Abstract: The East Asian summer monsoon brings a large amount of precipitation in East China every year, which is the main source of water resources for China. At the same time, it often causes the severe flooding disasters. The Chinese meteorologists and hydrologists have realized that the moisture transport intensity, the extent and persistence of summer monsoon may play a crucial role in extreme rainstorm processes. This branch of moisture transport belt may be termed as the East Asian summer monsoon moisture transport belt. It can be categorized in the atmospheric river (AR) coined internationally, but it is not a fully same conception, due to its unique regional feature of the East Asian summer monsoon. The monsoon moisture transport belt is a main producer of excessively heavy rainfalls and disastrous floods in this region. Based on the data of the past hundred years, this paper made an update review of the characteristics and formation reasons of the East Asian summer monsoon moisture transport belt. Taking the five strongest continuous heavy rain processes in the Haihe River, Yellow River, Huaihe River and Yangtze River in the past hundred years as examples, the important role of the monsoonal moisture transport belt is analyzed. Finally, it is proposed that climate warming can affect the global water cycle through four aspects, including holding more water vapor in the atmosphere, changes of the atmospheric circulations and radiation forcing with climate warming as well as the regional impact of aerosols.
Abstract: The water vapor transport in the atmosphere is important for the global water cycle, climate system, and ecological environment. The water vapor transport over China is a critical influential factor for the spatial pattern of drought and flood in China. The interannual and interdecadal variability of the water vapor transport over China is affected by the El Niño-Southern Oscillation, sea surface temperature, North Atlantic Oscillation, and Pacific Decadal Oscillation. This paper reviewed recent studies regarding the interannual and interdecadal variability of water vapor transport over China, including the water vapor transport associated with the interannual and interdecadal variability of precipitation in eastern China, the water vapor transport associated with the interdecadal variation of Mei-Yu features, the influences of tropical sea surface temperatures on the water vapor transport over China, and so on. Moreover, the recent advances in water vapor transport over the Tibetan Plateau are also reviewed.
Abstract: Remote sensing is widely used and plays an irreplaceable role in integrated watershed management and watershed science. This paper focuses on the definition, progress and prospective of watershed remote sensing, and provides a systematic summary of relevant watershed remote sensing data products. Watershed remote sensing studies the analysis capabilities for underlying structure, water cycle, water resources, water hazards and watershed ecology and provides related remote sensing data products. These products are gradually becoming continuously updated public products and services that can meet the requirements for timeliness, completeness, continuity and high accuracy of monitoring information for integrated watershed management. The combination of Watershed remote sensing and cloud computing could reduce the bottleneck of the generation of watershed remote sensing data products. Combined with and cloud services, the difficulty and cost of watershed remote sensing data products application can be reduced, which will be the mainstream direction of watershed remote sensing towards practicality, thus providing comprehensive information support for integrated watershed management.
Abstract: Air humidity is one of the most important meteorological elements, which is closely related to the temperature and precipitation. Long-term trend of air humidity reflects the change of climate system. According to the third national report on climate change of China, relative humidity over China has demonstrated a sharp decrease around the year 2003, probably due to the substitution of manual stations with automatic stations around the same year. Further research that involves using more data on homogenous relative humidity is required. This study includes daily temperature, precipitation, and relative humidity data corrected by the Meteorological Information Center of China Meteorological Administration and showing good homogeneity at 824 meteorological stations over China during the period from 1961 to 2010. Linear regression analysis, Mann-Kendall trend test and partial correlation analysis methods were used to detect long-term trends of the vapour pressure and relative humidity over China and the impact of temperature and precipitation changes on the trends. The results indicated the following: ① Annual average vapour pressure nationwide is increasing generally, with 90.3% of the stations showing increasing trends. In terms of seasons, vapour pressure mainly exhibits an increasing trend in different seasons across the country, with exception of a decreasing trend in the Loess Plateau and Yunnan-Guizhou Plateau areas and the lower reaches of the Yangtze River basin in spring and summer and in South China in autumn. ② Annual average relative humidity nationwide is generally decreasing, with 64.1% of the stations showing decreasing trends. Stations with increasing trends are mainly distributed as follows:from northern Hebei to northern Liaoning, from southern Shaanxi to Huang Huai, western Sichuan, and most areas of the Northwestern District of China. In terms of seasons, in spring, summer and autumn, the relative humidity in most areas of central and eastern China decreases on the whole, whereas, in winter, most areas show increasing trends except Northeast China and Yunnan which show decreasing trends. ③ The annual average vapour pressure nationwide is mainly positively correlated with the temperature and precipitation, where the positive correlation with the temperature is stronger than that with the precipitation. The annual mean relative humidity is generally negatively correlated with the temperature whereas it is mainly positively correlated with the precipitation.
Abstract: In this article, we reviewed the history of the development of hydrological science in People's Republic of China for the past 70 years. We also discussed the basic scientific questions of hydrology and its current frontier, which include the hydrosphere and its interface with other spheres of the earth, the hydrological cycle system and the disturbance of human activities to it, the hydro-observation and the methodology of hydrology research, the application of hydrological knowledge, etc. Based on these studies, we suggest to divide the hydrological science into five sub-disciplines:General hydrology, Hydro-meteorology, Land-hydrology, Eco-hydrology, and Applied hydrology.
Abstract: The significant changes in the cryosphere have produced a series of effects on the cryospheric hydrological processes. This paper comprehensively reviews the recent 20 years, especially the new progress in the research on the changes in cryospheric hydrological processes in China, which mainly include glacial meltwater, snowmelt runoff, and frozen ground hydrology. The main progresses in the study on changes in glacial meltwater manifest as:a comprehensive study on glacial meltwater at different scales was carried out, it was found that the glacial meltwater showed continuously increase, and whether the "peak point" of the glacial meltwater have appeared has scientifically identified and some basic understandings has obtained, and the modelling on glacial meltwater process had made significant progress. In the study on snowmelt runoff changes, the snowmelt runoff contribution rate to river runoff in various basins were basically grasped by estimating the snowmelt runoff and found that the snowmelt runoff changes in China vary greatly, and it increased in some basins while decreased in some basins. The changes in the start melting period in China are universal with other basins in the world, and the prominent feature is the advance of the peak value. In the study of frozen ground hydrology, the studies on the relationship between surface water, interflow in active layer soil, supra-permafrost water revealed the coupling mechanism of gravity and thermodynamics in the formation of runoff in permafrost regions. The impacts of permafrost change on surface runoff has already appeared, which mainly appears as increase in the winter (dry season) runoff. It also found that the permafrost degradation has a direct replenishment effect on river runoff, and the amount of recharge may have reached a certain level in some basins.
Abstract: To explore the evolution characteristics of global land surface water resources in the changing environment is a hot and difficult issue in the current hydrological and water resources research. Improving the accuracy of hydrological forecast in the ungauged basins is important for accurate evaluation of global surface water resources. To solve this problem, we first divided the global climate ecological division, compared five parameter transplant methods, and found that the combination of inverse distance spatial interpolation method and physical similarity method has the highest simulation accuracy, and then analyzed the evolution characteristics of surface water resources in the world, continents and key regions from 1960 to 2016. The results are as follows:229 climate-ecological subareas are obtained based on 13 climate regions and ecological indictors, using the Köppen-Geiger classifications method and the unsupervised classification method. The global surface water resources is 41.06 trillion m3, showing a significant decrease trend. The surface water resources show significant decreaing trend in North America and Africa. The level 4 water resources zones with declining surface water resources trend are mainly distributed in North America, North of South America and Central Africa.
Abstract: During the past years, urban floods/waterlogging disaster is becoming a big challenge due to the joint impact of global climate change and rapid urbanization, which is becoming an important factor affecting urban public security in China, and seriously restricting the sustainable and healthy development of economics and society. The study on the disaster mechanism and risk assessment of urban flood/waterlogging disaster under the changing environment is the important basis to improve urban flood/waterlogging control and disaster reduction system, and enhance the urban flood control and waterlogging reduction capacity. In this study, the influence mechanism of climate change and urbanization on urban flood/waterlogging disaster was investigated, and the driving factors and disaster mechanism of urban flood/waterlogging disaster were analyzed systematically. The methods of risk assessment and risk zoning on urban flood/waterlogging disaster were also reviewed, and the sponge city demonstration area in Jinan City was selected as a case study to analyze and compare risk zoning of urban flood/waterlogging disaster.
Abstract: The trend of the Yellow River sediment load in future is related to the development of the river basin management strategy in the new era. It has great significance to clarify the sediment load feature for the determination of future trend, especially under the typical and extreme precipitation. The study emphases on the sediment load fluctuation in the typical large sediment discharge years in 2013 and 2018, and the typical extreme heavy precipitation in 2017, based on analyzing the character and future trend of the sediment load. The result showed that the sediment load discharge decreased extremely in a stage style on century scales from 1919 to 2018, particularly those decreased to 244 million tons after 2000. The sediment load discharge from the Toudaoguai to the Tongguan region decreased 82% than that from the similar upstream rivers years, and the flood discharge decreased around 50%—85% from each extreme precipitation, along with the improvement of the erosion environment in the Loess Plateau. The typical extreme heavy precipitation did not generate the large sediment discharge in 2017 which confirmed that the ecological construction of soil and water conservation played a great significance for reducing sediment into the Yellow River. The fluctuation of the Yellow River sediment load is affected by the deposition from the waterways and the release from the reservoirs by the results of sediment source in 2013 and 2018 in the new era.
Abstract: The human activity and climate change have significantly altered the river flow and spatio-temporal distribution of flood process, which directly impact on design flood in the downstream section. The effects of upper reservoir construction and regulation on downstream hydrologic regime are reviewed, the main research contents of design flood theory and method in cascade reservoir operation period are proposed. We mainly discuss non-stationary flood frequency analysis method and the most likely flood regional combination method based on copula function, and compare their practicability. We recommend using design floods and flood control water level in reservoir operation period, and suggest further research references and directions.
Abstract: In the last 70 years, China has made great achievements in the treatment of the Huaihe River basin. Now the main stream of the middle and lower reaches of Huaihe River and the Hongzehu Lake have become the key areas for further treatment. This paper systematically sorts out the main contradiction changes in the treatment of the Huaihe river basin in the new period, from the perspective of strategic status improvement of the river basin, economic and social development, evolution of natural environment and changes in water issues. The strategic thinking and suggestions for comprehensive treatment of the middle and lower reaches of the Huaihe River basin are also put forward, from the aspects of basic research on water and sediment, reveal of targeted problems, restructuration of rivers and lakes, and comprehensive treatment measures. This paper also introduces the contents and technical methods of further research on the evolution and treatment of the main stream of Huaihe River and the Hongzehu Lake, as well as the preliminary research results and conclusions, from the following four aspects: the revolution law of rainfall and flood in the main stream and tributaries, the characteristics of sediment in the main stream of Huaihe River and the Hongzehu Lake and their variation law, the present situation and the flood control effect and coordination of the planned project, and the proposal for combination scheme of engineering measures. This paper can provide a reference for the planning and designing of the Huaihe River basin treatment in the new period.
Abstract: Climate change has intensified the conflict between economic and ecological water demands, and brought challenges to the ecological operation of hydropower plants. This study examined the effect of climate change on hydropower generation and ecological operation of hydropower plants, and investigated the response of the interactions between power generation and ecological water demand to climate change. The hydropower operation model and the future streamflow projections modeled by climate projections of several global climate models are used. The downstream cascade of Lancang River hydropower plants was used as a case study. Results show that the overall streamflow and hydrological variability were predicted to increase under climate change, and the ecological flow destruction rate was also predicted to increase. The benefit of hydropower generation and its ecological effects varied more among different operational schemes than among different climate change scenarios, indicating that future conflicts between hydropower generation and ecological water demand are largely inevitable. The increase in hydrological variability caused by climate change can exacerbate the conflict between hydropower generation and ecological water demand, causing larger costs of ecological degradation when retaining the current hydropower benefits.
Abstract: This paper discussed the general conceptions on environmental flow (e-flow). Emphasis was laid on relationship between the dynamic change of ecosystem and factors resulted by hydrological change especially by the change of flow velocity whereby to estimate e-flows. Moreover, this paper introduced a Chinese e-flow method—ecological hydraulic radius approach (EHRA)—which basis is ecological velocity and ecological hydraulic radius. EHRA estimates e-flow fully accounting for information of biota, e.g., flow velocity requirement of fish during spawning seasons, and information of rivers, such as water level, flow velocity, roughness. In addition, this paper generally described the application of EHRA in estimation of e-flow by considering pollutants degradation, requirement of fish on flow velocity, balance of river-course with erosion and sedimentation processes. What is worth noticing is that the ecological flow velocity for e-flow estimation in this paper refers to both the flow velocity suitable for biota and the flow velocity variation induced dynamic factors (e.g., ecological geomorphology, fluvial factors), which can enlarge the conception of ecohydrology and broaden its application.
Abstract: This paper summarizes the evolution of engineering water conservancy, environment water conservancy, resources water conservancy and ecological water conservancy in our country. Moreover, the research progress, developing tendency and characteristics of ecological water conservancy worldwide is explored. Corresponding results demonstrate that ecological water conservancy is a way of water resources utilization in the time of ecological civilization, which serves the sustainable development of human society through implementing water conservancy and developing economy with the gist of respecting and protecting ecological environment. Present paper elucidates the connotation, definition and development mode of generalized ecological water conservancy, and proposes following conclusions and academic viewpoints:① Generalized ecological water conservancy explores specific measures and ways in ecological water conservancy to meet the demands of human society and healthy water ecosystem through selecting water resources and water cycle operation as primary ecological elements from the multiple perspectives of energy exchange, biological links, structural balance and cycle and transformation in watershed ecosystem. ② This paper presents engineering and ecological security system for the full-process and lifecycle (i.e. planning and design, construction management and ecological regulation) of water conservancy project. In particular, ecological regulation is incorporated into the full-service period of water conservancy project. Furthermore, we highlight that basin-scale ecological regulation is the most effective measure to protect and restore ecosystem in the "post-dam era". ③ We suggest dominating the spatial dimension of ecological water conservancy, promoting optimal design of ecological-production-living spaces, ensuring the reasonable allocation of ecological-production-living water use, and optimizing the relationship among general life, production and ecology from the perspective of ecological environment, social economy and water cycle regulation in the system of planning and governance of territorial space to realize ecology protection and high-quality development of society and further promoting the innovative development of ecological water conservancy.
Abstract: Eco-environmental conservation has been a long challenge and even bottleneck for sustainable hydropower development. This study comprehensively reviewed the advances of researches on river damming impacts on biogeochemical cycling and thereby the aquatic eco-environment effects, zoobenthos habitat, fish habitat and migration routes, as well as structure and non-structure conservation measures. It analyzed the current challenges in fundamental researches and engineering applications as well as the underlying reasons, and highlighted the core aspects for future investigations. These include:① Long-term in-situ monitoring to discover the interception, transformation and transport processes of biogenic elements, and reveal the associated mechanism as well as the accumulated eco-environmental impacts; ② Reservoir induced changes in effective accumulated temperature regime for fish gonadal development and critical temperature regime for fish spawning, and consequently their joint effects on fish reproduction. In particular, the study pointed out the irrationality of some mandatory measures for indigenous fish conservation at present, and proposed the options such as ecological flow and tributary habitat compensation for high dams, and finally it provided some novel technologies to quantitatively assess the efficiency of conservation measures.