The cosmic-ray neutron technology is a novel method for upscaling soil moisture,holding significant importance in drought monitoring,soil water storage estimation,calibration of remote sensing products,and data assimi...The cosmic-ray neutron technology is a novel method for upscaling soil moisture,holding significant importance in drought monitoring,soil water storage estimation,calibration of remote sensing products,and data assimilation of land surface models.However,most studies conducted soil moisture measurement experiments using static Cosmic-Ray Neutron Sensors(CRNS)and are often limited to a single landscape,lacking in-situ measurement for the cosmic-ray neutron rover across various landscapes.This study carried out soil moisture observation experiments using a cosmic-ray neutron rover in nine grassland plots,nine farmland plots,and nine desert plots of the Heihe River Basin,Northwest China.The neutron counts displayed clear variations among different plots,and an equation could represent the relationship between neutron intensity and multiple variables near the ground.The parameter N0 was the smallest for grassland and greatest for desert,and there was a significant negative correlation between Normalized Difference Vegetation Index and N0(P<0.05).Furthermore,the performance of CRNS notably improved after considering soil lattice water and soil organic matter.The Root Mean Square Error(RMSE)between the measured and oven-dried soil moisture increased with radius.Soil moisture measured by CRNS strongly supported the 100 m diameter footprint assumption(RMSE<0.044 g/g).The study offers valuable insights into the application and promotion of cosmic-ray neutron technology across various landscapes within a basin.展开更多
The long-term productivity of a soil is greatly influenced by cation exchange capacity(CEC).Moreover,interactions between dominant base cations and other nutrients are important for the health and stability of grassla...The long-term productivity of a soil is greatly influenced by cation exchange capacity(CEC).Moreover,interactions between dominant base cations and other nutrients are important for the health and stability of grassland ecosystems.Soil exchangeable base cations and cation ratios were examined in a 11-year experiment with sheep manure application rates 0–1,500 g/(m2?a) in a semi-arid steppe in Inner Mongolia of China,aiming to clarify the relationships of base cations with soil p H,buffer capacity and fertility.Results showed that CEC and contents of exchangeable calcium(Ca2+),magnesium(Mg2+),potassium(K+) and sodium(Na+) were significantly increased,and Ca2+ saturation tended to decrease,while K+ saturation tended to increase with the increases of sheep manure application rates.The Ca2+/Mg2+ and Ca2+/K+ ratios decreased,while Mg2+,K+ and Na+ saturations increased with increasing manure application rates.Both base cations and CEC were significantly and positively correlated with soil organic carbon(SOC) and soil p H.The increases of SOC and soil p H would be the dominant factors that contribute to the increase of cations in soil.On a comparison with the initial soil p H before the experiment,we deduced that sheep manure application could partly buffer soil p H decrease potentially induced by atmospheric deposition of nitrogen and sulfur.Our results indicate that sheep manure application is beneficial to the maintenance of base cations and the buffering of soil acidification,and therefore can improve soil fertility in the semi-arid steppes of northeastern China.展开更多
The urban water system theory is an extension of the basin water system science on an urban scale, providing a new systematic solution for the unbalanced human-water relationship and severe water challenges, such as w...The urban water system theory is an extension of the basin water system science on an urban scale, providing a new systematic solution for the unbalanced human-water relationship and severe water challenges, such as waterlogging, black and odorous water, and ecological degradation caused by urbanization. Most existing studies on urban water systems have focused on individual water cycle processes linked with water supply and sewage treatment plants, but mutual feedback between the water cycle and its associated material circulation and water ecology, as well as human processes, still needs further exploration. In this paper, the concept, theory, and technical methodology of the urban water system were developed based on the water cycle and basin water system science. The Urban Water System 5.0(UWS 5.0) model was developed by integrating the Time Variant Gain rainfall-runoff Model with Urban water system(TVGM_Urban) in different underlying surface conditions for analyzing the natural-social water cycle processes and their associated water environmental and ecological processes and the influence of multiscale sponge measures. Herein, five major simulation functions were realized: rainfall-runoff-nonpoint source pollutant load,water and pollutant transportations through the drainage network system, terminal regulation and purification, socioeconomic water cycle, and water system assessment and regulation. The location for the case study used in this paper was Wuhan City. The findings showed that the entire urban water system should consider the built-up area and its associated rivers and lakes as the research object and explore the integrations among the urban natural-social water cycle and river regulations inside and outside of the city as well as the effects of socioeconomic development and sponge measures on the water quantity-quality-ecology processes. The UWS 5.0 model efficiently simulated the urban rainfall-runoff process, total nitrogen(TN) and total phosphorus(TP) concentrations in water bodies, and characteristic indicators of socioeconomic development. For the rainfall-runoff simulations, the correlation coefficient and Nash-Sutcliffe efficiency(NSE) fall under the excellent and good classes, respectively. For the TN and TP concentration simulations, results exhibited good bias and the correlation coefficients exceeded 0.90 for 78.1% of the sampled sites. The simulation of 18 socioeconomic indicators provided excellent bias, correlation coefficient, and NSE values of 100%, 83.3%, and 69.4% to total indicators, respectively. Based on the well-calibrated UWS 5.0 model, the source sponge,artificial enhancement, and source reduction-path interception-terminal treatment measures were optimized, which considerably mitigated waterlogging, black and odorous water, and lake eutrophication, respectively. The mitigation performance revealed that the maximum inundated area for a once-in-10-year rainfall event was reduced by 32.6%, the removal ratio of the black and odorous water area was 65%, the comprehensive trophic state index of water bodies was reduced by 37%, and the green development level of Wuhan City in 2020 increased from 0.56 to 0.67. This study is expected to advance the intersection and development of multidisciplinary fields(e.g., urban hydrology, environmental science, and ecology) and offer an important theoretical and technical basis for solving urban complex water issues and promoting green development of cities.展开更多
Flash floods present significant heterogeneity over both space and time due to diverse topographic,geomorphologic,and hydro-meteorological conditions of catchments.Accurate identification and simulation of typical fla...Flash floods present significant heterogeneity over both space and time due to diverse topographic,geomorphologic,and hydro-meteorological conditions of catchments.Accurate identification and simulation of typical flash flood types are of great significance for the mitigation of flash flood disasters at the national scale.Three flood peak indices and dynamic indices were adopted to characterize the behavioral variability of flash floods.The typical flash flood types and corresponding behavior indices were identified and simulated using statistical analysis(i.e.,principal component analysis,dynamic K-means clustering,and analysis of similarity)and hydrological modelling(i.e.,HEC and XAJ models).There were 177 flash flood events at the hourly scale being selected for case study from eight catchments with various climatic and geographic characteristics.Results showed that all the flash flood events were clustered into three types(named Types 1,2,and 3).Type 1 was characterized by low peak flow intensity,early flood peak occurrence time,and thin flood process with short duration.Type 2 was characterized by low peak flow intensity,late flood peak occurrence time,and flat flood process with long duration.Type 3 was characterized by high peak flow intensity and late flood peak occurrence time.Flash flood types showed high consistency with their influencing factors(e.g.,catchment forest ratio and drainage area,occurrence time and magnitude of maximum storm intensity,and concentration of a storm event).The simulation performances were basically the same for HEC and XAJ models.As for flash flood event simulations,the average relative error varied from 23.25%to 27.98%,from 11.95%to 18.19%,and from 8.30%to18.25%for Types 1,2 and 3,respectively.The average Nash-Sutcliffe efficiency coefficient varied from 0.39 to 0.54,from 0.76 to 0.85,and from 0.86 to 0.91,respectively.As for the six flash flood behavior indices simulations,the average relative rootmean-square error(RMSEr)varied from 0.37 to 0.69,from 0.37 to 0.41,and from 0.18 to 0.25 for Types 1,2,and 3,respectively.The average correlation coefficient(r)varied from 0.52 to 0.68,from 0.78 to 0.85,and from 0.88 to 0.94,respectively.The flood peak indices were the best simulated for Types 2 and 3 with RMSEr varying from 0.18 to 0.28 and r varying from 0.86 to 0.91.The flood dynamic indices were the best simulated for Type 3 with RMSEr varying from 0.19 to 0.21 and r varying from 0.91 to0.97.The study provided detailed flood information supports for flood management at catchment scale,and also provided new insights into flash flood simulations in small and medium-sized catchments from perspective of flood behavioral processes.展开更多
The regulation and spatial differences of urban runoffs are of great concern in contemporary hydrological research.However,owing to a shortage of basic data sources and restrictions on urban hydrological simulation fu...The regulation and spatial differences of urban runoffs are of great concern in contemporary hydrological research.However,owing to a shortage of basic data sources and restrictions on urban hydrological simulation functions,simulating and investigating the regulation mechanism behind rainfall-runoff processes remain significantly challenging.In this study,the Time Variant Gain Model(TVGM),a hydrological nonlinear system model,was extrapolated to the hydrodynamic model of an urban drainage network system by integrating it with the widely used Stormwater Management Model(SWMM)to adequately simulate urban runoff events while considering various underlying surfaces and runoff routing modes,such as surface,drainage network and river runoff,in urban regions(i.e.,TVGM-SWMM).Moreover,runoff events were characterized using the following four runoff regime metrics:runoff coefficient,capture ratio of annual runoff volume,standardized flood timescale,and the ratio of occurrence time differences between flow and rainfall peak to event duration(peak flow delay time).The characteristics and spatial differences of urban runoff regulations were investigated,and the key impact factors and their relative contributions were identified using multivariate statistical analyses.Four communities were selected as our study areas,consisting of communities from Beijing,Shenzhen,Wuhan,and Chongqing.Our results showed that the TVGM-SWMM performed considerably better than SWMM alone.The comprehensive simulation accuracy of 60%of the events(12/20)improved by 4-86%,with the bias improving the most,followed by the efficiency coefficient.Barring the runoff coefficient,significant spatial differences were identified at the patch scale for the runoff regime metrics,with differences of 0.43,0.22,and 0.16(p<0.05).The key impact factors were the pipe length(r=0.51)in the drainage network system and the forest area ratios(r=0.56),sponge measures(r=0.52),grassland(r=0.48),and impervious surface(r=0.46)in the underlying surfaces.The contributions of the drainage network system and the underlying surfaces were 4.27%and 37.83%,respectively.Regulation in the Beijing community,dominated by grassland regulation,delayed and reduced the peak flow and total runoff volume.In the Shenzhen community,sharp and thin runoff events were mainly generated by impervious surfaces and were not adequately regulated.Forest regulation was the dominant regulation type in the Wuhan community,which reduced the total runoff volume and delayed the peak flow.Waterbody regulation was the primary regulation type in the Chongqing community,which reduced the total runoff volume and peak flow.This study aims to introduce a comprehensive theoretical and technical assessment of the hydrological effects of urbanization and the performance of sponge city construction and provide a reference for urban hydrological model improvements in China.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42071044,42230720)the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(No.XDA23060304)the Youth Innovation Promotion Association CAS(No.2020420).
文摘The cosmic-ray neutron technology is a novel method for upscaling soil moisture,holding significant importance in drought monitoring,soil water storage estimation,calibration of remote sensing products,and data assimilation of land surface models.However,most studies conducted soil moisture measurement experiments using static Cosmic-Ray Neutron Sensors(CRNS)and are often limited to a single landscape,lacking in-situ measurement for the cosmic-ray neutron rover across various landscapes.This study carried out soil moisture observation experiments using a cosmic-ray neutron rover in nine grassland plots,nine farmland plots,and nine desert plots of the Heihe River Basin,Northwest China.The neutron counts displayed clear variations among different plots,and an equation could represent the relationship between neutron intensity and multiple variables near the ground.The parameter N0 was the smallest for grassland and greatest for desert,and there was a significant negative correlation between Normalized Difference Vegetation Index and N0(P<0.05).Furthermore,the performance of CRNS notably improved after considering soil lattice water and soil organic matter.The Root Mean Square Error(RMSE)between the measured and oven-dried soil moisture increased with radius.Soil moisture measured by CRNS strongly supported the 100 m diameter footprint assumption(RMSE<0.044 g/g).The study offers valuable insights into the application and promotion of cosmic-ray neutron technology across various landscapes within a basin.
基金funded by the National Natural Science Foundation of China (41371251,31370009)the National Basic Research Program of China (2011CB403204)
文摘The long-term productivity of a soil is greatly influenced by cation exchange capacity(CEC).Moreover,interactions between dominant base cations and other nutrients are important for the health and stability of grassland ecosystems.Soil exchangeable base cations and cation ratios were examined in a 11-year experiment with sheep manure application rates 0–1,500 g/(m2?a) in a semi-arid steppe in Inner Mongolia of China,aiming to clarify the relationships of base cations with soil p H,buffer capacity and fertility.Results showed that CEC and contents of exchangeable calcium(Ca2+),magnesium(Mg2+),potassium(K+) and sodium(Na+) were significantly increased,and Ca2+ saturation tended to decrease,while K+ saturation tended to increase with the increases of sheep manure application rates.The Ca2+/Mg2+ and Ca2+/K+ ratios decreased,while Mg2+,K+ and Na+ saturations increased with increasing manure application rates.Both base cations and CEC were significantly and positively correlated with soil organic carbon(SOC) and soil p H.The increases of SOC and soil p H would be the dominant factors that contribute to the increase of cations in soil.On a comparison with the initial soil p H before the experiment,we deduced that sheep manure application could partly buffer soil p H decrease potentially induced by atmospheric deposition of nitrogen and sulfur.Our results indicate that sheep manure application is beneficial to the maintenance of base cations and the buffering of soil acidification,and therefore can improve soil fertility in the semi-arid steppes of northeastern China.
基金supported by National Natural Science Foundation of China (NO. 41401036)China Postdoctoral Science Foundation (NO. 2015T81070, 2014M560818)West Light Foundation of the Chinese Academy of Sciences
文摘soil water distribution;;wetting pattern;;film-mulched furrows;;furrow irrigation;;HYDRUS-2D
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA23040301)the National Natural Science Foundation of China(Grant No.42071041)。
文摘The urban water system theory is an extension of the basin water system science on an urban scale, providing a new systematic solution for the unbalanced human-water relationship and severe water challenges, such as waterlogging, black and odorous water, and ecological degradation caused by urbanization. Most existing studies on urban water systems have focused on individual water cycle processes linked with water supply and sewage treatment plants, but mutual feedback between the water cycle and its associated material circulation and water ecology, as well as human processes, still needs further exploration. In this paper, the concept, theory, and technical methodology of the urban water system were developed based on the water cycle and basin water system science. The Urban Water System 5.0(UWS 5.0) model was developed by integrating the Time Variant Gain rainfall-runoff Model with Urban water system(TVGM_Urban) in different underlying surface conditions for analyzing the natural-social water cycle processes and their associated water environmental and ecological processes and the influence of multiscale sponge measures. Herein, five major simulation functions were realized: rainfall-runoff-nonpoint source pollutant load,water and pollutant transportations through the drainage network system, terminal regulation and purification, socioeconomic water cycle, and water system assessment and regulation. The location for the case study used in this paper was Wuhan City. The findings showed that the entire urban water system should consider the built-up area and its associated rivers and lakes as the research object and explore the integrations among the urban natural-social water cycle and river regulations inside and outside of the city as well as the effects of socioeconomic development and sponge measures on the water quantity-quality-ecology processes. The UWS 5.0 model efficiently simulated the urban rainfall-runoff process, total nitrogen(TN) and total phosphorus(TP) concentrations in water bodies, and characteristic indicators of socioeconomic development. For the rainfall-runoff simulations, the correlation coefficient and Nash-Sutcliffe efficiency(NSE) fall under the excellent and good classes, respectively. For the TN and TP concentration simulations, results exhibited good bias and the correlation coefficients exceeded 0.90 for 78.1% of the sampled sites. The simulation of 18 socioeconomic indicators provided excellent bias, correlation coefficient, and NSE values of 100%, 83.3%, and 69.4% to total indicators, respectively. Based on the well-calibrated UWS 5.0 model, the source sponge,artificial enhancement, and source reduction-path interception-terminal treatment measures were optimized, which considerably mitigated waterlogging, black and odorous water, and lake eutrophication, respectively. The mitigation performance revealed that the maximum inundated area for a once-in-10-year rainfall event was reduced by 32.6%, the removal ratio of the black and odorous water area was 65%, the comprehensive trophic state index of water bodies was reduced by 37%, and the green development level of Wuhan City in 2020 increased from 0.56 to 0.67. This study is expected to advance the intersection and development of multidisciplinary fields(e.g., urban hydrology, environmental science, and ecology) and offer an important theoretical and technical basis for solving urban complex water issues and promoting green development of cities.
基金supported by the National Natural Science Foundation of China(Grant No.41807171)the National Key Research and Development Program of China(Grant No.2016YFC0400902)the China National Flash Flood Disaster Prevention and Control Project(Grant No.JZ0145B2017)。
文摘Flash floods present significant heterogeneity over both space and time due to diverse topographic,geomorphologic,and hydro-meteorological conditions of catchments.Accurate identification and simulation of typical flash flood types are of great significance for the mitigation of flash flood disasters at the national scale.Three flood peak indices and dynamic indices were adopted to characterize the behavioral variability of flash floods.The typical flash flood types and corresponding behavior indices were identified and simulated using statistical analysis(i.e.,principal component analysis,dynamic K-means clustering,and analysis of similarity)and hydrological modelling(i.e.,HEC and XAJ models).There were 177 flash flood events at the hourly scale being selected for case study from eight catchments with various climatic and geographic characteristics.Results showed that all the flash flood events were clustered into three types(named Types 1,2,and 3).Type 1 was characterized by low peak flow intensity,early flood peak occurrence time,and thin flood process with short duration.Type 2 was characterized by low peak flow intensity,late flood peak occurrence time,and flat flood process with long duration.Type 3 was characterized by high peak flow intensity and late flood peak occurrence time.Flash flood types showed high consistency with their influencing factors(e.g.,catchment forest ratio and drainage area,occurrence time and magnitude of maximum storm intensity,and concentration of a storm event).The simulation performances were basically the same for HEC and XAJ models.As for flash flood event simulations,the average relative error varied from 23.25%to 27.98%,from 11.95%to 18.19%,and from 8.30%to18.25%for Types 1,2 and 3,respectively.The average Nash-Sutcliffe efficiency coefficient varied from 0.39 to 0.54,from 0.76 to 0.85,and from 0.86 to 0.91,respectively.As for the six flash flood behavior indices simulations,the average relative rootmean-square error(RMSEr)varied from 0.37 to 0.69,from 0.37 to 0.41,and from 0.18 to 0.25 for Types 1,2,and 3,respectively.The average correlation coefficient(r)varied from 0.52 to 0.68,from 0.78 to 0.85,and from 0.88 to 0.94,respectively.The flood peak indices were the best simulated for Types 2 and 3 with RMSEr varying from 0.18 to 0.28 and r varying from 0.86 to 0.91.The flood dynamic indices were the best simulated for Type 3 with RMSEr varying from 0.19 to 0.21 and r varying from 0.91 to0.97.The study provided detailed flood information supports for flood management at catchment scale,and also provided new insights into flash flood simulations in small and medium-sized catchments from perspective of flood behavioral processes.
基金supported by the Subproject of Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA23040301)the National Natural Science Foundation of China(Grant No.42071041)。
文摘The regulation and spatial differences of urban runoffs are of great concern in contemporary hydrological research.However,owing to a shortage of basic data sources and restrictions on urban hydrological simulation functions,simulating and investigating the regulation mechanism behind rainfall-runoff processes remain significantly challenging.In this study,the Time Variant Gain Model(TVGM),a hydrological nonlinear system model,was extrapolated to the hydrodynamic model of an urban drainage network system by integrating it with the widely used Stormwater Management Model(SWMM)to adequately simulate urban runoff events while considering various underlying surfaces and runoff routing modes,such as surface,drainage network and river runoff,in urban regions(i.e.,TVGM-SWMM).Moreover,runoff events were characterized using the following four runoff regime metrics:runoff coefficient,capture ratio of annual runoff volume,standardized flood timescale,and the ratio of occurrence time differences between flow and rainfall peak to event duration(peak flow delay time).The characteristics and spatial differences of urban runoff regulations were investigated,and the key impact factors and their relative contributions were identified using multivariate statistical analyses.Four communities were selected as our study areas,consisting of communities from Beijing,Shenzhen,Wuhan,and Chongqing.Our results showed that the TVGM-SWMM performed considerably better than SWMM alone.The comprehensive simulation accuracy of 60%of the events(12/20)improved by 4-86%,with the bias improving the most,followed by the efficiency coefficient.Barring the runoff coefficient,significant spatial differences were identified at the patch scale for the runoff regime metrics,with differences of 0.43,0.22,and 0.16(p<0.05).The key impact factors were the pipe length(r=0.51)in the drainage network system and the forest area ratios(r=0.56),sponge measures(r=0.52),grassland(r=0.48),and impervious surface(r=0.46)in the underlying surfaces.The contributions of the drainage network system and the underlying surfaces were 4.27%and 37.83%,respectively.Regulation in the Beijing community,dominated by grassland regulation,delayed and reduced the peak flow and total runoff volume.In the Shenzhen community,sharp and thin runoff events were mainly generated by impervious surfaces and were not adequately regulated.Forest regulation was the dominant regulation type in the Wuhan community,which reduced the total runoff volume and delayed the peak flow.Waterbody regulation was the primary regulation type in the Chongqing community,which reduced the total runoff volume and peak flow.This study aims to introduce a comprehensive theoretical and technical assessment of the hydrological effects of urbanization and the performance of sponge city construction and provide a reference for urban hydrological model improvements in China.
