长江河口絮凝泥沙颗粒粒径与浮泥形成现场观测

分别于2006年枯(2月)和洪(8月)季利用较先进又较实用的现场观测仪器,对长江河口絮凝泥沙颗粒粒径、浮泥体及变化过程,以及与此相关的动力因子进行了现场现测,获得一批最新原始观测数据.观测数据显示:长江河口悬沙主要来源于长江流域的细颗粒冲泻质,小于32μm的细颗粒泥沙占80%以上,悬沙单颗粒粒径均值为3.6～6.8μm.在洪季流域来沙集中期,悬沙颗粒较细,均值为3.6～5.5μm,而枯季流域来沙少,悬沙颗粒略粗,均值为5.9～6.8μm;长江河口细颗粒泥沙絮凝环境良好,实测平均絮凝颗粒粒径为61.5μm,是分散单颗粒粒径的10倍多,最小絮凝颗粒粒径为27.4μm,最大为107μm,最大絮凝颗粒出现在0.4～0.7m/s的中等流速时段.在盐水到达的上界线徐六泾区域实测絮凝颗粒粒径相对较小,均值为32.6～60.4μm,而南北槽最大浑浊带区域絮凝颗粒粒径最大,均值为57.3～79.2μm,实测洪季絮凝颗粒粒径比枯季大,洪季均值为60.4～79.2μm,枯季均值为42.5～66.6μm.此外,长江河口浮泥发育与细颗粒泥沙絮凝快速沉降有关,而最大浮泥层常常发生在最大絮凝颗粒粒径出现的后期时段,故长江河口细颗粒絮凝沉降是浮泥形成的主要物质来源.     

NaCl对细颗 粒泥沙静水絮凝沉降动力学模式的影响

细颗粒泥沙的絮凝沉降对泥沙输移、土壤渗透性以及污染物迁移有重要作用. 在泥沙初始浓度为5g/L、10g/L、20g/L时, 作者用吸管法研究了不同浓度NaCl对细颗粒泥沙静水絮凝沉降的影响, 认为细颗粒泥沙相对浓度随时间的变化符合双曲线型动力学模式, 泥沙絮凝沉降越快, 研究发现泥沙中值沉速(中值粒径)随泥沙初始浓度和NaCl浓度的增大而增大, 但泥沙初始浓度和NaCl浓度较高时渐超缓慢; 细颗粒泥沙絮凝度与分散粒径呈幂函数关系, 细颗粒泥沙絮凝临界粒径为0.0245mm.     

NaCl对细颗粒泥沙静水絮凝沉降动力学模式的影响

细颗粒泥沙的絮凝沉降对泥沙输移、土壤渗透性以及污染物迁移有重要作用。在泥沙初始浓度为5g/L、10g/L、20g/L时，作者用吸管法研究了不同浓度NaCl对细颗粒泥沙静水絮凝沉降的影响，认为细颗粒泥沙相对浓度随时间的变化符合双曲线型动力学模式，泥沙絮凝沉降越快，研究发现泥沙中值沉速（中值粒径）随泥沙初始浓度和NaCl浓度的增大而增大，但泥沙初始浓度和NaCl浓度较高时渐趋缓慢；细颗粒泥沙絮凝度与分散粒径呈幂函数关系，细颗粒泥沙絮凝临界粒径为0．0245mm。     

长江河口控制站泥沙絮凝特性研究

基于2008-2014年逐月现场激光粒度仪(LISST)在长江口徐六泾的定点观测数据,分析了河口控制站徐六泾的悬沙絮凝特性,研究给出絮团粒径与有效密度及沉速的关系。统计表明絮团平均粒径变化范围20~120μm,比分散颗粒中值粒径(平均5.3μm)大一到两个数量级。絮团的分形维数主要在1.8~2.4,有效密度变化范围70~600kg/m~3,其随絮团增大呈减小趋势。洪枯季对比表明,洪季絮团沉降速度比枯季大18%,平均沉速分别为0.26mm/s和0.22mm/s,比以往估算得到的长江口浑浊带絮团沉速小。由此说明为更好认识流域到河口的泥沙输运过程,有必要针对长江河口不同区域进行分段的研究。     

紊动对黏性细颗粒泥沙絮凝沉降影响的试验研究

利用室内环形水槽及高倍摄像设备,定量研究了不同悬沙浓度及紊动剪切对黏性细颗粒泥沙絮凝沉降特性的影响。试验中观测到的絮团粒径为分散颗粒的几倍到几十倍,絮团中值粒径随着水体紊动剪切的增大呈先增大后减小的变化趋势,最大的中值粒径约为150μm,出现在紊动剪切为30 1/s条件下。悬沙浓度的增大促进絮团的发育,在350 mg/L条件下形成的絮团整体粒径比150 mg/L条件下的更大。絮团中值沉降速度在0.7～3.4 mm/s之间,絮团最大的中值沉速出现在紊动强度最大时65 1/s,此时所形成的絮团结构密实,有效密度较大。絮团有效密度随着粒径的增大而减小,研究表明,采用变分形维数方法,对有效密度随粒径变化的模拟结果与试验结果吻合较好。     

长江口浑浊带絮凝体特性

2005年1月,在长江口浑浊带所在的南槽水域,利用现场激光粒度仪(LISST-100),在不扰动天然细颗粒泥沙絮凝体的情况下,定点连续测量了涨落潮变化过程中表层水体细颗粒泥沙絮凝体的级配谱;并用OBS-3A和ADP同步测得表层水体的含沙量、盐度和流速.数据分析表明,在长江口浑浊带水域存在明显的粘性细颗粒泥沙絮凝现象,絮凝体的形成和破碎过程非常明显:水流动力条件直接导致絮凝体的破碎,盐水则促进絮凝体的形成;水流流速和盐度的变化分别造成了絮凝体的四分之一日和半日周期的变化,在长江口浑浊带水域盐度对粘性细颗粒泥沙絮凝的影响比水动力条件的影响更大且更快;粘性细颗粒泥沙发生絮凝现象的临界粒径为32.5μm左右.这为长江口浑浊带形成机制及长江口粘性细颗粒泥沙动力沉积过程的研究提供了依据.     

粘性细颗粒泥沙絮凝研究概述

以絮凝动力学理论(Smoluchowski方程)、胶体稳定性理论(DLVO理论)和分形几何(Fractal Geometry)在絮凝研究中的应用为线索，回顾了粘性细颗粒泥沙絮凝结构，絮团沉速，以及影响絮凝因素(泥沙粒径、浓度、电解质阳离子、温度和水流紊动等)等方面的研究成果；综述了絮团的尺寸、密度、沉速、破坏强度及碰撞频率函数的分形几何描述方式；介绍了快速絮凝和慢速絮凝的分形生长模型，以及絮凝发育过程数值模拟的研究进展．针对河流泥沙在矿物组成、颗粒尺度、表面电荷分布和水中盐分多样性的特点，以及粘性细颗粒泥沙絮凝研究的特殊性，提出进一步深化粘性细颗粒泥沙絮凝研究的建议．     

AlCl3、MgCl2、CaCl2和腐殖酸对高浊度体系细颗粒泥沙絮凝的影响

以细颗粒泥沙为主的河口区往往存在最大浑浊带,对高浊度体系细颗粒泥沙的絮凝研究有助于了解最大浑浊带的形成机制。本文通过实验研究AlCl3,MgCl2,CaCl2和腐殖酸四种絮凝剂对长江口细颗粒泥沙浊度变化的影响,从絮凝率、絮团粒径和Zeta电位变化三方面综合分析了四种絮凝剂对泥沙絮凝的作用机理。结果表明:1)随着金属离子浓度增大细颗粒泥沙絮凝率逐渐增大,粒径增大,而电位绝对值变小;随着腐殖酸浓度增大细颗粒泥沙絮凝率降低,粒径增大,电位绝对值增大;2)各絮凝剂单独存在时的絮凝机理与多组分复合絮凝作用机理有明显不同,C-P-OM复合絮凝模式能够较好地揭示长江口高浊度区细颗粒泥沙絮凝体的形成机制。     

长江口细颗粒泥沙沉降速度室内试验研究

对细颗粒泥沙的基本特性尤其是沉降特性进行深入探索有助于解决泥沙学科很多悬而未决的问题。在查阅大量中外文献的基础上,借助大型可温控自动搅拌沉降试验筒,对长江口天然细颗粒泥沙的沉降机理展开了室内试验。结果表明:含沙量和粒径均是影响细颗粒泥沙沉速的重要因子,并进一步推断细颗粒泥沙絮凝沉降的过程可能是一个絮凝体、絮网结构"网捕-重构"的过程。     

珠江磨刀门河口洪季泥沙絮凝机理研究

基于珠江磨刀门河口2013年7月现场观测的悬浮物资料,综合同步测验的盐度、流速、悬沙浓度、水温,以及室内泥沙粒度分析数据,探讨了该区域泥沙絮凝特征及其主要影响因素,结果发现:磨刀门悬沙现场粒径平均达91.7μm,而平均分散粒径仅29.3μm;小潮泥沙絮凝较大潮明显,潮周期内憩流时刻絮团最大,可达200μm;絮凝效应垂向差异显著,表现为中层最大而表、底层较小;功率谱分析得到现场粒径具有3h、8h和24h的变化周期,其中8h与平均落潮周期相近,24h则与全潮周期相近。研究表明,控制磨刀门悬沙絮凝的因素主要为流速,絮凝临界流速约45cm/s;盐度则在弱动力条件下(流速50cm/s)控制着河口泥沙絮凝,最佳絮凝盐度为21‰;悬沙浓度和温度对絮凝影响不显著;垂向水动力及盐度差异是导致絮凝效应垂向差异的主要原因。     

Seminar on Water and Energy,Stockholm, Sweden,August 21, 2005

Abstract

In Europe the implementation of the Water Framework Directive (WFD) will have major implications for water resources management. Part of the Directive requires Member States to implement a comprehensive system of controls (licences) on the allocation and abstraction (withdrawal) of surface and groundwater resources. This paper describes the development of a procedure to help assess and set abstraction licences for agricultural irrigation. The methodology is described with reference to Scotland, a country with limited abstraction control previously and where irrigation is supplemental to rainfall. The methodology combines spatial climatic information using a Geographical Information System (GIS) with data derived from a water balance computer model. The procedure enables the volumetric irrigation demand in a ‘design’ dry year for a given site to be estimated, taking into account local variations in climate, soil type, land use and irrigation practices. The approach provides a scientifically robust framework to allow the regulatory authority to assess the ‘reasonable’ water requirements of individual irrigators and hence develop allocations to satisfy the range of competing demands (e.g. agriculture, industry, and environment) on water resources. The methodology is applicable in other temperate countries where water abstraction controls are required and where appropriate datasets are available. The application of the procedure and its methodological limitations are described.     

长江中游四大家鱼发江生态水文因子分析及生态水文目标确定

基于长江中游四大家鱼发江量历次调查数据,采用宜昌站作为长江中游水文情势变化分析的控制站,基于其1900~2004年共105年的日径流资料,采用每年5~6月涨水过程数、总涨水日数、平均每次涨水过程日数等3项生态水文指标,分析了四大家鱼发江量与3项生态水文因子的变化关系,认为产卵场所处江段每年5~6月的总涨水日数是决定家鱼苗发江量多寡的一个重要环境因子。根据IHA方法,对宜昌站105年来的生态水文指标分析表明,长江宜昌站生态水文过程的改变并不明显,5~6月总涨水日数变化趋势不显著,显示长江中游影响四大家鱼苗发江量的生态流量过程改变不明显,与前人得出的葛洲坝枢纽修建后四大家鱼的产卵条件和卵苗江汛规律没有变化这一认识一致。但是,随着三峡水库的运行,下游河道的生态环境流量过程会有较大改变,本文建议三峡水库的调控以保障长江中游每年5~6月的总涨水日数维持在22.1±7.2范围内为生态水文目标,即可从生态环境流量过程方面补偿水利工程对中游四大家鱼鱼苗发江量的影响。     

Stakeholder-driven,enquiry-driven,or stakeholder-relevant,enquiry-driven science?

There is currently debate within the international hydrological community on whether hydrological science should give priority to providing measurements, knowledge, and understanding pre-determined as being needed by stakeholders, or priority to more basic enquiry-driven science that will stimulate the continued health and growth of hydrology as an important Earth science discipline. Two recent major international initiatives in hydrology reflect these two perspectives. One, the Hydrology for the Environment, Life, and Policy (HELP) program, is primarily fostered by UNESCO-IHP and is focused on stimulating the stakeholder-driven hydrological science required in specific catchments that have become members of a global network. The second, the decade on Prediction in Ungauged Basins (PUB), which is appropriately managed by IAHS, is primarily driven by scientific enquiry and is focused on creating new scientific methods and understanding, albeit with practical application ultimately in mind. This paper summarizes the nature, origins, growth, and progress of these two international programs but also describes the subtly different approach that has been adopted by the U.S. National Science Foundation's (NSF's) Center for Sustainability of semi-Arid Hydrology and Riparian Areas (SAHRA). NSF is a federal agency whose primary goal is to ‘enable the future’ by stimulating novel science. Because SAHRA is a federally-funded entity supported by an agency with this goal, the Center clearly cannot operate in stakeholder-driven, response mode in competition with the already effective private U.S. consultancy industry. Nonetheless, SAHRA's mission is to create knowledge and build understanding that will enhance the prospects of sustainable water management in semi-arid regions, especially the southwestern U.S. To resolve this apparent conflict, SAHRA looks ahead to future stakeholder needs and builds its research agenda around selected critical stakeholder-relevant questions that require substantial and sustained investment in basic, multidisciplinary, enquiry-driven science. This paper describes SAHRA's approach and reports on associated research and outreach activities.     

水-能源-粮食纽带关系定量研究方法综述

在总结水-能源-粮食纽带关系研究中, 使用频率较高或潜力较大的 8 种水-能源-粮食纽带关系定量研究方法为: 水-能源-粮食纽带关系工具 2.0( WEF Nexus Tool 2.0) ; 生命周期评价( LCA) ; 可计算的一般均衡模型( CGE) ; 系统动力学模型( SD) ; 气候、土地、能源与水资源策略( CLEWS) ; 基于社会生态系统代谢的多尺度综合评价( MuSIASEM ) ; 市场配置/ 市场配置系统集成模型( MARKAL/ TIMES) 和水资源评价规划模型-长期能源替代规划系统 ( WEAP2LEAP) 。通过总结各研究方法的产生、发展及特性, 并引用案例讨论其适用范围, 分析其优缺点和在使用 时需要注意的问题。在此基础上, 对未来水2能源2粮食纽带关系定量研究方法的发展趋势进行讨论, 认为伴随可持 续发展问题关注度的上升与水-能源-粮食纽带关系内在机理的挖掘, 未来的水-能源-粮食纽带关系定量研究方法将 更加注重量化的精确性和数据的互通以及跨学科研究和多方法的耦合。本文可为水-能源-粮食纽带关系定量研究方法的选择和更新优化提供参考。     

Growth,Reproduction, Mortality,Distribution, and Biomass of Freshwater Drum in Lake Erie

Predominant age-groups in the Lake Erie freshwater drum Aplodinotus grunniens population were 3, 4, and 5 as determined from gill net, trap net, bottom trawl, and midwater trawl samples. Age and growth calculations indicated that females grew faster than males. However, the length-weight relation did not differ between sexes and was described by the equation: log W = ?5.4383 + 3.1987 log L. Some males became sexually mature at age 2 and all were mature by age 6. Females matured 1 year later than males. Three sizes of eggs were present in ovaries; the average total number was 127,000 per female for 20 females over a length range of 270 to 478 mm. Seasonal analysis of the ovary-body weight ratio indicated that spawning extended from June to August. A total annual mortality rate of 49% for drum aged 4 through 11 was derived from catch-curve analysis. Freshwater drum were widely distributed throughout Lake Erie in 1977–1979, the greatest concentration being in the western basin. They moved into warm, shallow water (less than 10 m deep) during summer, and returned to deeper water in late fall. Summer biomass estimates for the western basin, based on systematic surveys with bottom trawls, were 9,545 t in 1977 and 2,333 t in 1978.     

Survival,Growth, and Movement of Subadult Humpback Chub,Gila Cypha,in the Little Colorado River,Arizona

Ecologists estimate vital rates, such as growth and survival, to better understand population dynamics and identify sensitive life history parameters for species or populations of concern. Here, we assess spatiotemporal variation in growth, movement, density, and survival of subadult humpback chub living in the Little Colorado River, Grand Canyon, AZ from 2001–2002 and 2009–2013. We divided the Little Colorado River into three reaches and used a multistate mark‐recapture model to determine rates of movement and differences in survival and density between sites for different cohorts. Additionally, site‐specific and year‐specific effects on growth were evaluated using a linear model. Results indicate that summer growth was higher for upstream sites compared with downstream sites. In contrast, there was not a consistent spatial pattern across years in winter growth; however, river‐wide winter growth was negatively related to the duration of floods from 1 October to 15 May. Apparent survival was estimated to be lower at the most downstream site compared with the upstream sites; however, this could be because in part of increased emigration into the Colorado River at downstream sites. Furthermore, the 2010 cohort (i.e. fish that are age 1 in 2010) exhibited high apparent survival relative to other years. Movement between reaches varied with year, and some years exhibited preferential upstream displacement. Improving understanding of spatiotemporal effects on age 1 humpback chub survival can help inform current management efforts to translocate humpback chub into new locations and give us a better understanding of the factors that may limit this tributary's carrying capacity for humpback chub. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

River channel cutoff dynamics,Sacramento River,California, USA

We measured patterns of river channel migration and cutoff between 1904 and 1997 on a 160 km meandering alluvial reach of the Sacramento River by intersecting a sequential set of river channel centrelines mapped from a field survey and aerial photography. We identified approximate dates and locations of cutoffs and quantified cutoff dimensions. Twenty‐seven chute and 11 partial cutoffs occurred over this 93‐year time interval, with an average of one cutoff approximately every 2.5 years or 0.0029 cutoffs per kilometre per year. The average rate of lateral channel change was over the study period was 5.5 ± 0.6 m year^?1 (approximately 0.02 channel widths per year) due to progressive migration and cutoff combined. An average of 5% of the total channel length moved laterally via chute cutoff at a rate of 22.1 ± 3.3 m year^?1 versus 94% of channel length that moved via progressive migration at a rate of 4.7 ± 0.5 m year^?1. The remaining 1% of channel length migrated via partial cutoff at a rate of 13.0 ± 2.8 m year^?1. Although channel cutoff was less predominant mode of channel change than progressive migration in terms of channel length, an average of 20% of the total floodplain area change between successive centrelines was attributable to cutoffs. Peak cutoff frequency was concentrated temporally between 1964 and 1987 and was also spatially clustered in specific active sub‐reaches along the valley axis over the entire study period. We hypothesize that the probability of channel cutoff is a function of both channel geometry and discharge. Bends that experienced chute cutoff displayed an average sinuosity of 1.97 ± 0.1, an average radius of curvature of 2.1 ± 0.2 channel widths and an average entrance angle of 111 ± 7°, as opposed to average values for bends migrating progressively of 1.31 ± 0.01, 2.8 ± 0.1 and 66 ± 1°, respectively. The sinuosity of Sacramento River bends experiencing chute cutoff appears to have been consistently declining from 2.25 ± 0.35 channel widths in 1904 to 1.54 ± 0.23 channel widths in 1987. We hypothesize that this trend may be due in part to the influence of land‐use changes, such as the conversion of riparian forest to agriculture, on the ‘erodibility’ of bank and floodplain materials. For the post‐dam flow regime (1937 on), cutoff frequency was significantly correlated with an estimate of cumulative overbank flow. Copyright © 2010 John Wiley & Sons, Ltd.     

淮河治理与河湖江海的关系

根据淮河近千年演变记录、近百年实测的河床演变资料以及治淮的经验教训,论述黄河夺淮使淮河中下游发生本质性变化,加重了洪涝灾害和治理的难度,治淮不仅要研究淮河自身,还应研究和处理淮河与黄河、洪泽湖、长江和大海的关系。认为保留洪泽湖一定的蓄水功能,实施河湖分开,扩大入海通道,消除洪泽湖作为中游侵蚀基准面的负面效应,利用疏浚和溯源冲刷调整淮河中游河床纵剖面等措施,是提高已有治淮工程防洪标准、减轻洪涝灾害的治本方向。