final product, and briefly analyze virtual water calculation cases at national, administrative region, and catchment scales. In the section on regional virtual water trade assessment, the paper analyzes the service condition of two methods, the method moving from top to bottom and the method moving from bottom to top. In the section on the changing mechanisms of virtual water, the paper summarizes several driving force analytical methods, such as structural decomposition analysis. Based on the summary of research advances, the paper discusses problems deserving further exploration and proposes research directions for virtual water in the future, including accuracy improvement of the virtual water calculation model, the effect of price leverage on virtual water, acombined evaluation system for the volume and quality of virtual water, and improvement of the strategy forand optimization of virtual water.

Abstract:Based on evaluation of the significance of research on reasonable sharing of the agricultural water price, this paper reviews the research progress in reasonable sharing of the agricultural water price in China and abroad, and analyzes the main research achievements systematically. A scale for reasonable sharing of the agricultural water price is summarized. The main problems in the research are pointed out: (1) a lack of studies on the theory of agricultural water price sharing; (2) a lack of quantitative research on the sharing scale for agricultural water price; and (3) a lack of rationality in the evaluation method for agricultural water price sharing. Finally, future directions for research on reasonable sharing of the agricultural water price are described.