共查询到20条相似文献,搜索用时 78 毫秒
1.
针对多沙河流河床冲淤调整幅度大,冲淤交替发生,特别是一些大型水库的建成运用,不同程度地改变了原有河床的冲淤演变规律,直接影响引水渠首取水能力,导致渠首闸乃至整个输水渠系不断改建的现实问题,着重分析三门峡水库和小浪底水库不同运行阶段对河床冲淤的影响,比较有坝式引水和无坝式引水的两种情况及存在的问题,论证了不同渠首闸布置形式对变动河床的适应性;重点介绍了一种适用于多沙河流灌区取水条件经常调整的分层取水方法;概述了分层取水闸的结构设计和运行管理简况,以黄河下游小开河引水闸为例,并与黄河下游已改建的单层渠首闸作比较。结果表明:多层渠首闸能够分层取水,应对不同水沙情况,适应河床调整,保证设计引水流量,延长渠首闸使用寿命,有利于渠首闸闸前闸后引水渠的长期运用,使灌区工程效益得到有效发挥。 相似文献
2.
洞子村水电站工程位于黄河支流湟水下游干流上,是甘肃省湟水河下游河段水电梯级开中规划的第五级电站.工程建成后主要用于发电。在可行性研究设计过程中研究了2种开发方案,即引水式开发方案和河床式开发方案,其中河床式开发方案选定上、下2条坝线进行比较。表2个。 相似文献
3.
边界条件对三峡坝下游河床演变影响 总被引:3,自引:0,他引:3
河流发育和河床演变受多种因素的影响,其中边界条件是重要的因素之一.根据已有河床组成、地质钻孔成果,阐述了三峡坝下游河道边界条件,总结了三峡坝下游河段河床演变特点,分析不同的边界条件对坝下游河床演变的影响.分析表明,基岩质或硬土石质河岸边界对河床剧烈演变起制约作用;砂-土二元边界河岸抗冲性很差,对河床演变的约束力较弱,主要体现在下荆江;粘性土质河岸对弯道的发展起重要的抑制作用;护岸及河控工程很大程度上抑制了河床横向变形,但易造成河床的纵向较剧烈变化. 相似文献
4.
福州市区内河引水冲污工程已破土动工,引水对内河河床演变的效应,冲污对闽江水域水质的影响,这两个问题都极为重要,不可忽视,应当列入议程。 相似文献
5.
随着经济建设的快速发展,人类为开发利用水资源而兴建了大量水库和引水工程,改变了河流的水沙系列,为防洪和开发滩涂进行的河道整治影响甚至改变了河床的自然演变。人类活动已成为影响河床演变的一个重要因素、我们在改变河床自然演变规律、取得工程效益的同时,也将可能在为工程本身付出相应的代价。为了使河道整治更好地适应河床演变规律,减少河道工程的负作用,本文分析了汾河下游河道整治工程对河床演变的影响,以便为以后的河道整治提供一些参考。1汾河下游河道概况晋中与临汾交界王庄以下至入黄口庙前为汾河下游。按照河型大致分… 相似文献
6.
介绍了西阳河和李家河引水工程的基本情况。通过计算降水量、地表径流以及基流,得到引水工程坝址上游的来水量,并对来水量进行了月分配,扣除下游生态用水、蒸发渗漏损失水量后,得到不同保证率情况下引水工程的可引水量。通过分析,认为李家河引水工程引水后不会对流域其他用水户的用水造成影响。 相似文献
7.
8.
葛洲坝枢纽下游河段河床演变分析 总被引:2,自引:0,他引:2
为研究三峡施工期及运用后,葛洲坝枢纽下游河段河床演变及水位变化对航运的影响,根据实测资料,对葛洲坝枢纽下游河段的水沙过程及河床演变、宜昌水位下降的情况进行了分析.认为近坝段经过葛洲坝施工期及正常运行期,河床已处于相对平衡.宜昌枯水位的降低主要是由于泥沙补给减少、人工采挖沙石骨料以及近坝段河床明显冲刷造成的.坝下游枯水航道问题可通过调度和工程措施途径解决. 相似文献
9.
10.
为研究毛阿提引水枢纽上下游冲淤演变状况及消能防冲效果,对毛阿提引水枢纽设计方案进行了系列动床试验,试验测定了各典型流量下枢纽上、下游河床、整治段冲淤演变情况,冲淤变化历时、冲淤范围和冲刷深度。结果表明:毛阿提引水枢纽总体布置基本合理,消能防冲效果良好。根据试验结果,给出了实际运行中的各个闸门的运行方式,供运行管理单位调度方参考。更多还原 相似文献
11.
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
12.
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
13.
14.
15.
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
16.
17.
18.
简述天湖水电站投运以来各种故障的表现形式,分析其原因,提出了相应的处理方法及措施,并对合理利用国内外设备提出建议。 相似文献
19.
Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd. 相似文献
20.
NUMERICAL STUDY OF WAVE EFFECTS ON SURFACE WIND STRESS AND SURFACE MIXING LENGTH BY THREE-DIMENSIONAL CIRCULATION MODELING 总被引:1,自引:0,他引:1
LIANG Bing-chen LI Hua-jun LEE Dong-yong 《水动力学研究与进展(B辑)》2006,18(4):397-404
1. INTRODUCTION Coastal and continental shelf regions are characterized by intensive interaction between wave and current. These regions are of great economic significance to mankind. Therefore, the modeling of wave and current as well as their mutual int… 相似文献