深圳市不透水表面扩展对径流量的影响

以深圳市为研究区,综合遥感技术和L-THIA模型,改进模拟所需的地表覆被参数,模拟不透水表面扩展对城区径流量的影响。结果表明:深圳市不透水表面百分比在15a间扩展非常快,从1990年的26.5%扩展至2005年的49.3%,扩大了1.9倍；导致2005年日径流量比1990年在小雨情景时增长了136.2%,中雨时增长了83.7%,大雨时增长了59.5%,暴雨时增长了40.8%;导致2005年比起1990年，丰水年的年径流量增加了43.35%,枯水年的年径流量增加了54.85%。小雨情景中受不透水表面扩展的影响大于暴雨情景,枯水年受不透水表面扩展的影响大于丰水年。从空间分布上看,径流深大的地区不透水程度高,径流深值较大区域为城市核心区,需要注意防洪和排涝。应用L-THIA模型模拟快速城市化、无水文监测资料地区的不透水表面扩展导致的径流量变化,可取得良好效果,模拟结果可为城市洪涝灾害规划等提供依据。     

沩水流域中上游径流对不透水面扩张的响应

为研究径流对不透水面扩张的响应,通过建立沩水流域中上游HSPF模型,构建研究区2000-2015年不透水面扩张情景,探究该区域径流对不透水面扩张的响应。结果表明:HSPF模型月流量模拟精度较高,在本研究区有良好的适用性;在2000-2015年研究区不透水面扩张情景下,研究区不透水面扩张会引起年径流深小幅增长,不透水面扩张对枯水期径流深的影响大于对汛期径流深的影响,且不透水面扩张对枯水年径流深的影响最大,平水年次之,丰水年最小;相较于整个研究区,主城区与研究区不透水面扩张对径流深的影响在趋势上是一致的,但是主城区的影响程度比研究区大。     

不透水面扩张对郑州主城区降水特征的影响

为探究下垫面变化对高密度城市地区降水的影响,基于遥感技术反演郑州主城区1990—2019年的不透水面分布信息,并分析了其扩张特征;采用回归模型探讨不透水面比例与降水特征变化的相关性,识别了显著影响主城区降水的不透水面比例阈值,并采用城郊对比法多角度揭示了不透水面扩张对主城区降水的影响程度。结果表明：郑州主城区不透水面扩张趋势显著,扩张形态呈单一核心的“摊大饼”式扩张;不透水面比例与城郊降水强度比呈二次多项式函数关系,对主城区降水产生显著影响的阈值是30%;不透水面扩张导致主城区雨岛效应显著,增雨系数最高达1.39,主城区暴雨发生概率高于郊区53%,降水集中期晚于郊区约8 d,对主城区主汛期降水量变化的贡献率达44.39%;不透水面因具有高蓄热、低渗透的固有特征,对地表热力、动力条件具有显著影响,已成为城市化影响降水的主要影响因素之一。     

九江市中心城区下垫面变化及其径流响应

在快速城市化的大背景下,城市地区下垫面变化是影响径流过程的重要因素。以江西省九江市中心城区为例,解译并分析1987—2018年土地利用/覆被变化(land use and cover change, LUCC)特征,利用城市时变增益非线性模型研究不同下垫面条件下的径流特征。结果表明:1987—2018年九江市中心城区(浔阳区、濂溪区、柴桑区)不透水面比例从0.49%上升为10.58%;典型年降雨条件下径流系数从0.31增长到0.38;场次洪峰流量增加了10%。不透水面比例是研究区流量变化的主导因素,其他下垫面类型及降雨条件的变化加剧了产汇流过程的时变性和复杂性,而绿地和水体的调蓄作用将抵消一部分由不透水面扩张引起的径流增大效应。     

泾河平凉市区段径流量变化特征及其影响因素分析

基于平凉水文站(1974-2015年)径流量、温度、降水量和崆峒水库水文站(1977-2015年)径流量资料,应用多种统计分析方法,对泾河平凉市区段径流量年内分配的不均匀性和径流量的年际变化进行了分析,同时对影响径流量变化的因素进行了讨论。结果表明:泾河平凉市区段径流量年内变化呈现不均匀分配,但不均匀性有减小的趋势;泾河平凉市区段径流量年际变化较大,枯水年明显多于丰水年,径流量总体呈现出减小的趋势;影响泾河平凉市区段径流量变化的因素主要为上游崆峒水库站年径流量,人为活动对泾河平凉市区段径流量的影响主要在1993年以后:1994-2009年起到减小的作用,2010-2015年起到增大的作用。     

北京市区快速城市化进程中的内涝现状及成因分析

随着城市建成区的不断扩张,不透水面激增,城市内涝问题日趋严重,已经影响到城市各项功能的正常运转,造成的社会和经济损失也不断增加。通过分析北京典型暴雨内涝事件"2012.7.21"内涝点的分布特征和规律,了解北京五环以内的城市内涝状况,总结导致城市内涝频发的原因,结合2012年至今北京市治理城市内涝的效果,提出治理内涝的建议。结果表明,城市化进程中,城市不透水面的增加导致雨水径流迅速增长,从而造成建成区不透水面密集的区域以及地势较低的立交桥区内涝严重。因此,可以从改造桥区设施和建设海绵城市这两个方面着手进行内涝治理,以期改善桥区积水和建成区不透水面密集现状,从而减轻和缓解北京城市内涝问题。     

用季节指数法进行年径流量时段分配

年径流量的准确预报,为小库预报和洪水调度、兴利调度、管理运用等提供了保证。而它的时段分配是水库调蓄的关键,特别是调蓄能力差的水库就显得更加重要。实践表明,可利用季节指数法进行年径流量的时段分配。一、年径量有随季节变动的趋势,这种季节变动是指一年中特定单位时期(如季、日、旬间)的波动,有来水淡季、旺季和高峰期。这种波动是气候因素所致,因为年降水是影响年径流量变化的主导因子。不论是少水年群和平水年群及丰水年群,降水量具有一定的年际变化,这是出现年径流量波动的原因。而这种变化,又带有一定的规律     

不透水面影响下海岛淡水透镜体的形成与演化

以某海岛的水文地质资料为基础,对研究区水文地质条件进行概化,并使用Visual MODFLOW软件构建了该海岛淡水透镜体的二维模型,通过改变不透水面的覆盖范围,模拟透镜体形态及储水量的变化.数值模拟结果表明,初始状态下岛屿淡水透镜体的最大厚度约为15.6 m;在设置不透水面后,淡水透镜体大约在15 a之后再次达到稳定状态,设置不透水面一侧的淡水透镜体下界面轮廓向内凹陷,淡水透镜体的最大厚度减小至14.6 m,岛屿地下淡水储量减少了20.23％.对影响淡水透镜体的4种影响因素进行灵敏度分析,结果表明给水度对岛屿地下淡水储量影响最大,其后依次为降雨入渗补给系数、渗透系数和不透水面覆盖范围.     

土地覆被和气候变化对拉萨河流域径流量的影响

以拉萨水文站上游流域为研究对象,利用分布式水文模型SWAT对拉萨河流域水文过程进行模拟,分别用1995～2000和2003～2006年两个时间段的实测数据对模型进行校准和验证。结果显示月径流模拟相关系数和模拟效率系数分别为0.88和0.84。在此基础上通过建立情景模拟,探讨拉萨河流域气候波动和土地覆被变化对径流产流量的影响。结果表明:气候变化对年径流量影响显著,在各种模拟假设情景中最多可以使径流量增加89%。土地覆被变化相对于气候变化对径流量的年际影响较弱,但对径流量的季节变化影响显著。     

渭河源区水文气象要素演变趋势及阶段性分析

研究渭河源区水文气象要素变化特征,并进一步分析各个要素之间的相互关系,为渭河源区水资源的合理开发利用提供科学依据与技术支撑。采用坎德尔秩次相关、斯波曼秩次相关、线性趋势回归检验法对渭河源区水文气象要素变化趋势进行检验,利用M-K检验法找出各要素的突变年份,运用多元线性回归分析法分析不同阶段降雨、蒸发量对径流量的影响程度。结果表明:近30年来渭河源区年降水量与四季降水量均呈不显著减少趋势,年蒸发量与春、夏季蒸发量呈显著增加趋势,年径流量与夏季径流量呈显著减少趋势,冬季径流量呈不显著增加趋势。年降水量和年径流量均在1993年发生显著性突变,年蒸发量在1990年发生显著性突变。分析得出:1981-1993年年径流量变化主要受降水量变化影响,1994-2010年径流量变化主要受蒸发量变化影响。     

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。     

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。     

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.