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1.
Sandbars are of vital ecological and environmental significance, which however, have been intensively influenced by human activities. Morphodynamic processes of sandbars along the Yichang-Chenglingji Reach of the Changjiang River, the channel immediately downstream of the Three Gorges Dam(TGD), are assessed based on remote sensing images between 2000 and 2016. It can be found that the entire area of sandbars reduces drastically by 19.23% from 149.04 km~2 in 2003 to 120.38 km~2 in 2016, accompanied with an increase in water surface width. Owing to differences in sediment grain size and anti-erosion capacity, sandbar area in the upstream sandy gravel reach(Yichang-Dabujie) and downstream sandy reach(Dabujie-Chenglingji) respectively decreases by 45.94%(from 20.79 km~2 to 11.24 km~2) and 14.93%(from 128.30 km~2 to 109.14 km~2). Furtherly, morphological evolutions of sandbars are affected by channel type: in straight-microbend channel, mid-channel sandbars exhibit downstream moving while maintaining the basic profile; in meandering channel, point sandbars show erosion and deposition in convex and concave bank respectively, with mid-channel sandbars distributing sporadically; in bending-branching channel, point sandbars experience erosion and move downstream while mid-channel sandbars show erosion in the head part along with retreating outline. We document that the primary mechanism of sandbars shrinkages along the Yichang-Chenglingji Reach can be attributed to TGD induced suspended sediment concentration decreasing and increasing in unsaturation of sediment carrying capacity. Additionally, channel type can affect the morphological evolution of sandbars. Along the Yichang-Chenglingji Reach, sandbars in straight-microbend channel are more affected by water flow than that in bending-branching channel.  相似文献   

2.
The spatio-temporal pattern of the global water resource has significantly changed with climate change and intensified human activities. The regional economy and ecological environment are highly affected by terrestrial water storage(TWS), especially in arid areas. To investigate the response relationships between TWS and changing environments(climate change and human activities) in Central Asia, we used the Gravity Recovery and Climate Experiment(GRACE) data, Climatic Research Unit(CRU) climate data and Moderate Resolution Imaging Spectroradiometer(MODIS) remote sensing data products(MOD16A2, MOD13A3 and MCD12Q1) from 2003 to 2013, as well as the slope and Pearson correlation analysis methods. Results indicate that:(1) TWS in about 77% of the study area decreased from 2003 to 2013. The total change volume of TWS is about 2915.6 × 108 m~3. The areas of decreased TWS are mainly distributed in the middle of Central Asia, while the areas of increased TWS are concentrated in the middle-altitude regions of the Kazakhstan hills and Tarim Basin.(2) TWS in about 5.91% of areas, mainly distributed in the mountain and piedmont zones, is significantly positively correlated with precipitation, while only 3.78% of areas show significant correlation between TWS and temperature. If the response time was delayed by three months, there would be a very good correlation between temperature and TWS.(3) There is a significantly positive relationship between TWS and Normalized Difference Vegetation Index(NDVI) in 13.35% of the study area.(4) The area of significantly positive correlation between TWS and evapotranspiration is about 31.87%, mainly situated in mountainous areas and northwestern Kazakhstan. The reduction of regional TWS is related to precipitation more than evaporation. Increasing farmland area may explain why some areas show increasing precipitation and decreasing evapotranspiration.(5) The influences of land use on TWS are still not very clear. This study could provide scientific data useful for the estimation of changes in TWS with climate change and human activities.  相似文献   

3.
气候变化对水文水资源影响的研究进展   总被引:20,自引:1,他引:19  
气候变化成为21 世纪世界最重大的环境问题之一,愈来愈引起国际社会和各国政府的重视和关注。研究 气候变化对水文水资源的影响,对于理解和解决可能引起的与工业、农业、城市发展等经济领域密切相关的水文水 资源系统的规划管理、开发利用、运行管理、环境保护、生态平衡等问题具有重要的理论意义和现实意义。本文主要 从研究方法、气候变化情景的生成技术、与水文模型接口技术和水文模拟技术等几个方面综合概述了气候变化对 水文水资源的影响,同时提出存在的问题与展望。  相似文献   

4.
目前,关于里海的两个主要问题是水位变化及其生态条件。历史上,里海的海水入侵和衰退对该区域的生活和生产有很大影响。应用地质数据、历史数据和考古数据,以及观测数据,本文对地质历史时期里海水位的变化、年度和季度变化以及短期的波动进行了研究。文章对解释里海水位波动的两种不同的方法进行了论述,并认为里海水位变化是受地质、水文气候和水量平衡以及人类活动等因素的影响的多级过程,其中主要影响因素为水文气候的变化。  相似文献   

5.
气候变化的海拔依赖性在世界上大多数山脉地区已有报道,但导致这种变异的原因尚不明确。本研究利用中国四个不同的观测和再分析资料数据集,主要研究气候变暖对海拔的依赖性,结果表明:无论是在青藏高原地区还是中国其他地区,气候变暖的程度与海拔高度的一致性并不明显。但是,气候变暖与不同海拔水汽的变异具有很好的相关性。比湿度较低时,气温变化随比湿度的增加而升高;当比湿度上升到一定值,气温变化则随比湿度的增加而下降。而地表温度变化的最大值出现在比湿度2.0–3.0 g kg~(-1)范围内。因此,本研究揭示了水汽对气候变暖的海拔依赖性起到调节作用。  相似文献   

6.
The varied altitudinal gradient of climate and vegetation is further complicated by mass elevation effect(MEE), especially in high and extensive mountain regions. However, this effect and its implications for mountain altitudinal belts have not been well studied until recently. This paper provides an overview of the research carried out in the past 5 years. MEE is virtually the heating effect of mountain massifs and can be defined as the temperature difference on a given elevation between inside and outside of a mountain mass. It can be digitally modelled with three factors of intra-mountain base elevation(MBE), latitude and hygrometric continentality; MBE usually acts as the primary factor for the magnitude of MEE and, to a great extent, could represent MEE. MEE leads to higher treelines in the interior than in the outside of mountain masses. It makes montane forests to grow at 4800–4900 m and snowlines to develop at about 6000 m in the southern Tibetan Plateau and the central Andes, and large areas of forests to live above 3500 m in a lot of high mountains of the world. The altitudinal distribution of global treelines can be modelled with high precision when taking into account MEE and the result shows that MEE contributes the most to treeline distribution pattern. Without MEE, forests could only develop upmost to about 3500 m above sea level and the world ecological pattern would be much simpler. The quantification of MEE should be further improved with higher resolution data and its global implications are to be further revealed.  相似文献   

7.
Energy is consumed at every stage of the cycle of water production, distribution, end use, and recycled water treatment. Understanding the nexus of energy and water may help to minimize energy and water consumption and reduce environmental emissions. However, the interlinkages between water and energy have not received adequate attention. To address this gap, this paper disaggregates and quantifies the energy consumption of the entire water cycle process in Beijing. The results of this study show that total energy consumption by water production, treatment and distribution, end use, and recycled water reuse amounts to 55.6 billion kWh of electricity in 2015, or about 33% of the total urban energy usage. While water supply amount increased by only 10% from 2005 to 2015, the related energy consumption increased by 215% due to water supply structural change. The Beijing municipal government plans to implement many water saving measures in the area from 2016 to 2020, however, these policies will increase energy consumption by 74 million kWh in Beijing. This study responds to the urgent need for research on the synergies between energy and water. In order to achieve the goal of low-energy water utilization in the future, water and energy should be integrated in planning and management.  相似文献   

8.
In this study, the spatial distribution and changing trends of agricultural heat and precipitation resources in Northeast China were analyzed to explore the impacts of future climate changes on agroclimatic resources in the region. This research is based on the output meteorological data from the regional climate model system for Northeast China from 2005 to 2099, under low and high radiative forcing scenarios RCP4.5(low emission scenario) and RCP8.5(high emission scenario) as proposed in IPCC AR5. Model outputs under the baseline scenario, and RCP4.5 and RCP8.5 scenarios were assimilated with observed data from 91 meteorological stations in Northeast China from 1961 to 2010 to perform the analyses. The results indicate that:(1) The spatial distribution of temperature decreases from south to north, and the temperature is projected to increase in all regions, especially under a high emission scenario. The average annual temperature under the baseline scenario is 7.70°C, and the average annual temperatures under RCP4.5 and RCP8.5 are 9.67°C and 10.66°C, respectively. Other agricultural heat resources change in accordance with temperature changes. Specifically, the first day with temperatures ≥10°C arrives 3 to 4 d earlier, the first frost date is delayed by 2 to 6 d, and the duration of the growing season is lengthened by 4 to 10 d, and the accumulated temperature increases by 400 to 700°C·d. Water resources exhibit slight but not significant increases.(2) While the historical temperature increase rate is 0.35°C/10 a, the rate of future temperature increase is the highest under the RCP8.5 scenario at 0.48°C/10 a, compared to 0.19°C/10 a under the RCP4.5 scenario. In the later part of this century, the trend of temperature increase is significantly faster under the RCP8.5 scenario than under the RCP4.5 scenario, with faster increases in the northern region. Other agricultural heat resources exhibit similar trends as temperature, but with different specific spatial distributions. Precipitation in the growing season generally shows an increasing but insignificant trend in the future, with relatively large yearly fluctuations. Precipitation in the eastern region is projected to increase, while a decrease is expected in the western region. The future climate in Northeast China will change towards higher temperature and humidity. The heat resource will increase globally, however its disparity with the change in precipitation may negatively affect agricultural activities.  相似文献   

9.
全球气候变化导致全球海洋酸化、冰雪融化、气温持续升高、极端天气发生频率增多,进而对社会经济系统产生深远影响。随着气候变化的加剧,抵抗气候风险能力较强的工业领域也遭受了严重的损失。目前,工业领域的脆弱性不断加深,工业经济损失的绝对量也在不断增长,定量评估工业经济损失是制定应对气候变化政策的重要依据,通过梳理当前的研究进展,可以为工业经济的评估提供思路和方法。因此,本文对工业领域受气候变化影响的正负面效应进行概述,发现不同工业部门受到气候变化的影响略有不同,部分区域的采矿业对气温升高的响应为正向,但风暴、干旱以及降雨会破坏采矿业的正常生产经营活动;制造业大多是室内作业,抵抗极端气候的能力相对较强,部分产业反应机制复杂;建筑业的损失多集中在间接损失,通过电力成本提高等反馈;电力、热力及水的生产和供应业在遭受极端气候时会出现传输供应损失,且作为碳排放最大的行业,其减排成本短期内会影响该部门的经济增长。工业部门为了应对气候变化付出了较大的适应和减缓成本,因此通过模型量化评估工业经济的损失,有利于制定合理的政策,保证工业经济平稳有序的增长。  相似文献   

10.
近年来,畜牧业的持续增长导致了内蒙古草原生态系统的严重退化。以往的放牧实验表明,放牧对全球植被类型存在着广泛的影响,但目前仍然缺乏研究来识别区域特定植被群落对放牧的响应。本文对内蒙古不同类型草地在不同放牧强度和放牧时长下的植被盖度(VC)、植被密度(PD)、总生物量(TB)、地上生物量(AGB)、地下生物量(UGB)和Shannon-Weaver指数(SI)进行了Meta分析。结果表明,放牧显著降低了VC、TB、AGB、UGB和PD值。放牧对内蒙古草原生物量产生的负面影响高于全球而低于全国平均水平。在中等放牧强度和时长条件下,内蒙古草甸草原TB值补偿性生长增加了40%。荒漠草原和草甸草原的SI与放牧强度呈负相关。放牧期间AGB、PD和SI的变化百分比与试验年的平均气温呈二次方关系。随着试验年年平均降水量的增加,放牧对UGB和SI的负面影响先减小后增大,放牧对VC的负面影响呈三次方关系。  相似文献   

11.
River basin reservoir construction affects water and sediment transport processes in downstream reaches. The downstream impact of the Three Gorges Projects(TGP) has started to become apparent:(1) reduction in flood duration and discharge, and significant reduction in sediment load. Although there was some restoration in downstream sediment load, the total amount did not exceed the pre-impoundment annual average;(2) in 2003–2014, the d 0.125 mm(coarse sand) load was restored to some degree, and to a maximum at Jianli Station, which was mainly at the pre-impoundment average. After restoration, erosion and deposition characteristics of the sediment was identical to that before impoundment. The degree of restoration during 2008–2014 was less than during 2003–2007;(3) after TGP impoundment, there was some restoration in d 0.125 mm(fine sand) sediment load, however, it was lower than the pre-impoundment average;(4) due to riverbed compensation, the d 0.125 mm sediment load recovered to a certain degree after impoundment, however, the total did not exceed 4400×10~4 t/y. This was mainly limited by flood duration and the average flow rate, and was less affected by upstream main stream, tributaries, or lakes. Restoration of d 0.125 mm suspended sediment was largely controlled by upstream main stream, tributaries, and lakes, as well as by riverbed compensation. Due to bed armoring, riverbed fine suspended sediment compensation capability was weakened;(5) during 2003–2007 and 2008–2014, Yichang to Zhicheng and upper Jingjiang experienced coarse and fine erosion,lower Jingjiang experienced coarse deposition and fine erosion, Hankou to Datong had coarse deposition and fine erosion, and Chenglingji and Hankou was characterized by coarse deposition and fine sand erosion in 2003–2007, and coarse and fine erosion in 2008–2014. This difference was controlled by flood duration and number at Luoshan Station.  相似文献   

12.
The special geography and human environment of the Qinghai-Tibet Plateau has created the unique hydrochemical characteristics of the region's natural water, which has been preserved in a largely natural state. However, as the intensity of anthropogenic activities in the region has continued to increase, the water environment and hydrochemical characteristics of the Qinghai-Tibet Plateau have altered. In this study, water samples from the western, southern, and northeastern border areas of the Qinghai-Tibet Plateau, where human activities are ongoing, were collected, analyzed, and measured. The regional differences and factors controlling them were also investigated. The key results were obtained as follows.(1) Differences in the physical properties and hydrochemical characteristics, and their controlling factors, occurred in the different boundary areas of the Qinghai-Tibet Plateau. These differences were mainly the consequence of the geographical environment and geological conditions.(2) The water quality was good and suitable for drinking, with most samples meeting GB(Chinese national) and WHO(World Health Organization) drinking water standards.(3) The chemical properties of water were mainly controlled by the weathering of carbonates and the dissolution of evaporative rocks, with the former the most influential.(4) The biological quality indicators of natural water in the border areas were far superior to GB and WHO drinking water standards.  相似文献   

13.
在全球对气候变暖和碳减排日益关注的背景下,研究外商直接投资对碳排放的影响具有重要意义。本文基于1990–2017年的数据,运用Johansen协整检验方法和误差修正模型实证检验了外商直接投资(FDI)对老挝碳排放的影响。实证结果显示:FDI与老挝碳排放具有长期的均衡关系;FDI增长在短期内将会增加老挝的碳排放,FDI与老挝碳排放的关系支持环境库兹涅茨曲线变化,即倒"U"型变化。中国是老挝最重要的外商投资国家,老挝是共建"绿色丝绸之路"的重要节点国家,中国在对老挝当前和未来的投资过程中应进一步加强生态环境保护,提升老挝资源环境承载力。  相似文献   

14.
本文在采用经济学分析方法,在理论上解析了农业劳动力非农就业对农地利用的影响。作为理性经济人的农民对劳动力在两个部门的配置和不同质量土地的利用方式上遵循收益最大化原则和"均衡原理"。非农收益较高、劳动力之间存在比较优势,其结果是农地经营的劳动力投入数量和质量降低。劳动力成为农户土地利用决策的主要约束条件,一方面,由于质量较好的土地仍然有较高的经营收益,所以农户不会放弃这些土地的经营,甚至采取集约化利用的方式;另一方面,质量较差的土地容易被粗放化利用,收益极低的土地容易被边际化。本文的分析为农业政策和生态建设政策提供了学术基础。农业劳动力非农就业且务农机会成本上升,将导致质量差的土地退出农业生产,这需要政府决策者应给予高度重视。  相似文献   

15.
Glaciers and snow are major constituents of solid water bodies in mountains; they can regulate the stability of local water sources. However, they are strongly affected by climate change. This study focused on the Tianshan Mountains, using glacier and snow datasets to analyse variations in glaciers, snow, water storage, and runoff. Three typical river basins(Aksu, Kaidou, and Urumqi Rivers) were selected to interpret the impacts of glacier and snow changes on regional water resources in the Tianshan Mountains. The results exhibited a nonlinear functional relationship between glacial retreat rate and area, demonstrating that small glacial retreat is more sensitive under climate change. Further, the glacial retreat rate at the low-middle elevation zone was seen to be faster than that at the high elevation zone. The regional average terrestrial water storage(TWS) decrease rate in the Tianshan Mountains was –0.7±1.53 cm/a during 2003–2015. The highest TWS deficit region was located in the central part of the Tianshan Mountains, which was closely related to sharp glacial retreats. The increases in glacier and snow meltwater led to an increase in runoff in the three typical river basins, especially that of the Aksu River(0.4×10~8 m~3/a). The decreasing and thinning of areas, and increasing equilibrium line altitude(ELV) of glaciers have been the major causes for the decrease in runoff in the three river basins since the mid-1990 s. Therefore, the results reveal the mechanisms causing the impacts of glaciers and snow reduction in mountains on regional water resources under climate change, and provide a reference for water resources management in the mountainous river basins.  相似文献   

16.
China's economy has undergone rapid transition and industrial restructuring. The term "urban industry" describes a particular type of industry within Chinese cities experiencing restructuring. Given the high percentage of industrial firms that have either closed or relocated from city centres to the urban fringe and beyond, emergent global cities such as Shanghai, are implementing strategies for local economic and urban development, which involve urban industrial upgrading numerous firms in the city centre and urban fringe. This study aims to analyze the location patterns of seven urban industrial sectors within the Shanghai urban region using 2008 micro-geography data. To avoid Modifiable Areal Unit Problem(MAUP) issue, four distance-based measures including nearest neighbourhood analysis, Kernel density estimation, K-function and co-location quotient have been extensively applied to analyze and compare the concentration and co-location between the seven sectors. The results reveal disparate patterns varying with distance and interesting co-location as well. The results are as follows: the city centre and the urban fringe have the highest intensity of urban industrial firms, but the zones with 20–30 km from the city centre is a watershed for most categories; the degree of concentration varies with distance, weaker at shorter distance, increasing up to the maximum distance of 30 km and then decreasing until 50 km; for all urban industries, there are three types of patterns, mixture of clustered, random and dispersed distribution at a varied range of distances. Consequently, this paper argues that the location pattern of urban industry reflects the stage-specific industrial restructuring and spatial transformation, conditioned by sustainability objectives.  相似文献   

17.
退耕还林的目标之一是减贫,因此退耕还林对农户收入的影响备受关注。本文研究了退耕还林实施13年以后,该工程对农户收入的影响。基于四川省岷江上游2012年329个农户的调查资料,结合分位数回归和多元线性回归模型分析退耕还林的当前影响。同时,比较了退耕户和非退耕户的社会和人口学特征。结果表明,退耕户和非退耕户的社会和人口学特征不存在明显差别。2012年,退耕还林对各个收入水平农户的收入都没有产生明显的影响,对减贫没有产生明显影响。这说明,到2012年岷江上游退耕还林工程已经不能明显增加农户的收入,建议调整实施方案以兼顾生态保护和扶贫。  相似文献   

18.
构建城市生产率评价指数,运用Moran指数和LISA集群图对2008–2018年期间我国286个地级市生产性服务业集聚与城市生产率水平的空间集群效应进行了分析,结果发现我国生产性服务业集聚和城市生产率在空间上高度相关,城市生产性服务业集聚的高值区同样是生产率的高值集聚区,而生产性服务业集聚水平较低的城市其生产率也较低。进一步采用空间计量模型实证检验了生产性服务业集聚对我国城市生产率的作用效应,研究结果显示,生产性服务业集聚能有效提高我国城市生产率,但不同板块城市的生产性服务业集聚对生产率的影响存在较大差异,生产性服务业专业化集聚对东部地区的城市生产率影响效应更大,对中部、东北、西部的影响系数相对较小,生产性服务业多样化集聚对城市生产率的正向效应在西部、中部和东北部地区较为明显,但对东部城市的促进作用较小。  相似文献   

19.
围栏封育是西藏政府用来保护生态环境的重要举措之一。这项工程不仅会改变围栏区域的植被特征,也会影响藏北地区的地表热量平衡。关于现行的围栏封育工程对当地热量平衡影响的信息却很少,我们从当地的农牧局收集了藏北各县围栏的范围坐标,将其空间数据化,并基于卫星遥感数据和地表热量平衡系统的模型计算,来探究围栏封育后地表温度、地表反照率和蒸散的变化情况。这些变化会影响藏北高原的地表热量平衡和陆表温度。研究发现日间和夜间的陆表温度变化趋势呈现出非对称日变化,日间的升温幅度大于夜间的降温幅度;反照率的增加导致藏北高原吸收的短波辐射减少,引起陆表温度降低,中部地区降温幅度最大,达到了每10年下降0.4?0.5℃;东部地区降温幅度最小,为每10年下降0.1?0.2℃;蒸散的减少导致潜热能量输送减少,引起的地表温度升高最大的地区在中部地区,升温幅度大于每10年上升1℃,升温最小的地区在西北部,升温幅度为每10年上升0?0.1℃。  相似文献   

20.
The complex relationship between the Yangtze River and Poyang Lake controls the exchange of water and sediment between the two,and exerts effects on water resources,flooding,shipping,and the ecological environment.The theory of energy is applied in this paper to investigate the physical mechanisms that determine the nature of the contact between the Yangtze River and Poyang Lake and to establish an energy differenceindex to quantify the interactions between the two systems.Data show that Fe values for this interaction have increased since the 1950s,indicating a weakening in the river effect while the lake effect has been enhanced.Enclosure of the Three Gorges Reservoir(TGR)has also significantly influenced the relationship between the river and the lake by further reducing the impacts of the Yangtze River.The river effect also increases slightly during the dry season,and decreases significantly at the end of the flooding period,while interactions between the two to some extent influence the development of droughts and floods within the lake area.Data show that when the flow of the five rivers within this area is significant and a blocking effect due to the Yangtze River is also clearly apparent,floods occur easily;in contrast,when the opposite is true and the flow of the five rivers is small,and the Yangtze River can accommodate the flow,droughts occur frequently.Construction and enclosure of the TGR also means that the lake area is prone to droughts during September and October.  相似文献   

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