According to the relationships among state transition probability matrixes with different step lengths, an improved Markov chain model based on autocorrelation and entropy techniques was introduced. In the improved Ma...According to the relationships among state transition probability matrixes with different step lengths, an improved Markov chain model based on autocorrelation and entropy techniques was introduced. In the improved Markov chain model, the state transition probability matrixes can be adjusted. The steps of the historical state of the event, which was significantly related to the future state of the event, were determined by the autocorrelation technique, and the impact weights of the event historical state on the event future state were determined by the entropy technique. The presented model was applied to predicting annual precipitation and annual runoff states, showing that the improved model is of higher precision than those existing Markov chain models, and the determination of the state transition probability matrixes and the weights is more reasonable. The physical concepts of the improved model are distinct, and its computation process is simple and direct, thus, the presented model is sufficiently general to be applicable to the prediction problems in hydrology and water resources.展开更多
In this study, several kinds of flexible protective materials sprayed with polyurea elastomers (hereinafter referred to as polyurea elastomer protective material) were adopted to meet the abrasion resistance require...In this study, several kinds of flexible protective materials sprayed with polyurea elastomers (hereinafter referred to as polyurea elastomer protective material) were adopted to meet the abrasion resistance requirement of hydraulic structures, and their abrasion resistances against the water flow with suspended load or bed load were studied systematically through tests. Natural basalt stones were adopted as the abrasive for simulation of the abrasion effect of the water flow with bed load, and test results indicate that the basalt stone is suitable for use in the abrasion resistance test of the flexible protective material. The wear process of the polyurea elastomer protective material is stable, and the wear loss is linear with the time of abrasion. If the wear thickness is regarded as the abrasion resistance evaluation factor, the abrasion resistance of the 351 pure polyurea is about twice those of pure polyurea with a high level of hardness and aliphatic polyurea, and over five times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with suspended load. It is also about 50 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load. Overall, the abrasion resistance of pure polyurea presented a decreasing trend with increasing hardness. Pure polyurea with a Shore hardness of D30 has the best abrasion resistance, which is 60 to 70 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load, and has been recommended, among the five kinds of pure polyurea materials with different hardness, in anti-abrasion protection of hydraulic structures.展开更多
Variation trends of water resources in the Xiangjiang River Basin over the coming decades have been investigated using the variable infiltration capacity(VIC) model and 14 general circulation models'(GCMs') pr...Variation trends of water resources in the Xiangjiang River Basin over the coming decades have been investigated using the variable infiltration capacity(VIC) model and 14 general circulation models'(GCMs') projections under the representative concentration pathway(RCP4.5) scenario. Results show that the Xiangjiang River Basin will probably experience temperature rises during the period from 2021 to2050, with precipitation decrease in the 2020 s and increase in the 2030 s. The VIC model performs well for monthly discharge simulations with better performance for hydrometric stations on the main stream of the Xiangjiang River than for tributary catchments. The simulated annual discharges are significantly correlated to the recorded annual discharges for all the eight selected target stations. The Xiangjiang River Basin may experience water shortages induced by climate change. Annual water resources of the Xiangjiang River Basin over the period from 2021 to 2050 are projected to decrease by 2.76% on average within the range from-7.81% to 7.40%. It is essential to consider the potential impact of climate change on water resources in future planning for sustainable utilization of water resources.展开更多
Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction amon...Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction among hydrology–vegetation–soils/rock fractures along the karst subsurface profile. We reviewed isotopic and geochemical interpretations on tracing water sources for plant uptake, quantifying watershed outlet flow composition and residence times, and evaluating long-term evolution among climate–landscape–hydrology in the karst critical zone. In this paper, the application of the hydro-geochemical analysis on the above aspects in the karst areas of southwest China was summarized.展开更多
By taking the Yong River for example in this paper, based on the multiple measured data during 1957 to 2009, the change process of runoff, tide feature, tidal wave, tidal influx and sediment transport are analyzed. Th...By taking the Yong River for example in this paper, based on the multiple measured data during 1957 to 2009, the change process of runoff, tide feature, tidal wave, tidal influx and sediment transport are analyzed. Then a mathematical model is used to reveal the influence mechanism on hydrodynamic characteristics and sediment transport of the wading engineering groups such as a tide gate, a breakwater, reservoirs, bridges and wharves, which were built in different periods. The results showed the hydrodynamic characteristics and sediment transport of the Yong River changed obviously due to the wading engineering groups. The tide gate induced deformation of the tidal wave, obvious reduction of the tidal influx and weakness of the tidal dynamic, decrease of the sediment yield of flood and ebb tide and channel deposition. The breakwater blocked estuarine entrances, resulting in the change of the tidal current and the reduction of the tidal influx in the estuarine area. The large-scale reservoirs gradually made the decrease of the Yong River runoff. The bridge and wharf groups took up cross-section areas, the cumulative affection of which caused the increase of tidal level in the tidal river.展开更多
Climate change has significantly affected hydrological processes and increased the frequency and severity of water shortage,droughts and floods in northeast China.A study has been conducted to quantify the influence o...Climate change has significantly affected hydrological processes and increased the frequency and severity of water shortage,droughts and floods in northeast China.A study has been conducted to quantify the influence of climate change on the hydrologic process in the Tao’er River Basin(TRB),one of the most prominent regions in northeast China for water contradiction.The Soil and Water Assessment Tool(SWAT)model was calibrated and validated with observed land use and hydro-climatic data and then employed for runoff simulations at upper,middle and lower reaches of the river basin for different climate change scenarios.The results showed that a gradual increase in temperature and decrease in annual precipitation in the basin was projected for the period 2020-2050 for both representative concentration pathways(RCP)4.5 and 8.5 scenarios.The climate changes would cause a decrease in annual average runoff at basin outlet by 12 and 23 million m^(3) for RCP4.5 and 8.5,respectively.The future runoff in the upstream and midstream of the basin during 2020-2050 would be-10.8% and-12.1% lower than the observed runoff compared to the base period for RCP4.5,while those would be-5.3% and-10.7%lower for RCP8.5.The future runoff will decrease at three hydrology stations for the assumed future climate scenarios.The results can help us understand the future temperature and precipitation trends and the hydrological cycle process under different climate change scenarios,and provide the basis for the rational allocation and management of water resources under the influence of future climate change in the TRB.展开更多
The hydraulic characteristics of artificial waterfalls constitute an important research area for both academia and industry.As yet,the hydraulic parameters used in the hydraulic design of landscape waterfalls are not ...The hydraulic characteristics of artificial waterfalls constitute an important research area for both academia and industry.As yet,the hydraulic parameters used in the hydraulic design of landscape waterfalls are not well understood for use in qualitative and quantitative analyses.Due to their complicated shapes and appearances,it remains a challenging problem to design or simulate realistic waterfall scenes.In this paper,we present a hybrid model and an efficient numerical method for simulating the hydraulic characteristics of waterfalls and investigate the critical flow in waterfall design and the adherent flow phenomenon.We fit empirical equations to predict the size and shape of different waterfall flow patterns to provide a basis for the design and construction of waterscapes in the real world.We then apply our work to an artificial waterfall in Kraal Jiang River and the results demonstrate that our model achieves desirable control qualities and good agreement in a real-world application.展开更多
Ported wall extensions are important hydraulic structures used to reduce crosscurrents in upper approaches to locks.The effect of such extensions located upstream of a solid guard wall on flow characteristics depends ...Ported wall extensions are important hydraulic structures used to reduce crosscurrents in upper approaches to locks.The effect of such extensions located upstream of a solid guard wall on flow characteristics depends on many factors,including geometric and hydraulic parameters.In this study,the hydraulic performance of ported wall extensions was experimentally investigated in terms of the permeability coefficient,expanding angle,extension length,and flow depth.The results demonstrate that the dimensionless maximum transverse velocity is closely related to the permeability coefficient,expanding angle,and flow depth.By contrast,the dimensionless eddy length mainly depends on the permeability coefficient,expanding angle,and extension length.Furthermore,the optimum permeability coefficient increases with the expanding angle or flow depth,and it is approximately constant for different extension lengths.These results have the potential to provide direct guidance for the design of effective ported wall extensions in upper approaches to locks.展开更多
Vulnerability to natural disasters falls into three categories: exposure, resistance, and resilience, where resilience mainly refers to the capability of a pressure-bearing system to recover by returning to its initi...Vulnerability to natural disasters falls into three categories: exposure, resistance, and resilience, where resilience mainly refers to the capability of a pressure-bearing system to recover by returning to its initial state, that is, the ability to adapt to disaster pressure. Resilience is a major subject of research on disaster prevention and mitigation. This research mainly focuses on the ability of the hydraulic structure to recover from the significant impacts of typhoons. According to the load/unload response ratio theory, the degree of instability by which nonlinear systems can be identified according to the difference between load and unload responses was analyzed. This analysis was used as a basis to study the resilience of a hydraulic structure. Taking the Yangtze River embankments under the impact of Typhoon Matsa as an example, the ability of the typical sections of different types of embankments to adapt to the significant impact of the typhoon, i.e., the resilience of the hydraulic structure, is described with the help of the load/unload response ratio (L). The results of the calculated resilience reflect the actual conditions of the structure and can be used to determine the applicability of the embankment section. The load/unload response ratio theory is one of the effective tools for calculating the resilience of hydraulic structures under the significant impacts of typhoons.展开更多
Material distribution characteristics during sliding and depositing is particularly significative to investigate the internal structure and spatial variation of landslide dams,which are fundamentally determining the m...Material distribution characteristics during sliding and depositing is particularly significative to investigate the internal structure and spatial variation of landslide dams,which are fundamentally determining the mechanical and hydraulic behavior and the susceptibility to cause dam failure.However,limited by longevity shortages and special geographic environments,the material distribution characteristics and their formation mechanisms are difficult to observe in the field.Therefore,an experimental apparatus modeling a landslide dam was developed in this paper,designing three sampling methods with two valley states.The internal deposit characteristics,void ratio variation and relative content of the particle size range(PSR)were analyzed,and the mechanics of deposit structure were also delicately ascertained.The results indicate that granular material deposited in valley shows a structure of inverse grain size accumulation in both vertical and horizontal directions,exhibiting spatial variability of particle gradation and void ratio.The characteristic PSR decreases from 22-30 mm in the two-dimensional state to 10-14 mm in the threedimensional state.Vibration excitation and vibration sieve are the intrinsic mechanisms of granular flow segregation,intrinsically inducing the formation of inverse grading deposit structures.Consequently,spatial variability in size is mainly trig gered by segregation,whereas coarse particle content and deposition boundaries merely exacerbate the difference degree.展开更多
As a typical nonlinear wave,forward-leaning waves can be frequently encountered in the near-shore areas,which can impact coastal sediment transport significantly.Hence,it is of significance to describe the characteris...As a typical nonlinear wave,forward-leaning waves can be frequently encountered in the near-shore areas,which can impact coastal sediment transport significantly.Hence,it is of significance to describe the characteristics of the boundary layer beneath forward-leaning waves accurately,especially for the turbulent boundary layer.In this work,the linearized turbulent boundary layer model with a linear turbulent viscosity coefficient is applied,and the novel expression of the near-bed orbital velocity that has been worked out by the authors for forward-leaning waves of arbitrary forward-leaning degrees is further used to specify the free stream boundary condition of the bottom boundary layer.Then,a variable transformation is found so as to make the equation of the turbulent boundary layer model be solved analytically through a modified Bessel function.Consequently,an explicit analytical solution of the turbulent boundary layer beneath forward-leaning waves is derived by means of variable separation and variable transformation.The analytical solutions of the velocity profile and bottom shear stress of the turbulent boundary layer beneath forward-leaning waves are verified by comparing the present analytical results with typical experimental data available in the previous literature.展开更多
This paper presents a review of the state-of-the-art research and its applications developed at Hohai University relating to the hydrodynamic and morphological processes in the Yangtze Estuary. Longitudinal, lateral, ...This paper presents a review of the state-of-the-art research and its applications developed at Hohai University relating to the hydrodynamic and morphological processes in the Yangtze Estuary. Longitudinal, lateral, and horizontal flow circulations have been revealed based on the measurements with acoustic Doppler current profilers (ADCP). The hydrodynamic mechanism at diversion points as well as the changing patterns of flow and sediment flux in the Yangtze Estuary has been investigated through long-term data analysis. A field survey has been carried out to detect the saltwater intrusion from the North Branch to South Branch. Different numerical models of flow motion, sediment transport, and saltwater intrusion have been developed to simulate the complicated processes and to evaluate the effects of engineering projects. The morphological processes of wetlands over a time scale of decades have been analyzed with an established database. Ideas for further research on the bio-geomorphological model system and long-term evolution mechanisms are put forward.展开更多
The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudin...The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudinal and transverse dispersivities were investigated in both head-control and flux-control inland boundary systems. It shows that uncertainties and sensitivities of predicted results vary in different boundary systems. With the same designed matrix of uncertain factors in simulation experiments, the variance of predicted positions and thickness in the flux-control system is much larger than that predicted in the head-control system. In a head-control system, the most sensitive factors for the predicted position of the mixing zone are inland freshwater head and transverse dispersivity. However, the predicted position of the mixing zone is more sensitive to saturated hydraulic conductivity in a flux-control system. In a head-control system, the most sensitive factors for the predicted thickness of the mixing zone include transverse dispersivity, molecular diffusivity, porosity, and longitudinal dispersivity, but the predicted thickness is more sensitive to the saturated hydraulic conductivity in a flux-control system. These findings improve our understandings for the development of seawater-freshwater mixing zone during seawater intrusion processes, and give technical support for groundwater resource management in coastal aquifers.展开更多
As major contributor to the blue carbon sink,intertidal zones play a crucial role in the global carbon cycle.In recent years,more attention has been given to the carbon cycle in intertidal wetlands.However,due to high...As major contributor to the blue carbon sink,intertidal zones play a crucial role in the global carbon cycle.In recent years,more attention has been given to the carbon cycle in intertidal wetlands.However,due to highly variable and uncertain environmental conditions,it is difficult to clarify the quantitative relationship between soil respiration and environmental factors through in-situ experiments.In this study,the response of soil respiration characteristics to variations in the temperature and water table was investigated using a monitoring apparatus of CO_(2)flux at the soil-air interface in the intertidal zone.The results showed that soil respiration flux was significantly correlated with temperature,and the correlation best fitted the DoseResp function.Meanwhile,the respiration flux was enhanced with the descent of water table,a relationship could be described by a quadratic function.The effect of the water table on soil respiration became more pronounced with the rise of temperature.These results provide significant clarification of the impact of human activities on the carbon cycle in bare intertidal zones and as well as support for numerical simulations of the carbon cycle in bare intertidal zones.展开更多
Significant changes in water cycle elements/processes have created serious challenges to regional sustainability and high-quality development in the Yellow River Basin in China.It is necessary to investigate the impac...Significant changes in water cycle elements/processes have created serious challenges to regional sustainability and high-quality development in the Yellow River Basin in China.It is necessary to investigate the impacts of climate change and human activities on hydrological evolution and disaster risk from a holistic perspective of the basin.This study developed initiatives to clarify the mechanisms of hydrological evolution in the human-influenced Yellow River Basin.The proposed research method includes:(1)a tool to simulate multiple factors and a multi-scale water cycle using a grid-based spatiotemporal coupling approach,and(2)a new algorithm to separate the responses of the water cycle to climate change and human impacts,and de-couple the eco-environmental effects using artificial intelligence techniques.With this research framework,key breakthroughs are expected to be made in the understanding of the impacts of land cover change on the water cycle and blue/green water redirection.The outcomes of this research project are expected to provide theoretical support for ecological protection and water governance in the basin.展开更多
Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes.However,little is known about the interactions between successional an...Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes.However,little is known about the interactions between successional and existing species of different growth forms,particularly under the low light and high nutrient conditions of eutrophic lakes.We measured the functional traits of mature Vallisneria natans(Lour.)Hara plants and Potamogeton crispus L.shoots in monoculture and mosaic patterns under different light and nutrient conditions.The effect of light on functional traits of the submerged macrophyte species was more significant than that of nutrients,but the reverse was true for P.crispus biomass allocation.Moreover,interspecific interactions affected only the submerged macrophytes under the low light condition and varied with species.Specifically,the interaction of P.crispus to V.natans was biased towards competition,while the interaction of V.natans to P.crispus was converted from facilitation to competition by eutrophication,particularly in the homogenous mosaic growth pattern.This study demonstrates that sufficient light is a prerequisite and patch planting is an effective means to form a multispecies submerged vegetation system.In addition,we emphasize that the coexistence of eutrophication and low light will likely result in a competition between submerged macrophytes thus simplifying the vegetation,even if their growth forms and growing seasons are different.These findings help explain the collapse of multispecies submerged vegetation and guide the restoration of aquatic plants in eutrophic lakes.展开更多
High-rise intake towers in high-intensity seismic areas are prone to structural safety problems under vibration.Therefore,effective and low-cost anti-seismic engineering measures must be designed for protection.An int...High-rise intake towers in high-intensity seismic areas are prone to structural safety problems under vibration.Therefore,effective and low-cost anti-seismic engineering measures must be designed for protection.An intake tower in northwest China was considered the research object,and its natural vibration characteristics and dynamic response were first analyzed using the mode decomposition response spectrum method based on a three-dimensional finite element model.The non-dominated sorting genetic algorithm-II(NSGA-II)was adopted to optimize the anti-seismic scheme combination by comprehensively considering the dynamic tower response and variable project cost.Finally,the rationality of the original intake tower antiseismic design scheme was evaluated according to the obtained optimal solution set,and recommendations for improvement were proposed.The method adopted in this study may provide significant references for designing anti-seismic measures for high-rise structures such as intake towers located in high-intensity earthquake areas.展开更多
In the context of global warming,drought events occur frequently.In order to better understanding the process and mechanism of drought occurrence and evolution,scholars have dedicated much attention on drought propaga...In the context of global warming,drought events occur frequently.In order to better understanding the process and mechanism of drought occurrence and evolution,scholars have dedicated much attention on drought propagation,mainly focusing on drought propagation time and propagation probability.However,there are relatively few studies on the sensitivities of drought propagation to seasons and drought levels.Therefore,we took the Heihe River Basin(HRB)of Northwest China as the case study area to quantify the propagation time and propagation probability from meteorological drought to agricultural drought during the period of 1981–2020,and subsequently explore their sensitivities to seasons(irrigation and non-irrigation seasons)and drought levels.The correlation coefficient method and Copula-based interval conditional probability model were employed to determine the drought propagation time and propagation probability.The results determined the average drought propagation time as 8 months in the whole basin,which was reduced by 2 months(i.e.,6 months)on average during the irrigation season and prolonged by 2 months(i.e.,10 months)during the non-irrigation season.Propagation probability was sensitive to both seasons and drought levels,and the sensitivities had noticeable spatial differences in the whole basin.The propagation probability of agricultural drought at different levels generally increased with the meteorological drought levels for the upstream,midstream,and southern downstream regions of the HRB.Lesser agricultural droughts were more likely to be triggered during the irrigation season,while severer agricultural droughts were occurred mostly during the non-irrigation season.The research results are helpful to understand the characteristics of drought propagation and provide a scientific basis for the prevention and control of droughts.This study is of great significance for the rational planning of local water resources and maintaining good ecological environment in the HRB.展开更多
Due to the difference in density between the discharge effluent and coastal water,partially treated wastewater is often discharged into the marine environment as a buoyant jet via submarine outfalls with multiport dif...Due to the difference in density between the discharge effluent and coastal water,partially treated wastewater is often discharged into the marine environment as a buoyant jet via submarine outfalls with multiport diffusers.The dilution characteristics of effluent discharge(dual buoyant jets)in a wavy cross-flow environment were studied in a laboratory.The planar laser-induced fluorescence technique was used to obtain the concentration data of the jets.The effects of different environmental variables on the diffusion and dilution characteristics of the jets were examined through physical experiments,dimensional analysis,and empirical formulations.It was found that the dilution process of the dual jets could be divided into two components:the original jet component and the effluent cloud component.The jet-to-current velocity ratio was the main parameter affecting the concentration levels of the effluent cloud.The merging of the two jets increased the jet concentration in the flow field.When the jets traveled further downstream,the axial dilution increased gradually and then increased significantly along the axis.Under the effects of strong waves,the concentration contours branched into two peaks,and the mean dilution became more significant than under the effects of weak waves.Therefore,the dilution of the effluent discharge was expected to be significant under strong wave effects because the hydrodynamic force increased.A dilution equation was derived to improve our understanding of the dilution process of buoyant jets in a wavy cross-flow environment.This equation was used to determine the influences of the jet-to-current velocity ratio,wave-to-current velocity ratio,and Strouhal number on the minimum jet dilution.It revealed that the wave and buoyancy effects in effluent discharges were significant.展开更多
基金Under the auspices of Major Special Technological Program of Water Pollution Control and Management (No.2009ZX07106-001)National Natural Science Foundation of China (No. 51079037, 50909063)
文摘According to the relationships among state transition probability matrixes with different step lengths, an improved Markov chain model based on autocorrelation and entropy techniques was introduced. In the improved Markov chain model, the state transition probability matrixes can be adjusted. The steps of the historical state of the event, which was significantly related to the future state of the event, were determined by the autocorrelation technique, and the impact weights of the event historical state on the event future state were determined by the entropy technique. The presented model was applied to predicting annual precipitation and annual runoff states, showing that the improved model is of higher precision than those existing Markov chain models, and the determination of the state transition probability matrixes and the weights is more reasonable. The physical concepts of the improved model are distinct, and its computation process is simple and direct, thus, the presented model is sufficiently general to be applicable to the prediction problems in hydrology and water resources.
基金supported by the National Natural Science Foundation of China(Grants No.51109143 and 51209144)the Natural Science Foundation of Jiangsu Province(Grant No.BK2011109)the Foundation of Nanjing Hydraulic Research Institute(Grant No.Y113004)
文摘In this study, several kinds of flexible protective materials sprayed with polyurea elastomers (hereinafter referred to as polyurea elastomer protective material) were adopted to meet the abrasion resistance requirement of hydraulic structures, and their abrasion resistances against the water flow with suspended load or bed load were studied systematically through tests. Natural basalt stones were adopted as the abrasive for simulation of the abrasion effect of the water flow with bed load, and test results indicate that the basalt stone is suitable for use in the abrasion resistance test of the flexible protective material. The wear process of the polyurea elastomer protective material is stable, and the wear loss is linear with the time of abrasion. If the wear thickness is regarded as the abrasion resistance evaluation factor, the abrasion resistance of the 351 pure polyurea is about twice those of pure polyurea with a high level of hardness and aliphatic polyurea, and over five times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with suspended load. It is also about 50 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load. Overall, the abrasion resistance of pure polyurea presented a decreasing trend with increasing hardness. Pure polyurea with a Shore hardness of D30 has the best abrasion resistance, which is 60 to 70 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load, and has been recommended, among the five kinds of pure polyurea materials with different hardness, in anti-abrasion protection of hydraulic structures.
基金supported by the National Natural Science Foundation of China(Grants No.41330854 and 41371063)the National Key Research and Development Programs of China(Grants No.2016YFA0601601 and2016YFA0601501)
文摘Variation trends of water resources in the Xiangjiang River Basin over the coming decades have been investigated using the variable infiltration capacity(VIC) model and 14 general circulation models'(GCMs') projections under the representative concentration pathway(RCP4.5) scenario. Results show that the Xiangjiang River Basin will probably experience temperature rises during the period from 2021 to2050, with precipitation decrease in the 2020 s and increase in the 2030 s. The VIC model performs well for monthly discharge simulations with better performance for hydrometric stations on the main stream of the Xiangjiang River than for tributary catchments. The simulated annual discharges are significantly correlated to the recorded annual discharges for all the eight selected target stations. The Xiangjiang River Basin may experience water shortages induced by climate change. Annual water resources of the Xiangjiang River Basin over the period from 2021 to 2050 are projected to decrease by 2.76% on average within the range from-7.81% to 7.40%. It is essential to consider the potential impact of climate change on water resources in future planning for sustainable utilization of water resources.
基金supported by the National Natural Scientific Foundation of China(No.41571130071)
文摘Focusing on sustainability of water resources and ecology in the complex karst critical zone, we illustrated functions of the hydro-geochemical analysis on hydrology from the aspects of connection and interaction among hydrology–vegetation–soils/rock fractures along the karst subsurface profile. We reviewed isotopic and geochemical interpretations on tracing water sources for plant uptake, quantifying watershed outlet flow composition and residence times, and evaluating long-term evolution among climate–landscape–hydrology in the karst critical zone. In this paper, the application of the hydro-geochemical analysis on the above aspects in the karst areas of southwest China was summarized.
基金financially supported by the National Science Foundation for Distinguished Young Scholars of China(Grant No.51125034)the National Natural Science Foundation of China(Grant Nos.51279046 and 50909037)the Fundamental Research Funds for the Central Universities(Grant No.2010B01114)
文摘By taking the Yong River for example in this paper, based on the multiple measured data during 1957 to 2009, the change process of runoff, tide feature, tidal wave, tidal influx and sediment transport are analyzed. Then a mathematical model is used to reveal the influence mechanism on hydrodynamic characteristics and sediment transport of the wading engineering groups such as a tide gate, a breakwater, reservoirs, bridges and wharves, which were built in different periods. The results showed the hydrodynamic characteristics and sediment transport of the Yong River changed obviously due to the wading engineering groups. The tide gate induced deformation of the tidal wave, obvious reduction of the tidal influx and weakness of the tidal dynamic, decrease of the sediment yield of flood and ebb tide and channel deposition. The breakwater blocked estuarine entrances, resulting in the change of the tidal current and the reduction of the tidal influx in the estuarine area. The large-scale reservoirs gradually made the decrease of the Yong River runoff. The bridge and wharf groups took up cross-section areas, the cumulative affection of which caused the increase of tidal level in the tidal river.
基金the Key R&D Projects of Jilin Provincial Science and Technology Department(20200403070SF)Young Top-Notch Talent Support Program of National High-level Talents Special Support Plan+2 种基金National Key R&D Program of China(NO.2017YFC0403506)China Water Resource Conservation and Protection Project(No.126302001000150005)Strategic Consulting Projects of Chinese Academy of Engineering(NO.2016-ZD-08-05-02)。
文摘Climate change has significantly affected hydrological processes and increased the frequency and severity of water shortage,droughts and floods in northeast China.A study has been conducted to quantify the influence of climate change on the hydrologic process in the Tao’er River Basin(TRB),one of the most prominent regions in northeast China for water contradiction.The Soil and Water Assessment Tool(SWAT)model was calibrated and validated with observed land use and hydro-climatic data and then employed for runoff simulations at upper,middle and lower reaches of the river basin for different climate change scenarios.The results showed that a gradual increase in temperature and decrease in annual precipitation in the basin was projected for the period 2020-2050 for both representative concentration pathways(RCP)4.5 and 8.5 scenarios.The climate changes would cause a decrease in annual average runoff at basin outlet by 12 and 23 million m^(3) for RCP4.5 and 8.5,respectively.The future runoff in the upstream and midstream of the basin during 2020-2050 would be-10.8% and-12.1% lower than the observed runoff compared to the base period for RCP4.5,while those would be-5.3% and-10.7%lower for RCP8.5.The future runoff will decrease at three hydrology stations for the assumed future climate scenarios.The results can help us understand the future temperature and precipitation trends and the hydrological cycle process under different climate change scenarios,and provide the basis for the rational allocation and management of water resources under the influence of future climate change in the TRB.
基金supported by Tianjin Youth Research Program of Application Foundation and Advanced Technology(No.15JCQNJC08000)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.51321065)+1 种基金the National Natural Science Foundation of China(No.51509182)Open Foundation from State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University(No.2014491211)
文摘The hydraulic characteristics of artificial waterfalls constitute an important research area for both academia and industry.As yet,the hydraulic parameters used in the hydraulic design of landscape waterfalls are not well understood for use in qualitative and quantitative analyses.Due to their complicated shapes and appearances,it remains a challenging problem to design or simulate realistic waterfall scenes.In this paper,we present a hybrid model and an efficient numerical method for simulating the hydraulic characteristics of waterfalls and investigate the critical flow in waterfall design and the adherent flow phenomenon.We fit empirical equations to predict the size and shape of different waterfall flow patterns to provide a basis for the design and construction of waterscapes in the real world.We then apply our work to an artificial waterfall in Kraal Jiang River and the results demonstrate that our model achieves desirable control qualities and good agreement in a real-world application.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2018YFB1600403)the Natural Science Foundation of Chongqing,China(Grant No.cstc2020jcyj-bshX0043).
文摘Ported wall extensions are important hydraulic structures used to reduce crosscurrents in upper approaches to locks.The effect of such extensions located upstream of a solid guard wall on flow characteristics depends on many factors,including geometric and hydraulic parameters.In this study,the hydraulic performance of ported wall extensions was experimentally investigated in terms of the permeability coefficient,expanding angle,extension length,and flow depth.The results demonstrate that the dimensionless maximum transverse velocity is closely related to the permeability coefficient,expanding angle,and flow depth.By contrast,the dimensionless eddy length mainly depends on the permeability coefficient,expanding angle,and extension length.Furthermore,the optimum permeability coefficient increases with the expanding angle or flow depth,and it is approximately constant for different extension lengths.These results have the potential to provide direct guidance for the design of effective ported wall extensions in upper approaches to locks.
基金supported by the National Natural Science Foundation of China (Grants No.50909066 and51179108)
文摘Vulnerability to natural disasters falls into three categories: exposure, resistance, and resilience, where resilience mainly refers to the capability of a pressure-bearing system to recover by returning to its initial state, that is, the ability to adapt to disaster pressure. Resilience is a major subject of research on disaster prevention and mitigation. This research mainly focuses on the ability of the hydraulic structure to recover from the significant impacts of typhoons. According to the load/unload response ratio theory, the degree of instability by which nonlinear systems can be identified according to the difference between load and unload responses was analyzed. This analysis was used as a basis to study the resilience of a hydraulic structure. Taking the Yangtze River embankments under the impact of Typhoon Matsa as an example, the ability of the typical sections of different types of embankments to adapt to the significant impact of the typhoon, i.e., the resilience of the hydraulic structure, is described with the help of the load/unload response ratio (L). The results of the calculated resilience reflect the actual conditions of the structure and can be used to determine the applicability of the embankment section. The load/unload response ratio theory is one of the effective tools for calculating the resilience of hydraulic structures under the significant impacts of typhoons.
基金financial support from the National Natural Science Foundation of China(U2040221)the fund on basic scientific research project of nonprofit central research institutions(Y321001)。
文摘Material distribution characteristics during sliding and depositing is particularly significative to investigate the internal structure and spatial variation of landslide dams,which are fundamentally determining the mechanical and hydraulic behavior and the susceptibility to cause dam failure.However,limited by longevity shortages and special geographic environments,the material distribution characteristics and their formation mechanisms are difficult to observe in the field.Therefore,an experimental apparatus modeling a landslide dam was developed in this paper,designing three sampling methods with two valley states.The internal deposit characteristics,void ratio variation and relative content of the particle size range(PSR)were analyzed,and the mechanics of deposit structure were also delicately ascertained.The results indicate that granular material deposited in valley shows a structure of inverse grain size accumulation in both vertical and horizontal directions,exhibiting spatial variability of particle gradation and void ratio.The characteristic PSR decreases from 22-30 mm in the two-dimensional state to 10-14 mm in the threedimensional state.Vibration excitation and vibration sieve are the intrinsic mechanisms of granular flow segregation,intrinsically inducing the formation of inverse grading deposit structures.Consequently,spatial variability in size is mainly trig gered by segregation,whereas coarse particle content and deposition boundaries merely exacerbate the difference degree.
基金Project supported by the National Key R&D Program of China(No.2022YFC3204303)the National Natural Science Foundation of China(Nos.12202503,12132018,and 52394254)。
文摘As a typical nonlinear wave,forward-leaning waves can be frequently encountered in the near-shore areas,which can impact coastal sediment transport significantly.Hence,it is of significance to describe the characteristics of the boundary layer beneath forward-leaning waves accurately,especially for the turbulent boundary layer.In this work,the linearized turbulent boundary layer model with a linear turbulent viscosity coefficient is applied,and the novel expression of the near-bed orbital velocity that has been worked out by the authors for forward-leaning waves of arbitrary forward-leaning degrees is further used to specify the free stream boundary condition of the bottom boundary layer.Then,a variable transformation is found so as to make the equation of the turbulent boundary layer model be solved analytically through a modified Bessel function.Consequently,an explicit analytical solution of the turbulent boundary layer beneath forward-leaning waves is derived by means of variable separation and variable transformation.The analytical solutions of the velocity profile and bottom shear stress of the turbulent boundary layer beneath forward-leaning waves are verified by comparing the present analytical results with typical experimental data available in the previous literature.
基金supported by the National Basic Research Program of China(973Program,Grant No.2010CB429002)the Fundamental Research Funds for the Central Universities(Grant No.2012B06514)+1 种基金the Special Fund of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering at Hohai University(Grant No.2009585812)the Qing Lan Project of Jiangsu Province
文摘This paper presents a review of the state-of-the-art research and its applications developed at Hohai University relating to the hydrodynamic and morphological processes in the Yangtze Estuary. Longitudinal, lateral, and horizontal flow circulations have been revealed based on the measurements with acoustic Doppler current profilers (ADCP). The hydrodynamic mechanism at diversion points as well as the changing patterns of flow and sediment flux in the Yangtze Estuary has been investigated through long-term data analysis. A field survey has been carried out to detect the saltwater intrusion from the North Branch to South Branch. Different numerical models of flow motion, sediment transport, and saltwater intrusion have been developed to simulate the complicated processes and to evaluate the effects of engineering projects. The morphological processes of wetlands over a time scale of decades have been analyzed with an established database. Ideas for further research on the bio-geomorphological model system and long-term evolution mechanisms are put forward.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51309091,51239003 and 51279045)the Postdoctoral Science Foundation of China(Grant No.2012M520989)
文摘The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudinal and transverse dispersivities were investigated in both head-control and flux-control inland boundary systems. It shows that uncertainties and sensitivities of predicted results vary in different boundary systems. With the same designed matrix of uncertain factors in simulation experiments, the variance of predicted positions and thickness in the flux-control system is much larger than that predicted in the head-control system. In a head-control system, the most sensitive factors for the predicted position of the mixing zone are inland freshwater head and transverse dispersivity. However, the predicted position of the mixing zone is more sensitive to saturated hydraulic conductivity in a flux-control system. In a head-control system, the most sensitive factors for the predicted thickness of the mixing zone include transverse dispersivity, molecular diffusivity, porosity, and longitudinal dispersivity, but the predicted thickness is more sensitive to the saturated hydraulic conductivity in a flux-control system. These findings improve our understandings for the development of seawater-freshwater mixing zone during seawater intrusion processes, and give technical support for groundwater resource management in coastal aquifers.
基金supported by the National Natural Science Foundation of China(Grant No.U2040209)the Open Funds of the Key Laboratory of Ocean Space Resource Management Technology of Ministry of Natural Resources(Grant No.KF-2021-108)the Fundamental Research Funds for the Central Universities(Grant No.B210204001).
文摘As major contributor to the blue carbon sink,intertidal zones play a crucial role in the global carbon cycle.In recent years,more attention has been given to the carbon cycle in intertidal wetlands.However,due to highly variable and uncertain environmental conditions,it is difficult to clarify the quantitative relationship between soil respiration and environmental factors through in-situ experiments.In this study,the response of soil respiration characteristics to variations in the temperature and water table was investigated using a monitoring apparatus of CO_(2)flux at the soil-air interface in the intertidal zone.The results showed that soil respiration flux was significantly correlated with temperature,and the correlation best fitted the DoseResp function.Meanwhile,the respiration flux was enhanced with the descent of water table,a relationship could be described by a quadratic function.The effect of the water table on soil respiration became more pronounced with the rise of temperature.These results provide significant clarification of the impact of human activities on the carbon cycle in bare intertidal zones and as well as support for numerical simulations of the carbon cycle in bare intertidal zones.
基金supported by the National Natural Science Foundation of China(Grant No.U2243203),the Fundamental Research Funds for the Central Universities(Grants No.B200204029 and B220201011),and the Natural Science Foundation of Jiangsu Province(Grant No.BK20210368).
文摘Significant changes in water cycle elements/processes have created serious challenges to regional sustainability and high-quality development in the Yellow River Basin in China.It is necessary to investigate the impacts of climate change and human activities on hydrological evolution and disaster risk from a holistic perspective of the basin.This study developed initiatives to clarify the mechanisms of hydrological evolution in the human-influenced Yellow River Basin.The proposed research method includes:(1)a tool to simulate multiple factors and a multi-scale water cycle using a grid-based spatiotemporal coupling approach,and(2)a new algorithm to separate the responses of the water cycle to climate change and human impacts,and de-couple the eco-environmental effects using artificial intelligence techniques.With this research framework,key breakthroughs are expected to be made in the understanding of the impacts of land cover change on the water cycle and blue/green water redirection.The outcomes of this research project are expected to provide theoretical support for ecological protection and water governance in the basin.
基金Supported by the National Natural Science Foundation of China (Nos.U2240207,41971043,51809178)the Guangxi Key Research and Development Program of China (No.2018AB36010)。
文摘Constructing multispecies submerged vegetation systems and maintaining stable seasonal succession is crucial for restoring shallow eutrophic lakes.However,little is known about the interactions between successional and existing species of different growth forms,particularly under the low light and high nutrient conditions of eutrophic lakes.We measured the functional traits of mature Vallisneria natans(Lour.)Hara plants and Potamogeton crispus L.shoots in monoculture and mosaic patterns under different light and nutrient conditions.The effect of light on functional traits of the submerged macrophyte species was more significant than that of nutrients,but the reverse was true for P.crispus biomass allocation.Moreover,interspecific interactions affected only the submerged macrophytes under the low light condition and varied with species.Specifically,the interaction of P.crispus to V.natans was biased towards competition,while the interaction of V.natans to P.crispus was converted from facilitation to competition by eutrophication,particularly in the homogenous mosaic growth pattern.This study demonstrates that sufficient light is a prerequisite and patch planting is an effective means to form a multispecies submerged vegetation system.In addition,we emphasize that the coexistence of eutrophication and low light will likely result in a competition between submerged macrophytes thus simplifying the vegetation,even if their growth forms and growing seasons are different.These findings help explain the collapse of multispecies submerged vegetation and guide the restoration of aquatic plants in eutrophic lakes.
基金supported by the National Natural Science Foundation of the China/Yalong River Joint Fund Project (No.U1765205).
文摘High-rise intake towers in high-intensity seismic areas are prone to structural safety problems under vibration.Therefore,effective and low-cost anti-seismic engineering measures must be designed for protection.An intake tower in northwest China was considered the research object,and its natural vibration characteristics and dynamic response were first analyzed using the mode decomposition response spectrum method based on a three-dimensional finite element model.The non-dominated sorting genetic algorithm-II(NSGA-II)was adopted to optimize the anti-seismic scheme combination by comprehensively considering the dynamic tower response and variable project cost.Finally,the rationality of the original intake tower antiseismic design scheme was evaluated according to the obtained optimal solution set,and recommendations for improvement were proposed.The method adopted in this study may provide significant references for designing anti-seismic measures for high-rise structures such as intake towers located in high-intensity earthquake areas.
基金Projects(SQ2021YFC3000080, 2020YFC1511900) supported by the National Key Research and Development Program of ChinaProject(51739008) supported by the National Natural Science Foundation of China。
基金supported by the National Natural Science Foundation of China (41101038)the Belt and Road Special Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering (2021nkms03)
文摘In the context of global warming,drought events occur frequently.In order to better understanding the process and mechanism of drought occurrence and evolution,scholars have dedicated much attention on drought propagation,mainly focusing on drought propagation time and propagation probability.However,there are relatively few studies on the sensitivities of drought propagation to seasons and drought levels.Therefore,we took the Heihe River Basin(HRB)of Northwest China as the case study area to quantify the propagation time and propagation probability from meteorological drought to agricultural drought during the period of 1981–2020,and subsequently explore their sensitivities to seasons(irrigation and non-irrigation seasons)and drought levels.The correlation coefficient method and Copula-based interval conditional probability model were employed to determine the drought propagation time and propagation probability.The results determined the average drought propagation time as 8 months in the whole basin,which was reduced by 2 months(i.e.,6 months)on average during the irrigation season and prolonged by 2 months(i.e.,10 months)during the non-irrigation season.Propagation probability was sensitive to both seasons and drought levels,and the sensitivities had noticeable spatial differences in the whole basin.The propagation probability of agricultural drought at different levels generally increased with the meteorological drought levels for the upstream,midstream,and southern downstream regions of the HRB.Lesser agricultural droughts were more likely to be triggered during the irrigation season,while severer agricultural droughts were occurred mostly during the non-irrigation season.The research results are helpful to understand the characteristics of drought propagation and provide a scientific basis for the prevention and control of droughts.This study is of great significance for the rational planning of local water resources and maintaining good ecological environment in the HRB.
基金supported by the Fundamental Research Funds for the Central Universities of China(Grant No.B200202057)and the National Natural Science Foundation of China(Grant No.51979076)。
文摘Due to the difference in density between the discharge effluent and coastal water,partially treated wastewater is often discharged into the marine environment as a buoyant jet via submarine outfalls with multiport diffusers.The dilution characteristics of effluent discharge(dual buoyant jets)in a wavy cross-flow environment were studied in a laboratory.The planar laser-induced fluorescence technique was used to obtain the concentration data of the jets.The effects of different environmental variables on the diffusion and dilution characteristics of the jets were examined through physical experiments,dimensional analysis,and empirical formulations.It was found that the dilution process of the dual jets could be divided into two components:the original jet component and the effluent cloud component.The jet-to-current velocity ratio was the main parameter affecting the concentration levels of the effluent cloud.The merging of the two jets increased the jet concentration in the flow field.When the jets traveled further downstream,the axial dilution increased gradually and then increased significantly along the axis.Under the effects of strong waves,the concentration contours branched into two peaks,and the mean dilution became more significant than under the effects of weak waves.Therefore,the dilution of the effluent discharge was expected to be significant under strong wave effects because the hydrodynamic force increased.A dilution equation was derived to improve our understanding of the dilution process of buoyant jets in a wavy cross-flow environment.This equation was used to determine the influences of the jet-to-current velocity ratio,wave-to-current velocity ratio,and Strouhal number on the minimum jet dilution.It revealed that the wave and buoyancy effects in effluent discharges were significant.