宜昌至沙市段水位流量关系变化及影响因素分析

长江中游河段水位流量关系受多种因素的综合影响,呈现出较为复杂和不规律的特点。研究了洪水涨落率、来水顶托和水库调度等因素对水位流量关系的影响。根据实测资料,对宜昌站、枝城站和沙市站的水位流量关系变化进行分析,并讨论了沿程水位下降趋势和比降的变化规律。结果表明,洪水涨落率是控制各站水位流量关系曲线的主要影响因素,来水顶托和水库调节仅对水位流量关系曲线产生局部影响。宜昌至枝城段和枝城至沙市段的水位和比降变化规律恰好相反。研究成果对水文预报、水文资料整编、水文分析计算和河演分析工作具有较大参考价值。     

三峡水库建库前后荆江低水水位流量关系分析

三峡水库蓄水运用以后,由于库区泥沙淤积,清水下泄,下游河道必然受到影响。通过对三峡水库建库前后荆江河段主要水文测站多年的实测资料对比,分析了水库建库前后荆江河段主要控制站宜昌、枝城、沙市、监利的断面面积及低水水位流量关系变化。分析结果表明,受水库蓄水后清水下泄影响,荆江河段尤其是枝城、沙市站断面下切较大,低水水位流量关系线下移,同流量级下水位降低;宜昌站由于前期受葛洲坝工程影响,断面已基本稳定,受三峡工程运行影响不大。     

三峡出库急变洪水波传播规律及其对水文测报的影响

针对三峡-葛洲坝水库联合调度产生的急变洪水波,基于二维非恒定流水动力学模型,计算实测及概化的典型调度过程下洪水波在坝下段(葛洲坝至枝城)传播时的水力要素,分析洪水波涨落速率、断波最终流量、持续时间等不同因素对急变洪水波传播规律的影响。结果表明:急变洪水波涨落速率越大、持续时间越长,洪水波以断波特征向下传播越明显;宜昌站流量在断波波峰到达后仍存在小幅度变化;宜昌站水位流量关系线绳套范围随断波涨落速率增大而增大,当断波持续时间8 h以上时,绳套曲线趋于稳定;涨水波对宜昌站水文测报的影响时间更长。     

长江中下游地区旱涝异常的水汽输送结构特征及其变化趋势

本文采用箱格网整层水汽净收支及其边界流定量综合分析技术方案,分析了长江中下游旱涝过程中低纬间水汽输送结构特征及其年代际变化趋势.发现了中低纬西太平洋-南海区域存在副高变化显著区,且该区500hPa高度年际变化与东亚夏季风的强弱和中低纬间整层水汽输送结构特征以及长江中下游夏季降水密切相关.对东亚夏季风在中低纬关键区"箱格网"整层水汽输送收支距平状况的分析,发现长江中下游涝年夏季中低纬间呈反气旋式而旱年呈气旋式时水汽输送"相关链"结构,副高变化显著区500hPa高度距平序列与整层水汽输送的合成相关矢亦描述了上述长江中下游洪涝异常中低纬区间水汽输送反气旋式"相关链"图像.研究还表明20世纪80～90年代东亚夏季风减弱背景下,中低纬间反气旋式水汽输送"相关链"特征增强趋势显著,其与中国东部夏季降水年代际变化趋势吻合.     

三峡工程蓄水前后长江中游水位流量变化分析

随着三峡水库蓄水运行,清水下泄导致坝下游河段受到不同程度的冲刷,使得江湖关系发生变化。对长江中游主要控制站三峡工程蓄水运用前后水文数据进行统计分析,结果表明：三峡工程蓄水运用后,清水下泄冲刷下游河道深槽部分,长江河段总体同流量下水位下降,其中以汉口以上河段水位下降明显,且对低水影响明显。三峡工程蓄水运用后,三口河道分流比继续减少,断流时枝城水位有升高趋势,分流河道逐渐萎缩,荆江过流量增大。     

减灾科普

正Q:水文预报是什么?预报对象有哪些?A:水文预报就是根据前期和现时的水文、气象等信息,对未来一定时段内水文情势作出的定性或定量预报。水文顶报按预见期的长短,分为短期、中期、长期预报。按预报对象分为:(1)洪水预报。主要预报暴雨洪水、融雪洪水的洪峰水位(或流量)、洪峰出现时间、洪水涨落过程和洪水总量等。(2)枯季径流预报。主要预报枯季径流量、最低水位及其出现时间。(3)墒情预报。分析土壤水分的动态变化,预报农作物生长所需的墒情。(4)地下水位预报。分析地下水动态变化,预报地下水蓄量及水位升降等。(5)冰情预报。     

遥测水位系统在利辛水文测区的运用

为提升流量巡测能力和水文服务水平，开展了遥测水位系统在利辛水文测区的水位流量巡测、洪峰流量巡测、洪水测验指导等相关研究和应用。近年测区洪水测验结果证明，该系统的运用是保证水文巡测工作质量的必要条件，对测区巡测起到关键作用，可有效提升巡测效率和水文测验质量。     

潮汐河口区洪潮水位相关关系模式研究

以中山市境内感潮河段几个主要站点的潮位过程数据为识别对象,采用多元逐步回归相关模式,分别从年水文系列样本的自动筛选入库和敏感参数因子选定两方面,建立了莺哥咀-横门的东部报汛相关模型和莺哥咀-灯笼山的西部报汛相关模型。研究成果表明,潮汐河口水文预报应以水位预报为主。剔除了上游马口洪水流量信息、增加参数自动更新的多元逐步回归模式结构简单、清晰、快捷,准确性较高,能适用于该区域各报汛站点的水位自动预报。     

黄河宁蒙河段2018年汛期水沙特性分析

2018年黄河流域发生多次强降雨过程,干流先后形成3次编号洪水,宁蒙河段高水位、大流量持续近3个月。分析了宁蒙河段汛期雨水情特点、洪水演进以及含沙量变化过程;通过套绘洪水期石嘴山及以下水文断面,计算了相同水位下的断面面积,绘制水位—断面面积关系曲线,分析了汛期宁蒙河段典型断面的冲淤变化以及过流能力。结果表明:2018年汛期宁蒙测区平均降雨量、来水量较历年均值总体偏多,出现3场较大的洪水过程,水位偏高,大流量持续时间长,宁夏河段出现3场较大的沙峰过程;汛期宁蒙石嘴山以下水文断面总体表现为冲刷,河道过洪能力明显提高;除头道拐断面以外,石嘴山以下各水文断面均发生较明显的冲刷。     

长江流域洪水相关因素及对策

长江流域资源丰富、人口密集。20世纪长江流域的3次大洪涝造成了巨大损失,所以研究流域洪水相关因子,探寻洪涝规律意义重大。天文地理、大气环流、厄尔尼诺以及拉尼娜等因素是造成长江流域大洪水的主要因素,人为因素加重了洪涝灾害。全球变暖的大环境,将会加快大气水循环,增加降水量。同时指出,长江流域洪水治理值得反思,用于防洪的堤坝存在潜在危险。长江流域防洪压力最大的荆江段,在高堤防高水位形势下,加上大堤管涌、岸崩、可能的地震等致灾因素的共同作用下,可能会北向溃堤,造成巨大灾难。最后提出了一些建议,希望能为长江流域防洪减灾尽到微薄之力。     

地下厂房施工过程的三维非线性数值模拟分析

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。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

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.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

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.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

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.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

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. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

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.     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。