明渠水流阻力研究现状分析

只有正确深入地把握水流阻力规律,才能掌握解决水力学及河流动力学中各种实际问题的主动性。本文通过系统评述和研究分析前人成果,对相关问题有所澄清。历史上曾经影响较大且不需要调整参数的杜博公式、艾特魏因公式、曼宁第二公式,可反映曼宁公式所代表的平均情况,但难以像曼宁公式那样能够适应自然界复杂多变的摩阻特性。至于巴辛公式,若将其河道粗糙特征的系数与曼宁糙率系数建立关系,同样能够适用于水流阻力计算。对于动床阻力问题,众多学者已认识到水流强度、河床形态的变化及流体中含沙浓度的重要影响,也通过不同角度建立了一些经验或半经验公式。为能找出实用性强或精度高的计算公式,还必须注重分析水流、河床与泥沙运动之间相互影响的内在机理,尤其需要在各种因子的影响机理及计算途径上开展深入研究。     

平原地区城市内河调水增氧与曝气增氧的比较

为了解决平原地区城市内河溶解氧过低问题,在数学模型推演的基础上,以常州市典型内河为例进行计算,比较调水增氧与曝气增氧的效果和成本差异,为投资与管理决策提供技术支撑。分析结果表明,在平原地区城市内河,调水增氧与曝气增氧的效果与成本主要受上游可调入河水溶解氧水平、河道自由流量、调水水泵动力效率、曝气设备增氧动力效率等因素影响。当上游河道溶解氧水平较高、河道自由流量较小时,调水增氧较为适宜,否则应考虑采取曝气增氧。在常州市内河河道,曝气增氧的溶解氧达标率、运行电耗和总体成本等指标均优于调水增氧,是更为适宜的河道增氧方式。     

Nutrients and water level fluctuations: A study of three aquatic plants

Water holes characteristic of the middle sections of fragmented, lowland, semi‐arid rivers act as refuge areas for biota during low flow and drought. However, river regulation and catchment development has altered the hydrological and nutrient status of these refuges. A series of artificial ponds were used to imitate these habitats and experiments were designed to determine whether stochastically fluctuating water levels with maximum amplitude of 65 cm would counteract the influence of nutrient enrichment on the growth of three key aquatic plant species. The species (Cyperus gymnocaulos, Triglochin procerum and Typha domingensis) represented different functional groups that inhabit contrasting zones across the elevation gradient. Each species was grown at a different elevation within the experiment reflecting each species' elevation preference and supplied with the equivalent to 0, 10 or 30 g N m^?2 year^?1. Under a static water regime nutrient enrichment doubled the total biomass of all three species. In contrast under a fluctuating water regime, nutrient addition did not influence total biomass of either T. domingensis or T. procerum and the performance of C. gymnocaulos was reduced by ca. 30%. These data suggest that if environmental flows were managed to provide a natural stochastically fluctuating water regime, this would nullify the influence of nutrient enrichment and limit the distribution and spread of invasive species such as Typha, that exists under the current altered conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Flow structure through pool‐riffle sequences and a conceptual model for their sustainability in gravel‐bed rivers

Detailed field measurements and simulations of three‐dimensional flow structure were used to develop a conceptual model to explain the sustainability of self‐formed pool‐riffle sequences in gravel‐bed rivers. The analysis was conducted at the Red River Wildlife Management Area in Idaho, USA, and enabled characterization of the flow structure through two consecutive pool‐riffle sequences, including: identification of jet concentration and dissipation zones, and the development of local turbulence features (i.e. vertical and horizontal eddies) under different flow conditions. Three‐dimensional hydraulic simulations were used to evaluate how the flow structure varies across a range of flow conditions and with different degrees of sediment aggradation within the upstream pool. The analysis demonstrated a significant influence of the residual pool depth on the flow structure, with reduced residual depth causing a shift in the orientation of the jet and a reduction in the influence of vertical eddies and the size and intensity of horizontal eddies. The proposed conceptual model seeks to explain the sustainability of pools in terms of the flow structure in pool‐riffle morphology and how this flow structure will change as a result of altered external forcing, such as upstream sediment delivery or changes in bank stability. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a fish‐based index of biotic integrity (FIBI) for monitoring riverine ecosystems in the Lake Victoria drainage Basin,Kenya

The long term monitoring of aquatic ecosystems based on chemical analysis is expensive resulting in a lack of time series data for management purposes thus necessitating the need for new cost effective methodologies. This study developed a fish‐based index of biotic integrity (FIBI) for monitoring environmental conditions in riverine ecosystems within the Lake Victoria Basin, Kenya. The fish fauna in the basin is poorly studied, less diverse and ecologically specialized than the temperate fauna that provided the origins of the Index of Biotic Integrity. Fish samples were collected by electrofishing from 24 sites during baseflow periods in February, March and July 2004. Validation data were collected from 7 sites with varying levels of degradation. Fish samples were identified, counted and grouped into different trophic groups, relative tolerance to pollution, habitat guild and whether exotic or native to riverine environment. Thirty‐three candidate metrics were evaluated for responsiveness to habitat quality and twelve were selected for inclusion in the final index. The index classified 6 of the 7 validation sites according to their levels of degradation. As a bioassessment tool, the index was useful in laying the basis for long‐term monitoring of rivers in the Lake Victoria drainage basin. Copyright © 2010 John Wiley & Sons, Ltd.     

一维河流水团示踪试验数据的模糊线性回归

将模糊线性回归的概念引入分析河流水团示踪试验数据、确定河流水质参数的计算过程中,建立计算河流水质参数的模糊线性回归模型,利用该模型能计算出不同置信水平下水质参数的取值范围。算例验证结果表明,应用模糊线性回归模型可以有效地确定河流的水质参数,且计算过程具有一定的稳定性、可靠性和灵活性,模糊线性回归模型是分析河流水团示踪试验数据、确定河流水质参数的一种有效的途径。     

大庆市河湖连通工程园林景观影响评价

工程项目区位于大庆市东部低湿草甸草原区,湿草甸及芦苇泡沼发育,具有黑龙江省西部湿草甸及芦苇泡沼典型景观。根据风景质量评价标准,对项目区的风景进行了定量评价,评价为B级,并用景观敏感度影响评价方法,提出合适的保护措施。     

浅谈平原河网地区防洪系统的调度

根据太湖流域防洪调度实际情况,对其气象信息、实时水位及其特征值等水情信息和实时工情分析,进行防洪形势分析。按照太湖流域防洪调度规则,进防洪调度的仿真计算,形成供决策者参考的调度方案。     

二元驱动的河湖历史演变及其启示

以河湖历史演变过程为研究对象,分析了演变的驱动力及其作用特征、影响因素,提出河湖演变呈现出由自然-人工二元平行驱动向二元交错驱动发展的趋势。针对在人为改变河湖水系的历史过程中曾出现过的问题和风险,重点讨论了当前水系布局规划需要思考的问题,包括自然地理分异、气候变化、成本效益、生态环境等。建议拓展研究的维度和尺度,合理利用自然情势并关注人类活动潜在而深远的影响,多途径削减不利影响,以构建满足水资源合理配置、兴利除害、生态环境保护等社会需求的江河湖库水系格局。     

苏北平原河网区典型农村中小河流水体氮磷赋存特征

以苏北平原河网区的盐城市射阳县某个典型圩区(面积12.73km2)为例,通过连续15个月对圩区内沟渠河流水体采样分析,研究苏北平原河网区中小河流地表水氮磷赋存特征。结果表明:研究区域中小河流水体氮磷超标严重,水体处于富营养化状态。所有水样品总氮质量浓度均超过GB 3838—2002《地表水Ⅲ类水质标准》(ρ=1.0 mg/L),79%的总氮质量浓度超过Ⅴ类水质标准(ρ=2.0 mg/L);73%的总磷质量浓度超过Ⅲ类水体标准(ρ=0.2 mg/L),39%的样品超过Ⅴ类水质标准。地表水氮素和磷素主要以溶解态形式存在;硝态氮是溶解态总氮主要赋存形态,相应的比例约为60%,铵态氮比例最少,约为10%;溶解态活性磷是溶解态磷素主要赋存形态,约为80%。畜禽养殖相对集中区域地表水氮素和磷素浓度高于其他区域;中沟、干渠等小型河流水体在夏季存在水质分层现象。