南水北调中线工程冬季输水冰情的数值模拟

南水北调中线工程总干渠是由明渠和各种过水建筑物组成的树状系统,特点是线路长、过水建筑物类型多、冰水动力学响应过程复杂。本文将冰情发展模型与树状明渠系统复杂内边界条件下的渠道非恒定流模型进行集成耦合,开发了大型长距离调水工程冬季输水冰情数值模拟平台,提出了树状明渠系统复杂内边界条件的等效变换方法和计算冰盖前缘动态发展的虚拟流动法。根据实测的沿线气象资料和设计资料,利用该平台系统模拟了在寒冷气温条件下总干渠初冰、冰盖形成、发展和消融过程。分析了冬季输水的冰情特性及冰期输水能力,提出了冰期安全运行的水力控制条件,通过对典型年总干渠敞流期、冰盖形成期、稳封期、调度期以及开河全过程的模拟,给出了安全运行输水调度方案及建议。     

黄河下游2010年汛前调水调沙河势监测分析

利用环境减实卫星遥感监测影像,分析了2010年黄河调水调沙下游河势现状,并通过对比近几年河势变化情况,分析了调水调沙对河势的影响。结果表明:①经过多年调水调沙,黄河下游河道主槽刷深,过流能力大大增强,河势也相对稳定;②一些原来靠溜较好的工程,如驾部、南裹头、马庄、马渡险工等,有脱河脱溜的趋势,建议对这些河段加强河势变化监测;③在多年调水调沙作用下,毛庵—三官庙、黑岗口—东坝头河段工程靠溜状况趋好,河势逐步向有利方向发展,尤其是柳园口—欧坦工程河段,大部分原来不靠河的工程开始逐步靠溜,当前河势较为顺畅。     

相应流量自动化实时报汛技术研究与应用

为了研制相应流量计算模型,对常用的相应流量计算模型的适用范围、精度进行了分析,包括单一线模型、单值化模型、动态差分模型、经验绳套模型。针对不同流量的计算方法,结合人机交互技术,建立了相应流量计算模型。通过选择具有不同水位流量关系的典型水文测站,对模型的预报精度进行了验证。验证结果表明：一次洪水过程的大部分时段预报结果与实测结果吻合较好,预报精度提高;测站水位流量关系的静态单值化精度对相应流量自动化实时报汛精度影响很大,是今后继续深入研究的一个方向。     

长江南京八卦洲汊道治理与沿岸经济发展探讨

长江南京八卦洲汊道左汊缓慢衰退、分流比减小,河床淤积抬高,影响了沿岸大型企业集群的运行安全。介绍了八卦洲汊道已实施的整治工程和效果,结合汊道沿江地区的经济发展状况,提出保持河势长期稳定和充分利用岸线资源等汊道整治需求,提出系统整治的指导思想和初步方案,并针对具体的整治要点和难点提出针对性建议,以期提供适合岸线开发利用的水域条件,促进沿岸经济可持续发展。     

水情自动监测系统在牡丹江上游防汛中的应用

水情自动监测系统是通过及时收集上游雨量、水位等水文信息进行分析,提前获得水情预报,在水文水资源监测自动化、现代化建设中发挥积极的作用。该系统在牡丹江流域防汛使用过程中设置合理、性能稳定、运行可靠。     

荆江河段水沙条件与主流线特征关系研究

荆江河段的主流变化主要表现为弯曲分汊段的主支汉交替及单一弯道段深泓半径的变化,综合考虑两者关系,提出了能描述荆江分汉段及单一弯道段主流线特点的无量纲常数--弯曲特征数r,并针对同一河段分析了汛期平均流量、洪峰变差系数、年输沙量及输沙指数等水沙条件变化与主流线变化的对应关系.结果表明:汛期平均流量较小、水流相对饱和度低、来水来沙过程较为均匀使得滩槽高差较小,横断面向宽浅发展,从而减弱河道对水流的约束,弯曲特征数较小,主流顺直;反之主流向弯曲发展.     

Spatial variability of thermal regimes and other environmental determinants of stream fish communities in the Great Lakes Basin,Ontario, Canada

Temperature is one of the most important environmental variables in stream ecosystems because it affects the growth, survival and distribution of stream biota. This study examined if the spatial variability of thermal regimes and 18 other environmental variables were associated with fish communities in watersheds throughout the Great Lakes Basin (GLB), Ontario. The thermal regimes were defined as regimes 1, 2 and 3 and had maximum water temperatures of 26.4, 28.4 and 23.5°C, and spring warming rates of 0.20, 0.12 and 0.10 °C d^?1, respectively. The spatial variability of the thermal regimes (VTR) within the watersheds was summarized into four VTR groups: S1, S2, M23 and M123. Stream sites in S1 watersheds had temperatures characteristic of regime 1 whereas stream sites in S2 watersheds followed regime 2. M23 watersheds had sites with a mix of regimes 2 and 3 whereas M123 watersheds had all three thermal regimes at sites throughout watersheds. Canonical correspondence analysis (CCA) indicated that 16% of the variation in fish communities was related to the spatial VTR in the watersheds. Forward selection CCA indicated that elevation, the S1 VTR group, sparse forest cover, wetland area, base flow index (groundwater discharge potential), flow and industrial stress explained 42% of the variance in the fish communities. Simplified indicator species analysis (ISA) showed that different species could be used as indicators for each of the VTR groups. Human activities such as industrial development, deforestation, groundwater withdrawal and flow alteration all may affect the environmental variables related to stream fish communities. Copyright © 2010 John Wiley & Sons, Ltd.     

陕西省水情信息自动化建设存在的问题与对策

陕西省属旱涝频发的省份之一,随着经济社会的迅猛发展,洪、旱灾害所造成的损失越来越大,水情信息的准确快捷显得尤为重要。总结了陕西省水情信息自动化建设的现状,分析了存在的问题,提出了相应的对策,以促进陕西省水情信息自动化建设健康可持续发展,为防汛抗旱和水资源管理提供强有力的技术支撑。     

变速恒频双馈风力发电机网侧变换器研究

描述了变速恒频双馈风力发电机双PWM网侧变换器的结构特点和运行原理。在分析了双PWM网侧变换器在三相静止坐标系下的数学模型基础上,导出了两相同步旋转坐标系下的数学模型。为变速恒频风力发电机交流励磁电源控制器设计提供了理论依据。     

Modeling sediment resuspension and transport induced by storm wind in Apalachicola Bay, USA

Sediment is an important environmental factor for aquatic ecosystem and oyster productivities of Apalachicola Bay located in Florida, USA. Based on the data analysis in this study, surface wind speed is highly correlated to the turbidity of water column, which results from sediment resuspension and transport in the Apalachicola Bay. In this paper, an application of a 3D sediment transport model to predict the wind-induced sediment transport in Apalachicola Bay is described. The sediment model is coupled with a 3D hydrodynamic module in the Environmental Fluid Dynamics Code (EFDC) model that provides information on estuarine circulation and salinity transport under normal temperature conditions. The hydrodynamic model was calibrated with field observations of water levels and salinity. The sediment transport model solves the transport equation with sources and sinks terms to describe sediment deposition and resuspension. The coupled hydrodynamic and sediment transport models were used to investigate wind-induced total suspended sediments (TSS) resuspension and transport in the bay. For the period June 1–July 30, 2005 two storm events with strong winds gave model results of TSS concentrations that compared well with the field observations. Model simulations reasonably reproduce the sudden increase of sediment concentrations during the storm events. Maximum sediment concentrations in the bay during the two storm events were 10 times or more than those in the pre-storm conditions. Spatial sediment transport from model simulations indicate active sediment resuspension and transport near areas of highly productive oyster beds. The model predictions of TSS and salinity can be used as inputs to an oyster dynamic model (Wang, H., Huang, W., Harwell, M., Edmiston, L., Johnson, E., Hsieh, P., Milla, K., Christensen, J., Stewart, J., Liu, X., 2008. Modeling eastern oyster population dynamics in response to changing environment in Apalachicola Bay, Florida. Journal of Ecological Modeling 211, 77–89) to support the ecological study of oyster growth and mortality in the aquatic ecosystem of Apalachicola Bay.