By using data of hourly rainfall with all of the meteorological stations in the upper reaches of Hunhe River (Qingyuan Section), the digital elevation model, the land use and the disasters data etc., the storm flood p...By using data of hourly rainfall with all of the meteorological stations in the upper reaches of Hunhe River (Qingyuan Section), the digital elevation model, the land use and the disasters data etc., the storm flood process which happened on 16 August 2013 is reproduced simulated based on the rainstorm flooding of FloodArea model, also the flooding simulation and its effectiveness have been carried out. Conclusions are drawn as follows: there is a sharp rise of the flood depth falling behind the change of rainfall three or four hours. As the accumulation of the precipitation, the water level has increased, and when the precipitation process stops, the flood pooled into midstream and downstream gradually. According to the disaster investigation, in both the aspects of flooding scope and flooding depth of warning spots, the simulation result of FloodArea model agrees with the fact. It indicates that the FloodArea model generates good simulation effect in the upper reaches of Hunhe River (Qingyuan Section). Combined with population and GDP information, in the whole river, about eighty-three thousand people were affected by flooding, also one billion and five hundred seventy five million RMB of gross domestic product was lost. When the flood depth deepens and the flooding scope increases, correspondingly the loss rate of population and GDP rises and the flood risk increases.展开更多
Under the background of the uplift of the Qinghai-Tibet Plateau, the settlements in the upper reaches of the Min River are significantly affected by the mountain environment, and their spatial distribution is typical ...Under the background of the uplift of the Qinghai-Tibet Plateau, the settlements in the upper reaches of the Min River are significantly affected by the mountain environment, and their spatial distribution is typical and representative. In this study, the relationship between settlements and topography, rivers and transportation, and the spatial distribution patterns of settlements, such as the aggregation and orientation characteristics of settlements, have been studied. The main conclusions include: 1) The settlement density decreases with the increase of elevation, slope, and distance from rivers and roads;76.25% and 63.17% of the settlements are distributed in the range of elevation 1500 - 3000 m and slope 6° - 25°, the upper reaches of the Min River are mostly alpine valley terrain, the bottom of the river has a low altitude, the landscape is undulating. The warm and humid climate is suitable for farming, conducive to agricultural production, and an ideal living environment for mountain residents. 2) The nuclear density of the settlement is distributed in strips along the axis of the river, and the closer to the river, the greater the nuclear density value. 3) Mathematical statistical methods were applied for the first time to realize the quantitative expression of the coupling of settlement and river direction. The influence of topographic conditions in different watersheds on the coupling degree of settlement extension and river flow direction was revealed. The slope of the fitted straight line between the settlement and river direction was 0.897, and the two directions were consistent. Except for the mainstream of the Min River, the larger values of the standard deviation ellipse flattening of settlements in each basin appeared in the upper reaches of the bay, and the overall trend showed a gradual decrease from the upstream to the downstream, which was consistent with the topographic change characteristics of the basin.展开更多
The upper reaches of the Yellow River in northeastern Tibetan Plateau are geohazards areas.The evolution of the Yellow River,chronology of some landslides,and spatiotemporal distribution characteristics of super large...The upper reaches of the Yellow River in northeastern Tibetan Plateau are geohazards areas.The evolution of the Yellow River,chronology of some landslides,and spatiotemporal distribution characteristics of super large scale and giant landslides within the region are summarized using paleoclimate evidence,and the relationship between the intensive landslide period and climatic changes since the Last Glacial period is analyzed.It is concluded that (1) Super large scale and giant landslides are distributed widely within the region,particularly in the Qunke-Jianzha basin.(2) The chronological sequence of landslides is established by dating the slip zones of landslides and analyzing the relations between landslides and their overlying or underlying loess formations.Five landslide development periods are determined:53-49 ka BP,33-24 ka BP,10-8 ka BP,5-3.5 ka BP,and the present.(3) These correspond closely to warm and wet periods during the last 100,000 years,i.e.,two weak paleosol development stages of Malan loess deposited during the last Glacial period in the Chinese loess Plateau,L1-4 and L1-2 that belong to the marine oxygen isotope stage 3,the last deglaeial period,the Holocene Optimum,and the modern global warming period.(4) Landslide triggers may be closely linked to warm and wet periods related to rapid climatic transitions.展开更多
Human settlements are the place where human beings live,among which the rural settlements can be regarded as a reflection of human-land relationship in mountain areas because their vertical distribution is greatly inf...Human settlements are the place where human beings live,among which the rural settlements can be regarded as a reflection of human-land relationship in mountain areas because their vertical distribution is greatly influenced by the specific geographical environment and ecological conditions of mountains.Based on field investigation,this paper uses physical,geographical,and ecological theories to make a comprehensive study of rural settlements and mountain disasters in the upper Min River,which is an ecologically fragile area with high-frequency disasters(collapse,landslide,debris flow,etc.) and a minority inhabit district.By applying these modern scientific theories,this paper attempts to shed some light on the relationship between rural settlements and mountain disasters.Consequently,an in-depth understanding of this relationship was achieved as follows:(1) Rural settlements and mountain disasters are mainly distributed in the intercepted flows of water and soil; and both quantity and quality of arable lands in mountains are important indicators of these flows.(2) The Small Watershed Management Project is a complex system of rural settlements and mountain disasters that interacts with and constrains the ecological system.By this project,the human survival will be better guaranteed.Being fundamental for the ecological reconstruction,the coupling mechanism of rural settlements and mountain disasters is not only an engine to promote harmonious development between human and nature,but also a bridge to link them.展开更多
Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-...Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20<sup>th</sup> century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).展开更多
Several argillaceous platforms lie along the Yellow River(YR) of the eastern Guide Basin, northeastern Tibetan Plateau, and their compositions, formation processes, and geomorphic evolution remain debated. Using fie...Several argillaceous platforms lie along the Yellow River(YR) of the eastern Guide Basin, northeastern Tibetan Plateau, and their compositions, formation processes, and geomorphic evolution remain debated. Using field survey data, sample testing, and high-resolution remote sensing images, the evolution of the Erlian mudflow fans are analyzed. The data show significant differences between fans on either side of the YR. On the right bank, fans are dilute debris flows consisting of sand and gravel. On the left bank, fans are viscosity mudflows consisting of red clay. The composition and formation processes of the left bank platforms indicate a rainfall-induced pluvial landscape. Fan evolution can be divided into two stages: early-stage fans pre-date 16 ka B.P., and formed during the last deglaciation; late-stage fans post-date 8 ka B.P.. Both stages were induced by climate change. The data indicate that during the Last Glacial Maximum, the northeastern Tibetan Plateau experienced a cold and humid climate characterized by high rainfall. From 16–8 ka, the YR cut through the Erlian early mudflow fan, resulting in extensive erosion. Since 8 ka, the river channel has migrated south by at least 1.25 km, and late stage mudflow fan formation has occurred.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
Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits (SWDs) was found interbedded in the Holocene Ioe...Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits (SWDs) was found interbedded in the Holocene Ioess-paleosol sequence at the Guchuanzhen site (GCZ). These palaeoflood SWDs were studied by field observations and laboratory analyses including concentrations of chemical elements and optically stimulated luminescence (OSL) dating. The results showed that the palaeoflood SWDs were the result of the secondary separations of the surface soil and weathered soil layers during the process of water transport and deposition, and without obvious weathering during soil development. These extraordinary flood events were dated back to 3,200-3,000 a B.P. with the OSL method and checked by archaeological dating of the human remains retrieved from the profile. These extraordinary flood events were therefore considered as regional expression of known climatic events and demonstrated the climatic instability in the Holocene. This result is important for understanding the effects of global climate change on the dynamics of river systems.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 geological structures and abundant ra...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 geological structures and abundant rainfall. The distribution of debris flows has regularity in the regions with different landform, geological 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 precipitation; (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 Engineering, 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 disasters prevention and soil conservancy.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
The sediment load and river sedimentation of the upper reaches of YangtzeRiver has been undergoing constant changes as complex landform, large mountain area and plentifulprecipitation make the drainage area of Yangtze...The sediment load and river sedimentation of the upper reaches of YangtzeRiver has been undergoing constant changes as complex landform, large mountain area and plentifulprecipitation make the drainage area of Yangtze River very vulnerable to watererosion and gravityerosion. Through analyzing the hydrological and sediment load statistics recorded by majorhydrological stations along Yangtze River since 1950s, and editing the accumulation graph of annualrunoff volume and annual sediment load, wefind out that the suspended-sediment of Yangtze river hasbeen decreasing year by year in Wulong Hydrological Station on Wujiang River, Beibei HydrologicalStation on Jialingjiang River, Lijiawan Hydrological Station on Tuojiang River and GaochangHydrological Station on Minjiang River, Yichang Hydrological Station, Cuntan Hydrological Stationalong Yangtze River mainstream share the same experience too. But the statistics obtained atPingshan Hydrological Station on Jinshajiang River shows the sedimentload there has increased.Taking ecological construction, hydraulic engineering construction and precipitation changes intoconsideration, 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 forfurther study of river sediment changes of the upper reaches of Yangtze River, and measures tocontrol river sedimentation.展开更多
Under artificially simulated conditions, the water purification effects of Lythrum salicaria, Typha minima, Scirpus validus, Iris wilsonii and their configurations were studied. The results showed that various aquatic...Under artificially simulated conditions, the water purification effects of Lythrum salicaria, Typha minima, Scirpus validus, Iris wilsonii and their configurations were studied. The results showed that various aquatic plants and their configurations showed purification effects for total nitrogen(TN), nitrate nitrogen(NO_3^-), total phosphorus(TP), orthophosphate(PO_4^(3-)) and chemical oxygen demand(COD) in water body, and the purification effects of aquatic plant configurations were better than those of single ones. Regression analysis was conducted for dynamics of various water quality indicators. The removal rates of TN and COD within 50 d by the combination of L. salicaria and I. wilsonii were 73.83% and 77.4%, respectively, with the best purification effect; the removal rate of NO_3^- within 20 d by the combination of S. validus and I. wilsonii was 89.41%; and the combination of S. validus and I. wilsonii showed the best removal effect for TP and PO43-, of which the 50-d removal rates were 88.98% and 92.39%, respectively. Reasonable choice of local aquatic plants and their optimal combinations can be applied in the improvement of water quality of rivers.展开更多
[Objective] Species composition and flora of vascular plants in the middle and upper reaches of the Yarlung Zangbo River were analyzed,to provide scientific basis for the estimation and protection of plant diversity,c...[Objective] Species composition and flora of vascular plants in the middle and upper reaches of the Yarlung Zangbo River were analyzed,to provide scientific basis for the estimation and protection of plant diversity,construction of ecological security shelter for the Tibetan Plateau.[Methods] In the middle and upper reaches of the Yarlung Zangbo River,quadrat (line transect) method was applied to investigate the phytocoenoses in sample plots,and relative literature was used to analyze the floristic composition and floristic element of vascular plants in the middle and upper reaches of the Yarlung Zangbo River.[Results]① There are 96 species (including subspecies and variations),69 genera of 35 vascular plant families,accounting for 16.83%,5.48%,1.66% and 11.63%,2.02%,0.31% of total vascular plant families,genera and species in Tibet and China.② There are 24 monotypic-genus families,accounting for 68.57% of the total family number in the local area;22 monotypic-species families,accounting for 62.86% of the total family number in the local area.Local flora shows the characteristics of ancient relict,such as Euphorbiaceae,Rubiaceae,Liliaceae and Ranunculaceae,they are all ancient primitive groups of the third flora and the fourth flora.③ Local vascular plant genera fall into 10 areal types and 8 variations.④ Temperate elements are much more than tropical elements,R/T is 0.19,indicating that vascular plants have typical temperate nature and residual tropical nature.There are only a few endemic genera,but more endemic species to the local area,and these species are closely related,of which there are some transitional species,indicating that local flora is too young to experience more differentiation and specialization.⑤ There are 24 Chinese endemic species,accounting for 25% of total number of species in the local area;among which there are 12 endemic species to Tibet,accounting for 50% of endemic species to China,12.5% of total number of species in the local area.Four key wild plant species are included in the second batch of national key protection.[Conclusions]① There are scarce plant groups in the local area.② Among the obvious advantages,single-genus (species) families possess the absolute advantage,and the flora has ancient origins.③ The local flora has diversified distribution types,and the complicated geographical elements.④ Temperate species possess obvious advantages,and the flora is young.⑤ Rich unique and rare species have high species diversity protection and research value.展开更多
Taking Zhongba County, Angren County, Rikaze City located at the Upper and Middle Reaches of Yarlung Zangbo River as landscape units , this paper studied the difference of the landscape pattern under various degrees o...Taking Zhongba County, Angren County, Rikaze City located at the Upper and Middle Reaches of Yarlung Zangbo River as landscape units , this paper studied the difference of the landscape pattern under various degrees of human disturbance in the three areas. The results showed that: the three areas all reflected the same characteristic of landscape pattern in Qinghai-Tibet Plateau, the natural landscapes were in the absolute dominant position. However, from Zhangba to Rikaze, with human disturbance intensity increasing, anthropogenic features of landscapes became more and more outstanding, In Zhongba, the landscape structure appeared to be simpler with coarse grains and a less rich diversity, Conversely, in Rikaze, the landscape showed a complicated shape with finer grains and a relatively richer diversity, This reflected that the impact of human activities to natural landscape behaved a gradually-growing trend from the upper reach to the middle one of Yarlung Zangbo River Basin.展开更多
This paper explores and identifies the rules of the unsteady evolution of COD in the upper and middle reaches of Minjiang River through multi-scale analysis on the weekly COD data for the last six years provided by th...This paper explores and identifies the rules of the unsteady evolution of COD in the upper and middle reaches of Minjiang River through multi-scale analysis on the weekly COD data for the last six years provided by the Water Quality Monitoring Station,Minjiang River Bridge,Leshan City,Sichuan Province.The results of the wavelet analysis indicate that the COD index oscillates alternatively and differently at each time-scale in an oneyear cycle,and the density of COD,subjected to the runoff volume,the effects of Wenchuan Earthquake and agricultural seeding and industrial construction,etc.,is high in winter and spring,mild in summer and autumn.展开更多
The southwest mountainous area is a frequent debris flow disaster area in<span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> Chin...The southwest mountainous area is a frequent debris flow disaster area in<span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> China, which poses a serious threat to the regional roads and greatly affects the normal traffic operation and the safety of residents’ lives and property. The debris flow risk assessment of highway can quantify the threat degree of debris flow to the roads. In this paper, from the perspective of villages and towns, taking the upper reaches of Minjiang River as the research area, four factors including road network density, highway disaster resistance capacity, population density and highway cost are selected, and the weight is obtained by using entropy weight method, and the debris flow vulnerability evaluation results of highway are obtained by weighted calculation. Four indexes of debris flow density, shape factor, relative height difference and annual rainfall are selected to evaluate the debris flow hazard of highway by using the information method. Based on the vulnerability and hazard evaluation results, the ri</span><span style="font-family:Verdana;">sk of highway debris flow is evaluated, and the results are classified and</span><span style="font-family:Verdana;"> discussed. The results show that: the risk of debris flow on the upper reaches of Minjiang River is relatively low, the overall spatial distribution shows a trend of high in the East and low in the west, and the overall risk of township roads in Wenchuan county is the highest;The risk of debris flow is generally high within </span></span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">-10 to 30</span><span style="font-family:Verdana;"> km from the central fault zone of Longmenshan.</span></span></span></span>展开更多
<span style="font-family:""><span style="font-family:Verdana;">Water resource is an important supporting material for life support system and eco</span><span style="f...<span style="font-family:""><span style="font-family:Verdana;">Water resource is an important supporting material for life support system and eco</span><span style="font-family:Verdana;">nomic development, and the sustainable development and utilization of water resource </span></span><span style="font-family:Verdana;">are</span><span style="font-family:Verdana;"> the guarantee of social sustainable development. The upper Minjiang River is the most important source of water supply for the Chengdu Plain. With the water resources of the upper Minjiang River facing the problems of overall water volume reduction, flood and water pollution, etc.</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> based on the optimal allocation theory, this paper constructs an optimal allocation model of water resourc</span><span style="font-family:Verdana;">es in the upper reaches of the Minjiang River, analyzes its characteristics and proposes some relevant countermeasures and suggestions to solve the existing problems, aiming to provide reference</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> for the sustainable utilization of water resources in the upper reaches of the Minjiang River.展开更多
文摘By using data of hourly rainfall with all of the meteorological stations in the upper reaches of Hunhe River (Qingyuan Section), the digital elevation model, the land use and the disasters data etc., the storm flood process which happened on 16 August 2013 is reproduced simulated based on the rainstorm flooding of FloodArea model, also the flooding simulation and its effectiveness have been carried out. Conclusions are drawn as follows: there is a sharp rise of the flood depth falling behind the change of rainfall three or four hours. As the accumulation of the precipitation, the water level has increased, and when the precipitation process stops, the flood pooled into midstream and downstream gradually. According to the disaster investigation, in both the aspects of flooding scope and flooding depth of warning spots, the simulation result of FloodArea model agrees with the fact. It indicates that the FloodArea model generates good simulation effect in the upper reaches of Hunhe River (Qingyuan Section). Combined with population and GDP information, in the whole river, about eighty-three thousand people were affected by flooding, also one billion and five hundred seventy five million RMB of gross domestic product was lost. When the flood depth deepens and the flooding scope increases, correspondingly the loss rate of population and GDP rises and the flood risk increases.
文摘Under the background of the uplift of the Qinghai-Tibet Plateau, the settlements in the upper reaches of the Min River are significantly affected by the mountain environment, and their spatial distribution is typical and representative. In this study, the relationship between settlements and topography, rivers and transportation, and the spatial distribution patterns of settlements, such as the aggregation and orientation characteristics of settlements, have been studied. The main conclusions include: 1) The settlement density decreases with the increase of elevation, slope, and distance from rivers and roads;76.25% and 63.17% of the settlements are distributed in the range of elevation 1500 - 3000 m and slope 6° - 25°, the upper reaches of the Min River are mostly alpine valley terrain, the bottom of the river has a low altitude, the landscape is undulating. The warm and humid climate is suitable for farming, conducive to agricultural production, and an ideal living environment for mountain residents. 2) The nuclear density of the settlement is distributed in strips along the axis of the river, and the closer to the river, the greater the nuclear density value. 3) Mathematical statistical methods were applied for the first time to realize the quantitative expression of the coupling of settlement and river direction. The influence of topographic conditions in different watersheds on the coupling degree of settlement extension and river flow direction was revealed. The slope of the fitted straight line between the settlement and river direction was 0.897, and the two directions were consistent. Except for the mainstream of the Min River, the larger values of the standard deviation ellipse flattening of settlements in each basin appeared in the upper reaches of the bay, and the overall trend showed a gradual decrease from the upstream to the downstream, which was consistent with the topographic change characteristics of the basin.
基金financially supported by the National Nature Science Foundation of China under Grant No. 41372333, 40802089, 41172158China Geological Survey (grant No. 1212011220123)
文摘The upper reaches of the Yellow River in northeastern Tibetan Plateau are geohazards areas.The evolution of the Yellow River,chronology of some landslides,and spatiotemporal distribution characteristics of super large scale and giant landslides within the region are summarized using paleoclimate evidence,and the relationship between the intensive landslide period and climatic changes since the Last Glacial period is analyzed.It is concluded that (1) Super large scale and giant landslides are distributed widely within the region,particularly in the Qunke-Jianzha basin.(2) The chronological sequence of landslides is established by dating the slip zones of landslides and analyzing the relations between landslides and their overlying or underlying loess formations.Five landslide development periods are determined:53-49 ka BP,33-24 ka BP,10-8 ka BP,5-3.5 ka BP,and the present.(3) These correspond closely to warm and wet periods during the last 100,000 years,i.e.,two weak paleosol development stages of Malan loess deposited during the last Glacial period in the Chinese loess Plateau,L1-4 and L1-2 that belong to the marine oxygen isotope stage 3,the last deglaeial period,the Holocene Optimum,and the modern global warming period.(4) Landslide triggers may be closely linked to warm and wet periods related to rapid climatic transitions.
基金financially supported by the National Natural Science Foundation of China(Grant No.41101164 and 41371185)Directional Project of Institute of Mountain Hazards and Environment of Chinese Academy of Sciences(Grant No.SDS-135-1204-01)the key project of Education Department of Sichuan Province(Grant No.13ZA0160)
文摘Human settlements are the place where human beings live,among which the rural settlements can be regarded as a reflection of human-land relationship in mountain areas because their vertical distribution is greatly influenced by the specific geographical environment and ecological conditions of mountains.Based on field investigation,this paper uses physical,geographical,and ecological theories to make a comprehensive study of rural settlements and mountain disasters in the upper Min River,which is an ecologically fragile area with high-frequency disasters(collapse,landslide,debris flow,etc.) and a minority inhabit district.By applying these modern scientific theories,this paper attempts to shed some light on the relationship between rural settlements and mountain disasters.Consequently,an in-depth understanding of this relationship was achieved as follows:(1) Rural settlements and mountain disasters are mainly distributed in the intercepted flows of water and soil; and both quantity and quality of arable lands in mountains are important indicators of these flows.(2) The Small Watershed Management Project is a complex system of rural settlements and mountain disasters that interacts with and constrains the ecological system.By this project,the human survival will be better guaranteed.Being fundamental for the ecological reconstruction,the coupling mechanism of rural settlements and mountain disasters is not only an engine to promote harmonious development between human and nature,but also a bridge to link them.
基金supported by the National Natural Science Foundation of China(91025002,30970492)the National Key Technology Research&Development Program(2012BAC08B05)the Key Project of the Chinese Academy of Sciences(KZZD-EW-04-05)
文摘Long-term temperature variability has significant effects on runoff into the upper reaches of inland rivers. This paper developed a tree-ring chronology of Qilian juniper (Sabina przewalskii Kom.) from the upper tree-line of the middle Qilian Mountains within the upper reaches of Heihe River Basin, Northwest China for a long-term reconstruction of temperature at the study site. In this paper, tree-ring chronology was used to examine climate-growth associations considering local climate data obtained from Qilian Meteorological Station. The results showed that temperatures correlated extremely well with standardized growth indices of trees (r=0.564, P<0.001). Tree-ring chronology was highest correlated with annual mean temperature (r=0.641, P<0.0001). Annual mean temperature which spans the period of 1445–2011 was reconstructed and explained 57.8% of the inter-annual to decadal temperature variance at the regional scale for the period 1961–2011. Spatial correlation patterns revealed that reconstructed temperature data and gridded temperature data had a significant correlation on a regional scale, indicating that the reconstruction represents climatic variations for an extended area surrounding the sampling sites. Analysis of the temperature reconstruction indicated that major cold periods occurred during the periods of 1450s–1480s, 1590s–1770s, 1810s–1890s, 1920s–1940s, and 1960s–1970s. Warm intervals occurred during 1490s–1580s, 1780s–1800s, 1900s–1910s, 1950s, and 1980s to present. The coldest 100-year and decadal periods occurred from 1490s–1580s and 1780s–1800s, respectively, while the warmest 100 years within the studied time period was the 20<sup>th</sup> century. Colder events and intervals coincided with wet or moist conditions in and near the study region. The reconstructed temperature agreed well with other temperature series reconstructed across the surrounding areas, demonstrating that this reconstructed temperature could be used to evaluate regional climate change. Compared to the tree-ring reconstructed temperature from nearby regions and records of glacier fluctuations from the surrounding high mountains, this reconstruction was reliable, and could aid in the evaluation of regional climate variability. Spectral analyses suggested that the reconstructed annual mean temperature variation may be related to large-scale atmospheric–oceanic variability such as the solar activity, Pacific Decadal Oscillation (PDO) and El Ni?o–Southern Oscillation (ENSO).
基金financially supported by the National Nature Science Foundation of China under Grant No.41372333,41172158China Geological Survey(grant No.1212011220123)
文摘Several argillaceous platforms lie along the Yellow River(YR) of the eastern Guide Basin, northeastern Tibetan Plateau, and their compositions, formation processes, and geomorphic evolution remain debated. Using field survey data, sample testing, and high-resolution remote sensing images, the evolution of the Erlian mudflow fans are analyzed. The data show significant differences between fans on either side of the YR. On the right bank, fans are dilute debris flows consisting of sand and gravel. On the left bank, fans are viscosity mudflows consisting of red clay. The composition and formation processes of the left bank platforms indicate a rainfall-induced pluvial landscape. Fan evolution can be divided into two stages: early-stage fans pre-date 16 ka B.P., and formed during the last deglaciation; late-stage fans post-date 8 ka B.P.. Both stages were induced by climate change. The data indicate that during the Last Glacial Maximum, the northeastern Tibetan Plateau experienced a cold and humid climate characterized by high rainfall. From 16–8 ka, the YR cut through the Erlian early mudflow fan, resulting in extensive erosion. Since 8 ka, the river channel has migrated south by at least 1.25 km, and late stage mudflow fan formation has occurred.
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funded by the National Natural Science Foundation of China(41030637)the Science and Technology Project of Baoji City(14SFGG-2)+1 种基金the Fundamental Research Funds for Key Subject Physical Geography of Baoji University of Arts and ScienceShaanxi Province and the Key Library Program of Education Department of Shaanxi Province(15JS008)
文摘Palaeohydmlogical investigations were carried out in the Guchuan Basin in the upper reaches of the Weihe River valley, China. A set of palaeoflood slackwater deposits (SWDs) was found interbedded in the Holocene Ioess-paleosol sequence at the Guchuanzhen site (GCZ). These palaeoflood SWDs were studied by field observations and laboratory analyses including concentrations of chemical elements and optically stimulated luminescence (OSL) dating. The results showed that the palaeoflood SWDs were the result of the secondary separations of the surface soil and weathered soil layers during the process of water transport and deposition, and without obvious weathering during soil development. These extraordinary flood events were dated back to 3,200-3,000 a B.P. with the OSL method and checked by archaeological dating of the human remains retrieved from the profile. These extraordinary flood events were therefore considered as regional expression of known climatic events and demonstrated the climatic instability in the Holocene. This result is important for understanding the effects of global climate change on the dynamics of river systems.
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 geological structures and abundant rainfall. The distribution of debris flows has regularity in the regions with different landform, geological 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 precipitation; (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 Engineering, 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 disasters prevention and soil conservancy.
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.
文摘The sediment load and river sedimentation of the upper reaches of YangtzeRiver has been undergoing constant changes as complex landform, large mountain area and plentifulprecipitation make the drainage area of Yangtze River very vulnerable to watererosion and gravityerosion. Through analyzing the hydrological and sediment load statistics recorded by majorhydrological stations along Yangtze River since 1950s, and editing the accumulation graph of annualrunoff volume and annual sediment load, wefind out that the suspended-sediment of Yangtze river hasbeen decreasing year by year in Wulong Hydrological Station on Wujiang River, Beibei HydrologicalStation on Jialingjiang River, Lijiawan Hydrological Station on Tuojiang River and GaochangHydrological Station on Minjiang River, Yichang Hydrological Station, Cuntan Hydrological Stationalong Yangtze River mainstream share the same experience too. But the statistics obtained atPingshan Hydrological Station on Jinshajiang River shows the sedimentload there has increased.Taking ecological construction, hydraulic engineering construction and precipitation changes intoconsideration, 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 forfurther study of river sediment changes of the upper reaches of Yangtze River, and measures tocontrol river sedimentation.
基金Sponsored by Key Technology Research and Development Program of Hebei Province(15227652D)Dynamic Control Technology of Sandy Land Protection Forest System Structure in Northern North China(2016YFC0500802-06)
文摘Under artificially simulated conditions, the water purification effects of Lythrum salicaria, Typha minima, Scirpus validus, Iris wilsonii and their configurations were studied. The results showed that various aquatic plants and their configurations showed purification effects for total nitrogen(TN), nitrate nitrogen(NO_3^-), total phosphorus(TP), orthophosphate(PO_4^(3-)) and chemical oxygen demand(COD) in water body, and the purification effects of aquatic plant configurations were better than those of single ones. Regression analysis was conducted for dynamics of various water quality indicators. The removal rates of TN and COD within 50 d by the combination of L. salicaria and I. wilsonii were 73.83% and 77.4%, respectively, with the best purification effect; the removal rate of NO_3^- within 20 d by the combination of S. validus and I. wilsonii was 89.41%; and the combination of S. validus and I. wilsonii showed the best removal effect for TP and PO43-, of which the 50-d removal rates were 88.98% and 92.39%, respectively. Reasonable choice of local aquatic plants and their optimal combinations can be applied in the improvement of water quality of rivers.
基金Supported by National Key R&D Program of china(2016YFC0502006)Major Science and Technology Projects of Tibet(Z2016C01G01/02)
文摘[Objective] Species composition and flora of vascular plants in the middle and upper reaches of the Yarlung Zangbo River were analyzed,to provide scientific basis for the estimation and protection of plant diversity,construction of ecological security shelter for the Tibetan Plateau.[Methods] In the middle and upper reaches of the Yarlung Zangbo River,quadrat (line transect) method was applied to investigate the phytocoenoses in sample plots,and relative literature was used to analyze the floristic composition and floristic element of vascular plants in the middle and upper reaches of the Yarlung Zangbo River.[Results]① There are 96 species (including subspecies and variations),69 genera of 35 vascular plant families,accounting for 16.83%,5.48%,1.66% and 11.63%,2.02%,0.31% of total vascular plant families,genera and species in Tibet and China.② There are 24 monotypic-genus families,accounting for 68.57% of the total family number in the local area;22 monotypic-species families,accounting for 62.86% of the total family number in the local area.Local flora shows the characteristics of ancient relict,such as Euphorbiaceae,Rubiaceae,Liliaceae and Ranunculaceae,they are all ancient primitive groups of the third flora and the fourth flora.③ Local vascular plant genera fall into 10 areal types and 8 variations.④ Temperate elements are much more than tropical elements,R/T is 0.19,indicating that vascular plants have typical temperate nature and residual tropical nature.There are only a few endemic genera,but more endemic species to the local area,and these species are closely related,of which there are some transitional species,indicating that local flora is too young to experience more differentiation and specialization.⑤ There are 24 Chinese endemic species,accounting for 25% of total number of species in the local area;among which there are 12 endemic species to Tibet,accounting for 50% of endemic species to China,12.5% of total number of species in the local area.Four key wild plant species are included in the second batch of national key protection.[Conclusions]① There are scarce plant groups in the local area.② Among the obvious advantages,single-genus (species) families possess the absolute advantage,and the flora has ancient origins.③ The local flora has diversified distribution types,and the complicated geographical elements.④ Temperate species possess obvious advantages,and the flora is young.⑤ Rich unique and rare species have high species diversity protection and research value.
文摘Taking Zhongba County, Angren County, Rikaze City located at the Upper and Middle Reaches of Yarlung Zangbo River as landscape units , this paper studied the difference of the landscape pattern under various degrees of human disturbance in the three areas. The results showed that: the three areas all reflected the same characteristic of landscape pattern in Qinghai-Tibet Plateau, the natural landscapes were in the absolute dominant position. However, from Zhangba to Rikaze, with human disturbance intensity increasing, anthropogenic features of landscapes became more and more outstanding, In Zhongba, the landscape structure appeared to be simpler with coarse grains and a less rich diversity, Conversely, in Rikaze, the landscape showed a complicated shape with finer grains and a relatively richer diversity, This reflected that the impact of human activities to natural landscape behaved a gradually-growing trend from the upper reach to the middle one of Yarlung Zangbo River Basin.
文摘This paper explores and identifies the rules of the unsteady evolution of COD in the upper and middle reaches of Minjiang River through multi-scale analysis on the weekly COD data for the last six years provided by the Water Quality Monitoring Station,Minjiang River Bridge,Leshan City,Sichuan Province.The results of the wavelet analysis indicate that the COD index oscillates alternatively and differently at each time-scale in an oneyear cycle,and the density of COD,subjected to the runoff volume,the effects of Wenchuan Earthquake and agricultural seeding and industrial construction,etc.,is high in winter and spring,mild in summer and autumn.
文摘The southwest mountainous area is a frequent debris flow disaster area in<span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> China, which poses a serious threat to the regional roads and greatly affects the normal traffic operation and the safety of residents’ lives and property. The debris flow risk assessment of highway can quantify the threat degree of debris flow to the roads. In this paper, from the perspective of villages and towns, taking the upper reaches of Minjiang River as the research area, four factors including road network density, highway disaster resistance capacity, population density and highway cost are selected, and the weight is obtained by using entropy weight method, and the debris flow vulnerability evaluation results of highway are obtained by weighted calculation. Four indexes of debris flow density, shape factor, relative height difference and annual rainfall are selected to evaluate the debris flow hazard of highway by using the information method. Based on the vulnerability and hazard evaluation results, the ri</span><span style="font-family:Verdana;">sk of highway debris flow is evaluated, and the results are classified and</span><span style="font-family:Verdana;"> discussed. The results show that: the risk of debris flow on the upper reaches of Minjiang River is relatively low, the overall spatial distribution shows a trend of high in the East and low in the west, and the overall risk of township roads in Wenchuan county is the highest;The risk of debris flow is generally high within </span></span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">-10 to 30</span><span style="font-family:Verdana;"> km from the central fault zone of Longmenshan.</span></span></span></span>
文摘<span style="font-family:""><span style="font-family:Verdana;">Water resource is an important supporting material for life support system and eco</span><span style="font-family:Verdana;">nomic development, and the sustainable development and utilization of water resource </span></span><span style="font-family:Verdana;">are</span><span style="font-family:Verdana;"> the guarantee of social sustainable development. The upper Minjiang River is the most important source of water supply for the Chengdu Plain. With the water resources of the upper Minjiang River facing the problems of overall water volume reduction, flood and water pollution, etc.</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> based on the optimal allocation theory, this paper constructs an optimal allocation model of water resourc</span><span style="font-family:Verdana;">es in the upper reaches of the Minjiang River, analyzes its characteristics and proposes some relevant countermeasures and suggestions to solve the existing problems, aiming to provide reference</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> for the sustainable utilization of water resources in the upper reaches of the Minjiang River.