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长江口滨海湿地长期以来对上海市经济发展起着重要作用,但近年来,湿地生态系统生态特征发生巨大变化,呈严重衰退趋势。基于卫星影像数据及实地调查等资料,分析其资源淤涨和侵蚀的变化显示,除横沙东滩外,崇明东滩、九段沙、南汇边滩都转为侵蚀,边滩湿地总体转为侵蚀趋势明显,湿地不断退化;导致湿地退化的主要原因为流域来沙量不断减小、人工围滩造地强度不断加大及全球气候变化及海平面上升的影响。为此提出相关措施,以期解决长江口湿地存在的问题,为滩涂资源的合理开发利用提供参考,促进湿地的进一步健康发展。 相似文献
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为科学利用和有效保护长江口滩涂资源,基于多年上海市滩涂资源报告及长江口河势演变分析等相关成果,全面分析了长江口及其重点区域滩涂资源的变化和成因,并提出了加强九段沙湿地自然保护区生态保护建设,持续加强长江口的系统监测和综合研究以及加快实施长江口综合整治开发规划确定的北支缩窄和横沙东滩、南汇东滩促淤圈围工程的建议对策。 相似文献
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河口边滩湿地利用与保护的平衡正成为目前湿地保护与管理亟需解决的问题,但国内外对河口边滩湿地的研究较少。在系统总结国内外湿地生态功能评价方法和研究成果的基础上,针对河口边滩湿地的特点,从生态系统健康评价和生态系统服务功能价值两个方面,初步构建了河口边滩湿地功能评价的指标体系。该体系奠定了开展湿地功能和健康评估的技术基础,以期为湿地保护与管理以及功能利用提供决策支持。 相似文献
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长江口南槽航道是长江口乃至整个长江流域发挥通航、生态作用的关键区域之一。为评估长江口南槽航道一期治理工程对邻近海域以及九段沙生态敏感区的影响,考虑航道的航运、生态、资源节约以及协调等因素,设置完整性及独立性较强的南槽航道治理工程评价指标体系。利用群决策层次分析法赋予权重,采用模糊综合评价法对航道健康水平进行评价,并对结果进行敏感度分析。结果表明:长江口南槽航道工程生态健康水平“优秀”隶属度最高,航道工程生态效果较好。总体上航道治理工程没有破坏航道及生态敏感区的各项功能,并且对于航道的通航功能有很大提高,但对于航道及九段沙湿地生物生境的改善作用较小。评价结果对准则权重的20%~90%幅度波动敏感性不高,具有较高的稳定性和可靠性。 相似文献
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长江口南汇东滩滩地地貌演变分析 总被引:3,自引:0,他引:3
南汇东滩位于长江口与杭州湾的交汇带,受长江径流、来沙、波浪、潮汐和人类活动的影响,滩地地貌演变复杂。近百年来,南汇东滩北冲南淤,呈整体向东南伸展的演变趋势。波浪和潮流的共同作用,控制着南汇东滩滩坡和滩地走向,形成了岸、滩、槽平面发散的地貌形态。近年来,受长江口深水航道治理工程的影响,南汇东滩上段冲刷,下段淤积,地貌形态总体变化不大。没冒沙是南汇东滩上的次生沙体,形成于上个世纪的20年代,形成以来虽经历复杂的演变过程,但多年来沙嘴(或沙脊)的位置和走向基本保持稳定。南汇东滩平缓且稳定的滩坡、丰富的泥沙供应和适当的潮流、波浪动力是没冒沙长期稳定的内在机理。 相似文献
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《人民长江》2021,52(6)
为防止上海市横沙东滩浅滩大面积侵蚀和长江口深水航道疏浚土外抛入海造成的资源浪费和环境污染,根据横沙东滩生物生境特点对横沙东滩进行分区,利用长江口深水航道疏浚土上岸生态成陆。通过研究长江口疏浚土历史数据、长江口生物生境需求与长江口滩涂湿地发展特点,提出根据生境需求按照等深线0 m以上、-2~0 m、-2~-5 m滩涂面积比例为1∶1∶2塑造横沙东滩生态基底方案,设置"T坝"进行生态基底保育,并分为鸻鹬类主栖息区(A区)、苇塘区(B区)、雁鸭类主栖息区(C区)、鸟类食物种植区(D区)4个生态功能区,最终形成生态成陆示范区。该研究方案可为滩涂生态修复提供理论基础及技术支撑。 相似文献
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崇明东滩湿地位于长江入海口,是一处快速演替的潮滩湿地,动植物资源丰富、植被自然演替明显,是290多种鸟的重要栖息地,达到全球种群数量1%的鸟类有12种。东滩湿地互花米草的快速扩张、水上捕捞作业的影响、人工养殖鱼塘的大量萎缩使得鸟类栖息地不断丧失。崇明东滩湿地的保育从不同鸟类对栖息地的需求着手,通过对自然生境中互花米草的控制、植被分布的调整、水位的调控、土著作物和底栖动物的培育,增加生物种类和数量,使互花米草得到有效控制、生态环境更趋健康、人与自然更加和谐、鸟类有效栖息地显著增加、湿地景观异质可视、保护区管理更趋便利,实现了湿地在自然资源、环境教育、观光观鸟、生态保护宣传、科学考察和研究等方面的可持续利用。 相似文献
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根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。 相似文献
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The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects. 相似文献
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Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river. 相似文献
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In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment. 相似文献
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V. K. Konovalov O. V. Yashkin V. V. Ermakov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2008,42(2):105-109
A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed
in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash
and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers
of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional
components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect
dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system,
configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants
of dry ash utilization and the advantages of producing of size-separated particles are considered.
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Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008). 相似文献
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Peter B. Bayley 《河流研究与利用》1991,6(2):75-86
The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed. 相似文献