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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 Koppen- 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 FROM AUTHOR]

With the increasing impacts of both climate change and human activities, river basins were usually facing multiple water issues, which can impact water quantity, water environment, aquatic ecology and sediments. Simultaneously, increased frequencies of extreme hydrological events, such as droughts and floods, were observed. Thus, systematic management and retardation of extreme hydrological events became crucial goals of integrated water basin management. Raising the regulation capacity to multiple water cycling processes in a river basin is an important pathway. In this paper, based on the judgement of the China's major water issues, we analyzed the shortage of traditional water basin management, which relied on changing status of water cycling processes, end-of-pipe control technologies and the process dissociation. We analyzed the overall demand of solving water problems from a systematic level under the changing environment, the general idea of the ecological sponge-smart river basins construction, and proposed the theoretical framework and the critical research questions of the ecological sponge-smart river basins. The construction of ecological sponge-smart river basins should base on ① taking full consideration of the evolutional rules of multiple water cycling processes; ② regulating human activities, including exploring water and land resources; ③ achieving the joint regulation among the surface-soil-underground hydrological processes, including water quantity, water quality, sediments and aquatic ecosystem. We aimed to utmost retard extreme hydrological events, construct and improve comprehensive service functions of a river basin and achieve the conservations of the ecological functions of the ecosystems, including mountains, rivers, farmland, forests and lakes. [ABSTRACT FROM AUTHOR]

In order to meet the significant demands of enhancing our interdisciplinary research ability and protecting the national interests in the field of global change and response, this research is to focus on the evolution of atmosphere-land surface-hydrological processes in the context of global change, and to integrate the new disciplinary theory and technological progress in meteorology, climatology, hydrology, water resources, and system engineering. According to the technological scheme of mechanism recognition-law understanding-situation diagnosis, researchers will publish the global terrestrial gridded data of generalized water resources and water cycle flux of spatial resolution, streamflow and flood events of river channels from 1st order through fourth order in the past sixty years, by taking long series of highly-dense prototype observation, multi-scale mechanism experiment, numerical simulation with physical mechanisms and geographical information technology as a key support, and making full use of the functions and advantages of cloud-platform storage, computing and management. The outcomes of this research project would provide an important foundation for China's participating in global climate negotiation and international climate governance, and implementing national strategies, such as ‘the Belt and Road Initiative’, so as to produce a remarkable socioeconomic benefits. [ABSTRACT FROM AUTHOR]

Extreme climate events will have a serious impact on terrestrial ecosystem services and human social life. Based on the three CMIP5 climate models, the temporal and spatial variation characteristics of extreme climate in the Yellow River Basin under the future scenarios of RCP2.6, RCP4.5 and RCP8.5 were studied. The results show that under RCP2.6, RCP4.5 and RCP8.5 scenarios, the rising rates of daily maximum temperature in the watershed are 0.052 ℃/10 a, 0.170 ℃/10 a and 0.470 ℃/10 a, respectively, and the rising rates of daily minimum temperature are 0.029 ℃/10 a, 0.170 ℃/10 a and 0.460 ℃/10 a, respectively. The spatial distribution law of the daily maximum temperature and daily minimum temperature is consistent, showing an upward trend from the headwaters of the upper Yellow River to the middle and lower reaches. The overall annual precipitation of the Yellow River Basin under the future scenario shows a weak increase trend. By the end of the 21st century, the increase of annual precipitation under the high emission scenario will become larger. [ABSTRACT FROM AUTHOR]

The drought-limited water level (flow) of a river section is an important indicator of drought in the basin. This can be used as the key basis for starting an emergency response and guiding drought-relief dispatch in water conservancy projects. In this paper, with the aim to examine the related concepts and technical problems of the drought limit water level in the river section, the connotation of the drought limit water level (flow) of the river section is improved. It is the threshold that characterizes the dry state of the river, to determine the water shortage risk and its effect on the social economy and ecological environment. Considering the different degrees of drought and the laws on water use in drought periods, a method for determining the drought limit water level (flow) that is suitable for different types of river sections is proposed from the perspective of grading and staging. The applicability and sustainability of the algorithm for resource use and otherwise constrained river sections are verified with examples from the Lintong section of the Weihe River and the Liaojiawan section of the Fuhe River. This study provides a general algorithm to support flood and drought disaster prevention departments in setting drought limit water level (flow) in river sections and can provide a scientific basis and technical support for drought warning decision-making. [ABSTRACT FROM AUTHOR]

Inner Mongolia AutonomousRegion has a dry climate with little rain and frequent droughts. There will be heavy rain in the context of perennial drought, resulting in serious flooding. Flood is the second most serious disaster in Inner Mongolia after drought. The disasters caused by drought and flood account for more than 80 percent of the total losses caused by natural disasters. From the perspective of drought and flood disasters, the characteristics of drought and flood evolution and the influence of driving forces in Inner Mongolia Autonomous Region were studied. It reconstructed the drought and flood grade series in Inner Mongolia Autonomous Region of the past 547 years. By using Mann-Kendall test, B-G algorithm, CEEMDAN, cross wavelet and Markov chain mathematical model, the evolution law and change features of drought and flood were analyzed. The results show that from 1470 to 2016, the drought and flood sequences in Inner Mongolia evolve from frequent drought period to frequent flood period at a rate of 0.012/（10 a）. The drought and flood grading series in Inner Mongolia Autonomous Region can be divided into three periods. The rate of drought and flood grade shows a trend of increasing, decreasing and increasing. The cycles of each component of the series in Inner Mongolia Autonomous Region show different inter-annual oscillation and inter-decadal fluctuation respectively. The dominant state of drought and flood transfer tends to be normal on the whole. At the resonance period, compared with NAO, PDO, ENSO and other climatic factors, SSN and AO have a greater impact on drought and flood in Inner Mongolia Autonomous Region. [ABSTRACT FROM AUTHOR]

Aiming at the problems of spatial mismatch of water and land resources, lack of total water resources and low utilization of land resources, this paper establishes a joint optimal allocation model of regional water and land resources considering mutual feedback relationship based on the dualistic water cycle theory. This model consists of water production module, water and land resources joint allocation module and land simulation module, and takes maximum GDP and maximum regional vegetation coverage based on ecological green equivalent (EGE-RVC) as the objective functions. A three-layer nested algorithm coupling constraint method ( CSM), successive approximation (SA) method and nonlinear programming (NLP) is proposed to solve the model. The proposed model and method are validated by taking Luoyang City of Henan Province as a research example. The results show that the available water volume in Luoyang City increases by 44. 63 million m 3, the GDP increases by 12. 5%, and the EGE- RVC increases by 2. 6%. The water shortage rate of each land type has decreased to varying degrees. The research results can provide a new idea and technical reference for the research on the optimal allocation of regional water and land resources. [ABSTRACT FROM AUTHOR]

Ecological conservation and high-quality development of the Yellow River Basin have become a major national strategy and the water issue is one of the main factors affecting the harnessing and protection of the Yellow River. This paper analyzed the main water problems in the Yellow River Basin at the present stage from the four aspects of water-sand relationship, water resources utilization, water ecological environment and soil and water resources and analyzed the development trend of the water issue in the Yellow River Basin. The crux of the water issue in the Yellow River Basin is the disharmony of water and soil resources and neglecting the “point-line-surface” relationship in water resources allocation and the separation of groundwater and surface water control in water resources management. Finally, from the perspective of "nature-function coordination", this paper put forward the main ideas to deal with the water issues in the Yellow River Basin and proposed to systematically deal with the water issues in the Yellow River Basin from four aspects of joint distribution of water and soil resources, construction of three-dimensional water network, precise water and sediment regulation and improvement of intelligent supervision system. [ABSTRACT FROM AUTHOR]

Drought-limited water level (DLWL) is an important indicator for early warning against droughts and can be used to guide the drought-relief operation at reservoirs. This study aims to build a determination algorithm to specify the DLWL for different types of reservoirs. We define the DLWL of a reservoir as the water level at which the water supply system reaches the critical point of drought and water shortage. By introducing the double layer of operation and guarantee periods as control parameters, a general algorithm for DLWL suitable for multi-year, annual, and seasonal regulation of reservoirs is proposed, which is used to form a reservoir drought-resistant operation strategy. The Zhangfeng Reservoir and Hechuan Reservoir were used to verify the feasibility and rationality of the double-layer sliding algorithm for the multi-year and seasonal regulation of reservoirs, respectively. The results show that by setting the DLWL, the serious water shortage in drought years can be effectively alleviated; the water shortage rate and period in each industrial sector can be significantly reduced. This study provides a general algorithm to the flood and drought disaster prevention department to set a DLWL and guide the drought-relief operation of the reservoir, which can provide the scientific basis and technical support required for drought prevention. [ABSTRACT FROM AUTHOR]

Discussing the changing characteristics of extreme climate events in the Yellow River Basin under the background of global climate change is of great significance for effectively dealing with extreme climate events and their secondary disasters. Based on the observation data of historical climatic factor indicators in the basin from 1961 to 2005, ten CMIP5 models were selected, and the daily deviation correction method was used for bias correction for the model simulation data, and the indicators before and after the correction were compared. From the change trend and spatial distribution, evaluated the data simulated by the CMIP5 model, and selected climate models suitable for the basin. The results show that the daily maximum air temperature simulated by 10 CMIP5 models all show an upward trend, and the rising rate is between 0.18 and 0.35 t/10 a. The daily minimum temperature rise rate simulated by most CMIP5 models is between 0.20 and 0.41 t /10 a. The annual precipitation simulated by the MPI, GFDL, CSIRO and CCSM4 models shows a downward trend. The relative error of each model simulation is small, the temperature simulated by MPI, MIR005, GFDL and other models shows an overestimation level in the middle and lower reaches of the Yellow River, and the maximum 1-day precipitation simulated by most models shows an underestimation level in the middle and lower reaches of the Yellow River. Through data comparison, the three most suitable climate models for the Yellow River basin, GFDL, FGOALS and CCSM4 are selected. [ABSTRACT FROM AUTHOR]

With global warming, extreme precipitation events occur frequently, easily causing natural disasters such as landslides and floods. Studying the response relationship between extreme precipitation and changes in dew point and surface temperature can provide a reliable basis for the prediction of future extreme precipitation trends and disaster risk research. Taking the Loess Plateau in northern Shaanxi as the research area, based on the data of six meteorological stations from 1970 to 2017, six extreme precipitation indices were selected, and the temporal and spatial evolution of their extreme precipitation indices were analyzed by linear trend method, moving average method and spatial interpolation method. and the response characteristics of extreme precipitation to changes in dew point and surface temperature, and assess their robustness. The results show that: from 1970 to 2017, the dew point and surface temperature of the Loess Plateau in northern Shaanxi showed a fluctuating upward trend, and the extreme precipitation index in addition to the continuous humidity index showed a slight downward trend. The maximum precipitation in the 5-day and 5-day period both showed an upward trend, and showed the characteristics of "high in the south and low in the north". The response relationship between daily extreme precipitation and dew point temperature showed a monotonically increasing trend, and the response intensity was on a C-C scale, while the response relationship between daily extreme precipitation and surface temperature showed a Hook structure. The C-C scale is in the C-C scale at the other four stations, and the response intensity of the daily extreme precipitation and dew point temperature is smaller than that of the surface temperature. Compared with surface temperature, the response relationship between extreme precipitation and dew point temperature is more robust. [ABSTRACT FROM AUTHOR]

China has a very large number of reservoirs, and the operation of high-density reservoir networks impacts the terrestrial water cycle and the land- atmosphere moisture and energy exchange, which brings challenges to the understanding of hydrological processes and the hydrologic simulation and forecasting. In this regard, this study focuses on the Poyang Lake basin (PLB) and over 1000 reservoirs in the basin, and developed a reservoir network scheme in terms of the reservoir water balance, reservoir release rules, and routing methods with the sectioned two-dimensional diffusion wave equation. The scheme was then fully coupled to the land surface- hydrological model CLHMS through surface water, subsurface water, evapotranspiration and energy balance. Results indicate that the scheme can well capture the reservoir operation, and can enhance the accuracy of streamflow simulation; the reservoirs in the PLB can decrease the runoff by 3. 7% —6. 0% in the wet season, increase the runoff by 5. 9% — 12. 6% in the dry season, and decrease the multi- year average runoff by 0. 6% —1. 5% for the Gan, Fu and Xin River. Spatially, reservoirs have a more prominent regulating effect on the streamflow in the middle and northern part of the basin. The newly modified land surface-hydrologic model in this study can provide an analyzing tool and model basis for multidisciplinary research of atmosphere, hydrology and water resources, thereby supporting the sustainable use of water resources in areas under changing environment. [ABSTRACT FROM AUTHOR]