Catchment erosion not only shapes various landforms of the earth’s surface but also affects the rates of chemical weathering and CO_(2) absorption by controlling the exposure of rock fragments,and thus acts as a regu...Catchment erosion not only shapes various landforms of the earth’s surface but also affects the rates of chemical weathering and CO_(2) absorption by controlling the exposure of rock fragments,and thus acts as a regulator of the global climate.Therefore,studying the occurrence and controlling factors of catchment erosion can improve our understanding of topographic evolution and long-term climate change.This paper introduces the“comminution age”method based on (^(234)U/^(238)U) of sediment detrital components and its applications to indicate the catchment erosion depth,which is widely applied to different depositional environments.In tectonically stable regions,where there is shallow erosion,the sediment output from the catchment is usually accompanied by a low (^(234)U/^(238)U).On the other hand,where there is deep erosion,the (^(234)U/^(238)U) of the downstream sediments is usually high.In tectonically active regions,deep erosion is common,and the sediment erosion process is subject to rapid material transport,such as landslide-induced sediment displacement.Since the sediment exposure history is short,the (^(234)U/^(238)U) of the detrital components is close to 1,thus reaching“secular equilibrium”.The comminution age method is promising in terms of tracing catchment erosion depths at the orbital scale.Furthermore,this method is also sensitive to the erosion changes caused by rapid climate changes and human activities.展开更多
The application of fallout radionuclides in soil erosion investigations and related sediment budget studies has provided a widely used tool for improving understanding of soil erosion and sediment transfer processes.H...The application of fallout radionuclides in soil erosion investigations and related sediment budget studies has provided a widely used tool for improving understanding of soil erosion and sediment transfer processes.However,most studies using fallout radionuclides undertaken to date have focussed on small areas.This focus on small areas reflects both the issues addressed and practical constraints associated with sample collection and analysis.Increasing acceptance of the important role of fine sediment in degrading aquatic habitats and in the transfer and fate of nutrients and contaminants within terrestrial and fluvial systems has emphasised the need to consider larger areas and the catchment or regional scale.The need to upscale existing approaches to the use of fallout radionuclides to larger areas represents an important challenge.This contribution provides a brief review of existing and potential approaches to upscaling the use of fallout radionuclides and presents two examples where such approaches have been successfully applied.These involve a national scale assessment of soil erosion rates in England and Wales based on 137Cs measurements and an investigation of the sediment budgets of three small/intermediate-size catchments in southern Italy.展开更多
Water resource is the important factor for sustainable development in Weigan River catchments in western China. Based on ecological hydrology principles, the coupling relation between water and salt is monitored and a...Water resource is the important factor for sustainable development in Weigan River catchments in western China. Based on ecological hydrology principles, the coupling relation between water and salt is monitored and analyzed. The water quality for irrigation in oasis ecosystem has a larger variable range in arid area, which depending on the input water resource and underground water mineralization degree and water chemical component on the catchments scale, the water and salt coupling is decided by the climate condition and soil feature and vegetation characteristics as well as human activity. Meanwhile, temporal and spatial change between water and salt is quite complicated. The environmental management should be paid attention to considering in irrigation area in the catchments.展开更多
Specific Catchment Area （SCA） is defined as the upstream catchment area of a unit contour. As one of the key terrain parameters, it is widely used in the modeling of hydrology, soil erosion and ecological environmen...Specific Catchment Area （SCA） is defined as the upstream catchment area of a unit contour. As one of the key terrain parameters, it is widely used in the modeling of hydrology, soil erosion and ecological environment. However, SCA value changes significantly at different DEM resolutions, which inevitably affect terrain analysis results. SCA can be described as the ratio of Catchment Area （CA） and DEM grid length. In this paper, the scale effect of CA is firstly investigated. With Jiuyuangou Gully, a watershed about 70 km2 in northern Shaanxi Province of China, as the test area, it is found that the impacts of DEM scale on CA are different in spatial distribution. CA value in upslope location becomes bigger with the decrease of the DEM resolution. When the location is close to downstream areas the impact of DEM scale on CA is gradually weakening. The scale effect of CA can be concluded as a mathematic trend of exponential decline. Then, a downscaling model of SCA is put forward by introducing the scale factor and the location factor. The scaling model can realize the conversion of SCA value from a coarse DEM resolution to a finer one at pixel level. Experiment results show that the downscaled SCA was well revised, and consistent with SCA at the target resolution with respect to the statistical indexes, histogram and spatial distribution. With the advantages of no empirical parameters, the scaling model could be considered as a simple and objective model for SCA scaling in a rugged drainage area.展开更多
Previous studies have demonstrated that offline land surface models(LSMs)and global hydrological models(GHMs)can reasonably reproduce streamflow in large river basins.Global reanalyses supply fine spatiotemporal runof...Previous studies have demonstrated that offline land surface models(LSMs)and global hydrological models(GHMs)can reasonably reproduce streamflow in large river basins.Global reanalyses supply fine spatiotemporal runoff estimates,but they are not fully intercompared and evaluated in China.This study assesses the routed-runoff from five offline LSM/GHM runs(VIC-CN05.1,CLM-CFSR,CLM-ERAI,CLM-MERRA,and CLM-NCEP)and three reanalysis datasets(ERAI/Land,JRA55,and MERRA-2)against the gauged streamflow(26 stations)in major Chinese river basins during 1980–2008.The Catchment-based Macro-scale Floodplain model(CaMa-Flood)is employed to route those runoff datasets to the hydrological stations.Four statistical quantities,including the correlation coefficient(R),standard deviation(STD),Nash–Sutcliffe efficiency coefficient(NSE),and relative error(RE),along with a ranking method,are used to quantify the quality of those products.The results show that the spatial patterns of both modeled and observed streamflow in summer are similar,but their magnitudes are different.Except for MERRA-2,the other products can reproduce well the interannual variability of streamflow in both the Yangtze and Yellow River basins.All products generally underestimate the magnitude and variance of monthly streamflow,while VIC-CN05.1 and JRA55 are closer to observations compared to other products.The correlation coefficients for all products are overall larger than 0.61,with the highest value(0.85)from VIC-CN05.1.In addition to CLM-MERRA,MERRA-2,and CLM-NCEP with relatively small precipitation,other products can simulate peak flow well with positive NSEs up to 0.41(ERAI/Land).Considerable uncertainties exist among the eight products at the Yellow River outlet,which might be because the LSMs ignore frequent human activities.Based on the above statistics,performances of the eight runoff products are ranked in descending order as follows:VIC-CN05.1,ERAI/Land,JRA55,CLM-CFSR,CLM-ERAI,MERRA-2,CLM-MERRA,and CLM-NCEP,which provides a reference for flood/hydro展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2022YFF0800504)the National Natural Science Foundation of China (Grant Nos.41991324,42273057,42076063)+1 种基金the Natural Science Foundation of Shanghai (Grant Nos.20ZR1460400,21590712700)State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,CAS (Grant No.SKLLQG2222)。
文摘Catchment erosion not only shapes various landforms of the earth’s surface but also affects the rates of chemical weathering and CO_(2) absorption by controlling the exposure of rock fragments,and thus acts as a regulator of the global climate.Therefore,studying the occurrence and controlling factors of catchment erosion can improve our understanding of topographic evolution and long-term climate change.This paper introduces the“comminution age”method based on (^(234)U/^(238)U) of sediment detrital components and its applications to indicate the catchment erosion depth,which is widely applied to different depositional environments.In tectonically stable regions,where there is shallow erosion,the sediment output from the catchment is usually accompanied by a low (^(234)U/^(238)U).On the other hand,where there is deep erosion,the (^(234)U/^(238)U) of the downstream sediments is usually high.In tectonically active regions,deep erosion is common,and the sediment erosion process is subject to rapid material transport,such as landslide-induced sediment displacement.Since the sediment exposure history is short,the (^(234)U/^(238)U) of the detrital components is close to 1,thus reaching“secular equilibrium”.The comminution age method is promising in terms of tracing catchment erosion depths at the orbital scale.Furthermore,this method is also sensitive to the erosion changes caused by rapid climate changes and human activities.
基金support of the International Atomic Energy Agency Coordinated Research Programme D1.20.11,and associated Technical Contract 15478 for the work reported in this contribution is gratefully acknowledgedThe work on the UK National Soil Erosion Inventory was funded by DEFRA contracts SP0411 and SP0413.
文摘The application of fallout radionuclides in soil erosion investigations and related sediment budget studies has provided a widely used tool for improving understanding of soil erosion and sediment transfer processes.However,most studies using fallout radionuclides undertaken to date have focussed on small areas.This focus on small areas reflects both the issues addressed and practical constraints associated with sample collection and analysis.Increasing acceptance of the important role of fine sediment in degrading aquatic habitats and in the transfer and fate of nutrients and contaminants within terrestrial and fluvial systems has emphasised the need to consider larger areas and the catchment or regional scale.The need to upscale existing approaches to the use of fallout radionuclides to larger areas represents an important challenge.This contribution provides a brief review of existing and potential approaches to upscaling the use of fallout radionuclides and presents two examples where such approaches have been successfully applied.These involve a national scale assessment of soil erosion rates in England and Wales based on 137Cs measurements and an investigation of the sediment budgets of three small/intermediate-size catchments in southern Italy.
文摘Water resource is the important factor for sustainable development in Weigan River catchments in western China. Based on ecological hydrology principles, the coupling relation between water and salt is monitored and analyzed. The water quality for irrigation in oasis ecosystem has a larger variable range in arid area, which depending on the input water resource and underground water mineralization degree and water chemical component on the catchments scale, the water and salt coupling is decided by the climate condition and soil feature and vegetation characteristics as well as human activity. Meanwhile, temporal and spatial change between water and salt is quite complicated. The environmental management should be paid attention to considering in irrigation area in the catchments.
基金Key Project of National Natural Science Foundation of China No.40930531 National Youth Science Foun-dation of China No.40901185 Specialized Research Fund for the Doctoral Program of Higher Education No.20093207120008
文摘Specific Catchment Area （SCA） is defined as the upstream catchment area of a unit contour. As one of the key terrain parameters, it is widely used in the modeling of hydrology, soil erosion and ecological environment. However, SCA value changes significantly at different DEM resolutions, which inevitably affect terrain analysis results. SCA can be described as the ratio of Catchment Area （CA） and DEM grid length. In this paper, the scale effect of CA is firstly investigated. With Jiuyuangou Gully, a watershed about 70 km2 in northern Shaanxi Province of China, as the test area, it is found that the impacts of DEM scale on CA are different in spatial distribution. CA value in upslope location becomes bigger with the decrease of the DEM resolution. When the location is close to downstream areas the impact of DEM scale on CA is gradually weakening. The scale effect of CA can be concluded as a mathematic trend of exponential decline. Then, a downscaling model of SCA is put forward by introducing the scale factor and the location factor. The scaling model can realize the conversion of SCA value from a coarse DEM resolution to a finer one at pixel level. Experiment results show that the downscaled SCA was well revised, and consistent with SCA at the target resolution with respect to the statistical indexes, histogram and spatial distribution. With the advantages of no empirical parameters, the scaling model could be considered as a simple and objective model for SCA scaling in a rugged drainage area.
基金Supported by the National Key Research and Development Program of China(2016YFA0602401)National Natural Science Foundation of China(41875106).
文摘Previous studies have demonstrated that offline land surface models(LSMs)and global hydrological models(GHMs)can reasonably reproduce streamflow in large river basins.Global reanalyses supply fine spatiotemporal runoff estimates,but they are not fully intercompared and evaluated in China.This study assesses the routed-runoff from five offline LSM/GHM runs(VIC-CN05.1,CLM-CFSR,CLM-ERAI,CLM-MERRA,and CLM-NCEP)and three reanalysis datasets(ERAI/Land,JRA55,and MERRA-2)against the gauged streamflow(26 stations)in major Chinese river basins during 1980–2008.The Catchment-based Macro-scale Floodplain model(CaMa-Flood)is employed to route those runoff datasets to the hydrological stations.Four statistical quantities,including the correlation coefficient(R),standard deviation(STD),Nash–Sutcliffe efficiency coefficient(NSE),and relative error(RE),along with a ranking method,are used to quantify the quality of those products.The results show that the spatial patterns of both modeled and observed streamflow in summer are similar,but their magnitudes are different.Except for MERRA-2,the other products can reproduce well the interannual variability of streamflow in both the Yangtze and Yellow River basins.All products generally underestimate the magnitude and variance of monthly streamflow,while VIC-CN05.1 and JRA55 are closer to observations compared to other products.The correlation coefficients for all products are overall larger than 0.61,with the highest value(0.85)from VIC-CN05.1.In addition to CLM-MERRA,MERRA-2,and CLM-NCEP with relatively small precipitation,other products can simulate peak flow well with positive NSEs up to 0.41(ERAI/Land).Considerable uncertainties exist among the eight products at the Yellow River outlet,which might be because the LSMs ignore frequent human activities.Based on the above statistics,performances of the eight runoff products are ranked in descending order as follows:VIC-CN05.1,ERAI/Land,JRA55,CLM-CFSR,CLM-ERAI,MERRA-2,CLM-MERRA,and CLM-NCEP,which provides a reference for flood/hydro
