Groundwater ‐ the disregarded component in lake water and nutrient budgets. Part 1: effects of groundwater on hydrology          下载免费PDF全文

Donald O. Rosenberry  Jörg Lewandowski  Karin Meinikmann  Gunnar Nützmann 《水文研究》2015,29(13):2895-2921

Lake eutrophication is a large and growing problem in many parts of the world, commonly due to anthropogenic sources of nutrients. Improved quantification of nutrient inputs is required to address this problem, including better determination of exchanges between groundwater and lakes. This first of a two‐part review provides a brief history of the evolution of the study of groundwater exchange with lakes, followed by a listing of the most commonly used methods for quantifying this exchange. Rates of exchange between lakes and groundwater compiled from the literature are statistically summarized for both exfiltration (flow from groundwater to a lake) and infiltration (flow from a lake to groundwater), including per cent contribution of groundwater to lake‐water budgets. Reported rates of exchange between groundwater and lakes span more than five orders of magnitude. Median exfiltration is 0.74 cm/day, and median infiltration is 0.60 cm/day. Exfiltration ranges from near 0% to 94% of input terms in lake‐water budgets, and infiltration ranges from near 0% to 91% of loss terms. Median values for exfiltration and infiltration as percentages of input and loss terms of lake‐water budgets are 25% and 35%, respectively. Quantification of the groundwater term is somewhat method dependent, indicating that calculating the groundwater component with multiple methods can provide a better understanding of the accuracy of estimates. The importance of exfiltration to a lake budget ranges widely for lakes less than about 100 ha in area but generally decreases with increasing lake area, particularly for lakes that exceed 100 ha in area. No such relation is evident for lakes where infiltration occurs, perhaps because of the smaller sample size. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

High‐resolution records of climate change in arid eastern central Asia during MIS 3 (51 600–25 300 cal a BP) from Wulungu Lake,north‐western China          下载免费PDF全文

Xiaonan Zhang  Aifeng Zhou  Can Zhang  Shengtun Hao  Yongtao Zhao  Chengbang An 《第四纪科学杂志》2016,31(6):577-586

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高铁震源地震信号的稀疏化建模          下载免费PDF全文

王晓凯  陈建友  陈文超  蒋一然  鲍铁钊  宁杰远 《地球物理学报》2019,62(6):2336-2343

我国每天有数千趟高铁列车运行在两万多公里的高铁线路上,不但会引起高铁路基的振动,还会激发出地震波.地震检波器所接收到的数据中不仅包含窄带分立谱特性的高铁震源地震信号,还包含宽频带特性的背景信号.如何实现从检波器所接收到的高铁震源地震数据中分离出高铁震源地震信号和宽频带背景信号是准确利用该类信号的关键.考虑到高铁震源地震信号与宽频带信号在频率域明显的形态特征差异,本文首次将形态成分分析这种信号分离手段引入到高铁震源地震信号处理中,实现高铁震源地震信号的稀疏化建模并进而实现从接收数据中分离出高铁震源地震信号以及宽频带背景信号.对北京大学在中国南方某高铁沿线采集到的大量高铁震源地震数据进行处理,结果表明:采用形态成分分析并结合分块坐标松弛算法,能够实现实际采集高铁震源地震数据中的高铁震源地震信号和宽频带信号的分离.  相似文献   

基于密度峰值聚类的中尺度涡轨迹自动追踪方法   总被引：1，自引：1，他引：0  

王辉赞  郭芃  倪钦彪  李佳讯 《海洋学报》2018,40(8):1-9

中尺度涡信息的提取包括涡旋的识别和轨迹追踪，其自动识别与追踪对于基于海量数据的中尺度涡分析十分重要。传统涡旋轨迹自动追踪方法一般需要预先设定搜索半径的阈值，存在一定的主观性。针对传统中尺度涡轨迹追踪方法存在的问题，论文从聚类的角度出发，提出基于密度峰值聚类算法实现对涡旋轨迹的自动追踪，并以南海中尺度涡追踪为例，将基于聚类的追踪算法与传统的相似度追踪算法进行比较分析。结果表明:（1）基于密度峰值聚类算法，可实现对海洋中尺度涡的自动追踪，该算法涡旋追踪准确率优于传统相似度算法；（2）该涡旋追踪算法对资料的完整性依赖度较低，特别是对于存在部分缺损数据的情况仍能较准确追踪；（3）该追踪算法克服了传统涡旋追踪算法需要预先设定搜索半径阈值的问题，自适应性更强。  相似文献   

地震地电阻率交流观测方法及观测实验     

王兰炜  张宇  张兴国  胡哲  王子影  马小溪 《大地测量与地球动力学》2019,39(7):738-742

介绍地震地电阻率交流观测的原理及方法、观测系统的要求及主要技术指标，并在受地铁干扰严重的江宁台进行实验观测。初步观测结果表明，该系统观测结果与直流观测结果相当，能满足台站实际观测需求，同时达到抗干扰目的。证明采用交流供电方法进行地电阻率观测，能够在较强干扰背景下获取较高的信噪比，很好地抑制城市地铁、轻轨以及其他因素引起的电磁干扰。
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Outburst susceptibility assessment of moraine‐dammed lakes in Western Himalaya using an analytic hierarchy process          下载免费PDF全文

Chander Prakash  R. Nagarajan 《地球表面变化过程与地形》2017,42(14):2306-2321

Glacier retreat results in the formation and expansion, and sometimes outburst, of moraine‐dammed lakes worldwide. Sudden outburst floods from such lakes have caused enormous damage to settlements and infrastructure located downstream. Such lakes located in the Himalayan region are highly prone to outburst floods due to climatic conditions and geotectonic settings. In this study, multi‐temporal Landsat images from 2002–2014, digital elevation models (DEMs), geomorphic analysis and modelling were used to assess the changes in glacial lakes and the outburst susceptibility of moraine‐dammed lakes in the Chandra–Bhaga basin of the north‐western Indian Himalaya. An inventory of lakes was developed using satellite data, thematic maps and ground‐based investigations for the Chandra–Bhaga basin. The total area of all glacial lakes (size >5000 m²) increased by 47% from 2002 to 2014, with a pronounced increase of 57% for moraine‐dammed lakes. Sixteen moraine‐dammed lakes were identified and assessed for outburst susceptibility using the analytic hierarchy process (AHP). Forty‐one reported glacial lake outburst flood (GLOF) events from moraine‐dammed lakes in Himalayan regions were analysed, culminating in the identification of 11 critical factors for assessing outburst susceptibility using the AHP, including those related to the lake area and change, surrounding terrain characteristics, dam geometry, regional seismicity and rainfall history. The past three GLOF events in the Himalayan region were used to validate the method and to classify moraine‐dammed lakes as having very high, high, medium or low outburst susceptibility. Eight lakes classified as very high and high outburst susceptibility should be further investigated in detail. The proposed AHP‐based approach is suitable for first‐order identification of critical lakes for prioritising future detailed investigation and monitoring of moraine‐dammed glacial lakes in the Himalayan region. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

A new tool to trace past human presence from lake sediments: the human‐specific molecular marker Bacteroides strain HF 183          下载免费PDF全文

JACEK MADEJA 《第四纪科学杂志》2015,30(4):349-354

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Tracking hydrological responses of a thermokarst lake in the Old Crow Flats (Yukon Territory,Canada) to recent climate variability using aerial photographs and paleolimnological methods     

Lauren A. MacDonald  Kevin W. Turner  Ann M. Balasubramaniam  Brent B. Wolfe  Roland I. Hall  Jon N. Sweetman 《水文研究》2012,26(1):117-129

Recent studies using remote sensing analysis of lake‐rich thermokarst landscapes have documented evidence of declining lake surface area in response to recent warming. However, images alone cannot identify whether these declines are due to increasing frequency of lake drainage events associated with accelerated thermokarst activity or to increasing evaporation in response to longer ice‐free season duration. Here, we explore the potential of combining aerial photograph time series with paleolimnological analyses to track changes in hydrological conditions of a thermokarst lake in the Old Crow Flats (OCF), Canada, and to identify their causes. Images show that the water level in lake OCF 48 declined markedly sometime between 1972 and 2001. In a sediment core from OCF 48, complacent stratigraphic profiles of several physical, geochemical, and biological parameters from ～1874–1967 indicate hydro‐limnological conditions were relatively stable. From ～1967–1989, declines in organic matter content, organic carbon isotope values, and pigment concentrations are interpreted to reflect an increase in supply of minerogenic sediment, and subsequent decline in aquatic productivity, caused by increased thermo‐erosion of shoreline soils. Lake expansion was likely caused by increased summer rainfall, as recorded by increased cellulose‐inferred lake‐water oxygen isotope compositions. Stratigraphic trends defining the lake expansion phase terminated at ～1989, which likely marks the year when the lake drained. Above‐average precipitation during the previous year probably raised the lake level and promoted further thermo‐erosion of the shoreline soils that caused the lake to drain. These are meteorological conditions that have led to other recent lake‐drainage events in the OCF. Thus, the decline in lake level, evident in the aerial photograph from 2001, is unlikely to have been caused by evaporation, but rather is a remnant of a drainage event that took place more than a decade earlier. After drainage, the lake began to refill, and most paleolimnological parameters approach levels that are similar to those during the stable phase. These findings indicate that combined use of aerial images and paleolimnological methods offers much promise for identifying the hydrological consequences of recent climatic variations on thermokarst lakes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

洪湖水位对不同时间尺度SPEI/SPI干旱指数的响应研究   总被引：2，自引：0，他引：2  

刘敏  秦鹏程  刘可群  夏智宏  王苗 《气象》2013,39(9):1163-1170

流域洪涝与干旱对流域水资源利用及生态平衡具有重要影响。探讨流域水文要素与气候因子的关系,是应用气候指数进行流域旱涝监测和影响评估的重要前提。基于四湖流域8个气象站及洪湖湖区水位代表站逐月观测资料,从月、季及连续时间序列月平均标准化水位距平与不同时间尺度SPEI/SPI干旱指数的相关分析,研究洪湖水位对不同时间尺度SPEI/SPI指数的响应。结果表明：四湖流域洪涝与干旱主要受降水控制,洪湖水位与SPEI/SPI干旱指数具有较好的相关性,但其相关程度因不同月份和季节及干旱指数的时间尺度存在一定差异,总体上洪湖水位与4~6个月时间尺度SPEI/SPI干旱指数相关性最为密切,表明洪湖水位对降水及蒸散发导致的水分盈亏的响应具有时滞效应和累积效应,当前月洪湖水位受当月及前3~5个月水分盈亏的共同影响。基于5个月时间尺度的SPEI/SPI干旱指数监测历史时期洪湖水位变化具有很好的一致性。研究结果为基于常规气象观测资料进行四湖流域旱涝监测提供了理论依据,同时可为其他流域旱涝监测与评估提供借鉴。  相似文献   

松辽盆地西部坡折带的成因演化及其对地层分布模式的控制作用   总被引：1，自引：0，他引：1  

王颖  王英民  王晓洲  辛仁臣  赵志魁  赵占银 《沉积学报》2005,23(3):498-506

大型坳陷湖盆中存在与海相盆地中陆坡相似的坡折带。松辽盆地西部发育套堡-双岗高位坡折带和红岗-海坨子低位坡折带两级坡折带,本次研究系统分析了坡折带的成因演化及对其地层分布的控制作用。早期两级坡折带都受到基底断裂的影响,后期发育过程中套堡-双岗高位坡折带物源的方向和侵蚀力是其主控因素,红岗-海坨子低位坡折带后期主要受沉积物的供应和差异压实作用的影响。套堡-双岗高位坡折带和沟槽的共同作用控制了沉积体系的展布,红岗-海坨子低位坡折带控制了低位域发育的范围。  相似文献