钉螺静水和动水沉降试验研究

推导了钉螺静水沉速，动水沉速和动水深降距离公式，这些公式是以螺龄为基本参数进行计算的，并通过试验了各项系数，分析了钉螺静水沉降和动水沉降的基本规律。     

钉螺的静水沉速及其在江河中扩散运动方式初探

 本文讨论了钉螺在水中运动的两个问题:钉螺的静水沉速和在江河中扩散运动方式。应用泥沙运动理论对钉螺静水沉速资料进行分析,研究钉螺在静水中沉降阻力系数变化规律和阻力系数与雷诺数的关系,从而了解了大小钉螺沉降的阻力性质,并建立了大螺、中螺和幼螺不同的沉速公式。钉螺在天然河道中的扩散方式与河道水流的水力因素有关,根据长江中游和汉江中下游河流的水流特性、输沙特点,并结合钉螺在静水中沉降运动规律,提出了钉螺在上述河道中扩散运动方式的判别式。由于活钉螺的生物、生态特征对其迁移、扩散具有     

钉螺截留装置的试验研究

针对钉螺主要通过吸附在各种载体上随水流漂移扩散的特点，研制了一种与渠首节制闸融为一体的钉螺截留装置。该装置由分离池，沉降池和集螺池组成，在分离池中，借助水跃水动力作用使钉螺与载体分离，然后被分离的钉螺借助重力的作用在低流速的沉降池中沉降到集螺池中，最后将钉螺中杀灭。     

黄河流域黏性泥沙群体沉速计算分析

针对黄河流域由黏性矿物组成的黏性泥沙群体沉降特征展开研究。基于泥沙颗粒受力分析和能量守恒定律,以处于稳态的泥沙颗粒为参照物,构建了泥沙颗粒水沙界面能量耗散物理图形;建立了考虑挟沙水流运动黏性系数和紊动黏性系数的泥沙群体沉速显式表达式,并采用黄河流域典型黏性泥沙红色砒砂岩颗粒开展了泥沙群体沉速试验研究。结果表明：红色砒砂岩组成的含沙水体中泥沙群体沉速整体随含沙量增大而减小并逐渐趋于定值;当垂向平均含沙量为0.34～0.45 kg/m³时,泥沙群体沉速表现为随含沙量的增加而增大。采用试验数据对建立的公式进行验证,公式能较合理地表达水流黏性和尾流分离对泥沙颗粒沉降阻力的影响。研究结果可为黄河流域黏性泥沙淤积和输移规律研究提供参考。     

动水中非均匀沙沉降规律的试验研究

本文介绍了利用自行设计的锥形沉降筒，进行非均匀沙动承中沉降试验的研究成果，提出了非均匀沙群体沉速公式。对非均匀抄各粒径组的沉速也进行了初步探讨，得到了非均匀抄各粒径组沉速的规律。最后利用实测的沉降资料，对非均匀沙群体沉速公式进行了验证，说明了非均匀沙群体沉速公式有较好的可靠性和精度：     

潮汐水流中细颗粒泥沙絮凝沉降的初步探讨

通常采用泥沙的静水沉速,以计算水流的挟沙能力,在理论上是不合适的.影响泥沙沉降的因素,在紊流中是水流的紊动扩散等,而静水中仅有布朗运动.此外,根据潮汐水流的原状水样试验及实测资料分析结果,都表明动水中泥沙的絮凝沉速较静水的絮凝沉速约大十余倍. 阿尔卡门等人认为细颗粒的紊动扩散与脉动流速平方的平均值及粒径的关系较大,就提出了紊动扩散系数公式(7).我们对该式的比例常数K_s进行尺度分析,并对天然河道的含沙量分布不均匀性提出了修正系数.最后求得泥沙絮凝前后粒数比的近似计算式(20),然后利用美国萨凡娜港湾和长江口的全潮观测资料,进行分析计算,计算结果与实测数据比较符合.此外,我们分析河道紊动强度与人工紊动试验流速梯度G之间关系,以验算实测资料,表明絮团尚未到达破裂程度.     

钉螺起动流速试验研究

 阐述了钉螺起动流速试验研究成果。由于钉螺对河床具有吸附作用，因而钉螺起动可概括为三种不同起动状态：第一种为定床有吸附力起动，起动流速在１．０ｍ／ｓ以上；第二种为动床有吸附力起动，起动流速约在０．３～０．４ｍ／ｓ之间；第三种为无吸附力起动，起动流速在０．１４～０．１９ｍ／ｓ之间。钉螺无吸附力起动可利用钉螺起动流速公式计算。     

钉螺在动水中运动特性研究

通过试验，研究了钉螺在动水中爬行运动和钉螺在动水中的起动流速，推导了钉螺在开厣状态下起流速公式，还根据试验结果描述闻不同流速区段钉螺运动特性，分析了钉螺在渠系中扩散方式，从而为防止钉螺扩散提供了理论依据。     

細顆粒泥沙在靜水中的沉降运动

在靜水中的泥沙沉速,是研究泥沙运动規律时的一个重要指标.本文首先从泥沙的靜水沉降和水流中起动的一般規律出发,給出了細顆粒泥沙界說的分析过程和結論,并討論了在分散体系和集成体系中有关細顆粒泥沙組靜水沉速的計量标准.其次从絮擬作用对于細顆粒泥沙靜水沉降的影响出发,分析并解释了細顆粒泥沙在靜水中沉降的一般性規律.最后給出了在各种情况下計算細顆粒泥沙靜水沉速的建議公式.     

矿浆管辺水力(车入)送的试验研究

原文在试验的基础上,根据水流挟沙原理,提出了明槽和管道输送高与低浓度矿浆的临界流速公式。今仅就高浓度输送的几个问题,提出如下讨论意见。一、关于输送矿浆浓度对沉速的影响和修正系数的问题。原文正确地认为,当浓度增大到某一值后,输送临界流速由上升而变为下降,其原因在于矿砂细粒子含量的增加,使得矿浆中粒子的比表面积有较大的改变,从而引起了浑水的物理化学性质的变化。但又认为这种质变是清水动滞性系数V_0按(11)式变为V_m,从而以与沉速成反比的关系使矿砂沉速由清水中的ω_0减少到ω_m,同时用修正系数(12)式来修正低浓度公式。经将(9)、(10)式和(13)、(14)式比较后可知,文中     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

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.     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

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。     

Changes in Summer Irrigated Crop Area and Water Use in Southeastern Turkey from 1993 to 2002: Implications for Current and Future Water Resources

Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold (from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead to improved management, and by extension, sustainability of water resources in the region.     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.     

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.