Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical c...Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use at the watershed. Five subwatersheds that can represent the whole watershed were chosen and their average annual precipitation, average annual surface runoff and current land use were calculated respectively in the grid model of the Wujiang River watershed based on the climate and hydrology data from 1965 to 2000 and the land-use data acquired in the year of 2000. Surface runoff is assumed to be a function of precipitation and land use and the multiple regression tool is used to determine the relationship between surface runoff, precipitation and present land use. Thus, the rainfall-runoff model for each land-use type has been established. When calibrating these models, the results show that the percent errors are all below 7%, which indicates that the accuracy of this simulation is high.展开更多
Through a simulation test carried out with soil columns (61.8 cm in diameter), the effect of precipitation on salt-water dynamics in soils was studied by in-situ monitoring of salt-water dynamics using soil salinity s...Through a simulation test carried out with soil columns (61.8 cm in diameter), the effect of precipitation on salt-water dynamics in soils was studied by in-situ monitoring of salt-water dynamics using soil salinity sensors and tensiometers. The results show that in the profile of whole silty loam soil, the surface runoff volume due to precipitation and the salt-leaching role of infiltrated precipitation increased with the depth of ground water; and in the profile with an intercalated bed of clay or with a thick upper layer of clay, the amount of surface runoff was greater but the salt-leaching role of precipitation was smaller than those in the profile of whole silty loam soil. In case of soil water being supplemented by precipitation, the evaporation of groundwater in the soil columns reduced, resulting in a great decline of salt accumulation from soil profile to surface soil. The effect of precipitation on the water regime of soil profile was performed via both water infiltration and water pressure transfer. The direct infiltration depth of precipitation was less than 1 m in general, but water pressure transfer could go up to groundwater surface directly.展开更多
Through a simulation test conducted with soil columns (61.8cm in diameter) in field condition,effect of crop planting upon the regulation of salt-water dynamics in soils was studied by monitoring of salt-water dynamic...Through a simulation test conducted with soil columns (61.8cm in diameter) in field condition,effect of crop planting upon the regulation of salt-water dynamics in soils was studied by monitoring of salt-water dynamics in situ,using soil salinity sensors and tensiometers.The results indicated that the amount of water absorbed by crops from the soil was generally larger than the decrement of water consumption from soil surface evaporation reduced by the crop covering the soil surface and improving the soil structure,therefore,under the conditions of crop growing and non-irrigation,water content in soil profile was less than that without crop growing,and the gradient of negative pressure of soil water in soil profile especially in the root zone was enlarged,thus causing the water flowing from subsoils into root zone and increasing the groundwater moving upwards into soil layer via capillary rise,so that the groundwater evaporation increased.Consequently,under the condition of crop growing,the salt was mainly accumulated towards the root zone rather than to the top soil.the accumulating rate of salt in groundwater via capillary rise of soil water to subsoils was increased thereby.展开更多
Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical proper- ties of watersheds and their nonpoint source (NPS) pollution po- tential at present. Urbanization ...Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical proper- ties of watersheds and their nonpoint source (NPS) pollution po- tential at present. Urbanization has changed the source, process and sink of urban NPS pollution, especially raised the pollution load of urban runoff NPS in receiving water. Urban runoff pollu- tion is a hot spot of research on NPS. This paper analyzed type, source and harm of the NPS pollutants of urban runoff and its influence on the receiving water. Through estimating NPS pollu- tion load of urban runoff and summarizing the law and character- istics of urban runoff NPS systemically, study on management and control of urban runoff NPS pollution was focused on the applica- tion of BMPs (best management practices). It is a fresh method- ology that management and control on NPS pollution from urban surface runoff was analyzed by methods of landscape ecology, environmental economics and environmental management. The paper provided a scientific reference for mitigating urban water environment pressure and an effective method for management and control of NPS pollution from urban surface runoff..展开更多
A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surf...A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surface hydraulic processes. In this CA model, the hillslope surface was subdivided into a series of discrete spatial cells with the same geometric features. At each time step, water and sediment were transported between two adjacent spatial cells. The flow direction was determined by a combination of water surface slope and stochastic assignment. The amounts of interchanged water and sediment were computed using the Chezy-Manning formula and the empirical sediment transport equation. The water and sediment discharged from the open boundary cells were considered as the runoff and the sediment yields over the entire hillslope surface. Two hillslope soil erosion experiments under simulated rainfall events were carried out. Cumulative runoff and sediment yields were measured, respectively. Then, the CA model was applied to simulate the water and soil erosion for these two experiments. Analysis of simulation results indicated that the size of the spatial cell, hydraulic parameters, and the setting of time step and iteration times had a large impact on the model accuracy. The comparison of the simulated and measured data suggested that the CA model was an applicable alternate for simulating the hillslope water flow and soil erosion.展开更多
A study was conducted in eight districts, viz., Faridkot, Moga, Ferozepur, Muktsar, Bathinda, Mansa, Barnala and Sangrur in south-western part of the Punjab, India to characterize aquifer strata by preparing a fence d...A study was conducted in eight districts, viz., Faridkot, Moga, Ferozepur, Muktsar, Bathinda, Mansa, Barnala and Sangrur in south-western part of the Punjab, India to characterize aquifer strata by preparing a fence diagram depicting sub-surface strata and distribution of groundwater quality. The sub-surface lithology drilled upto a depth of 60 m reveal the presence of top most layer of impervious strata comprising of clay upto the depth of 2 m to 5 m which impedes the percolation of surface runoff into the soil leading to surface flooding and water logging even in areas having saturated zone beyond the depth of 5 m. Thick pervious strata of 45 m to 50 m thickness is encountered in central and south-sentral part of the study area comprising of Bathinda, Muktsar and Mansa districts which at certain places are separated by one or two thin layers of impervious or semi-pervious strata comprising of clay and sand occasionally associated with ＂kankar＂ of thickness ranging between 2 m to 5 m. The northern, western and eastern parts, however, exhibit three to four layered pervious zones ranging in thickness from 5 m to 25 m separated by thin layers of impervious and semi pervious strata. The groundwater quality in about 6% of the study area in eight districts is fit, 18% is marginal and 76% is unfit for irrigation purpose.展开更多
In this study, the high-accuracy multisource integrated Chinese land cover （MICLCover） dataset was used in version 4 of the Community Land Model （CLM4） to assess how the new land cover information affected land su...In this study, the high-accuracy multisource integrated Chinese land cover （MICLCover） dataset was used in version 4 of the Community Land Model （CLM4） to assess how the new land cover information affected land surface simulation over China. Compared to the default land cover dataset in CLM4, the MICL data indicated lower values for bare soil （14.6% reduction）, nee- dleleaf tree （3.6%）, and broadleaf tree （1.9%）; higher values for shrub cover （1.8% increase）, grassland （9.9%）, cropland （5.0%）, glaciers （0.5%）, lakes （1.6%）, and wetland （1.1%）; and unchanged for urban areas. Two comparative CLM4 simulations were conducted for the 33-yr period from 1972 to 2004, one using the MICL dataset and the other using the default dataset. The results revealed that the MICL data produced a 0.3% lower mean annual surface albedo over China than the original data. The largest contributor to the reduced value was semiarid regions （2.1% reduction）. The MICL-data albedo value agreed more closely with observations （MODIS broad- band black-sky albedo products） over arid and semiarid regions than for the original data to some extent. The simulated average sensible heat flux over China increased by only 0.1 W m 2 owing to the reduced values in arid and semiarid regions, as opposed to increases in humid and semihumid regions, while an increased latent heat flux of I W m-2 was reflected in almost identical changes over the whole region. In addition, the mean annual runoff simulated by CLM4 using MICL data decreased by 6.8 mm yr-1, primarily due to large simulated decreases in humid regions.展开更多
A droplet undergoes spreading,rebounding or splashing when it impacts solid boundary,which is a typical phenomenon of free surface flow that exists widely in modern industry.Smoothed particle hydrodynamics(SPH)method ...A droplet undergoes spreading,rebounding or splashing when it impacts solid boundary,which is a typical phenomenon of free surface flow that exists widely in modern industry.Smoothed particle hydrodynamics(SPH)method is applied to numerically study the dynamical behaviors of the droplet impacting solid boundary,and both the spreading and rebounding phenomena of the droplet are reproduced in the simulation.The droplet deformation,flow fields and pressure fields inside the droplet at different moments are analyzed.Two important factors,the initial velocity and diameter,are discussed in determining the maximum spreading factor,revealing that the maximum spreading factor increases with the increase of the impact velocity and droplet diameter respectively.展开更多
The goal of this research was to determine the impact of nonionic surfactants on drag reduction effect in water and metal oxide nanofluid. Two nonionic surfactants （Rokacet 07 and Rokanol KT） and copper（II） oxide ...The goal of this research was to determine the impact of nonionic surfactants on drag reduction effect in water and metal oxide nanofluid. Two nonionic surfactants （Rokacet 07 and Rokanol KT） and copper（II） oxide wa- ter-based nanofluid were examined. Friction factors in a 4 mm diameter pipe for the Reynolds number between 8000 and 50000 were determined. Results showed that addition of nonionic surfactants caused the decrease of fric- tion factor in water and nanofluid. The drag reduction effect was similar in both cases. Presence of nanoparticles in the system has no great influence on drag reduction effect.展开更多
The mass stream function of zonal mean meridional circulation is calculated in terms of NCEP/NCAR monthly meridional wind speed and vertical velocity, and the climatic and anomalous features of zonal mean SST and meri...The mass stream function of zonal mean meridional circulation is calculated in terms of NCEP/NCAR monthly meridional wind speed and vertical velocity, and the climatic and anomalous features of zonal mean SST and meridional circulation are investigated. Results show that (1) a joint ascending branch of Northern and Southern Hadley circulation is on the side of the summer hemisphere near the equator ,being well consistent with the extremum of[]SST,and a strong descending by the winter-hemispheric side.(2)El Ni駉-related][SSTin low latitudes is an important outer-forcing source for anomaly meridional circulation, which is affected by seasonal variation of basic airflow and[]SST, and interannual and interdecadal changes of []SST.展开更多
Considering the short length of building roofs, a theoretical analysis of the first flush of roof runoff was conducted based on the kinematic wave and pollutant erosion equations. This mathematical derivation with ana...Considering the short length of building roofs, a theoretical analysis of the first flush of roof runoff was conducted based on the kinematic wave and pollutant erosion equations. This mathematical derivation with analytical solutions predicts pollutant mass first flush (MFF), mean concentration of initial runoff (MCIF), mean concentration of roof runoff (MCRR) with diversion of initial portion and residual mass available on the bed surface (RS) after the entire runoff under the condition of con-stant excess rainfall. And the effects of the associated influencing factors (roof length, roof gradient, roof surface roughness, rainfall intensity, rainfall duration, and erosion coefficients) on them were discussed while the values of parameters referred to the previous studies. The results showed that for roofs whose length is shorter than 20 m, both the increase in roof length and roof gradient and the decrease in roof surface roughness result in larger MFF and MCIF and smaller MCRR and RS, which is beneficial to water reuse and pollution reduction. The theoretical relationship between the first flush and the influencing factors may aid the planning and design of roof in terms of rainwater utilization or diffuse pollution control.展开更多
文摘Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use at the watershed. Five subwatersheds that can represent the whole watershed were chosen and their average annual precipitation, average annual surface runoff and current land use were calculated respectively in the grid model of the Wujiang River watershed based on the climate and hydrology data from 1965 to 2000 and the land-use data acquired in the year of 2000. Surface runoff is assumed to be a function of precipitation and land use and the multiple regression tool is used to determine the relationship between surface runoff, precipitation and present land use. Thus, the rainfall-runoff model for each land-use type has been established. When calibrating these models, the results show that the percent errors are all below 7%, which indicates that the accuracy of this simulation is high.
文摘Through a simulation test carried out with soil columns (61.8 cm in diameter), the effect of precipitation on salt-water dynamics in soils was studied by in-situ monitoring of salt-water dynamics using soil salinity sensors and tensiometers. The results show that in the profile of whole silty loam soil, the surface runoff volume due to precipitation and the salt-leaching role of infiltrated precipitation increased with the depth of ground water; and in the profile with an intercalated bed of clay or with a thick upper layer of clay, the amount of surface runoff was greater but the salt-leaching role of precipitation was smaller than those in the profile of whole silty loam soil. In case of soil water being supplemented by precipitation, the evaporation of groundwater in the soil columns reduced, resulting in a great decline of salt accumulation from soil profile to surface soil. The effect of precipitation on the water regime of soil profile was performed via both water infiltration and water pressure transfer. The direct infiltration depth of precipitation was less than 1 m in general, but water pressure transfer could go up to groundwater surface directly.
文摘Through a simulation test conducted with soil columns (61.8cm in diameter) in field condition,effect of crop planting upon the regulation of salt-water dynamics in soils was studied by monitoring of salt-water dynamics in situ,using soil salinity sensors and tensiometers.The results indicated that the amount of water absorbed by crops from the soil was generally larger than the decrement of water consumption from soil surface evaporation reduced by the crop covering the soil surface and improving the soil structure,therefore,under the conditions of crop growing and non-irrigation,water content in soil profile was less than that without crop growing,and the gradient of negative pressure of soil water in soil profile especially in the root zone was enlarged,thus causing the water flowing from subsoils into root zone and increasing the groundwater moving upwards into soil layer via capillary rise,so that the groundwater evaporation increased.Consequently,under the condition of crop growing,the salt was mainly accumulated towards the root zone rather than to the top soil.the accumulating rate of salt in groundwater via capillary rise of soil water to subsoils was increased thereby.
基金Key Program of Natural Science Foundation of China(No. 40576024).
文摘Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical proper- ties of watersheds and their nonpoint source (NPS) pollution po- tential at present. Urbanization has changed the source, process and sink of urban NPS pollution, especially raised the pollution load of urban runoff NPS in receiving water. Urban runoff pollu- tion is a hot spot of research on NPS. This paper analyzed type, source and harm of the NPS pollutants of urban runoff and its influence on the receiving water. Through estimating NPS pollu- tion load of urban runoff and summarizing the law and character- istics of urban runoff NPS systemically, study on management and control of urban runoff NPS pollution was focused on the applica- tion of BMPs (best management practices). It is a fresh method- ology that management and control on NPS pollution from urban surface runoff was analyzed by methods of landscape ecology, environmental economics and environmental management. The paper provided a scientific reference for mitigating urban water environment pressure and an effective method for management and control of NPS pollution from urban surface runoff..
基金Project supported by the National Science Fund for Distinguished Young Scholars of China (No. 40225004)the National Natural Science Foundation of China (No. 40471048)
文摘A novel quantitative cellular automata (CA) model that simulates and predicts hillslope runoff and soil erosion caused by rainfall events was developed by integrating the local interaction rules and the hillslope surface hydraulic processes. In this CA model, the hillslope surface was subdivided into a series of discrete spatial cells with the same geometric features. At each time step, water and sediment were transported between two adjacent spatial cells. The flow direction was determined by a combination of water surface slope and stochastic assignment. The amounts of interchanged water and sediment were computed using the Chezy-Manning formula and the empirical sediment transport equation. The water and sediment discharged from the open boundary cells were considered as the runoff and the sediment yields over the entire hillslope surface. Two hillslope soil erosion experiments under simulated rainfall events were carried out. Cumulative runoff and sediment yields were measured, respectively. Then, the CA model was applied to simulate the water and soil erosion for these two experiments. Analysis of simulation results indicated that the size of the spatial cell, hydraulic parameters, and the setting of time step and iteration times had a large impact on the model accuracy. The comparison of the simulated and measured data suggested that the CA model was an applicable alternate for simulating the hillslope water flow and soil erosion.
文摘A study was conducted in eight districts, viz., Faridkot, Moga, Ferozepur, Muktsar, Bathinda, Mansa, Barnala and Sangrur in south-western part of the Punjab, India to characterize aquifer strata by preparing a fence diagram depicting sub-surface strata and distribution of groundwater quality. The sub-surface lithology drilled upto a depth of 60 m reveal the presence of top most layer of impervious strata comprising of clay upto the depth of 2 m to 5 m which impedes the percolation of surface runoff into the soil leading to surface flooding and water logging even in areas having saturated zone beyond the depth of 5 m. Thick pervious strata of 45 m to 50 m thickness is encountered in central and south-sentral part of the study area comprising of Bathinda, Muktsar and Mansa districts which at certain places are separated by one or two thin layers of impervious or semi-pervious strata comprising of clay and sand occasionally associated with ＂kankar＂ of thickness ranging between 2 m to 5 m. The northern, western and eastern parts, however, exhibit three to four layered pervious zones ranging in thickness from 5 m to 25 m separated by thin layers of impervious and semi pervious strata. The groundwater quality in about 6% of the study area in eight districts is fit, 18% is marginal and 76% is unfit for irrigation purpose.
基金supported by the National Basic Research Program of China (Grants Nos. 2010CB951101 and 2010CB428403)the National Natural Science Foundation of China (Grant No. 91125016)
文摘In this study, the high-accuracy multisource integrated Chinese land cover （MICLCover） dataset was used in version 4 of the Community Land Model （CLM4） to assess how the new land cover information affected land surface simulation over China. Compared to the default land cover dataset in CLM4, the MICL data indicated lower values for bare soil （14.6% reduction）, nee- dleleaf tree （3.6%）, and broadleaf tree （1.9%）; higher values for shrub cover （1.8% increase）, grassland （9.9%）, cropland （5.0%）, glaciers （0.5%）, lakes （1.6%）, and wetland （1.1%）; and unchanged for urban areas. Two comparative CLM4 simulations were conducted for the 33-yr period from 1972 to 2004, one using the MICL dataset and the other using the default dataset. The results revealed that the MICL data produced a 0.3% lower mean annual surface albedo over China than the original data. The largest contributor to the reduced value was semiarid regions （2.1% reduction）. The MICL-data albedo value agreed more closely with observations （MODIS broad- band black-sky albedo products） over arid and semiarid regions than for the original data to some extent. The simulated average sensible heat flux over China increased by only 0.1 W m 2 owing to the reduced values in arid and semiarid regions, as opposed to increases in humid and semihumid regions, while an increased latent heat flux of I W m-2 was reflected in almost identical changes over the whole region. In addition, the mean annual runoff simulated by CLM4 using MICL data decreased by 6.8 mm yr-1, primarily due to large simulated decreases in humid regions.
基金Supported by the National Natural Science Foundation of China(No.51079095)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(No.51021004)
文摘A droplet undergoes spreading,rebounding or splashing when it impacts solid boundary,which is a typical phenomenon of free surface flow that exists widely in modern industry.Smoothed particle hydrodynamics(SPH)method is applied to numerically study the dynamical behaviors of the droplet impacting solid boundary,and both the spreading and rebounding phenomena of the droplet are reproduced in the simulation.The droplet deformation,flow fields and pressure fields inside the droplet at different moments are analyzed.Two important factors,the initial velocity and diameter,are discussed in determining the maximum spreading factor,revealing that the maximum spreading factor increases with the increase of the impact velocity and droplet diameter respectively.
基金Supported by the State Committee for Scientific Research(Poland)(NN209764040)Michal Drzazga received the Scholarship under the Project DoktoRIS-Scholarship Program for Innovative Silesia Co-financed by the European Union under the European Social Fund
文摘The goal of this research was to determine the impact of nonionic surfactants on drag reduction effect in water and metal oxide nanofluid. Two nonionic surfactants （Rokacet 07 and Rokanol KT） and copper（II） oxide wa- ter-based nanofluid were examined. Friction factors in a 4 mm diameter pipe for the Reynolds number between 8000 and 50000 were determined. Results showed that addition of nonionic surfactants caused the decrease of fric- tion factor in water and nanofluid. The drag reduction effect was similar in both cases. Presence of nanoparticles in the system has no great influence on drag reduction effect.
文摘The mass stream function of zonal mean meridional circulation is calculated in terms of NCEP/NCAR monthly meridional wind speed and vertical velocity, and the climatic and anomalous features of zonal mean SST and meridional circulation are investigated. Results show that (1) a joint ascending branch of Northern and Southern Hadley circulation is on the side of the summer hemisphere near the equator ,being well consistent with the extremum of[]SST,and a strong descending by the winter-hemispheric side.(2)El Ni駉-related][SSTin low latitudes is an important outer-forcing source for anomaly meridional circulation, which is affected by seasonal variation of basic airflow and[]SST, and interannual and interdecadal changes of []SST.
基金supported by the National Key Technology R&D Program of China (No. 2006BAK13B04)the Expo Shanghai Sci-Tech Program of Science and Technology Commission of Shanghai (No. 06dz05808), China
文摘Considering the short length of building roofs, a theoretical analysis of the first flush of roof runoff was conducted based on the kinematic wave and pollutant erosion equations. This mathematical derivation with analytical solutions predicts pollutant mass first flush (MFF), mean concentration of initial runoff (MCIF), mean concentration of roof runoff (MCRR) with diversion of initial portion and residual mass available on the bed surface (RS) after the entire runoff under the condition of con-stant excess rainfall. And the effects of the associated influencing factors (roof length, roof gradient, roof surface roughness, rainfall intensity, rainfall duration, and erosion coefficients) on them were discussed while the values of parameters referred to the previous studies. The results showed that for roofs whose length is shorter than 20 m, both the increase in roof length and roof gradient and the decrease in roof surface roughness result in larger MFF and MCIF and smaller MCRR and RS, which is beneficial to water reuse and pollution reduction. The theoretical relationship between the first flush and the influencing factors may aid the planning and design of roof in terms of rainwater utilization or diffuse pollution control.
