Response time and water origin in a steep nested catchment in the Italian Dolomites          下载免费PDF全文

Daniele Penna  Giulia Zuecco  Stefano Crema  Sebastiano Trevisani  Marco Cavalli  Luisa Pianezzola  Lorenzo Marchi  Marco Borga 《水文研究》2017,31(4):768-782

In this study, we investigate the surface flow time of rise in response to rainfall and snowmelt events at different spatial scales and the main sources originating channel runoff and spring water in a steep nested headwater catchment (Rio Vauz, Italian Dolomites), characterized by a marked elevation gradient. We monitored precipitation at different elevations and measured water stage/streamflow at the outlet of two rocky subcatchments of the same size, representative of the upper part of the catchment dominated by outcropping bedrock, at the outlet of a soil‐mantled and vegetated subcatchment of similar size but different morphology, and at the outlet of the main catchment. Hydrometric data are coupled with stable isotopes and electrical conductivity sampled from different water sources during five years, and used as tracers in end‐member mixing analysis, application of two component mixing models and analysis of the slope of the dual‐isotope regression line. Results reveal that times of rise are slightly shorter for the two rocky subcatchments, particularly for snowmelt and mixed rainfall/snowmelt events, compared to the soil‐mantled catchment and the entire Rio Vauz Catchment. The highly‐variable tracer signature of the different water sources reflects the geomorphological and geological complexity of the study area. The principal end‐members for channel runoff and spring water are identified in rainfall and snowmelt, which are the dominant water sources in the rocky upper part of the study catchment, and soil water and shallow groundwater, which play a relevant role in originating baseflow and spring water in the soil‐mantled and vegetated lower part of the catchment. Particularly, snowmelt contributes up to 64 ± 8% to spring water in the concave upper parts of the catchment and up to 62 ± 11% to channel runoff in the lower part of the catchment. These results offer new experimental evidences on how Dolomitic catchments capture and store rain water and meltwater, releasing it through a complex network of surface and subsurface flow pathways, and allow for the construction of a preliminary conceptual model on water transmission in snowmelt‐dominated catchments featuring marked elevation gradients.  相似文献   

Lateglacial/early Holocene palaeoenvironments in the southern North Sea Basin: new data from the Dudgeon offshore wind farm          下载免费PDF全文

Alex Brown  John Russell  Rob Scaife  Louise Tizzard  John Whittaker  Sarah F. Wyles 《第四纪科学杂志》2018,33(6):597-610

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海平面上升风险中国大陆沿海地区人口与经济暴露度     

高超  汪丽  陈财  罗纲  孙艳伟 《地理学报》2019,74(8):1590-1604

基于全球潮汐和浪涌再分析数据集,利用数字高程模型在ArcGIS空间分析工具支持下,提取了中国大陆沿海11个省市海平面上升可能淹没范围,结合人口、经济、土地利用数据构建海平面上升风险暴露度评估模型,评估中国大陆沿海地区海平面上升风险的人口和经济暴露度。结果表明：① 海平面上升风险可能淹没范围主要集中在长三角及苏北沿海、珠三角和环渤海等滨海平原地区,其中可能淹没范围最大的是江苏、上海等长三角地区;土地利用类型中受影响最严重的为耕地,约占受影响总面积的65%,其次为建设用地;② 基于2015年人口、经济统计数据,随着海平面上升水位值重现期的变化（10 a一遇至1000 a一遇）,海平面上升风险影响的人口和经济总量逐渐增加;对海平面上升风险暴露度而言,广州是暴露度等级最高的城市,高暴露度等级的区域仍集中于长三角及苏北沿海、珠三角、环渤海地区;③ 基于5种共享社会经济路径预估的人口和经济统计数据,随着海平面上升水位值重现期的变化,2025年和2100年受影响的人口、经济总量在不同路径下均呈增长趋势,常规发展路径下受影响的人口和经济总量最大,局部或不一致发展路径和不均衡发展路径下受影响的人口、经济低于其他3种路径;从重现期角度看,10 a一遇至1000 a一遇海平面上升风险的人口、经济暴露度向高暴露度等级转移;对比2025和2100年两时段的人口、经济暴露度,2100年的暴露度等级整体低于2025年。  相似文献   

Does sea-level rise have an impact on saltwater intrusion?     

Sun Woo ChangT. Prabhakar Clement  Matthew J. SimpsonKang-Kun Lee 《Advances in water resources》2011,34(10):1283-1291

Climate change effects are expected to substantially raise the average sea level. It is widely assumed that this raise will have a severe adverse impact on saltwater intrusion processes in coastal aquifers. In this study we hypothesize that a natural mechanism, identified here as the “lifting process,” has the potential to mitigate, or in some cases completely reverse, the adverse intrusion effects induced by sea-level rise. A detailed numerical study using the MODFLOW-family computer code SEAWAT was completed to test this hypothesis and to understand the effects of this lifting process in both confined and unconfined systems. Our conceptual simulation results show that if the ambient recharge remains constant, the sea-level rise will have no long-term impact (i.e., it will not affect the steady-state salt wedge) on confined aquifers. Our transient confined-flow simulations show a self-reversal mechanism where the wedge which will initially intrude into the formation due to the sea-level rise would be naturally driven back to the original position. In unconfined systems, the lifting process would have a lesser influence due to changes in the value of effective transmissivity. A detailed sensitivity analysis was also completed to understand the sensitivity of this self-reversal effect to various aquifer parameters.  相似文献   

The origin and disappearance of the late Pleistocene-early Holocene short-lived coastal wetlands along the Carmel coast, Israel     

Dorit Sivan  Noam Greenbaum  Guy Sisma-Ventura 《Quaternary Research》2011,76(1):83-92

The formation of short-lived backswamps along the Carmel coast of Israel coincides with the rapid global sea-level rise during the late Pleistocene-early Holocene transition. The current study shows that the wetland phenomena originated around 10,000 yr ago and dried up shortly before the local Pre-Pottery Neolithic humans settled on the wetland dark clay sediments 9430 cal yr BP. Palaeontological and stable-isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the Carmel coastal plain. The water body contained typical brackish calcareous fauna, with variable numerical abundance and low species richness of ostracods and foraminifera. The δ¹⁸O and δ¹³C of the ostracod Cyprideis torosa show close similarity to the present Pleistocene coastal aquifer isotopic values. This study therefore concludes that the wetlands were shallow-water bodies fed by groundwater, with no evidence of sea-water mixing. It seems that they developed as the result of high groundwater levels, transportation of sediments landward, and deposition of sand bars at the paleo-river mouths. It is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr.  相似文献   

S/P模式计算的冷却塔烟气抬升高度敏感性试验     

杨洪斌  刘玉彻  汪宏宇  邹旭东  张云海 《辽宁气象》2011,(5):38-41

德国VDI3784的S/P模式为三维流体动力学积分模式,其方程主要描述了无穷小体积元素的质量、动量、静态污染物质量浓度及能量的守恒。利用德国模式进行了冷却塔烟气排放不同参数、不同大气条件下烟气抬升高度的敏感性试验。结果表明：在影响烟气抬升高度的3个气象要素（风速、气温和湿度）中,风速和气温的变化对结果影响较大,而湿度影响较小。在D类稳定度,当环境风速从0.1 m/s增加到15.0 m/s时,抬升高度从711.7 m变为38.5 m。随着环境温度的升高,抬升高度明显单调变小;当稳定度为A类,环境温度从10升到40时,烟气抬升最大高度从688.9 m降低到45.1 m,降低了14倍多。而环境湿度的变化,对抬升高度的影响不是很明显。对于E类稳定度和F类稳定度,当环境湿度从20%增加到70%,最大抬升高度分别从115.3 m和84.6 m降到112.9 m和81.7 m,分别降低了3.43%和2.08%。在影响烟气抬升高度的其他3个因素（凉水塔直径、烟气出口速度和混合气体温度）中,混合气体温度的变化对结果影响较大,而凉水塔直径和烟气出口速度的影响较小。在各类稳定度条件下,当出口温度从20变到90时,烟气抬升高度增加1.2—13.3倍;在各类稳定度条件下,当凉水塔直径从30 m变到90 m,烟气抬升高度仅增加0.63—1.40倍;在各类稳定度条件下,当出口速度从2.5 m/s变到8.0 m/s,烟气抬升高度增加了0.24—0.74倍。  相似文献   

Seismic resistance capacity of beam–column connections in high‐rise buildings: E‐Defense shaking table test     

Yu‐Lin Chung  Takuya Nagae  Tomohiro Matsumiya  Masayoshi Nakashima 《地震工程与结构动力学》2011,40(6):605-622

A series of E‐Defense shaking table tests are conducted on a large‐scale test specimen that represents a high‐rise steel building. Two types of connections featuring the connection details commonly used in 1970s, in the early days of high‐rise construction in Japan, are adopted: the field‐welded connection consisting of welded unreinforced flanges and a bolted web type, and the shop‐welded connection in which the flanges and web are all‐welded to the column flange in the shop. To examine the seismic capacity of a total of 24 beam‐to‐column connections of the specimen, particularly when it is subjected to long‐period ground motion characterized not so much by large amplitude as by very many cycles of repeated loading, the test specimen is shaken repeatedly until the connections fractured. The test results indicate that a few of the field‐welded connections fractured from the bottom flange weld boundary in a relatively small cumulative rotation primarily due to the difficulties in ensuring the welding and inspection performance in the actual field welding. The shop‐welded connections are able to sustain many cycles of plastic rotation, with an averaged cumulative plastic rotation of 0.86 rad. Two shop‐welded connections exhibit ductile fractures but only after experiencing many cycles. The presence of RC floor slabs promotes the strain concentration at the toe of the weld access hole in the bottom flange by at least twice compared with the case without the slab, which had resulted in a decrease in the cumulative plastic rotation by about 50%. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

广西北海银滩侵蚀及其与海平面上升的关系   总被引：2，自引：0，他引：2  

黄鹄  戴志军  盛凯 《台湾海峡》2011,30(2):275-279

基于历史图件对比方法和Bruun法则对广西北海银滩岸线的侵蚀进行评估和预测.结果表明银滩在近30a内海岸侵蚀达10.40 m/a,其中人类活动作用是造成海岸侵蚀的主要因素,人类活动对岸线位置蚀退的影响贡献为98%;海平面上升导致岸线蚀退的贡献仅为2%.然而,在未来100 a内,基于历史图件对比分析估算的银滩侵蚀宽度可能超过1 000 m,银滩环境将会发生退化.因海平面上升而对岸线蚀退的贡献权重增加为9%.由于人类活动导致的银滩退化可以进行控制和预防,故对未来海平面上升引发的银滩环境退化应该予以重点关注.  相似文献   

双台子河口浅海相粉土承载力特征     

陶常飞  亓发庆  刘燕平  鞠春雨  曲伟  安丙杜  王方旗 《海岸工程》2011,30(2):38-42

双台子河口浅海相地层以粉土受物质组成、沉积环境影响,垂向上物理力学性质复杂多变,对海洋工程尤其是海洋钻井平台的安全存在显著影响.本研究以双台子河口-工程地质钻孔为例,结合海洋钻井平台实际插桩结果,对粉土层的桩基承载力特征进行了分析讨论,认为粉土层的力学性质差异是由于海平面阶梯状上升所导致,其力学参数选取应参考含水量、空...  相似文献   

海平面上升背景下中国沿海台风风暴潮脆弱性分析     

王康发生  尹占娥  殷杰 《热带海洋学报》2011,(6)

沿海地区既是我国人口、经济和社会发展的重要区域,又是自然灾害易发和频发区域。基于中国沿海1989—2008年台风风暴潮增水数据、航天飞机雷达地形测绘任务3秒数字高程模型(SRTM3 DEM)数据、2009年县级行政区数据、2005年100m土地利用栅格数据、2003年平方公里人口和国内生产总值(GDP)数据,进行了中国沿海海平面上升背景下的中国东部沿海台风风暴潮脆弱性分析。采用线性回归法得到海平面上升值,采用回归分析法得到风暴潮回归周期和相应潮高,采用高程面积法得到风暴潮土地利用淹没图,采用地统计法得到各高程内被淹县市土地利用面积、被淹人口和GDP。研究结果表明,珠江三角洲地区、长江三角洲和长江以北的江苏北部沿海地区、莱州湾及黄河三角洲和渤海湾与辽东湾地区是我国沿海三大主要台风风暴潮脆弱区,也是今后台风风暴潮重点预防地区;农田、水域与建设用地是沿海地区最易遭受风暴潮增水淹没的3种土地利用类型。  相似文献