Sichuan Basin is located in southwestern China and affected by a complex water vapor(WV)sources. Here, the spatial and temporal patterns of precipitation and extreme events are investigated by six indices of World Met...Sichuan Basin is located in southwestern China and affected by a complex water vapor(WV)sources. Here, the spatial and temporal patterns of precipitation and extreme events are investigated by six indices of World Meteorology Organization Commission, including annual precipitation total(AP), maximum daily precipitation(Max1d), intensity of rainfall over 1 mm/d(IR1), maximum and mean consecutive dry days(Max CDD, Mean CDD) and coefficient of variance. Based on 24 daily precipitation time series from 1951 to 2011, Mann-Kendall test is employed to quantify the significant level of these indices, from which the classification of precipitation change and its spatial patterns are obtained.Meanwhile, the probability distributions of these indices are identified by L-moment analysis and the Goodness-of-fit test, and the corresponding values are calculated by theoretical model at different return periods. The results reveal that the western basin displays normal drought: less AP and precipitation intensity while longer drought. The southern basin shows normal increase: larger AP and precipitation intensity but shorter CDD. However, in hilly region of the central basin and the transition zone between basin and mountains, precipitation changes abnormally: increasing both drought(one or both of Mean CDD and Max CDD) and precipitation intensity(one or both of Max1 d and IR1) no matter what the trend of AP is. Probability distribution models also demonstrate the complex patterns: a negative correlation between Max1 d and Max CDD in the west(R^2≥0.61) while a positive correlation in the east(R^2≥0.41) at all return periods. These patterns are induced by the changes in WV sources and the layout of local terrain. The increase of WV in summer and decrease in spring leads to the heavier rainfall and longer drought respectively. The large heat island effect of the basin contributes to a lower temperature in transition zones and more precipitation in the downwind area. These results are helpful in reevaluating the risk regionally and making better decisions on water resources management and disaster prevention.展开更多
Soil hydraulic parameters θs,α,n,Ks,L and θr of the van Genuchten-Mualem model were estimated using three pedotransfer functions(PTFs) based on soil properties for surface soils of the largest main tributary catchm...Soil hydraulic parameters θs,α,n,Ks,L and θr of the van Genuchten-Mualem model were estimated using three pedotransfer functions(PTFs) based on soil properties for surface soils of the largest main tributary catchment(the Jialing River) of the upper Yangtze River in China.The soil database was from the second national soil survey of China with a spatial 30 × 30 arc-second resolution.According to the statistical analysis of the differences between the continuous-PTFs-estimated values of soil hydraulic parameters for the study catchment and the reference values for a specific texture class provided in the development database of a specific PTF,best estimations were obtained using the W?sten PTF.The Rawls & Brakenssiek PTF was good estimation for parameter θr that was assumed as zero by W?sten PTF.The established higher θr(0.08%) and lower Ks(20 cm/d) and θs(0.43%) in the mid-downstream area relative to the other areas of the catchment could lead to larger amounts of surface runoff andconsequently provide higher energy to erode soil.Thus,these factors provide a supporting explanation for previously reported severe soil erosion occurring in this area.Spatial heterogeneity analysis for estimated hydraulic parameters in terms of semivariogram showed that the spatial correlation distance was in the range of 50-80 km and that the spatial variability(sill) was not large except for parameters Ks and L.The semi-variance with the exponential model at the zero distance(nugget) was 30%-50% of the sill.This study provided a practical PTF approach for estimating soil hydraulic properties from soil survey data at a large watershed scale.The estimation results could provide better insight into the mechanism of surface runoff and soil erosion,which is important to better understand and manage erosion in the catchment.展开更多
基金funded by open funding of Guizhou Provincial Key Laboratory of Public Big Data(Guizhou University, Grant No.2017BDKFJJ021)Special Science and Technology Funding of Guizhou Province Water Resources Department (KT201707)+1 种基金Guizhou Province Science and Technology Joint Founding (LH [2017]7617)China Postdoctoral Science Foundation (Grant No.2016M5 92671)
文摘Sichuan Basin is located in southwestern China and affected by a complex water vapor(WV)sources. Here, the spatial and temporal patterns of precipitation and extreme events are investigated by six indices of World Meteorology Organization Commission, including annual precipitation total(AP), maximum daily precipitation(Max1d), intensity of rainfall over 1 mm/d(IR1), maximum and mean consecutive dry days(Max CDD, Mean CDD) and coefficient of variance. Based on 24 daily precipitation time series from 1951 to 2011, Mann-Kendall test is employed to quantify the significant level of these indices, from which the classification of precipitation change and its spatial patterns are obtained.Meanwhile, the probability distributions of these indices are identified by L-moment analysis and the Goodness-of-fit test, and the corresponding values are calculated by theoretical model at different return periods. The results reveal that the western basin displays normal drought: less AP and precipitation intensity while longer drought. The southern basin shows normal increase: larger AP and precipitation intensity but shorter CDD. However, in hilly region of the central basin and the transition zone between basin and mountains, precipitation changes abnormally: increasing both drought(one or both of Mean CDD and Max CDD) and precipitation intensity(one or both of Max1 d and IR1) no matter what the trend of AP is. Probability distribution models also demonstrate the complex patterns: a negative correlation between Max1 d and Max CDD in the west(R^2≥0.61) while a positive correlation in the east(R^2≥0.41) at all return periods. These patterns are induced by the changes in WV sources and the layout of local terrain. The increase of WV in summer and decrease in spring leads to the heavier rainfall and longer drought respectively. The large heat island effect of the basin contributes to a lower temperature in transition zones and more precipitation in the downwind area. These results are helpful in reevaluating the risk regionally and making better decisions on water resources management and disaster prevention.
基金supported by the“Hundred Talents Program”of the Chinese Academy of Sciences and Sichuan Province,the National Basic Research Program of the Ministry of Science and Technology of China(Grant No.2012CB417101)the National Natural Science Foundation of China(Grant Nos.41171372 and 41471268)the CASSAFEA International Partnership Program for Creative Research Team(Grant No.KZZD-EWTZ06)
文摘Soil hydraulic parameters θs,α,n,Ks,L and θr of the van Genuchten-Mualem model were estimated using three pedotransfer functions(PTFs) based on soil properties for surface soils of the largest main tributary catchment(the Jialing River) of the upper Yangtze River in China.The soil database was from the second national soil survey of China with a spatial 30 × 30 arc-second resolution.According to the statistical analysis of the differences between the continuous-PTFs-estimated values of soil hydraulic parameters for the study catchment and the reference values for a specific texture class provided in the development database of a specific PTF,best estimations were obtained using the W?sten PTF.The Rawls & Brakenssiek PTF was good estimation for parameter θr that was assumed as zero by W?sten PTF.The established higher θr(0.08%) and lower Ks(20 cm/d) and θs(0.43%) in the mid-downstream area relative to the other areas of the catchment could lead to larger amounts of surface runoff andconsequently provide higher energy to erode soil.Thus,these factors provide a supporting explanation for previously reported severe soil erosion occurring in this area.Spatial heterogeneity analysis for estimated hydraulic parameters in terms of semivariogram showed that the spatial correlation distance was in the range of 50-80 km and that the spatial variability(sill) was not large except for parameters Ks and L.The semi-variance with the exponential model at the zero distance(nugget) was 30%-50% of the sill.This study provided a practical PTF approach for estimating soil hydraulic properties from soil survey data at a large watershed scale.The estimation results could provide better insight into the mechanism of surface runoff and soil erosion,which is important to better understand and manage erosion in the catchment.
