共查询到19条相似文献，搜索用时 171 毫秒
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现代的日地物理学是把太阳－行星际空间－地球作为一个统一的体系，研究体系中各层次的动力学过程及各层次间的相互耦合作用。太阳活动是引起该系统变化和扰动的主要源，太阳活动的研究在日地物理研究中受到特别的重视。太阳活动现象依其变化速率可被分成缓变型与爆发型两类。本文叙述日地系统学中缓变型大阳活动的研究进展，并且讨论它在９０年代所面临的问题。 相似文献
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黄河流域关中盆地史前大洪水研究——以周原漆水河谷地为例 总被引：3，自引：0，他引：3
史前大洪水是中国古代史研究不能回避的重大问题.通过野外考察研究,在关中盆地西部漆水河中游沿河谷阶地上,发现典型的全新世大洪水滞流沉积层,它们覆盖着龙山文化聚落—浒西庄遗址文化层.利用地层分析、磁化率和粒度成分测定、文化遗物鉴定、OSL和14C技术断代,证明在距今4300～4000年前,关中盆地经历了一个洪水期,发生了多次大洪水事件.在大洪水发生期间,漆水河谷沿河第二级阶地面以浒西庄遗址为代表的龙山文化早期（庙底沟二期）聚落和田地被淹没,同时,在更高阶地和黄土台原边沿地带,以赵家崖遗址为代表的龙山文化晚期（客省庄二期）聚落得到迅速发展.结合在泾河和北洛河河谷发现的史前大洪水的沉积学证据,揭示出了龙山文化晚期关中盆地普遍发生大洪水的客观事实.同时,也发现在距今3100～3000年前,即先周在周原＂岐邑＂时期,关中盆地漆水河谷和渭河河谷也曾经发生多次大洪水.这些研究成果,对于揭示区域气候水文变化对于全球变化的响应规律,阐明大洪水事件对于我国远古文化突变和社会转折的影响,具有十分重要的科学意义. 相似文献
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Zbigniew W. KUNDZEWICZ 《湖泊科学》2003,15(Z1):155-165
近期在很多地方洪水越来越频繁且破坏性更大.20世纪90年代以来全球大洪水造成社会经济财产巨大损失,30次大洪水每次总损失额均超过10×108美元.1990-1998年的9a时间的大洪水爆发的次数比1950-1985年期间Ma大洪水次数还要多.近年来中国大陆也遭受了若干重大洪水灾害(包括1996和1998年两次大的财产损失).与气候变率和变化相关的洪水灾害和易爆发程度的显著增加,这是当前最紧迫的问题.随着气温升高大气中持水量也增加,因此大规模强度的降水的可能性也增大.己观测到高而集中的大降水事件而且这种趋势在未来气候变暖条件下可能增加,大降水事件的增加是洪灾增加的必然条件.当然也有一些其它的非气象因素加剧洪灾的发生,比如土地利用变化(森林砍伐、城市化)导致土壤持水能力下降,径流系数增加;此外,人类占据了洪泛区,可能导致洪水损失增大.另外物质财富在洪泛区的积聚也导致了洪灾损失增加.毫无疑问,由于人类活动和气候的共同作用,未来洪水风险在很多地方可能增加.洪水易爆发程度被认为是暴露系数和调节能力的函数,而且在许多地方所有这些变量都可能增加.而随着暴露系数比人类调节能力增加快,因此洪水易爆发程度增大.然而,要完全从径流变化中区分气候因素导致的强烈自然变率还是直接的人为环境变化是很困难的.由于使用不同的假定情景和不同的气候模型,得到的未来环境的预测结果差异也很大.IPCC第三次评估报告中广泛讨论了气候变化与洪水之间的关系.IPCC第三次评估报告警告说,在东亚季风区非常湿润的季风季节出现的可能性非常大,进而会导致相应地区洪水风险增加.本文总结了迄今为此可收集到的有关长江洪水的资料.利用一些案例来分析研究未来假定情景下气候对水文的影响,并对东亚地区的模拟结果进行了讨论. 相似文献
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新安江模型在资料匮乏的长江中下游山区中小流域洪水预报应用 总被引：1，自引：0，他引：1
水文资料匮乏流域的洪水预报(PUBs)是水文科学与工程中一个尚未解决的重大挑战.中国湿润山区中小流域大多是水文资料匮乏的流域,在此地区进行洪水预报的重要手段之一就是水文模型参数的估计.对基于参数物理意义的估算方法(以下简称物理估算法)及两种区域化方法进行了研究,将其用于新安江模型参数的估算及移植.皖南山区的29个中小流域被选作水文资料丰富的测量流域,鄂西山区的3个中小流域被视为水文资料匮乏的目标流域,目的是研究目标流域与测量流域空间位置较远但物理条件相似时,区域化等方法是否可以有效估计模型参数.结果表明,即使目标流域与测量流域空间距离较远,区域化及物理估算法也能一定程度上减少参数估计导致的模型效率损失,且在研究区的最优参数估计方案为单流域物理相似法结合回归法及物理估算法.为长江中下游资料匮乏的山区中小流域提出了可行的新安江模型参数估计方案,为该地区的洪水预报提供指导. 相似文献
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1998年，长江流域发生了类似1954年的百年一遇全江性大洪水，1999年长江又发生了较大洪水。在上述背景下，长江中下游地区是否会发生中强震，需要进行认真的探讨。初步研究结果表明，长江大洪水之后3年内，鄂、湘沿江地区中经地震受长江大洪水的“耦合振荡”作用较大。 相似文献
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日地系统学中的太阳活动研究（Ⅱ）爆发型太阳活动—太阳耀斑 总被引：1，自引：0，他引：1
爆发型太阳活动是日地系统中重要的扰动源。本文介绍日地系统学中最剧烈的爆发型太阳活动－太阳耀斑的观测研究进展。综述了最近两个太阳周的地面与空间观测所得到的耀斑的物理图象和统计性质，简单讨论了空间观测设备的发展和面临的研究课题。 相似文献
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ENSO和长江大水对天文因子的响应研究 总被引：5，自引：1，他引：4
ENSO（厄尔尼诺和南方涛动的总称）对世界尺度的天气气候有影响,本文用概率论统计检验方法,查明长江大水与ENSO以及ENSO与天文因子的相关关系,并系统分析了三者之间的相关关系。结果表明:ENSO事件对天文物理主周期和天文特征有明显的响应,长江大水年对太阳活动特征、节气日的月相年变化和ENSO也有显著的响应关系。这些关系对长江大水的准确预测有重要价值。文中对天文物理因子对ENSO和大水的影响机理进行了探讨。 相似文献
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Flood hazard mapping using synthesis hydraulic and geomorphic properties at watershed scale 总被引：2，自引：1，他引：1
Alireza Motevalli Mehdi Vafakhah 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(7):1889-1900
The occurrence of natural phenomena such as floods has caused serious consequences for human societies. The simulation of flood hazard maps and its depth in a river is one of the most complex processes in hydrology. In fact both geomorphological and hydraulic procedures for deriving the flood hazard maps and depth are imperfect at watershed scale. In this study, a combination of both procedures, using a probabilistic approach is used. Flood inundation maps for 2-, 10-, 25-,50- and 100-return period floods using flood routine within HEC-RAS in combination of Arc-GIS and topographic wetness index (TWI) map were produced. TWI threshold was identified using a maximum likelihood method in order to produce flood prone areas and calibrated over the reach of Zirab City. The correlation between TWI threshold and the flood depth was carried out and simple linear regression developed for various return periods. The resulting regression model is used in order to create flood hazard maps with various return periods at watershed scale. 相似文献
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由于受到水文观测资料时间短的限制,目前难以认识百年遇机率的极端洪水.为此,本文根据19世纪末历史文献的洪水灾害记录,利用流域水文模型,对太湖1889洪水年的流域产流、入湖汇流等水文特征和过程进行模拟.本研究设计了三套模拟实验:首先在现代气候控制实验基础上对1988-2002年时间系列和特大洪水年进行水文模拟和模型率定校验;其次,采用长江下游19世纪末的气候观测资料驱动,对极端年份1889年逐日洪水过程模拟;最后,为减少1 a洪水年模拟的不确定性,还采用蒙特卡罗Bootstrap法模拟了15 a的流域气候场,在5475 d样本下进行特征年份的水文模拟.模拟结果表明,1889年洪水期间产流在当年6月底达到最大,1%频率的径流深达8.6 mm/d,95%CI的误差在-2.94～3.26 mm/d之间.汇入太湖径流同期达到最大,1%频率的洪水流量达到1286.9 m3/s,95%CI的误差在-128.3～165.7 m3/s之间.根据洪水Log-Normal概率分布,计算1889洪水年的重现期为149 a.经Bootstrap法对误差置信区的模拟,95%CI检验在70～175 a间的重现期可信.该研究为延长20世纪洪水序列、拓展对百年时间尺度的特大洪水的认识提供了动力学模拟方面的科学依据. 相似文献
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ABSTRACTWith the rapid economic development and urbanization in Taihu Basin (eastern China), the river system has decayed and the connectivity of rivers and lakes has weakened, resulting in frequent floods. The impact of changes in river system structure on hydrological processes in the plain river network area was analysed against a background of urbanization. An indicator system was built to describe the quantitative, morphological and spatial structure of the river system. Analysis of the change in annual average and extreme water levels revealed the influencing mechanism of the changes in river system structure on the hydrological processes. The results indicate a decreasing tendency in the density of the river system in the study area, with a reduction in water surface ratio by about 20% in the past 50 years. Since the 1960s, the maximum and annual average water levels have increased. The degree of change in the mean monthly, annual lowest and annual highest water levels was great, with that in the non-flood season being higher than in the flood season. The decrease in the number of rivers directly reduced the storage and adjustable capacity of the basin. 相似文献
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Assessing the influence of the Merzbacher Lake outburst floods on discharge using the hydrological model SWIM in the Aksu headwaters,Kyrgyzstan/NW China 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Glacial lake outburst floods (GLOF) often have a significant impact on downstream users. Including their effects in hydrological models, identifying past occurrences and assessing their potential impacts are challenges for hydrologists working in mountainous catchments. The regularly outbursting Merzbacher Lake is located in the headwaters of the Aksu River, the most important source of water discharge to the Tarim River, northwest China. Modelling its water resources and the evaluation of potential climate change impacts on river discharge are indispensable for projecting future water availability for the intensively cultivated river oases downstream of the Merzbacher Lake and along the Tarim River. The semi‐distributed hydrological model SWIM was calibrated to the outlet station Xiehela on the Kumarik River, by discharge the largest tributary to the Aksu River. The glacial lake outburst floods add to the difficulties of modelling this high‐mountain, heavily glaciated catchment with poor data coverage and quality. The aims of the study are to investigate the glacier lake outburst floods using a modelling tool. Results include a two‐step model calibration of the Kumarik catchment, an approach for the identification of the outburst floods using the measured gauge data and the modelling results and estimations of the outburst flood volumes. Results show that a catchment model can inform GLOF investigations by providing ‘normal’ (i.e. without the outburst floods) catchment discharge. The comparison of the simulated and observed discharge proves the occurrence of GLOFs and highlights the influences of the GLOFs on the downstream water balance. © 2013 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd. 相似文献
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Qiang Zhang Yongqin David Chen Tao Jiang Xiaohong Chen Zufa Liu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(7):1001-1011
Sound understanding of hydrological alterations and the underlying causes means too much for the water resource management
in the Pearl River Delta. Incision of river channels plays the key role in the hydrological alterations. As for the causes
behind the river channel incision, sand dredging within the river network of the Pearl River Delta is usually assumed to play
the overwhelming role in changes of geometric shapes of the river channels. Based on thorough analysis of well-collected data
of channel geometry, streamflow, sediment load and water level, this study exposes new findings, investigating possible underlying
causes behind the changes of the geometric shapes of the river channels at the Sanshui and Makou station. The results of this
study indicate: (1) different changing properties of the geometric shapes are identified at the Sanshui and Makou stations.
Larger magnitude of changes can be found in the river channel geometry of the cross section at the Sanshui station when compared
to that at the Makou station. Lower water level due to fast riverbed downcutting at the Sanshui station than that at the Makou
station is the major reason why the reallocation of streamflow occurred and hence the hydrological alterations over the Pearl
River Delta; (2) depletion of sediment load as a result of construction of water reservoirs in the middle and upper Pearl
River basin, sand dredging mainly in the Pearl River Delta and heavy floods all contribute much to the incision or deposition
of the riverbed. Regulations of erosion and siltation process of the river channel often alleviate the incision of the river
channels after a relatively long time span, and which makes it even harder to differentiate the factors causing the river
channel incision; (3) the intensifying urbanization in the lower Pearl River basin greatly alters the underlying surface properties,
which has the potential to shorten the recession of the flood event and may cause serious scouring processes and this role
of flash floods in the incision of the river channels can not be ignored. This study is of great scientific and practical
merits in improving human understanding of regulations of river channels and associated consequences with respect to hydrological
alterations and water resource management, particularly in the economically booming region of China. 相似文献
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Hyperconcentrated floods, with sediment concentrations higher than 200 kg/m3, occur frequently in the Yellow River and its tributaries on the Loess Plateau. This paper studies the fluvial hydraulics of hyperconcentrated floods by statistical analysis and comparison with low sediment concentration floods. The fluvial process induced by hyperconcentrated floods is extremely rapid. The river morphology may be altered more at a faster rate by one hyperconcentrated flood than by low sediment concentration floods over a decade. The vertical sediment concentration distribution in hyperconcentrated floods is homogeneous. The Darcy–Weisbach coefficient of hyperconcentrated floods varies with the Reynolds number in the same way as normal open channel flows but a representative viscosity is used to replace the viscosity, η. If the concentration is not extremely high and the Reynolds number is larger than 2000, the flow is turbulent and the Darcy–Weisbach coefficient for the hyperconcentrated floods is almost the same as low sediment concentration floods. Serious channel erosion, which is referred to as ‘ripping up the bottom’ in Chinese, occurs in narrow‐deep channels during hyperconcentrated floods. However, in wide‐shallow channels, hyperconcentrated floods may result in serious sedimentation. Moreover, a hyperconcentrated flood may cause the channel to become narrower and deeper, thus, reducing the flood stage by more than 1 m if the flood event lasts longer than one day. The fluvial process during hyperconcentrated floods also changes the propagation of flood waves. Successive waves may catch up with and overlap the first wave, thus, increasing the peak discharge of the flood wave during flood propagation along the river course. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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An essential part of hydrological research focuses on hydrological extremes, such as river peak flows and associated floods, because of their large impact on economy, environment, and human life. These extremes can be affected by potential future environmental change, including global climate change and land cover change. In this paper, the relative impact of both climate change and urban expansion on the peak flows and flood extent is investigated for a small‐scale suburban catchment in Belgium. A rainfall‐runoff model was coupled to a hydrodynamic model in order to simulate the present‐day and future river streamflow. The coupled model was calibrated based on a series of measured water depths and, after model validation, fed with different climate change and urban expansion scenarios in order to evaluate the relative impact of both driving factors on the peak flows and flood extent. The three climate change scenarios that were used (dry, wet winter, wet summer) were based on a statistical downscaling of 58 different RCM and GCM scenario runs. The urban expansion scenarios were based on three different urban growth rates (low, medium, high urban expansion) that were set up by means of an extrapolation of the observed trend of urban expansion. The results suggest that possible future climate change is the main source of uncertainty affecting changes in peak flow and flood extent. The urban expansion scenarios show a more consistent trend. The potential damage related to a flood is, however, mainly influenced by land cover changes that occur in the floodplain. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Jurate Kriauciuniene Darius Jakimavicius Diana Sarauskiene Tadas Kaliatka 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(4):769-784
Particular attention is given to the reliability of hydrological modelling results. The accuracy of river runoff projection depends on the selected set of hydrological model parameters, emission scenario and global climate model. The aim of this article is to estimate the uncertainty of hydrological model parameters, to perform sensitivity analysis of the runoff projections, as well as the contribution analysis of uncertainty sources (model parameters, emission scenarios and global climate models) in forecasting Lithuanian river runoff. The impact of model parameters on the runoff modelling results was estimated using a sensitivity analysis for the selected hydrological periods (spring flood, winter and autumn flash floods, and low water). During spring flood the results of runoff modelling depended on the calibration parameters that describe snowmelt and soil moisture storage, while during the low water period—the parameter that determines river underground feeding was the most important. The estimation of climate change impact on hydrological processes in the Merkys and Neris river basins was accomplished through the combination of results from A1B, A2 and B1 emission scenarios and global climate models (ECHAM5 and HadCM3). The runoff projections of the thirty-year periods (2011–2040, 2041–2070, 2071–2100) were conducted applying the HBV software. The uncertainties introduced by hydrological model parameters, emission scenarios and global climate models were presented according to the magnitude of the expected changes in Lithuanian rivers runoff. The emission scenarios had much greater influence on the runoff projection than the global climate models. The hydrological model parameters had less impact on the reliability of the modelling results. 相似文献