Runoff is a major component of the water cycle, and its multi-scale fluctuations are important to water resources management across arid and semi-arid regions. This paper coupled the Distributed Time Variant Gain Mod...Runoff is a major component of the water cycle, and its multi-scale fluctuations are important to water resources management across arid and semi-arid regions. This paper coupled the Distributed Time Variant Gain Model （DTVGM） into the Community Land Model （CLM 3.5）, replacing the TOPMODEL-based method to simulate runoff in the arid and semi-arid regions of China. The coupled model was calibrated at five gauging stations for the period 1980-2005 and validated for the period 2006-2010. Then, future runoff （2010-2100） was simulated for different Representative Concentration Pathways （RCP） emission scenarios. After that, the spatial distributions of the future runoff for these scenarios were discussed, and the multi-scale fluctuation characteristics of the future annual runoff for the RCP scenarios were explored using the Ensemble Empirical Mode Decomposition （EEMD） analysis method. Finally, the decadal variabilities of the future annual runoff for the entire study area and the five catchments in it were investigated. The results showed that the future annual runoff had slowly decreasing trends for scenarios RCP 2.6 and RCP 8.5 during the period 2010-2100, whereas it had a non-monotonic trend for the RCP 4.5 scenario, with a slow increase after the 2050s. Additionally, the future annual runoff clearly varied over a decadal time scale, indicating that it had clear divisions between dry and wet periods. The longest dry period was approximately 15 years （2040-2055） for the RCP 2.6 scenario and 25 years （2045-2070） for the RCP 4.5 scenario. However, the RCP 8.5 scenario was predicted to have a long dry period starting from 2045. Under these scenarios, the water resources situation of the study area will be extremely severe. Therefore, adaptive water management measures addressing climate change should be adopted to proactively confront the risks of water resources.展开更多
Nanoindentation experiments were conducted under loading rates of 500–6000μN/s and applied peak loads of 4000-12000μN to measure the creep behavior of DD407 Ni-base single crystal superalloy at room temperature.Exp...Nanoindentation experiments were conducted under loading rates of 500–6000μN/s and applied peak loads of 4000-12000μN to measure the creep behavior of DD407 Ni-base single crystal superalloy at room temperature.Experimental results demonstrated that DD407 Ni-base single crystal superalloy had a good creep resistance,but its creep properties were sensitive to the loading rate and peak load.The fitting creep parameters significantly increased with increasing loading rate and peak load based on the Findley’s model,and the corresponding creep mechanism was governed by dislocation based on the calculation of creep stress exponent.During nanoindentation creep tests,it was found that the hardness and reduced modulus decreased with increasing the loading rate and peak load,and through a dimensionless analysis,it was also noted that the effect of the dimensionless loading rate was stronger than that of dimensionless peak load on the creep properties.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
This paper coupled a water-air two-phase hydrodynamic(WATPH)model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure(P_(w))response and the slope stability.Further...This paper coupled a water-air two-phase hydrodynamic(WATPH)model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure(P_(w))response and the slope stability.Furthermore,the sensitivities of the driving force and loess soil parameters were investigated.Results showed that the WATPH model simulated the height and rise of the depth to the water table reasonably well.The depth to water table before rainfall(H0)had a significant impact on the Lisse effect and the slope stability.When the H_(0) was less than approximately 1 m,the rainfall triggered a significant Lisse effect and decreased the slope factor of safety(F_(s)).When the rainfall intensity(R_(i))was higher than the saturated hydraulic conductivity(K_(s)),the Lisse effect and the F_(s) slightly changed with the increase of the R_(i),and the slope tended to be unstable with continuous rainfall.With increasing K_(s),the Lisse effect noticeably increased,and the minimum F_(s) quickly decreases.The analysis of the normalized sensitivity coefficient revealed that H_(0) had a dramatic impact on the Lisse effect and loess slope stability.The different R_(i) and K_(s) values had prominent influences on the Lisse effect and slight impacts on F_(s).展开更多
Climate projections by global climate models(GCMs)are subject to considerable and multi-source uncertainties.This study aims to compare the uncertainty in projection of precipitation and temperature extremes between C...Climate projections by global climate models(GCMs)are subject to considerable and multi-source uncertainties.This study aims to compare the uncertainty in projection of precipitation and temperature extremes between Coupled Model Intercomparison Project(CMIP)phase 5(CMIP5)and phase 6(CMIP6),using 24 GCMs forced by 3 emission scenarios in each phase of CMIP.In this study,the total uncertainty(T)of climate projections is decomposed into the greenhouse gas emission scenario uncertainty(S,mean inter-scenario variance of the signals over all the models),GCM uncertainty(M,mean inter-model variance of signals over all emission scenarios),and internal climate variability uncertainty(V,variance in noises over all models,emission scenarios,and projection lead times);namely,T=S+M+V.The results of analysis demonstrate that the magnitudes of S,M,and T present similarly increasing trends over the 21 st century.The magnitudes of S,M,V,and T in CMIP6 are 0.94-0.96,1.38-2.07,1.04-1.69,and 1.20-1.93 times as high as those in CMIP5.Both CMIP5 and CMIP6 exhibit similar spatial variation patterns of uncertainties and similar ranks of contributions from different sources of uncertainties.The uncertainty for precipitation is lower in midlatitudes and parts of the equatorial region,but higher in low latitudes and the polar region.The uncertainty for temperature is higher over land areas than oceans,and higher in the Northern Hemisphere than the Southern Hemisphere.For precipitation,T is mainly determined by M and V in the early 21 st century,by M and S at the end of the 21 st century;and the turning point will appear in the 2070 s.For temperature,T is dominated by M in the early 21 st century,and by S at the end of the 21 st century,with the turning point occuring in the 2060 s.The relative contributions of S to T in CMIP6(12.5%-14.3%for precipitation and 31.6%-36.2%for temperature)are lower than those in CMIP5(15.1%-17.5%for precipitation and 38.6%-43.8%for temperature).By contrast,the relative contributions of M in CMIP6(50.6%-59.8%for precipitation and 59.4%-60.3%for temperature)are higher than those in CMIP5(47.5%-57.9%for precipitation and 51.7%-53.6%for temperature).The higher magnitude and relative contributions of M in CMIP6 indicate larger difference among projections of various GCMs.Therefore,more GCMs are needed to ensure the robustness of climate projections.展开更多
Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime,for which traditional decoupled mathematical river mod-els based on simplified conservation equations are not ...Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime,for which traditional decoupled mathematical river mod-els based on simplified conservation equations are not applicable. A two-dimen-sional coupled mathematical model is presented,which is generally applicable to the fluvial processes with either intense or weak sediment transport. The governing equations of the model comprise the complete shallow water hydrodynamic equa-tions closed with Manning roughness for boundary resistance and empirical rela-tionships for sediment exchange with the erodible bed. The second-order Total-Variation-Diminishing version of the Weighted-Average-Flux method,along with the HLLC approximate Riemann Solver,is adapted to solve the governing equations,which can properly resolve shock waves and contact discontinuities. The model is applied to the pilot study of the flooding due to a sudden outburst of a real glacial-lake.展开更多
基金supported by the National Basic Research Program of China(2012CB956204)We acknowledge the modeling groups for providing the data for analysis,the Program for Climate Model Diagnosis and Intercomparison(PCMDI)the World Climate Research Programme’s(WCRP’s)Coupled Model Intercomparison Project for collecting and archiving the model output and organizing the data analysis
文摘Runoff is a major component of the water cycle, and its multi-scale fluctuations are important to water resources management across arid and semi-arid regions. This paper coupled the Distributed Time Variant Gain Model （DTVGM） into the Community Land Model （CLM 3.5）, replacing the TOPMODEL-based method to simulate runoff in the arid and semi-arid regions of China. The coupled model was calibrated at five gauging stations for the period 1980-2005 and validated for the period 2006-2010. Then, future runoff （2010-2100） was simulated for different Representative Concentration Pathways （RCP） emission scenarios. After that, the spatial distributions of the future runoff for these scenarios were discussed, and the multi-scale fluctuation characteristics of the future annual runoff for the RCP scenarios were explored using the Ensemble Empirical Mode Decomposition （EEMD） analysis method. Finally, the decadal variabilities of the future annual runoff for the entire study area and the five catchments in it were investigated. The results showed that the future annual runoff had slowly decreasing trends for scenarios RCP 2.6 and RCP 8.5 during the period 2010-2100, whereas it had a non-monotonic trend for the RCP 4.5 scenario, with a slow increase after the 2050s. Additionally, the future annual runoff clearly varied over a decadal time scale, indicating that it had clear divisions between dry and wet periods. The longest dry period was approximately 15 years （2040-2055） for the RCP 2.6 scenario and 25 years （2045-2070） for the RCP 4.5 scenario. However, the RCP 8.5 scenario was predicted to have a long dry period starting from 2045. Under these scenarios, the water resources situation of the study area will be extremely severe. Therefore, adaptive water management measures addressing climate change should be adopted to proactively confront the risks of water resources.
基金financial supports from the National Natural Science Foundation of China(Nos.11772236,11472195)。
文摘Nanoindentation experiments were conducted under loading rates of 500–6000μN/s and applied peak loads of 4000-12000μN to measure the creep behavior of DD407 Ni-base single crystal superalloy at room temperature.Experimental results demonstrated that DD407 Ni-base single crystal superalloy had a good creep resistance,but its creep properties were sensitive to the loading rate and peak load.The fitting creep parameters significantly increased with increasing loading rate and peak load based on the Findley’s model,and the corresponding creep mechanism was governed by dislocation based on the calculation of creep stress exponent.During nanoindentation creep tests,it was found that the hardness and reduced modulus decreased with increasing the loading rate and peak load,and through a dimensionless analysis,it was also noted that the effect of the dimensionless loading rate was stronger than that of dimensionless peak load on the creep properties.
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(No.41972248)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2019JM-146,2024JC-YBQN-0274)the Fundamental Research Funds for the Central Universities,CHD(No.300102293103).
文摘This paper coupled a water-air two-phase hydrodynamic(WATPH)model with the Iverson’s method to analyze the influence of the Lisse effect on the fast groundwater pressure(P_(w))response and the slope stability.Furthermore,the sensitivities of the driving force and loess soil parameters were investigated.Results showed that the WATPH model simulated the height and rise of the depth to the water table reasonably well.The depth to water table before rainfall(H0)had a significant impact on the Lisse effect and the slope stability.When the H_(0) was less than approximately 1 m,the rainfall triggered a significant Lisse effect and decreased the slope factor of safety(F_(s)).When the rainfall intensity(R_(i))was higher than the saturated hydraulic conductivity(K_(s)),the Lisse effect and the F_(s) slightly changed with the increase of the R_(i),and the slope tended to be unstable with continuous rainfall.With increasing K_(s),the Lisse effect noticeably increased,and the minimum F_(s) quickly decreases.The analysis of the normalized sensitivity coefficient revealed that H_(0) had a dramatic impact on the Lisse effect and loess slope stability.The different R_(i) and K_(s) values had prominent influences on the Lisse effect and slight impacts on F_(s).
基金Supported by the National Key Research and Development Program of China(2017YFA0603704)National Natural Science Foundation of China(51779176)China 111 Project(B18037)。
文摘Climate projections by global climate models(GCMs)are subject to considerable and multi-source uncertainties.This study aims to compare the uncertainty in projection of precipitation and temperature extremes between Coupled Model Intercomparison Project(CMIP)phase 5(CMIP5)and phase 6(CMIP6),using 24 GCMs forced by 3 emission scenarios in each phase of CMIP.In this study,the total uncertainty(T)of climate projections is decomposed into the greenhouse gas emission scenario uncertainty(S,mean inter-scenario variance of the signals over all the models),GCM uncertainty(M,mean inter-model variance of signals over all emission scenarios),and internal climate variability uncertainty(V,variance in noises over all models,emission scenarios,and projection lead times);namely,T=S+M+V.The results of analysis demonstrate that the magnitudes of S,M,and T present similarly increasing trends over the 21 st century.The magnitudes of S,M,V,and T in CMIP6 are 0.94-0.96,1.38-2.07,1.04-1.69,and 1.20-1.93 times as high as those in CMIP5.Both CMIP5 and CMIP6 exhibit similar spatial variation patterns of uncertainties and similar ranks of contributions from different sources of uncertainties.The uncertainty for precipitation is lower in midlatitudes and parts of the equatorial region,but higher in low latitudes and the polar region.The uncertainty for temperature is higher over land areas than oceans,and higher in the Northern Hemisphere than the Southern Hemisphere.For precipitation,T is mainly determined by M and V in the early 21 st century,by M and S at the end of the 21 st century;and the turning point will appear in the 2070 s.For temperature,T is dominated by M in the early 21 st century,and by S at the end of the 21 st century,with the turning point occuring in the 2060 s.The relative contributions of S to T in CMIP6(12.5%-14.3%for precipitation and 31.6%-36.2%for temperature)are lower than those in CMIP5(15.1%-17.5%for precipitation and 38.6%-43.8%for temperature).By contrast,the relative contributions of M in CMIP6(50.6%-59.8%for precipitation and 59.4%-60.3%for temperature)are higher than those in CMIP5(47.5%-57.9%for precipitation and 51.7%-53.6%for temperature).The higher magnitude and relative contributions of M in CMIP6 indicate larger difference among projections of various GCMs.Therefore,more GCMs are needed to ensure the robustness of climate projections.
基金the National Basic Research and Development Program of China (973 Program) (Grant No 2007CB14106)the National Natural Science Foundation of China (Grant No 50459001)the Key Project of Chinese Academy of Sciences (Grant No KZCX3-SW-357-02)
文摘Alluvial rivers may experience intense sediment transport and rapid bed evolution under a high flow regime,for which traditional decoupled mathematical river mod-els based on simplified conservation equations are not applicable. A two-dimen-sional coupled mathematical model is presented,which is generally applicable to the fluvial processes with either intense or weak sediment transport. The governing equations of the model comprise the complete shallow water hydrodynamic equa-tions closed with Manning roughness for boundary resistance and empirical rela-tionships for sediment exchange with the erodible bed. The second-order Total-Variation-Diminishing version of the Weighted-Average-Flux method,along with the HLLC approximate Riemann Solver,is adapted to solve the governing equations,which can properly resolve shock waves and contact discontinuities. The model is applied to the pilot study of the flooding due to a sudden outburst of a real glacial-lake.
