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161.
Casey R. Remmer Tanner Owca Laura Neary Johan A. Wiklund Mitchell Kay Brent B. Wolfe Roland I. Hall 《水文研究》2020,34(2):303-320
Hydrological monitoring in complex, dynamic northern floodplain landscapes is challenging, but increasingly important as a consequence of multiple stressors. The Peace-Athabasca Delta in northern Alberta, Canada, is a Ramsar Wetland of International Importance reliant on episodic river ice-jam flood events to recharge abundant perched lakes and wetlands. Improved and systematic monitoring of landscape-scale hydrological connectivity among freshwater ecosystems (rivers, channels, wetlands, and lakes) is needed to guide stewardship decisions in the face of climate change and upstream industrial development. Here, we use water isotope compositions, supplemented by measurements of specific conductivity and field observations, from 68 lakes and 9 river sites in May 2018 to delineate the extent and magnitude of spring ice-jam induced flooding along the Peace and Athabasca rivers. Lake-specific estimates of input water isotope composition (δI) were modelled after accounting for influence of evaporative isotopic enrichment. Then, using the distinct isotopic signature of input water sources, we develop a set of binary mixing models and estimate the proportion of input to flooded lakes attributable to river floodwater and precipitation (snow or rain). This approach allowed identification of areas and magnitude of flooding that were not captured by other methods, including direct observations from flyovers, and to demarcate flow pathways in the delta. We demonstrate water isotope tracers as an efficient and effective monitoring tool for delineating spatial extent and magnitude of an important hydrological process and elucidating connectivity in the Peace-Athabasca Delta, an approach that can be readily adopted at other floodplain landscapes. 相似文献
162.
Long- and short-term channel changes are documented and analysed for a historically unstable reach of the River Severn at Llandinam, mid-Wales. Long-term changes (the last 150 years), reconstructed from 10 archival sources, are characterized by channel planform switching between meandering (1836–1840 and 1948–1963) and braided (1884–1903 and 1975–present) phases. Short-term changes, monitored by detailed planform surveys over a 2·5 year period, showed smaller-scale channel adjustments involving channel switching, bar accretion and channel expansion. Phases of braiding at Llandinam have been triggered by extrinsic controls, primarily flooding, but intrinsic controls (floodplain sediments, planform evolution and channel gradient) have been influential in priming the reach prior to destabilization. Flow regulation on the River Severn since 1968 has partly frozen the planform of the contemporary braid zone. Management of channel planform adjustments, where environmental change is phased in over time, must be informed by a knowledge of the potential for triggered planform switches. In addition, the effects of environmental change on fluvial systems are often historically contingent upon the state of the channel at the time of impact. © 1998 John Wiley & Sons, Ltd. 相似文献
163.
Elke Vandekerkhove Maarten Van Daele Nore Praet Veerle Cnudde Peter J. Haeussler Marc De Batist 《Sedimentology》2020,67(1):364-389
Lake sediments in Eklutna Lake, Alaska, reveal the presence of turbidites within varved sequences. These turbidites, which result from flood events and earthquakes, show a similar macroscopic appearance. In order to use turbidites to reconstruct flood variability and/or seismic history in the lake basin, it is crucial to determine the trigger of the turbidity currents. This study examined the turbidite caused by the ad 1964 Great Alaska earthquake as well as turbidites linked to historical flood events in order to differentiate between these earthquake-triggered and flood-triggered turbidites. In a suite of samples from throughout the lake, distinctive proxies are identified that can be associated with event-specific flow characteristics. The study presents straightforward discrimination methods related to the sedimentology and geochemical components of the turbidites. These methods are also applicable to other lakes, particularly proglacial lakes where the sediment composition of onshore and offshore sources is similar. Finally, the discrimination of the turbidite trigger can be used to reconstruct the palaeoflood and seismic history. 相似文献
164.
埕北油田具有原油黏度高、油层渗透能力强和非均质性严重等特点,水驱开发效果差,剩余油储量大,而生产平台工作时间已达到设计使用寿命,急需高效、快速的提高采收率技术。针对埕北油藏地质、流体性质和开发现状,利用仪器检测和理论分析方法,开展了聚合物溶液、三元复合体系和改性三元复合体系性质和调驱效果实验研究。结果表明,与三元复合体系相比较,添加入Cr^3+后得到的改性三元复合体系在黏度和界面张力性质方面几乎没有发生变化,但其阻力系数和残余阻力系数有了较大幅度提高。在化学费用相近条件下,“调剖+三元复合驱”和改性三元复合驱要比三元复合驱增油效果好,采收率增幅可以达到15%以上。推荐埕北油田采用弱碱三元复合驱,三元复合体系配方组成为“大庆超高”聚合物(CP=1600~1800mg/L)+弱碱Na2CO3(CA=0.6%~1.0%)+重烷基苯石油磺酸盐(Cs=0.10%~0.15%)+有机铬(聚:Cr^3+=120:1~240:1)”,段塞组合方式为“0.025~0.05 PV Cr^3+聚合物凝胶+0.12~0.15PV三元复合体系”。 相似文献
165.
166.
海堤是海岸带地区社会经济活动的重要保护屏障。海岸侵蚀的加剧将导致海堤稳定性和安全性降低, 增加海岸带地 区遭受极端风暴洪水的风险, 进而影响到海岸带地区的安全。本文选择上海石化这一遭受海岸侵蚀较为严重的区域作为研究 区, 利用 GIS 分析了 1972—2020 年近岸海床侵蚀特征, 并基于 2000—2020 年-5 m 等深线变化评估了上海石化近岸海堤的 稳定性。结果表明: 1972—2020 年间上海石化前沿海床整体以侵蚀为主, 石化近岸东侧以及西侧局部的浅滩侵蚀明显, 城 市沙滩中段、第 6 次围堤处以及码头东岸海堤稳定性最低。基于上述研究结果, 考虑海堤稳定性薄弱段出现极端风暴洪水漫 堤或溃堤情景, 模拟并分析了上海石化 2010 年 、2030 年和2050 年遭受千年一遇极端风暴洪水的风险。结果显示: 在 2010 年基准年情景下, 受海岸侵蚀作用最明显的城市沙滩和第6 次围堤区域遭遇极端风暴洪水的风险最高, 到 2050 年, 当前稳 定性较好的海堤安全性也将大大降低, 与 2010 年相比, 上海石化近岸地区的直接经济损失将会增加近 3 倍。 相似文献
167.
168.
详细介绍了信号定时器的特点和工作原理,并给出一种基于现场可编程门阵列(FPGA)的风廓线雷达信号定时器的设计方法.该信号定时器在某风廓线雷达中成功应用,且运行可靠,效果良好. 相似文献
169.
Princinple of colloidal dispersion gels technologyColloidal dispersion gels are made of low concentrations of POlymer and crosslinker. Polymer concentrations normally range from 100 to 1200 ppm.In this concentration range, there is not enoughpolymer to fo… 相似文献
170.
Based on 23 U/Th analyses and 532 oxygen isotopic data, an averaged 80-a stalagmite oxygen isotopic composition series was
established through 95 to 56 thousand years before present (ka BP) from two speleothems in Shanbao Cave, Shennongjia, central
China. Shanbao Cave record (referred to as SB record) replicates well with Hulu Cave record, extending the characteristics
of millennial oscillations in East-Asian-Summer-Monsoon (EASM) to the past 95 ka. The trend of the SB record generally follows
mid-July solar insolation at 65°N, suggesting that mid-high northern latitude insolation, in the first order, controls changes
of EASM intensity. Millennial oscillations of EASM recorded in the stalagmites are well related to the Greenland interstadials
referred to as Dansgaard/Oeschger (D/O) events from 1 to 22, indicating that rapid ocean-atmosphere reorganization in North
Atlantic has a remote effect in EASM. The well-dated D/O events by stalagmites probably provide an absolute calibration for
chronologies of Greenland ice cores. The timings of D/O events in the SB record are different variously from those in Greenland
ice cores. For D/O 19 and 20, the age offsets between the stalagmites’ and the Greenland ice cores’ record are significant,
larger than the uncertainties of uranium-series dating. The two events in the SB record are younger than those in North GRIP
time scale by 1–2 ka, and older than the counterparts in GISP2 by approximately 3–4 ka. A comparison between the SB and Brazil
stalagmite record shows an anti-phase relation in millennial-scale monsoon precipitation between the two localities. This
supports a mode for the coupled ocean-atmosphere “See-saw”.
Supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD, No. 200227) and China
National Outstanding Youth Science Foundation (Grant No. 40225007) 相似文献