It is necessary to understand vegetation dynamics and their climatic controls for sustainable ecosystem management.This study examines the vegetation dynamics and the effect of climate change on vegetation growth in t...It is necessary to understand vegetation dynamics and their climatic controls for sustainable ecosystem management.This study examines the vegetation dynamics and the effect of climate change on vegetation growth in the pristine conditions of 58 woodland National Nature Reserves(NNRs)located in the upper Yangtze River basin(UYRB)in China which are little influenced by human activities.Changes in the normalized difference vegetation index(NDVI),precipitation,and temperature in the selected NNRs were observed and analyzed for the period between 1999 and 2015.The relationship between time-lag effect of climate and changes in the NDVI were assessed using Pearson correlations.The results showed three major trends.1)The NDVI increased during the study period;this indicates an increase in the amount of green vegetation,especially due to the warmer climate during the growing season.The NDVIs in March and September were significantly affected by the temperature of the previous months.Spring temperatures increased significantly(P<0.05)and there was a delay between climatic factors and their effect on vegetation,which depended on the previous season.In particular,the spring temperature had a delayed effect on the NDVI in summer.2)The way in which vegetation responds to climatic factors varied significantly across the seasons.Temperature had a greater effect on the NDVI in spring and summer and the effect was greater at higher altitudes.A similar trend was observed for precipitation,except for altitudes of 1000–2000 m.3)Temperature had a greater effect on the NDVI in spring and autumn at higher altitudes.The same trend was observed for precipitation in summer.These findings suggest that the vegetation found in NNRs in the upper reaches of the Yangtze River was in good condition between 1999 and 2015 and that the growth and development of vegetation in the region has not been adversely affected by climate change.This demonstrates the effectiveness of nature reserves in protecting regional ecology and minimizing anthropogenic effects.展开更多
As one of the most fragile alpine plateau and canyon areas in China,the upper reaches of the Yangtze River are the key areas of ecological construction in China.It is also a key area for poverty alleviation in the cou...As one of the most fragile alpine plateau and canyon areas in China,the upper reaches of the Yangtze River are the key areas of ecological construction in China.It is also a key area for poverty alleviation in the country.Therefore,it is necessary to take into account the dual goals of poverty reduction and ecological environment construction,and explore a win-win road of ecological construction and poverty alleviation in line with the reality of the upper reaches of the Yangtze River.Taking Xueshan Township,Luquan Yi and Miao Autonomous County,Yunnan Province,which is located in the poor mountainous area of the upper reaches of the Yangtze River as an example,based on many field investigations and existing investigation and statistical data,this paper analyzes the current situation and main problems of land use in Xueshan Township,and then puts forward measures and suggestions for rational utilization of land resources in Xueshan Township.This can provide a necessary reference for the next implementation of rural revitalization strategy and ecological construction.展开更多
Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitat...Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitation and topographical variables are established to extract the effect of topography on the annual and seasonal precipitation in the upper-middle reaches of the Yangtze River. Then, this paper uses a successive interpolation approach (SIA), which combines GIS techniques with the multiple regressions, to improve the accuracy of the spatial interpolation of annual and seasonal rainfall. The results are very satisfactory in the case of seasonal rainfall, with the relative error of 6.86%, the absolute error of 13.07 mm, the average coefficient of variation of 0.070, and the correlation coefficient of 0.9675; in the case of annual precipitation, with the relative error of 7.34%, the absolute error of 72.1 mm, the average coefficient of variation of 0.092, and the correlation coefficient of 0.9605. The analyses of annual mean precipitation show that the SIA calculation of 3-5 steps considerably improves the interpolation accuracy, decreasing the absolute error from 211.0 mm to 62.4 mm, the relative error from 20.74% to 5.97%, the coefficient of variation from 0.2312 to 0.0761, and increasing the correlation coefficient from 0.5467 to 0.9619. The SIA iterative results after 50 steps identically converge to the observed precipitation.展开更多
This paper discussed theory and methodologies of debris-flow risk assessment and established an implementation process according to indicators of debris-flow hazard degree,vulnerability,risk degree,etc. Among these me...This paper discussed theory and methodologies of debris-flow risk assessment and established an implementation process according to indicators of debris-flow hazard degree,vulnerability,risk degree,etc. Among these methodologies,historical and potential hazard degree was comprehensively considered into hazard assessment and hazard index was presented to indicate the debris-flow hazard degree. Regarding debris-flow vulnerability assessment,its statistical data and calculating procedure were based on the hazard-degree regionalization instead of administrative divisions,which improved the as-sessing scientificity and precision. These quantitative methodologies inte-grated with Geography Information System(GIS) were applied to the risk assessment of debris flows in the upper reach of Yangtze River. Its results were in substantial agreement on investigation data and the actual distribution of debris flows,which showed that these principles and methodologies were reasonable and feasible and can provide basis or reference for debris-flow risk assessment and disaster management.展开更多
Hydrological events should be described through several correlated variables, so multivariate HFA has gained popularity and become an active research field during recent years. However, at present multivariate HFA mai...Hydrological events should be described through several correlated variables, so multivariate HFA has gained popularity and become an active research field during recent years. However, at present multivariate HFA mainly focuses directly on fitting the frequency distribution without confirming whether the assumptions are satisfied. Neglecting testing these assumptions could get severely wrong frequency distribution. This paper uses multivariate Mann-Kendal testing to detect the multivariate trends of annual flood peak and annual maximum 15 day volume for four control hydrological stations in the?Upper Yangtze River Basin. Results indicate that multivariate test could detect the trends of joint variables, whereas univariate tests can only detect the univariate trends. Therefore, it is recommended to jointly apply univariate and multivariate trend tests to capture all the existing trends.展开更多
The upper Yangtze River region is one of the most frequent debris flow areas in China. The study area contains a cascade of six large hydropower stations located along the river with total capacity of more than 70 mil...The upper Yangtze River region is one of the most frequent debris flow areas in China. The study area contains a cascade of six large hydropower stations located along the river with total capacity of more than 70 million kilowatts. The purpose of the study was to determine potential and dynamic differences in debris flow susceptibility and intensity with regard to seasonal monsoon events. We analyzed this region's debris flow history by examining the effective peak acceleration of antecedent earthquakes,the impacts of antecedent droughts, the combined effects of earthquakes and droughts, with regard to topography, precipitation, and loose solid material conditions. Based on these factors, we developed a debris flow susceptibility map. Results indicate that the entire debris flow susceptibility area is 167,500 km^2, of which 26,800 km^2 falls within the high susceptibility area, with 60,900 km^2 in medium and 79,800 km^2 are in low susceptibility areas. Three of the six large hydropower stations are located within the areas with high risk of debris flows. The synthetic zonation map of debris flow susceptibility for the study area corresponds with both the investigation data and actual distribution of debris flows. The results of debris flow susceptibility provide base-line data for mitigating, assessing, controlling and monitoring of debris flows hazards.展开更多
Land use/land cover change (LUCC) is a focus of the research of global environmental changes. The middle and upper reaches of the Yangtze River, which are the most ecologically fragile mountainous area in China as wel...Land use/land cover change (LUCC) is a focus of the research of global environmental changes. The middle and upper reaches of the Yangtze River, which are the most ecologically fragile mountainous area in China as well as one of the areas in China with most notable LUCC, have been on the Chinese Government's list of priority areas for ecological restoration. This paper is to reveal the trend of LUCC and the ecological degradation arising from it, and to provide a basis for the future sustainable use of land resources in the region based on a detailed analysis of Yiliang County. Based on the county's land use/cover maps in 1960, 1980 and 2000 drawn with the aid of aerial photograph interpretation, field investigation and GIS based spatial-temporal data analysis, LUCC during 1960~2000 period and the ecological degradation arising from it were analyzed. Using the Markv model, the paper brings out a forecast of what the county's LUCC would be like if the county's current land use continues, as well as the reasons and countermeasures for restoring degraded ecosystems.展开更多
In the upper reaches of Yangtze River and other rivers of southwestern China,the debris flows develop and lead to most serious disasters because of the various landforms,complex geo-logical structures and abundant rai...In the upper reaches of Yangtze River and other rivers of southwestern China,the debris flows develop and lead to most serious disasters because of the various landforms,complex geo-logical structures and abundant rainfall. The distribution of debris flows has regularity in the regions with different landform,geo-logical structure,and precipitation. The regularities of distribution of debris flows are as following:① distributed in transition belts of different morphologic regions;② distributed in the area with strong stream trenching;③ distributed along fracture zones and seismic belts:④ distributed in the area with abundant precipita-tion;⑤ distribution of debris flow is azonal. The activity of abundant debris flows not only brings harm to Towns,Villages and Farmlands,Main Lines of Communication,Water-Power Engi-neering,Stream Channels etc.,but also induces strong water and soil loss. According to the present status of debris flow prevention,the problems in disasters mitigation and soil conservancy are found out,and the key works are brought up for the future disas-ters prevention and soil conservancy.展开更多
The sediment load and river sedimentation of the upper reaches of Yangtze River has been undergoing constant changes as complex landform, large mountain area and plentiful precipitation make the drainage area of Yangt...The sediment load and river sedimentation of the upper reaches of Yangtze River has been undergoing constant changes as complex landform, large mountain area and plentiful precipitation make the drainage area of Yangtze River very vulnerable to water erosion and gravity erosion. Through analyzing the hydrological and sediment load statistics recorded by major hydrological stations along Yangtze River since 1950s, and editing the accumulation graph of annual runoff volume and annual sediment load, we find out that the suspended-sediment of Yangtze river has been decreasing year by year in Wulong Hydrological Station on Wujiang River, Beibei Hydrological Station on Jialingjiang River, Lijiawan Hydrological Station on Tuojiang River and Gaochang Hydrological Station on Minjiang River, Yichang Hydrological Station, Cuntan Hydrological Station along Yangtze River mainstream share the same experience too. But the statistics obtained at Pingshan Hydrological Station on Jinshajiang River shows the sediment load there has increased. Taking ecological construction, hydraulic engineering construction and precipitation changes into consideration, the thesis analyses the causes for the sediment load decrease of Jialingjiang River, Tuojiang River, Minjiang River and Wujiang River and provides us both scientific foundation for further study of river sediment changes of the upper reaches of Yangtze River, and measures to control river sedimentation.展开更多
Due to the high elevation, complex terrain, severe weather, and inaccessibility, direct meteorological observations do not exist over large portions of the Tibetan Plateau, especially the western part of it. Satellite...Due to the high elevation, complex terrain, severe weather, and inaccessibility, direct meteorological observations do not exist over large portions of the Tibetan Plateau, especially the western part of it. Satellite rainfall estimates have been very important sources for precipitation information, particularly in rain gauge-sparse regions. In this study, Tropical Rainfall Measuring Mission(TRMM) Multi-satellite Precipitation Analysis(TMPA) products 3B42, RTV5V6, and RTV7 were evaluated for their applicability to the upper Yellow and Yangtze River basins on the Tibetan Plateau. Moreover, the capability of the TMPA products to simulate streamflow was also investigated using the Variable Infiltration Capacity(VIC) semi-distributed hydrological model. Results show that 3B42 performs better than RTV5V6 and RTV7, based on verification of the China Meteorological Administration(CMA) observational precipitation data. RTV5V6 can roughly capture the spatial precipitation pattern but overestimation exists throughout the entire study region. The anticipated improvements of RTV7 relative to RTV5V6 have not been realized in this study. Our results suggest that RTV7 significantly overestimates the precipitation over the two river basins, though it can capture the seasonal cycle features of precipitation. 3B42 shows the best performance in streamflow simulation of the abovementioned satellite products. Although involved in gauge adjustment at a monthly scale, 3B42 is capable of daily streamflow simulation. RTV5V6 and RTV7 have no capability to simulate streamflow in the upper Yellow and Yangtze River basins.展开更多
Understanding hydrological responses to rising levels of greenhouse gases are essential for climate and impact research.It is,however,often limited by a lack of long record of observational data to provide a basis for...Understanding hydrological responses to rising levels of greenhouse gases are essential for climate and impact research.It is,however,often limited by a lack of long record of observational data to provide a basis for understanding the longterm behavior of the climate system.Integrating reconstructed data and(global climate and hydrological)model simulations will help us to better understand the variability of climate and hydrology over timescales ranging from decades to centuries.In this study,we proposed an integrated approach to study flood variability in the upper reach of the Yangtze River over the last millennium to the end of the 21st century.To accomplish this,we first drove hydrological models using the precipitation and temperature from four Global Climate Models(GCM),BCC-CSM1.1,MIROC,MRI-CGCM3,and CCSM4,to simulate daily discharge for the upper reach of the Yangtze River during the period of the last millennium(850–1849),historical period(1850–2005),and a future period(2006–2099).Then,we evaluated whether the modeled precipitation,temperature,and extreme discharge had statistical properties similar to those shown in the documented dry-wet periods,temperature anomalies,and paleoflood records.Finally,we explored the extreme discharge variability using model simulations.The results indicate that:(1)The MIROC-ESM model,differing from the other three GCM models,revealed positive temperature changes from the warm period(Medieval Climate Anomaly;MCA)to the cold period(Little Ice Age;LIA),while the temperature variability of the other models was similar to the records.(2)The BCC-CSM1.1 model performed better than the others regarding correlations between modeled precipitation and documented dry-wet periods.(3)Over most of the subbasins in the upper Yangtze River,the magnitude of extreme discharge in the BCC-CSM1.1 model results showed that there was a decrease from the MCA to the LIA period and an increase in the historical period relative to the cold period,while a future increase was projected by the four GCMs under the influence of climate change.展开更多
Based on data of radiation fog events in Xuanen, Hubei province, 2010, this paper analyzes the microphysical process and evolution characteristics of radiation fogs with complicated substrate in the upper and middle r...Based on data of radiation fog events in Xuanen, Hubei province, 2010, this paper analyzes the microphysical process and evolution characteristics of radiation fogs with complicated substrate in the upper and middle reaches of the Yangtze River, and compares them with findings in other areas. Results are as follows: radiation fog in Xuanen is evidently weaker in droplet number concentration and liquid water content than land fogs in other areas. Its liquid water content fluctuates obviously, 0.01g/m3 with visibility of 1,000 meters, which is quite different from that in urban areas, but similar to the Nanling Mountains. Bi-modal droplet distribution is likely to occur in Xuanen mountain radiation fog(MRF) events. Statistical analysis shows that the observed droplet size distribution can be piecewise described well by the Gamma distribution. There is a positive correlation between liquid water content, fog droplet concentration and mean radius, especially in the development and dissipation stage. Condensation growth and droplet evaporation are major processes of Xuanen MRF. The dissipation time coincided with the time when the grass temperature reached the peak value, which indicated that dew evaporation is a key role in maintaining Xuanen MRF. In the early stage of dense fog's growth, droplets with diameter of over 20 micrometers can be observed with visibility of800-1,000 m, which might be caused by the transportation of low cloud droplets to earth's surface by turbulence. Big droplets in the initial stage correspond to higher water content, leading to the higher observed value of water content of Xuanen MRF.展开更多
Using the daily NCEP/NCAR reanalysis dataset and the observation rainfall data in China for the 1980-1997 period, features of severe summer rainfall over the upper reaches of the Yangtze River are investigated and the...Using the daily NCEP/NCAR reanalysis dataset and the observation rainfall data in China for the 1980-1997 period, features of severe summer rainfall over the upper reaches of the Yangtze River are investigated and then sources of moisture contributing to severe rainfall over eastern and western Sichuan Province (ES and WS for short) are examined with particular reference. It turns out that the severe rainfall occurring locally dominates summer rainfall over the upper reaches of the Yangtze River. Climatological rainfall and anomalous one constitute severe rainfall, but the latter accounts much for severe rainfall. The meridional moisture transport dominates the composite moisture transport on the occurrence day for ES region, while the zonal is equivalent to the meridional for WS region. Correlation between the moisture transport fluxes over the two regions of severe rainfall and other regions, the anomaly and variation of the moisture transport day by day during the period of severe rainfall lend a support for the conclusion that the meeting of the moisture from the West Pacific through the South China Sea (SCS) and the one from northwestern China exerts a vital effect on the occurrence of severe rainfall, which can not be neglected.展开更多
Identification of the planation surfaces (PSs)is key for utilizing them as a reference in studying the long- term geomorphological evolution of the Upper Yangtze River Basin in the Sichuan-Yurman region,Southwest Chin...Identification of the planation surfaces (PSs)is key for utilizing them as a reference in studying the long- term geomorphological evolution of the Upper Yangtze River Basin in the Sichuan-Yurman region,Southwest China.Using a combined method of DEM-based fuzzy logic and topographic and fiver profiles analysis and based on a comprehensive analysis of four morphometfic parameters:slope,curvature,terrain raggedness index, and relative height,we established the relevant fuzzy membership functions,and then calculated the membership degree (MD)of the study area.Results show that patches with a MD>80% and an area>0.4 km^2 correspond well to the results of Google Earth and field investigation,representing the PS remnants.They consist of 1764 patches with an altitude,area,mean slope,and relief of mostly 2000-2500 m above sea level (asl),0-10 km^2,4°-9°,0-500 m,respectively,covering 9.2% of the study area's landscape,dipping to southeast,decreasing progressively from northwest to southeast in altitude,and with no clear relation between each patch's altitude and slope,or relief.All these results indicate that they are remnants of once regionally continuous PSs which were deformed by both the lower crust flow and the faults in upper crust,and dissected by the network of Upper Yangtze River.Additionally,topographic and river profiles analysis show that three PSs (PS1-PS3)well developed along the main valleys in the Yongren-Huili region, indicating several phases of uplift then planation during the Late Cenozoic era.Based on the incision amount deduced from projection of relict river profiles on PSs, together with erosion rates,breakup times of the PS 1,PS2,and PS3 were estimated to be 3.47 Ma,2.19 Ma,and 1.45 Ma,respectively,indicating appearance of modem Upper Yangtze River valley started between the Pliocene to early Pleistocene.展开更多
The contribution of areal precipitation of the catchment from Cuntan to Yichang (Three Gorges area)to eight flood peaks of the Upper Yangtze River (the upper reaches of the Yangtze River) is diagnosed for 1998 flood s...The contribution of areal precipitation of the catchment from Cuntan to Yichang (Three Gorges area)to eight flood peaks of the Upper Yangtze River (the upper reaches of the Yangtze River) is diagnosed for 1998 flood season. A rainfall-runoff model is employed to simulate runoffs of this catchment. Comparison of observed and simulated runoffs shows that the rainfall-runoff model has a good capability to simulate the runoff over a large-scale river and the results describe the eight flood peaks very well Forecast results are closely associated with the sensitivity of the model to rainfall and the calibration processes. Other reasons leading to simulation errors are further discussed.展开更多
基金funded by the 135 Strategic Program of the Institute of Mountain Hazards and Environment,CAS(Grant No.SDS-135-1703)the Science and Technology Service Network Initiative of Chinese Academy of Sciences:Ecological Risk Assessment and Protection of the Yangtze River Economic Belt(KFJ-STS-ZDTP)
文摘It is necessary to understand vegetation dynamics and their climatic controls for sustainable ecosystem management.This study examines the vegetation dynamics and the effect of climate change on vegetation growth in the pristine conditions of 58 woodland National Nature Reserves(NNRs)located in the upper Yangtze River basin(UYRB)in China which are little influenced by human activities.Changes in the normalized difference vegetation index(NDVI),precipitation,and temperature in the selected NNRs were observed and analyzed for the period between 1999 and 2015.The relationship between time-lag effect of climate and changes in the NDVI were assessed using Pearson correlations.The results showed three major trends.1)The NDVI increased during the study period;this indicates an increase in the amount of green vegetation,especially due to the warmer climate during the growing season.The NDVIs in March and September were significantly affected by the temperature of the previous months.Spring temperatures increased significantly(P<0.05)and there was a delay between climatic factors and their effect on vegetation,which depended on the previous season.In particular,the spring temperature had a delayed effect on the NDVI in summer.2)The way in which vegetation responds to climatic factors varied significantly across the seasons.Temperature had a greater effect on the NDVI in spring and summer and the effect was greater at higher altitudes.A similar trend was observed for precipitation,except for altitudes of 1000–2000 m.3)Temperature had a greater effect on the NDVI in spring and autumn at higher altitudes.The same trend was observed for precipitation in summer.These findings suggest that the vegetation found in NNRs in the upper reaches of the Yangtze River was in good condition between 1999 and 2015 and that the growth and development of vegetation in the region has not been adversely affected by climate change.This demonstrates the effectiveness of nature reserves in protecting regional ecology and minimizing anthropogenic effects.
文摘As one of the most fragile alpine plateau and canyon areas in China,the upper reaches of the Yangtze River are the key areas of ecological construction in China.It is also a key area for poverty alleviation in the country.Therefore,it is necessary to take into account the dual goals of poverty reduction and ecological environment construction,and explore a win-win road of ecological construction and poverty alleviation in line with the reality of the upper reaches of the Yangtze River.Taking Xueshan Township,Luquan Yi and Miao Autonomous County,Yunnan Province,which is located in the poor mountainous area of the upper reaches of the Yangtze River as an example,based on many field investigations and existing investigation and statistical data,this paper analyzes the current situation and main problems of land use in Xueshan Township,and then puts forward measures and suggestions for rational utilization of land resources in Xueshan Township.This can provide a necessary reference for the next implementation of rural revitalization strategy and ecological construction.
基金The National 973 Project of China, No.2001CB309404 O versea O utstanding Youth Cooperation Project, N o. 40128001/D 05N ationalN aturalScience Foundation ofChina,N o.49375248 Zhejiang Province Science Research (C33)Project,N o.2004C33082
文摘Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitation and topographical variables are established to extract the effect of topography on the annual and seasonal precipitation in the upper-middle reaches of the Yangtze River. Then, this paper uses a successive interpolation approach (SIA), which combines GIS techniques with the multiple regressions, to improve the accuracy of the spatial interpolation of annual and seasonal rainfall. The results are very satisfactory in the case of seasonal rainfall, with the relative error of 6.86%, the absolute error of 13.07 mm, the average coefficient of variation of 0.070, and the correlation coefficient of 0.9675; in the case of annual precipitation, with the relative error of 7.34%, the absolute error of 72.1 mm, the average coefficient of variation of 0.092, and the correlation coefficient of 0.9605. The analyses of annual mean precipitation show that the SIA calculation of 3-5 steps considerably improves the interpolation accuracy, decreasing the absolute error from 211.0 mm to 62.4 mm, the relative error from 20.74% to 5.97%, the coefficient of variation from 0.2312 to 0.0761, and increasing the correlation coefficient from 0.5467 to 0.9619. The SIA iterative results after 50 steps identically converge to the observed precipitation.
基金the National Natural Science Foundation of China (40671153)the Scientific Research Fund of Hunan Provincial Education Department (05C175) the Knowledge Innovation Program of Chinese Academy Sciences (KZCX2- YW-302)
文摘This paper discussed theory and methodologies of debris-flow risk assessment and established an implementation process according to indicators of debris-flow hazard degree,vulnerability,risk degree,etc. Among these methodologies,historical and potential hazard degree was comprehensively considered into hazard assessment and hazard index was presented to indicate the debris-flow hazard degree. Regarding debris-flow vulnerability assessment,its statistical data and calculating procedure were based on the hazard-degree regionalization instead of administrative divisions,which improved the as-sessing scientificity and precision. These quantitative methodologies inte-grated with Geography Information System(GIS) were applied to the risk assessment of debris flows in the upper reach of Yangtze River. Its results were in substantial agreement on investigation data and the actual distribution of debris flows,which showed that these principles and methodologies were reasonable and feasible and can provide basis or reference for debris-flow risk assessment and disaster management.
文摘Hydrological events should be described through several correlated variables, so multivariate HFA has gained popularity and become an active research field during recent years. However, at present multivariate HFA mainly focuses directly on fitting the frequency distribution without confirming whether the assumptions are satisfied. Neglecting testing these assumptions could get severely wrong frequency distribution. This paper uses multivariate Mann-Kendal testing to detect the multivariate trends of annual flood peak and annual maximum 15 day volume for four control hydrological stations in the?Upper Yangtze River Basin. Results indicate that multivariate test could detect the trends of joint variables, whereas univariate tests can only detect the univariate trends. Therefore, it is recommended to jointly apply univariate and multivariate trend tests to capture all the existing trends.
基金supported by the National Natural Science Foundation of China (Grant No. 41661134012 and 41501012)the Taiwan Youth Visiting Scholar Fellowship of Chinese Academy of Sciences (Grant No. 2015TW2ZB0001)
文摘The upper Yangtze River region is one of the most frequent debris flow areas in China. The study area contains a cascade of six large hydropower stations located along the river with total capacity of more than 70 million kilowatts. The purpose of the study was to determine potential and dynamic differences in debris flow susceptibility and intensity with regard to seasonal monsoon events. We analyzed this region's debris flow history by examining the effective peak acceleration of antecedent earthquakes,the impacts of antecedent droughts, the combined effects of earthquakes and droughts, with regard to topography, precipitation, and loose solid material conditions. Based on these factors, we developed a debris flow susceptibility map. Results indicate that the entire debris flow susceptibility area is 167,500 km^2, of which 26,800 km^2 falls within the high susceptibility area, with 60,900 km^2 in medium and 79,800 km^2 are in low susceptibility areas. Three of the six large hydropower stations are located within the areas with high risk of debris flows. The synthetic zonation map of debris flow susceptibility for the study area corresponds with both the investigation data and actual distribution of debris flows. The results of debris flow susceptibility provide base-line data for mitigating, assessing, controlling and monitoring of debris flows hazards.
基金the result of the project(No.400610o6)funded by the National Natural Science Foundation of China.
文摘Land use/land cover change (LUCC) is a focus of the research of global environmental changes. The middle and upper reaches of the Yangtze River, which are the most ecologically fragile mountainous area in China as well as one of the areas in China with most notable LUCC, have been on the Chinese Government's list of priority areas for ecological restoration. This paper is to reveal the trend of LUCC and the ecological degradation arising from it, and to provide a basis for the future sustainable use of land resources in the region based on a detailed analysis of Yiliang County. Based on the county's land use/cover maps in 1960, 1980 and 2000 drawn with the aid of aerial photograph interpretation, field investigation and GIS based spatial-temporal data analysis, LUCC during 1960~2000 period and the ecological degradation arising from it were analyzed. Using the Markv model, the paper brings out a forecast of what the county's LUCC would be like if the county's current land use continues, as well as the reasons and countermeasures for restoring degraded ecosystems.
基金the Knowledge Innovation Program of Chinese Academy of Sciences (KZCX-SW-352)
文摘In the upper reaches of Yangtze River and other rivers of southwestern China,the debris flows develop and lead to most serious disasters because of the various landforms,complex geo-logical structures and abundant rainfall. The distribution of debris flows has regularity in the regions with different landform,geo-logical structure,and precipitation. The regularities of distribution of debris flows are as following:① distributed in transition belts of different morphologic regions;② distributed in the area with strong stream trenching;③ distributed along fracture zones and seismic belts:④ distributed in the area with abundant precipita-tion;⑤ distribution of debris flow is azonal. The activity of abundant debris flows not only brings harm to Towns,Villages and Farmlands,Main Lines of Communication,Water-Power Engi-neering,Stream Channels etc.,but also induces strong water and soil loss. According to the present status of debris flow prevention,the problems in disasters mitigation and soil conservancy are found out,and the key works are brought up for the future disas-ters prevention and soil conservancy.
文摘The sediment load and river sedimentation of the upper reaches of Yangtze River has been undergoing constant changes as complex landform, large mountain area and plentiful precipitation make the drainage area of Yangtze River very vulnerable to water erosion and gravity erosion. Through analyzing the hydrological and sediment load statistics recorded by major hydrological stations along Yangtze River since 1950s, and editing the accumulation graph of annual runoff volume and annual sediment load, we find out that the suspended-sediment of Yangtze river has been decreasing year by year in Wulong Hydrological Station on Wujiang River, Beibei Hydrological Station on Jialingjiang River, Lijiawan Hydrological Station on Tuojiang River and Gaochang Hydrological Station on Minjiang River, Yichang Hydrological Station, Cuntan Hydrological Station along Yangtze River mainstream share the same experience too. But the statistics obtained at Pingshan Hydrological Station on Jinshajiang River shows the sediment load there has increased. Taking ecological construction, hydraulic engineering construction and precipitation changes into consideration, the thesis analyses the causes for the sediment load decrease of Jialingjiang River, Tuojiang River, Minjiang River and Wujiang River and provides us both scientific foundation for further study of river sediment changes of the upper reaches of Yangtze River, and measures to control river sedimentation.
基金supported by the National Basic Research Program of China(the 973 Program,Grant No.2010CB951101)the Special Fund of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering of Hohai University(Grant No.1069-50985512)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant No.XDA05110102)
文摘Due to the high elevation, complex terrain, severe weather, and inaccessibility, direct meteorological observations do not exist over large portions of the Tibetan Plateau, especially the western part of it. Satellite rainfall estimates have been very important sources for precipitation information, particularly in rain gauge-sparse regions. In this study, Tropical Rainfall Measuring Mission(TRMM) Multi-satellite Precipitation Analysis(TMPA) products 3B42, RTV5V6, and RTV7 were evaluated for their applicability to the upper Yellow and Yangtze River basins on the Tibetan Plateau. Moreover, the capability of the TMPA products to simulate streamflow was also investigated using the Variable Infiltration Capacity(VIC) semi-distributed hydrological model. Results show that 3B42 performs better than RTV5V6 and RTV7, based on verification of the China Meteorological Administration(CMA) observational precipitation data. RTV5V6 can roughly capture the spatial precipitation pattern but overestimation exists throughout the entire study region. The anticipated improvements of RTV7 relative to RTV5V6 have not been realized in this study. Our results suggest that RTV7 significantly overestimates the precipitation over the two river basins, though it can capture the seasonal cycle features of precipitation. 3B42 shows the best performance in streamflow simulation of the abovementioned satellite products. Although involved in gauge adjustment at a monthly scale, 3B42 is capable of daily streamflow simulation. RTV5V6 and RTV7 have no capability to simulate streamflow in the upper Yellow and Yangtze River basins.
基金supported by the National Key Research and Development Program(Grant No.2017YFA0603702)the Research Council of Norway(FRINATEK Project 274310)。
文摘Understanding hydrological responses to rising levels of greenhouse gases are essential for climate and impact research.It is,however,often limited by a lack of long record of observational data to provide a basis for understanding the longterm behavior of the climate system.Integrating reconstructed data and(global climate and hydrological)model simulations will help us to better understand the variability of climate and hydrology over timescales ranging from decades to centuries.In this study,we proposed an integrated approach to study flood variability in the upper reach of the Yangtze River over the last millennium to the end of the 21st century.To accomplish this,we first drove hydrological models using the precipitation and temperature from four Global Climate Models(GCM),BCC-CSM1.1,MIROC,MRI-CGCM3,and CCSM4,to simulate daily discharge for the upper reach of the Yangtze River during the period of the last millennium(850–1849),historical period(1850–2005),and a future period(2006–2099).Then,we evaluated whether the modeled precipitation,temperature,and extreme discharge had statistical properties similar to those shown in the documented dry-wet periods,temperature anomalies,and paleoflood records.Finally,we explored the extreme discharge variability using model simulations.The results indicate that:(1)The MIROC-ESM model,differing from the other three GCM models,revealed positive temperature changes from the warm period(Medieval Climate Anomaly;MCA)to the cold period(Little Ice Age;LIA),while the temperature variability of the other models was similar to the records.(2)The BCC-CSM1.1 model performed better than the others regarding correlations between modeled precipitation and documented dry-wet periods.(3)Over most of the subbasins in the upper Yangtze River,the magnitude of extreme discharge in the BCC-CSM1.1 model results showed that there was a decrease from the MCA to the LIA period and an increase in the historical period relative to the cold period,while a future increase was projected by the four GCMs under the influence of climate change.
基金National Natural Science Foundation of China(41375138,41305120,41275151)Natural Science Foundation of Jiangsu Province,China(BK20130988)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education(20133228120002)Graduate Student Innovation Plan at the Universities of Jiangsu province(N0782002211)
文摘Based on data of radiation fog events in Xuanen, Hubei province, 2010, this paper analyzes the microphysical process and evolution characteristics of radiation fogs with complicated substrate in the upper and middle reaches of the Yangtze River, and compares them with findings in other areas. Results are as follows: radiation fog in Xuanen is evidently weaker in droplet number concentration and liquid water content than land fogs in other areas. Its liquid water content fluctuates obviously, 0.01g/m3 with visibility of 1,000 meters, which is quite different from that in urban areas, but similar to the Nanling Mountains. Bi-modal droplet distribution is likely to occur in Xuanen mountain radiation fog(MRF) events. Statistical analysis shows that the observed droplet size distribution can be piecewise described well by the Gamma distribution. There is a positive correlation between liquid water content, fog droplet concentration and mean radius, especially in the development and dissipation stage. Condensation growth and droplet evaporation are major processes of Xuanen MRF. The dissipation time coincided with the time when the grass temperature reached the peak value, which indicated that dew evaporation is a key role in maintaining Xuanen MRF. In the early stage of dense fog's growth, droplets with diameter of over 20 micrometers can be observed with visibility of800-1,000 m, which might be caused by the transportation of low cloud droplets to earth's surface by turbulence. Big droplets in the initial stage correspond to higher water content, leading to the higher observed value of water content of Xuanen MRF.
基金This paper is jointly supported by the National Natural Science Foundation of China under Grant Nos. 40375014, 40475029the National Basic Research Program of China under "973" Grant No. 2004CB418300.
文摘Using the daily NCEP/NCAR reanalysis dataset and the observation rainfall data in China for the 1980-1997 period, features of severe summer rainfall over the upper reaches of the Yangtze River are investigated and then sources of moisture contributing to severe rainfall over eastern and western Sichuan Province (ES and WS for short) are examined with particular reference. It turns out that the severe rainfall occurring locally dominates summer rainfall over the upper reaches of the Yangtze River. Climatological rainfall and anomalous one constitute severe rainfall, but the latter accounts much for severe rainfall. The meridional moisture transport dominates the composite moisture transport on the occurrence day for ES region, while the zonal is equivalent to the meridional for WS region. Correlation between the moisture transport fluxes over the two regions of severe rainfall and other regions, the anomaly and variation of the moisture transport day by day during the period of severe rainfall lend a support for the conclusion that the meeting of the moisture from the West Pacific through the South China Sea (SCS) and the one from northwestern China exerts a vital effect on the occurrence of severe rainfall, which can not be neglected.
基金the National Natural Science Foundation of China (Grant Nos.41471008 and 41730637)the United Fund of the National Scientific Foundation of China and Yunnan Province (U0933604)the Fundamental Research Funds for the Central Universities (lzujbky-2013-272).
文摘Identification of the planation surfaces (PSs)is key for utilizing them as a reference in studying the long- term geomorphological evolution of the Upper Yangtze River Basin in the Sichuan-Yurman region,Southwest China.Using a combined method of DEM-based fuzzy logic and topographic and fiver profiles analysis and based on a comprehensive analysis of four morphometfic parameters:slope,curvature,terrain raggedness index, and relative height,we established the relevant fuzzy membership functions,and then calculated the membership degree (MD)of the study area.Results show that patches with a MD>80% and an area>0.4 km^2 correspond well to the results of Google Earth and field investigation,representing the PS remnants.They consist of 1764 patches with an altitude,area,mean slope,and relief of mostly 2000-2500 m above sea level (asl),0-10 km^2,4°-9°,0-500 m,respectively,covering 9.2% of the study area's landscape,dipping to southeast,decreasing progressively from northwest to southeast in altitude,and with no clear relation between each patch's altitude and slope,or relief.All these results indicate that they are remnants of once regionally continuous PSs which were deformed by both the lower crust flow and the faults in upper crust,and dissected by the network of Upper Yangtze River.Additionally,topographic and river profiles analysis show that three PSs (PS1-PS3)well developed along the main valleys in the Yongren-Huili region, indicating several phases of uplift then planation during the Late Cenozoic era.Based on the incision amount deduced from projection of relict river profiles on PSs, together with erosion rates,breakup times of the PS 1,PS2,and PS3 were estimated to be 3.47 Ma,2.19 Ma,and 1.45 Ma,respectively,indicating appearance of modem Upper Yangtze River valley started between the Pliocene to early Pleistocene.
基金Commonweal Special Project of the Minislry of Water Resources of China, No.2007SHZ0901034 National Natural Science Foundation of China, No.40971012
Acknowledgements We are grateful to Data Center for Resources and Environmental Sciences of Chinese Academy of Sciences for providing the data of soil and to China Meteorological Administration for providing the data of precipitation.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 40175028 and 40475045.
文摘The contribution of areal precipitation of the catchment from Cuntan to Yichang (Three Gorges area)to eight flood peaks of the Upper Yangtze River (the upper reaches of the Yangtze River) is diagnosed for 1998 flood season. A rainfall-runoff model is employed to simulate runoffs of this catchment. Comparison of observed and simulated runoffs shows that the rainfall-runoff model has a good capability to simulate the runoff over a large-scale river and the results describe the eight flood peaks very well Forecast results are closely associated with the sensitivity of the model to rainfall and the calibration processes. Other reasons leading to simulation errors are further discussed.
