River runoff is affected by many factors, including long-term effects such as climate change that alter rainfall-runoff relationships, and short-term effects related to human intervention(e.g., dam construction, land-...River runoff is affected by many factors, including long-term effects such as climate change that alter rainfall-runoff relationships, and short-term effects related to human intervention(e.g., dam construction, land-use and land-cover change(LUCC)). Discharge from the Yellow River system has been modified in numerous ways over the past century, not only as a result of increased demands for water from agriculture and industry, but also due to hydrological disturbance from LUCC, climate change and the construction of dams. The combined effect of these disturbances may have led to water shortages. Considering that there has been little change in long-term precipitation, dramatic decreases in water discharge may be attributed mainly to human activities, such as water usage, water transportation and dam construction. LUCC may also affect water availability, but the relative contribution of LUCC to changing discharge is unclear. In this study, the impact of LUCC on natural discharge(not including anthropogenic usage) is quantified using an attribution approach based on satellite land cover and discharge data. A retention parameter is used to relate LUCC to changes in discharge. We find that LUCC is the primary factor, and more dominant than climate change, in driving the reduction in discharge during 1956–2012, especially from the mid-1980 s to the end-1990 s. The ratio of each land class to total basin area changed significantly over the study period. Forestland and cropland increased by about 0.58% and 1.41%, respectively, and unused land decreased by 1.16%. Together, these variations resulted in changes in the retention parameter, and runoff generation showed a significant decrease after the mid-1980 s. Our findings highlight the importance of LUCC to runoff generation at the basin scale, and improve our understanding of the influence of LUCC on basin-scale hydrology.展开更多
[Objective]The study aimed to simulate the production and transportation process of surface runoff,sediment and non-point source pollution in Xincai River basin based on SWAT model.[Method]On the basis of analyzing th...[Objective]The study aimed to simulate the production and transportation process of surface runoff,sediment and non-point source pollution in Xincai River basin based on SWAT model.[Method]On the basis of analyzing the principles of SWAT model,the correlative parameters of runoff,sediment and water quality were calibrated,then the spatial and temporal distribution of runoff,sediment and non-point source pollutants in Xincai River basin were studied by using SWAT model.[Result]The results of calibration and validation showed that SWAT model was reasonable and available,and it can be used to simulate the non-point source pollution of Xincai River basin.The simulation results revealed that the load of sediment and various pollutants was the highest in the rainy year,followed by the normal year,while it was the minimum in the dry year,indicating that the production of sediment and non-point source pollutants was closely related to annual runoff.[Conclusion]The research could provide scientific references for the prevention of non-point source pollution in a basin.展开更多
The rivers in Nepal are classified in terms of geographical regions but a more scientific classification such as on the ba-sis of morphology is clearly lacking. This study was done in 9 rivers namely Jhikhukhola of th...The rivers in Nepal are classified in terms of geographical regions but a more scientific classification such as on the ba-sis of morphology is clearly lacking. This study was done in 9 rivers namely Jhikhukhola of the Koshi system, Aandhikhola, Arungkhola, East Rapti, Karrakhola, Seti and main channel Narayani of the Gandaki system, and two independent systems within Nepal, Bagmati and Tinau. Among the morphologies, river bed or the substratum was taken as the main variable for the analysis which was categorized into 7 types as rocks, boulders, cobbles, pebbles, gravels, sand and silt. There were 23 sampling sites each with 2 stretches of around 100m in those rivers. The data were taken as a percentage, and to avoid biases it was observed visually by the same person for a complete year in every season. With 23 sites each with 2 stretches and 4 replicates corresponding to 4 seasons, there are altogether 184 observations, each termed as a case, that constitute this work. Canonical Discrimination Analysis (CDA) which is most suitable when the data pool is huge was applied to see if the rivers studied distinguish themselves in terms of its morphology. The result was remarkably successful and was close to the established regional classification of the rivers. This kind of river classification has great application in the utilization, conservation and restoration of the most important natural re-source of the country.展开更多
By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow...By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter representing the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.展开更多
The power-function exponent b of at-a-station hydraulic geometry(AHG)depicts the temporal response of river hydraulic parameters to changing discharge and is crucial for hydraulic modeling,habitat assessment,and river...The power-function exponent b of at-a-station hydraulic geometry(AHG)depicts the temporal response of river hydraulic parameters to changing discharge and is crucial for hydraulic modeling,habitat assessment,and river management.However,previous research,limited by field measurements,offers only a fragmentary understanding of the AHG exponent b in confined areas.Additionally,it remains challenging to establish the correlation between b and the climatic regime of a river.To offer a more comprehensive scope of AHG,this study assesses the width-discharge AHG exponents of 1,568 river reaches by pairing multi-temporal river width data from 1.19 million Landsat images with discharge observations from>17,000 gauge stations worldwide.The results show that b has a median value of 0.213,consistent with values reported in previous regional studies,but it exhibits complex relationships with 3 spatial dimensions-latitude,elevation,and drainage area.We further analyze the spatial variations in b against>200 physiographic and climatic factors,and find that reaches characterized by cohesive soil,high forest coverage,and less anthropogenic influences typically exhibit lower values of b,indicating a weaker response of width to discharge changes.By labeling 4 planimetric river morphologic types globally,we show that braided reaches exhibit the highest median of b,followed by straight,anabranching,and meandering reaches.The differences can be well explained by the climatic conditions of the river reaches as shown on the Budyko curve.This study lays the foundation for AHG research in ungauged regions using satellite remote sensing,expanding global hydraulic data and enhancing the understanding of the spatial variability and influencing factors of hydraulic geometry worldwide.展开更多
基金Under the auspices of Key Program of Chinese Academy of Sciences(No.KJZD-EW-TZ-G10)National Key Research and Development Program of China(No.2016YFA0602704)Breeding Project of Institute of Geographic Sciences and Natural Resources Research,CAS(No.TSYJS04)
文摘River runoff is affected by many factors, including long-term effects such as climate change that alter rainfall-runoff relationships, and short-term effects related to human intervention(e.g., dam construction, land-use and land-cover change(LUCC)). Discharge from the Yellow River system has been modified in numerous ways over the past century, not only as a result of increased demands for water from agriculture and industry, but also due to hydrological disturbance from LUCC, climate change and the construction of dams. The combined effect of these disturbances may have led to water shortages. Considering that there has been little change in long-term precipitation, dramatic decreases in water discharge may be attributed mainly to human activities, such as water usage, water transportation and dam construction. LUCC may also affect water availability, but the relative contribution of LUCC to changing discharge is unclear. In this study, the impact of LUCC on natural discharge(not including anthropogenic usage) is quantified using an attribution approach based on satellite land cover and discharge data. A retention parameter is used to relate LUCC to changes in discharge. We find that LUCC is the primary factor, and more dominant than climate change, in driving the reduction in discharge during 1956–2012, especially from the mid-1980 s to the end-1990 s. The ratio of each land class to total basin area changed significantly over the study period. Forestland and cropland increased by about 0.58% and 1.41%, respectively, and unused land decreased by 1.16%. Together, these variations resulted in changes in the retention parameter, and runoff generation showed a significant decrease after the mid-1980 s. Our findings highlight the importance of LUCC to runoff generation at the basin scale, and improve our understanding of the influence of LUCC on basin-scale hydrology.
文摘[Objective]The study aimed to simulate the production and transportation process of surface runoff,sediment and non-point source pollution in Xincai River basin based on SWAT model.[Method]On the basis of analyzing the principles of SWAT model,the correlative parameters of runoff,sediment and water quality were calibrated,then the spatial and temporal distribution of runoff,sediment and non-point source pollutants in Xincai River basin were studied by using SWAT model.[Result]The results of calibration and validation showed that SWAT model was reasonable and available,and it can be used to simulate the non-point source pollution of Xincai River basin.The simulation results revealed that the load of sediment and various pollutants was the highest in the rainy year,followed by the normal year,while it was the minimum in the dry year,indicating that the production of sediment and non-point source pollutants was closely related to annual runoff.[Conclusion]The research could provide scientific references for the prevention of non-point source pollution in a basin.
文摘The rivers in Nepal are classified in terms of geographical regions but a more scientific classification such as on the ba-sis of morphology is clearly lacking. This study was done in 9 rivers namely Jhikhukhola of the Koshi system, Aandhikhola, Arungkhola, East Rapti, Karrakhola, Seti and main channel Narayani of the Gandaki system, and two independent systems within Nepal, Bagmati and Tinau. Among the morphologies, river bed or the substratum was taken as the main variable for the analysis which was categorized into 7 types as rocks, boulders, cobbles, pebbles, gravels, sand and silt. There were 23 sampling sites each with 2 stretches of around 100m in those rivers. The data were taken as a percentage, and to avoid biases it was observed visually by the same person for a complete year in every season. With 23 sites each with 2 stretches and 4 replicates corresponding to 4 seasons, there are altogether 184 observations, each termed as a case, that constitute this work. Canonical Discrimination Analysis (CDA) which is most suitable when the data pool is huge was applied to see if the rivers studied distinguish themselves in terms of its morphology. The result was remarkably successful and was close to the established regional classification of the rivers. This kind of river classification has great application in the utilization, conservation and restoration of the most important natural re-source of the country.
基金supported by the National Natural Science Foundation of China (Nos. 50679061, 50709025,50749031)
文摘By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter representing the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.
基金supported by the National Natural Science Foundation of China(42371481)the Beijing Nova Program(20230484302)the Yunnan Provincial Science and Technology Project at Southwest United Graduate School(grant no.202302AO370012).
文摘The power-function exponent b of at-a-station hydraulic geometry(AHG)depicts the temporal response of river hydraulic parameters to changing discharge and is crucial for hydraulic modeling,habitat assessment,and river management.However,previous research,limited by field measurements,offers only a fragmentary understanding of the AHG exponent b in confined areas.Additionally,it remains challenging to establish the correlation between b and the climatic regime of a river.To offer a more comprehensive scope of AHG,this study assesses the width-discharge AHG exponents of 1,568 river reaches by pairing multi-temporal river width data from 1.19 million Landsat images with discharge observations from>17,000 gauge stations worldwide.The results show that b has a median value of 0.213,consistent with values reported in previous regional studies,but it exhibits complex relationships with 3 spatial dimensions-latitude,elevation,and drainage area.We further analyze the spatial variations in b against>200 physiographic and climatic factors,and find that reaches characterized by cohesive soil,high forest coverage,and less anthropogenic influences typically exhibit lower values of b,indicating a weaker response of width to discharge changes.By labeling 4 planimetric river morphologic types globally,we show that braided reaches exhibit the highest median of b,followed by straight,anabranching,and meandering reaches.The differences can be well explained by the climatic conditions of the river reaches as shown on the Budyko curve.This study lays the foundation for AHG research in ungauged regions using satellite remote sensing,expanding global hydraulic data and enhancing the understanding of the spatial variability and influencing factors of hydraulic geometry worldwide.
