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1.
《The Australian geographer》1995,26(1):71-86
The upper Nepean River has been progressively regulated for water supply to Sydney and Wollongong since 1886 by the Upper Nepean Water Supply Scheme which consists of four large dams, two small dams and two diversion weirs. Secular rainfall changes produced periods of high rainfall and large floods (flood‐dominated regimes) between 1857 and 1900 and 1947 and the present, and an intervening period (1901–46) of low rainfall and small floods (drought‐dominated regime). Upstream impoundment and flow regulation significantly reduced flood magnitudes for most return periods during both types of flood regimes. The probability distribution of mean daily flows was also changed significantly by flow regulation such that during the drought‐dominated regime, the high and low frequency flows were reduced substantially but the moderate frequency flows were increased due to dam releases; the change from a regulated drought‐dominated regime to a regulated flood‐ dominated regime resulted in a substantial increase in discharge for most durations; and increased water diversions to Wollongong during the current flood‐dominated regime produced a marked downward shift in the whole flow duration curve. Nepean Dam reduced downstream suspended sediment yields by two orders of magnitude because it traps in excess of 99 per cent of the inflowing suspended sediment load. Streamflow releases are urgently required from the two diversion weirs to improve downstream water quality and to ensure the viability of the resident ‘potentially threatened’ eastern Macquarie perch (Macquaria nov. sp.). 相似文献
2.
J. Platt Bradbury Steven M. Colman Richard L. Reynolds 《Journal of Paleolimnology》2004,31(2):151-165
Hypereutrophic Upper Klamath Lake has been studied for almost 50 years to evaluate the nature, cause, and effects of its very productive waters. Mitigation of undesirable effects of massive cyanobacterial blooms requires understanding their modern causes as well as their history. Knowledge of the pre-settlement natural limnology of this system can provide guidelines for lake restoration and management of land and water use strategies to maximize the benefits of this aquatic resource. This investigation uses a paleolimnological approach to document the nature and chronology of limnological and biological changes in Upper Klamath Lake for the past 200 years, covering the time when the lake was first described until today. A 45-cm gravity core, dated by 210Pb and diatom correlations, was analyzed for diatoms, pollen, akinetes (resting spores) of the cyanobacterium Aphanizomenon flos-aquae, reworked tephra shards, and sediment magnetic characteristics. Pollen profiles show little vegetation change during this time. In contrast, diatoms indicative of increased nutrient fluxes (P and Si) increase moderately, coinciding with the settlement of the region by Euro-Americans. Numerous settlement activities, including draining of lake-margin marshes, upstream agriculture and timber harvest, road construction, and boat traffic, may have affected the lake. Magnetic properties and reworked tephra suggest riparian changes throughout the basin and increased lithogenic sediment delivery to the lake, especially after 1920 when the marshes near the mouth of the Williamson River were drained and converted to agricultural and pasture land. Drainage and channelization also decreased the ability of the marshes to function as traps and filters for upstream water and sediments. Akinetes of Aphanizomenon flos-aquae record progressive eutrophication of Upper Klamath Lake beginning in the 20th century and particularly after 1920 when lake-margin marsh reclamation more than doubled. The coincidence of limnological changes and human activities following European settlement suggests a major impact on the Upper Klamath Lake ecosystem, although ascribing specific limnological changes to specific human activities is difficult. 相似文献
3.
长江上游社会经济因子对侵蚀产沙的影响 总被引：1，自引：0，他引：1
In recent years,the role of human activities in changing sediment yield has become more apparent for the construction of hydraulic engineering and water conservation projec-tions in the Upper Yangtze River,but it has not been evaluated at the macro scale.Taking Sichuan Province and Chongqing City as an example,this paper studies the relationship between socio-economic factors and sediment yield in the Upper Yangtze River based on section data in 1989 and 2007.The results show that sediment yield is significantly correlated with population density and cultivated area,in which the former appears to be more closely related to sediment yield.Moreover,in the relation of sediment yield vs.population density,a critical value of population density exists,below which the sediment yield increases with the increase of population density and over which the sediment yield increases with the decrease of population density.The phenomenon essentially reflects the influence of natural factors,such as topography,precipitation and soil property,and some human activities on sediment yield.The region with a higher population density than critical value is located in the east of the study area and is characterized by plains,hills and low mountains,whereas the opposite is located in the west and characterized by middle and high mountains.In the eastern region,more people live on the lands with a low slope where regional soil erosion is slight;therefore,sediment yield is negatively related with population density.In contrast,in the western region,the population tends to aggregate in the areas with abundant soil and water resources which usually lead to a higher intensity of natural erosion,and in turn,high-intensity agricultural practices in these areas may further strengthen local soil erosion.It is also found that popu-lation tends to move from the areas with bad environment and high sediment yield to the areas with more comfortable environment and less sediment yield.The natural factors have greater influence on sediment yield of western region than that of eastern region.Generally,the natural factors play a dominant role on sediment yield in the Upper Yangtze River. 相似文献
4.
Government Intervention in the Muda Irrigation Scheme, Malaysia: 'actors', expectations and outcomes
CLARE L. JOHNSON 《The Geographical journal》2000,166(3):192-214
At the dawn of the third millennium the problems associated with large-scale irrigation lie largely unresolved. The outcomes of government policies rarely correspond with expectations, leading to conflict and misunderstanding between federal governments, local agencies and farmers. This paper examines the mis-match of expectations between policy implementors and policy recipients in the implementation of one government policy (tertlary intervention) in the Muda irrigation scheme, Malaysia. The findings illustrate that this policy is not achieving the productivity increase or water saving expectations for which it was designed. Instead, tertiary intervention has increased the capacity of the farmers to unofficially control the distribution and supply of the water resource and to engage in off-farm productive and non-productive activities. This results in: a significant over-supply of water; the inefficient use of this supply; and a reduction in yields without a reduction in incomes. Importantly, tertiary intervention has enabled the farmers to diversify their livelihood strategies whilst retaining access to the rice-farming culture. The findings presented in this paper serve to illustrate the significance of 'actor'expectations on policy outcomes and agrarian change. 相似文献
5.
Upper Klamath Lake, in south-central Oregon, contains long sediment records with well-preserved diatoms and lithological variations that reflect climate-induced limnological changes. These sediment archives complement and extend high resolution terrestrial records along a north–south transect that includes areas influenced by the Aleutian Low and Subtropical High, which control both marine and continental climates in the western United States. The longest and oldest core collected in this study came from the southwest margin of the lake at Caledonia Marsh, and was dated by radiocarbon and tephrochronology to an age of about 45 ka. Paleolimnological interpretations of this core, based upon geochemical and diatom analyses, have been augmented by data from a short core collected from open water environments at nearby Howards Bay and from a 9-m core extending to 15 ka raised from the center of the northwestern part of Upper Klamath Lake. Pre- and full-glacial intervals of the Caledonia Marsh core are characterized and dominated by lithic detrital material. Planktic diatom taxa characteristic of cold-water habitats (Aulacoseira subarctica and A. islandica) alternate with warm-water planktic diatoms (A. ambigua) between 45 and 23 ka, documenting climate changes at millennial scales during oxygen isotope stage (OIS) 3. The full-glacial interval contains mostly cold-water planktic, benthic, and reworked Pliocene lacustrine diatoms (from the surrounding Yonna Formation) that document shallow water conditions in a cold, windy environment. After 15 ka, diatom productivity increased. Organic carbon and biogenic silica became significant sediment components and diatoms that live in the lake today, indicative of warm, eutrophic water, became prominent. Lake levels fell during the mid-Holocene and marsh environments extended over the core site. This interval is characterized by high levels of organic carbon from emergent aquatic vegetation (Scirpus) and by the Mazama ash (7.55 ka), generated by the eruption that created nearby Crater Lake. For a brief time the ash increased the salinity of Upper Klamath Lake. High concentrations of molybdenum, arsenic, and vanadium indicate that Caledonia Marsh was anoxic from about 7 to 5 ka. After the mid-Holocene, shallow, but open-water environments returned to the core site. The sediments became dominated (>80%) by biogenic silica. The open-water cores show analogous but less extreme limnological and climatic changes more typical of mid-lake environments. Millennial-scale lake and climate changes during OIS 3 at Upper Klamath Lake contrast with a similar record of variation at Owens Lake, about 750 km south. When Upper Klamath Lake experienced cold-climate episodes during OIS 3, Owens Lake had warm but wet episodes; the reverse occurred during warmer intervals at Upper Klamath Lake. Such climatic alternations apparently reflect the variable position and strength of the Aleutian Low during the mid-Wisconsin. 相似文献
6.
Daniel A. Valencio Juan F. A. Vilas José E. Mendía 《Geophysical Journal International》1977,51(1):59-74
Palaeomagnetic data from 182 hand samples collected in a rock sequence of about 620-m of red beds of Late Palaeozoic to Early Triassic age exposed in north-western Argentina (30.3° S 67.7° W), are given.
After cleaning, the majority of the Upper Palaeozoic samples (Middle Section of Paganzo Group) show reversed polarity and yield a palaeomagnetic pole at 78° S 249° E (α95 = 3°). They also record a polarity transition which we have correlated with the Middle Permian Quebrada del Pimiento Normal Event. The position of the palaeomagnetic pole and the K-Ar age of a basalatic sill at the base of the sequence support this correlation.
Stable remanent magnetization has been isolated in the majority of samples from the Upper Section of the Paganzo Group; it is predominantly reversed and reveals three normal events and also three geomagnetic excursions suggesting an Illawarra Zone age (post Kiaman, Late Tatarian-Early Scythian). The palaeomagnetic pole of the reversely magnetized samples is located at 75° S 285° E(α95 = 13°).
The red beds involved in this study are correlated with red beds from the Corumbataí Formation (State of Paraná, Brazil) and with igneous rocks from the Quebrada del Pimiento Formation (Province of Mendoza, Argentina).
The South American Middle and Upper Permian, Upper Permian—Lower Triassic, Lower, Middle and Upper Triassic and Middle Jurassic palaeomagnetic poles reflect a quasistatic period with mean pole at 82° S 244° E, (α95 = 4°) which followed the South American Late Palaeozoic polar shift. 相似文献
After cleaning, the majority of the Upper Palaeozoic samples (Middle Section of Paganzo Group) show reversed polarity and yield a palaeomagnetic pole at 78° S 249° E (α
Stable remanent magnetization has been isolated in the majority of samples from the Upper Section of the Paganzo Group; it is predominantly reversed and reveals three normal events and also three geomagnetic excursions suggesting an Illawarra Zone age (post Kiaman, Late Tatarian-Early Scythian). The palaeomagnetic pole of the reversely magnetized samples is located at 75° S 285° E(α
The red beds involved in this study are correlated with red beds from the Corumbataí Formation (State of Paraná, Brazil) and with igneous rocks from the Quebrada del Pimiento Formation (Province of Mendoza, Argentina).
The South American Middle and Upper Permian, Upper Permian—Lower Triassic, Lower, Middle and Upper Triassic and Middle Jurassic palaeomagnetic poles reflect a quasistatic period with mean pole at 82° S 244° E, (α
7.
黄河沙漠宽谷段水沙变化特征及驱动因素 总被引：1，自引：1，他引：0
根据定位观测、第一次全国水利普查、遥感影像解译的数据,利用MWP、双累计曲线、水土保持分析法、数学模拟等方法,分析了黄河上游水沙变化特征,评估了多元驱动因素对2000-2012年黄河下河沿-头道拐沙漠宽谷段水沙变化的贡献率。结果表明:与20世纪70年代以前的基准期相比,2000年以来径流量、输沙量同步减少,水沙关系也发生变化,单位径流量的输沙量明显减少;沙漠宽谷段径流量减幅沿程不断增加而输沙量减幅沿程变化不大,水沙年内分配较基准期发生倒置,来沙系数不断减小;灌区引水引沙、水土保持措施、水库拦沙、支流来水来沙、水库调蓄及河道冲淤是沙漠宽谷段水沙变化的主要影响因子;经济社会发展用水对沙漠宽谷段径流量减少的作用最大,贡献率为81%,其次是水库蓄泄量,占15%以上;水库拦沙对头道拐输沙量减少的贡献率最大,占41%,其次是支流水土保持措施,贡献率约占13%,入黄风沙减少的贡献率并不大,约为6%,而河道淤积量、灌区引沙量较基准期都是减少的,贡献率分别约为-41%和-8%;近10多年来降雨等自然因素对水沙变化的作用相对不大,起主要作用的是水库运用、水土保持、经济社会发展等人类活动因素。 相似文献
8.
While studies on gravel mantled and mixed alluvial bedrock rivers have increased in recent decades, few field studies have focused on spatial distributions of bedrock and alluvial reaches and differences between reach types. The objective of this work is to identify the spatial distribution of alluvial and bedrock reaches in the Upper Guadalupe River. We compare reach length, channel and floodplain width, sinuosity, bar length and spacing, bar surface grain size, and slope in alluvial and bedrock reaches to identify whether major differences exist between channel reach types. We find that local disturbances, interaction of the channel and valley sides, variation in lithology, and regional structural control contribute to the distribution of bedrock reaches in the largely alluvial channel. Alluvial and bedrock channel reaches in the Upper Guadalupe River are similar, particularly with respect to the distribution of gravel bars, surface grain size distributions of bars, and channel slope and width. Our observations suggest that the fluvial system has adjusted to changes in base level associated with the Balcones Escarpment Fault Zone by phased incision into alluvial sediment and the underlying bedrock, essentially shifting from a fully alluvial river to a mixed alluvial bedrock river. 相似文献
9.
劳动力转移的行为和经历对贫困农（牧）户的生计产生了并继续产生着复杂而深远的影响,并构成了留守家庭成员进行新的生计选择的背景和前提条件。在资本变动和要素约束下,西部民族地区农（牧）户进行着不同的生产决策,并形成不同类型的生计策略。以甘南牧区为例,通过解析劳动力转移的特征变量,总结典型的劳动力转移农（牧）户家庭主要的生计策略模式,揭示了甘南牧区劳动力转移对留守农（牧）户生计策略选择的作用关系,并得出相应的结论。结果表明：转移劳动力文化水平、劳动力转移的外出时间、务工去向与转移劳动力工种类型在一定程度上影响了留守农（牧）户生计策略的选择。这可为西部民族地区政府部门制定科学、合理、可持续的劳动力资源利用政策,促进当地农（牧）户生计的可持续发展提供参考依据。 相似文献
10.
Tin mining carried out on the Jos Plateau since the beginning of the last century has disturbed some 320 km2 of agricultural land. Formal attempts at reclamation of this land failed, but local farmers have developed a successful informal strategy for reclamation. This paper reports on a study undertaken to comprehend the farmers'informal' approach to soil fertility management. Their soil fertility management practices centre on the use of a complex combination of traditional organic manures and 'modern' inorganic fertilizers that they have developed entirely on the basis of experimentation. A central focus of this paper is therefore the empirical knowledge base of the farmers and an assessment of any underlying scientific explanations for their strategies, including an analysis of their assertion that different brands of NPK fertilizers differ in their nutrient value. This discussion is followed by a consideration of the difficulties in accessing and understanding empirical knowledge. It is concluded that farmers' knowledge and understanding of the values of different fertilizers and manures does have a scientific basis. It is argued that for further agricultural development to take place on the Jos Plateau, there must be synergy between farmers' empirical knowledge (which has led to the development of successful and effective soil fertility management strategies, unlike the attempts of the local 'scientific' communities) and scientific knowledge (which can identify health and environmental hazards which may not be immediately visible to farmers). 相似文献
11.
气候变化对生态脆弱区以自然资源为生计基础的农户产生了严重影响,急需寻求有效的适应策略。以地处青藏高原东缘的甘南高原为研究区,基于1963-2013年气象数据分析甘南高原气候变化趋势,采用入户调查数据分析了气候变化对农户生计的影响及农户采取的适应策略,并利用多元线性回归模型和多项logistic回归模型分析了影响农户适应策略选择的因素。结果显示：① 近50年甘南高原气温呈增加趋势,倾向率为0.23 ℃/10 a,降水呈减少趋势,倾向率为-5.21 mm/10a,63.45%的农户认为气候变化对其生计带来了严重影响;② 甘南高原农户的适应策略多样化指数为2.65,农户的人力资本、自然资本、金融资本及其对气候变化的严重性感知、适应效能感知及自我效能感知与适应策略多样化程度呈显著正相关;③ 甘南高原65.30%的农户采取各种组合型策略应对气候变化,尤以采取扩张+调整型组合策略的农户为多,农户的人力资本是影响其适应策略选择的最显著因素,社会资本与气候变化风险感知的影响次之,金融资本及气候变化适应效能感知的影响最弱。最后,提出提高农户适应气候变化能力的对策建议。 相似文献
12.
Transects of surface sediment samples were taken in 4 lakes from the Sylvania Wilderness Area, Upper Peninsula of Michigan. These surface samples were compared with diatom samples from a core taken in the Northwest basin of Crooked Lake, also from the Sylvania Wilderness Area. Weighted Averaging calibration was used to reconstruct lake depths in Crooked Lake using the diatom microfossils from the core and the surface samples to infer past lake depth. During the early Holocene the lake was dominated by planktonic species and diatom-inferred water depth was large – approx. 13 m. At about 6700 BP inferred water depth was 2 m and samples were dominated by Fragilaria construens var. venter – a species characteristic of shallow parts of the surface sample transects. From 6700 to 5000 BP reconstructed water level was at its shallowest. From 5000 to 3000 BP it increased. This rise in water level was marked by increasing abundances of Aulacoseira ambigua and occurred at the same time increasing percentages of hemlock pollen indicate increasing available moisture. Modern water depth was reached about 3000 BP. The water level changes at Crooked Lake are consistent with regional climate changes in the Upper Midwest during the Holocene. The lake was shallowest during the mid-Holocene warm period documented by other investigators. It deepened as the Midwestern climate became cooler and wetter during the late Holocene. 相似文献
13.
The aim of the study is the analysis of runoff and water quality changes in the Upper Oder River Basin above the Krapkowice gauging station (catchment area A = 10 720.6 km2).The issue of water quality is of particular importance to Poland, which has comparatively poor water resources compared with many countries of the European Union (EU). What is more, large pollutant loads in the upper course of the Oder pose huge problems for water consumers and users in its middle and lower course (including Germany) and pollute the Baltic Sea.Changes in 7 indices of water pollution, including BOD5 and COD (synthetic indices), sulphates, chlorides and suspended matter (mineral substances) and nitrates and phosphates (biogenic substances), were investigated for 8 monitoring sites. The study spans the period before and after political transformation in Poland and the Czech Republic, which significantly altered the economies of these countries. In addition, the patterns of runoff changes were analysed at 3 gauging stations: Chałupki, Krzyżanowice and Miedonia, which were also water quality monitoring points. The analysis encompassed 2 periods: 1970–2000 and 1991–2000.The results demonstrated that poor water quality in the Oder improved significantly during the 1990s, as the result of closure of many industries and plants, improvement of sewage treatment and noticeable increases in runoff causing greater dilution of pollutants.As the EU Water Framework Directive is implemented, better water and sewage management can be expected that will contribute to further improvement of water quality in the Oder. However, problems that remain to be solved are the issues of saline mine waters and surface washings and the long-term accumulation of many hazardous substances in bottom sediments in rivers and reservoirs. 相似文献
14.
利用2015年8月至2016年7月在印度河上游流域Bagrot山谷降水稳定同位素（δ18O和δD）观测结果以及当地气象资料,利用同位素示踪及统计分析方法,并结合HYSPLIT模型,对研究区降水稳定同位素变化特征、大气水线以及水汽来源进行了分析。结果表明,观测期间Bagrot山谷降水稳定同位素的季节变化明显,δ18O与δD秋冬季偏低,春夏季偏高,且与气温变化一致,存在显著的温度效应,而降水量效应不明显。而且发现,研究区局地大气水线截距和斜率均低于全球的,反映了降水过程中云下二次蒸发作用较为强烈,特别是,不同的降水形态导致该研究区局地大气水线的斜率和截距不同。当液态降水（降雨）发生时,由于在较为干旱的气候环境下,雨滴在降落的过程中受到二次蒸发相对较强,使得局地大气水线的斜率和截距偏低;而当固态降水（降雪）发生时,由于温度较低,受再循环水汽和二次蒸发的影响较小,导致局地大气水线的斜率和截距均偏高。Bagrot山谷及其周边地区,从南到北局地大气水线的斜率相差不大,而其截距总体上随着纬度升高而降低,可能与云下二次蒸发导致稳定同位素发生的不平衡分馏逐渐强烈有关。通过Bagrot山谷站点降水稳定同位素观测结果并结合HYSPLIT模型的后向追踪,研究还发现,研究区全年主要受西风环流以及局地环流的影响。但与研究区以北的临近站点（慕士塔格、和田等）相比有所不同,由于Bagrot山谷位置更靠南,其仍然偶尔受到来自南方的海洋性水汽影响。这一研究结果可能对该地区树轮稳定同位素记录的解译具有一定的指示意义。 相似文献
15.
The aim of this Q methodology study was to identify perceptions of farmers and agricultural specialists toward agricultural water poverty concept and its causes in Marvdasht County, Iran. Seventy five participants completed the Q sort procedure. Data analysis identified seven types of perceptions toward agricultural water poverty: Management-adherents, Adaptive-adherents, Fatalists, Support-seekers, Farmer blamer Pessimists, Technocratic Realists and Optimists. The first four types of perceptions were dominated by farmers and the last three by agricultural specialists. These different perspectives indicated that various individuals think differently about the nature, causes, effects and permanency of agricultural water poverty. Understanding the multiple meaning systems of agricultural water poverty for decision and policy makers will be critical as they may provide the basis for the development of more appropriate strategies to mitigate water poverty in agricultural sector. 相似文献
16.
长江上游包括青藏高原东南部、秦巴山地、四川盆地与云贵高原部分地区,在地理、地貌、气候、生物多样性方面都表现得极为复杂和丰富多彩,在世界山地中也占有举足轻重的位置。特别是复杂多样的山地垂直带谱更是欧亚大陆乃至世界山地垂直带研究中至关重要的组成部分。在地学信息图谱和数字山地垂直带体系的基础上,本文系统地收集和分析了长江上游共50个山地垂直带谱所体现的空间规律,河源区、横断山区、秦巴山区及贵州高原的垂直带谱类型多样并各具特色,且在经度和纬度方向又具有统一的分布规律,如雪线、林线、针叶林及阔叶林等的分布界线变化规律比较符合二次曲线规律,验证了大陆尺度上山地垂直带二次曲线模式假说。另外,山地垂直带分布规律又具有尺度效应,中小尺度上地形的影响作用表现得极为显著。 相似文献
17.
澜沧江-湄公河重金属污染评价及大坝影响(英文) 总被引：1，自引：1，他引：0
The resource development and changes of hydrological regime,sediment and water quality in the Mekong River basin have attracted great attentions.This research aimed to enhance the study on transboundary pollution of heavy metals in this international river.In this study,eight sampling sites were selected to collect the bed sand samples along the mainstream of the Mekong River.In addition,the contents of 5 heavy metal elements and their spatial variability along the mainstream of the river were analyzed.The geoaccumulation index(I geo) and potential ecological risk analysis were employed to assess heavy metal pollution status in the mainstream of the Mekong River.The results show that the average content of the heavy metal elements Zn is 91.43 mg/kg,Pb is 41.85 mg/kg,and As is 21.84 mg/kg in the bed sands of the Upper Mekong River,which are higher than those(Zn 68.17 mg/kg,Pb 28.22 mg/kg,As 14.97 mg/kg) in the Lower Mekong.The average content of Cr in the Lower Mekong is 418.86 mg/kg,higher than that in the Upper Mekong(42.19 mg/kg).Luang Prabang has a very high Cr concentration with 762.93 mg/kg and Pakse with 422.90 mg/kg.The concentration of Cu in all of the 8 sampling sites is similar,except for in Jiajiu with 11.70 mg/kg and Jiebei with 7.00 mg/kg.The results of the geoaccumulation index reveal that contaminations caused by Zn and Pb while Pb and As are more than those by Zn in Upper Mekong.Cr is the primary pollutant in the Lower Mekong,especially at Luang Prabang and Pakse.Slight pollution with As also occurs in Pakse.The potential ecological risk index indicates that the potential ecological risk of heavy metals in the mainstream of the Mekong River is low.We argue that the pollution of water quality and contamination of heavy metals in bed sediment caused by mining of mineral resources or geochemical background values in the Mekong is not transmitted from the Upper to the Lower Mekong because of the reservoir sedimentation and dilution along the river. 相似文献
18.
长江上游山区聚落与水土保持的耦合机制 总被引：2，自引：0，他引：2
运用地理学、生态学和物理学的理论，从全新的角度对长江上游山区聚落形成的环境机制进行了系统的分析，提出山区聚落与水土保持之间存在的内在联系：1．山区聚落场所地处山体的自然截流部位，山区耕地的数量和质量是人类聚落对山地坡面过程中水、土资源截流效果的指示器，截留的规模决定聚落规模；2．小流域综合治理是一个完整的截流或节流体系，水土保持的本质就是对山地坡面过程截留；3．通过水土保持，人类获得赖以生存的物质和能量。因此，水土保持是山区聚落生态建设的基础工程，是链接人口、资源与环境协调发展的纽带，沟通人文聚落与自然环境和谐共处的桥梁。 相似文献
19.
社会—生态系统视角下农户对禁牧政策的适应性——以宁夏盐池县为例 总被引：2，自引：2，他引：0
为了保护草原生态环境,2002年起国家全面实施“退牧还草”工程,在草原破坏严重的地区实施禁牧政策。政策实施后,草地生态明显恢复。作为草原最主要的经济活动主体和禁牧政策的最直接承受者,农户对政策的适应性直接影响政策的顺利进行以及生态环境恢复的可持续性。基于宁夏盐池县入户调查资料,研究了不同类型农户对禁牧政策的生态环境效应感知以及对禁牧政策适应能力感知,分析了不同类型农户对禁牧政策的应对策略,探讨了影响农户适应策略选择的主要因素。结果表明：（1）盐池县社会-生态系统尚处于不理想的系统稳态,生态系统恢复明显,但社会系统的适应性较低。农户普遍认为禁牧政策实施对生态环境有很大的改善,但对禁牧政策满意度感知处于中等水平,对禁牧政策适应能力的感知处于较低水平。由于生计方式和收入水平的差异,不同类型农户对禁牧政策的适应性感知差异较大。（2）不同类型农户采取不同适应策略应对禁牧政策实施造成的影响。纯农户适应策略以收缩型为主,兼业户和非农户以调节型为主,低收入和中等收入农户以收缩型为主,高收入农户以调节型为主。（3）农户对禁牧政策的适应成本、自我效能和农户拥有的人力资本、金融资本是影响农户适应性策略类型选择的主要因素。 相似文献
20.
This study provides a unique examination of Amish farmers’ awareness of water quality issues and their attitudes toward and use of agricultural conservation practices compared with small non-Amish farmers in Northeastern Indiana. There is minimal research about the conservation beliefs and behaviors of this growing and highly diverse ethnoreligious minority, who have faith-based technological restrictions and are often hesitant to work with community outsiders, especially the government. We find that, compared with non-Amish farmers, Amish farmers have limited awareness of the linkages between common agricultural practices and broader water quality problems and lower levels of adoption of conservation practices, with the exception of cover crops. This information is essential for conservation practitioners who need to work with a diverse range of agricultural producers to increase the uptake of conservation practices that address critical water quality concerns. 相似文献