长江口北港河势演变及趋势分析

根据长江口1977-2013年海图及2011-2012年北港洪枯季实测水沙、流速数据,结合历史资料对北港上、中、下三段南北港分流口、北港主槽、拦门沙河段的河势演变进行分析。结果表明:20世纪70至80年代南北港分流口河道更迭演变是导致北港河势变化的主要原因;1977-2001年为北港主河槽的调整期,河槽上段北偏,下段南偏;涨潮流导致北港北沙淤涨,且北港北汊分流比增多;目前北港洪、枯季落潮优势明显;洪季落潮输沙明显,枯季涨潮输沙较强;由于大量河口工程的建设,北港河势进入稳定期,适宜航道开发。     

长江口南北港分汊口控制工程对北港河势的影响

为识别长江口南北港分汊口控制工程对长江口南支北港河势的影响,利用控制长江口北港的两条固定监测断面在2002-2015年间9个年份实测的高分辨率、高精度水下地形数据,通过叠加对比分析,准确识别了剖面的水下地形变化特征。并通过"相邻年份剖面切面面积差值/剖面长度"的比值计算了不同年份间剖面地形的平均变化量,作为指示不同年份间剖面地形变化总体特征的指标,反映了剖面地形随时间变化的总体规律。结果表明:近十年来北港河势变化主要受到长江口南北港分汊口控制工程的影响,其影响特征在空间上差异显著,对北港上段(尤其南岸)河势影响明显,而对下段的影响有限(微弱变化主要发生在北岸);在时间上,北港上段和下段分别在工程竣工4年后和2年后达到稳定状态;2013年后北港河势趋于稳定,南北港分汊口控制工程已发挥显著作用,有利于北港航道开发。     

长江口北港河势演变分析

北港是长江河口的重要组成部分,近几十年来对北港的研究甚少。本文在前人研究的基础上,结合水文泥沙和地形资料,着重对北港中段(堡镇-团结沙水闸)近三十年来的河势变化进行分析。20世纪70年代以来,北港的河势变化经历了三个时期:(1)河势动荡时期(1972-1985年);(2)河势调整时期(1985-1996年);(3)河势相对稳定时期(1996年至今)。北港上口通道的变化是制约北港河势变化的主要原因。     

长江口北港河势演变趋势及工程影响分析

为研究20世纪末以来,长江口北港上口通道的河势变化及重大工程的影响,对北港历年-5 m和-10 m等深线变化、主泓线变化、典型断面形态变化进行分析。结果表明：北港主槽与其分流比存在一定程度的正相关性;20世纪末以来,北港上口分流通道相对稳定,但呈不断下移、逆时针偏转态势;北港逐步向单一河槽方向演变,主槽将恢复为上段偏北、下段偏南的微弯河道形态。分析结论说明：中央沙、青草沙工程的建成有利于继续维持北港这种发展态势,并使其在经过一段时间的调整后达到新的冲淤平衡。     

国务院批准长江口整治规划

近日,国务院批准了由长江水利委员会组织编制的《长江口综合整治开发规划要点报告》。《规划》明确,将通过实施河道整治、滩涂圈围、堤防工程、排灌工程、水源地建设,优选安排对河势稳定起主要控制作用的工程和满足淡水资源开发利用迫切要求的工程,逐步实现长江口综合整治2010、2020年目标。《规划》提出了长江口开发整治目标:近期到2010年,基本稳定南支上段河势,初步形成相对稳定的南、北港分流口,稳定分流南支上段河势,初步形成相对稳定的南、北港分流口,稳定分流态势;减缓北支淤积速率;减轻北支咸潮倒灌南支,改善南支淡水资源开发利用条件;适时启动白茆沙水道整治工程,满足近期航运发展对航道建设的需要;加快防洪工程及排灌工程建设步伐,达到近期防洪(潮)及排灌规划标准;初步抑制长江口局部水域水质恶化和生态环境衰退的趋势;合理开发新的岸线资源;适度圈围滩途,基本满足社会经济发展对土地资源的迫切需要。远期到2020年,进一步稳定和改善南北港分流口及北港的河势,全面改善南、北支淡水资源开发利用条件,进一步改善北港、南槽及北支的航道条件,促进河口地区生态环境进一步改善,全面达到长江口地区的防洪(潮)及排灌规划标准。长江口地区包括上海市和江...     

长江口北港拦门沙河段上段演变分析

根据水文泥沙观测和地形资料分析,三十多年来,在长江洪水造床作用、南北港分流口通道的兴衰更替以及北港分流分沙功能增强等因素作用下,北港拦门沙河段上段发生了较大变化,例六沙脊的形成及其沙尾下移;河道中央呈现纵长17km的水下沙脊,形成二槽一脊的W型复式河槽;团结沙外侧发育了北港北沙等地貌现象.     

长江口北港拦门沙河段演变分析

根据水文泥沙观测和地形资料分析,30多年来,在长江洪水造床作用、南北港分流口通道的兴衰更替以及北港分流分沙功能增强等因素作用下,北港拦门沙河段发生了较大变化,例六滧沙脊的形成及其沙尾下移;河道中央呈现纵长17km的水下沙脊,形成二槽一脊的W型复式河槽;团结沙外侧发育了北港口北沙等地貌现象。     

潼关——三门峡河段河势变化及其对库区冲淤的影响

汇流区黄河主流摆动常引起渭河河口位置及汇流方向的变化,下段河道河势随之改变。潼关－大禹渡段主流游荡,河床宽浅,水流分散;大禹渡－灵宝老城段河槽束窄,水流集中,河势以弯道发育为主;灵宝老城－－三门峡水库坝前段河势基本稳定。1977年大洪水以来,潼关－－大禹渡段河道主流摆动加剧,河槽展宽淤高。大禹渡以下湾道发育,弯曲半径变小,弯道河长增加。由此引起滩岸坍塌,河槽展宽坦化,河床淤积升高,同流量水位上升。     

近期长江口北港冲淤变化与微地貌特征

2014年7月11-18日和10月29-31日以多波束测深系统和浅地层剖面仪等先进现场测量仪器对长江口北港河槽进行走航测量,结合人类活动强干扰下的海图水深数据及河槽表层沉积物资料探讨近期长江口北港河槽冲淤变化与微地貌特征。结果表明:在流域来水量变化不明显,来沙量锐减的情况下,近年来长江口河口段中上游河槽整体上处于微冲刷环境,而青草沙水库工程的实施导致北港中段河槽的冲刷程度更甚且冲刷态势向下延伸。2002-2012年北港泥沙净冲刷量为6.54亿m3,平均每年冲刷0.65亿m3。在其冲刷环境的影响下,近期北港河槽底床上除发育平滑床底外,还广泛发育冲沟和凹坑等侵蚀性微地貌,而河槽受到冲刷将导致底沙推移质运动增强,同样有利于沙波微地貌的发育。沙波主要分布在河槽沉积物为细砂的北港中上段底床的大部分区域和拦门沙河段的局部区域。     

丰满水库坝下至河口段河道演变趋势分析

文章通过河床稳定性指标计算,结合平面套绘结果,分析第二松花江丰满水库坝下至河口段河势演变特征及演变趋势.河道平面形态以蜿蜒型和分汊型为主,横向多欠稳定;纵向上,丰满水库坝下至贾家崴子江段稳定,吉林市段存在下切,贾家崴子以下江段纵断面基本稳定.在堤防、护岸等工程的控制下,河道形势基本趋于稳定,下游分汊河段兴衰交替,具有一...     

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.     

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。     

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.     

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。     

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.     

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.