共查询到20条相似文献，搜索用时 15 毫秒
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D. A. Hughes 《河流研究与利用》2009,25(7):850-860
Existing hydrological approaches to support the determination of environmental water requirements (EWRs) were largely developed for perennial rivers and may not be applicable to ephemeral rivers, where the quantity and quality dynamics of pool storage and frequency of connection can be more important than flow rates. The current understanding of semi‐arid hydrological processes and how best to apply hydrological models in ephemeral systems is less well developed than for more humid regions. The paper reports on the application of monthly and daily time‐step rainfall‐runoff models to simulating the hydrology (including pool storage) of the Seekoei River basin, a tributary of the Orange River in the Northern Province, South Africa. The hydrological response of the basin is spatially variable, a relatively small part of the basin generating a large proportion of the total stream flow. The outputs from the hydrological models have been used as inputs to a simple water quality mass balance model designed to simulate the total dissolved solids (TDS) of both flow and pool storage. The results from both the water quantity and quality models are encouraging when compared with the available observed data. While there are no data to confirm the simulation results at sub‐basin scales, they do appear to be conceptually acceptable. The conclusion is that the results are adequate to support ecological studies in the determination of EWRs. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Julian C. Green 《河流研究与利用》2005,21(6):671-686
The proportion of a river channel containing vegetation (termed the blockage factor) has historically been determined in three ways: cross‐sectional, surface area and volumetric. The first two versions are two‐dimensional measures. Meanwhile, the three‐dimensional volumetric version is biased towards deeper sections of a reach. A fourth version of the blockage factor is proposed that does not have such limitations: the multi‐cross‐sectional blockage factor. Between five and nine cross‐sections were sampled to determine the four blockage‐factor versions for 35 river sites containing the clumped submergent macrophyte, Ranunculus subgenus Batrachium (water‐crowfoot). The ability of these four measures to act as predictors of vegetative channel resistance was then assessed. The vegetated proportion of individual cross‐sections was poorly related to the vegetation resistance of a channel reach, primarily due to the high spatial variability of patch‐forming macrophytes. The weighted median of all cross‐sectional blockage factors measured at each site produced the strongest relationship with vegetation resistance, though this was not significantly better than the volumetric or surface area versions. The resistance model using the surface‐area blockage factor gave a very high residual between predicted and calculated resistance for a mat‐forming macrophyte species, and this model is unlikely to hold for conditions other than baseflow. Likewise, the volumetric version is not expected to hold for sites that have more depth variability than those measured in this study. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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HUI Er-qing HU Xing-e JIANG Chun-bo MA Fang-kai ZHU Zhen-duo 《水动力学研究与进展(B辑)》2010,22(3):329-337
This study is focused on the effects of ecological factors (diameter and flexibility) and vegetation community composition on the drag coefficient related with vegetation. The single leafy shrub and three mixed communities (including shrub-grass, shrub-reed and reed-grass community) were studied. The flow velocity and water level were measured and used to calculate the drag coefficient based on the Bernoulli's equation, Darcy drag formula and the expression for the drag coefficient related with Darcy drag factor. The trend of the drag coefficient in the vertical direction was analyzed against flow depth, diameter, diameter Reynolds number, flow depth Reynolds number and relative roughness height in different discharges. The results show that beside the dense leafy shrubs community, the vertical trend of the drag coefficient among other cases against flow depth, diameter, diameter Reynolds number, flow depth Reynolds number and relative roughness height can be approximately expressed by power law functions under different flow discharges. Moreover, in a mixed community with two plants with distinctly different ecological factors, the one with the most distinct variations of ecological factors determines the vertical trend of the drag coefficient; the other one only affects the magnitude of the drag coefficient. Furthermore, if the ecological factors of the vegetation in the vertical direction are kept almost not changed, the drag coefficient can be approximately regarded as a constant. 相似文献
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河流生态修复技术研究进展 总被引：4，自引：0，他引：4
面对河流生态系统退化的现状,综合国内外对于城市河流生态修复技术的研究进展,指出我国目前在此领域存在的不足,并展望了未来城市河流生态修复技术的发展方向,为城市河流生态修复技术的发展提供理论依据。 相似文献
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明渠水流阻力研究现状分析 总被引：6，自引：2，他引：4
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。 相似文献
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This article discusses the transverse distributions of the depth averaged velocity and the Reynolds stress in a steady uniform flow in partially vegetated rectangular channels. The momentum equation is expressed in dimensionless form and solved to obtain the depth averaged velocity. The analytical solution of the velocity in dimensionless form shows that the depth-averaged velocity is determined by gravity and its distribution is mainly determined by the frictions due to water or vegetations. The analytical solution of the Reynolds stress is also obtained. A relationship between the second flow and the inertia is established and it is assumed that the former is proportional to the square of the depth averaged velocity. The Acoustic Doppler Velocimeter (Micro ADV) was used to measure the steady uniform flow with emergent artificial rigid vegetation. Comparisons between the measured data and the computed results show that our method does well in predicting the transverse distributions of the stream-wise velocity and the Reynolds stress in rectangular channels with partially vegetations. 相似文献
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含植物河道曼宁阻力系数的研究 总被引：12，自引：5，他引：7
含植物河道的水流阻力不仅仅来源于边壁,传统的曼宁公式不能够直接用来计算这种河道的糙率。本文基于水流阻力等效原则,首次提出了一系列等效水力参数的概念,建立了等效综合曼宁糙率系数和等效植物附加曼宁系数的计算公式,并给出了能否使用水深代替水力半径的判别参数。使用刚性圆柱棒进行水槽试验,对植物在非淹没和淹没条件下的曼宁系数进行了计算和比较。试验结果验证了理论分析提出的关于判别参数的结论,并且表明使用水深计算的糙率在植物非淹没条件下可以用来表示植物引起的附加阻力。本文提出的等效综合曼宁糙率系数计算公式包含了植物的物理特性,因此具有普遍的应用价值,可以用来进行实际工程中糙率的计算。 相似文献
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Aquatic habitat assessment and river restoration design require geospatially explicit maps of hydraulic conditions. Diverse mechanistic ecohydraulic models compute spatially explicit depth and velocity results to evaluate habitat suitability spatially as a function of these abiotic conditions. This study compared depth and velocity results from two‐dimensional (2D) and one‐dimensional (1D) hydraulic models with algorithms that laterally discretize 1D velocity and interpolate depth and velocity spatially based on the Laplacian heat mapping approach. These ‘conveyance distributed’ methods constitute ‘best 1D modelling practice’ and were compared with 2D results for the first time. The 1D and 2D models were applied to three morphologically distinct reaches (leveed, meandering, and anastomosing) for three flows (base, bankfull, and flood flows) of the partially regulated, gravel/cobble lower Yuba River in north–central California. The test metrics were the coefficient of determination (R2) and the median absolute residual ( ). These metrics quantified the incremental uncertainty 1D approximation incurs, results which make explicit cost–benefit processes of model selection possible. Finally, velocity residual maps were analysed to identify regions and processes where residuals were high, indicating divergence from the 1D assumptions. Paired data (1D–2D) fell between 0.94 ≥ R2 ≥ 1.00 (R2mean = 0.98 and R2median = 0.99) for depth and median absolute residuals were all 3.8 ≤ ≤ 7.2% (i.e. 50% of residuals are approximately within ±1.7 to 3.6%). Higher flows and lower gradient reaches had lower residuals and higher R2. Velocity diverged more, particularly for base flow in anastomosing reaches (0.42 < R2 < 0.58). One‐dimensional, conveyance distributed, assumptions performed better for other channel types, where 0.69 < R2 < 0.81 (R2mean = 0.75 and R2median = 0.77), with median absolute residuals between 9.6% > > 22.4% (i.e. ~ ± 4.6 to ±11.2%), where mean = 14.2% and median = 13% (~ ±7.1 and 6.5%). The conveyance distributed 1D velocity model performed best, where the orthogonal flow assumptions obtained and where side channels did not transition from backwater to conveying area between flows. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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基于流速分布曲线的几何特点,提出一种新的无量纲化方法,结合水槽实验数据的回归分析,对含植物明渠紊流流速分布律及流动分区进行了研究。基于流速梯度变化率的特点,确定两个特征高度,采用特征高度、特征高度位置处的流速、水深、最大流速4个变量定义了新的无量纲流速和高度,对实验得到的流速数据进行无量纲化处理,进一步拟合得到流速分布律。结果表明,提出的无量纲流速在自由水面附近呈对数分布,对数分布律区域以下到床面的区域可用4段函数表示。根据分布律适用的区域明确流动分区边界,发现边界高度与特征高度并不重合,但和混合层的上下边界近似相等。与其他研究的对比表明,提出的无量纲化方法和流速分段函数分布律以及流动分区对速度描述有效,具有较好的适用性。 相似文献
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《水动力学研究与进展(B辑)》1996,(1)
ＢＬＯＣＫＡＧＥＣＯＥＦＦＩＣＩＥＮＴＴＥＣＨＮＩＱＵＥＦＯＲＳＱＵＡＲＥＥＮＣＬＯＳＵＲＥＦＬＯＷＷＩＴＨＮＯＴＨＩＣＫＮＥＳＳＳＰＡＣＥＲＳ￥ＹｕＬｉ－ｒｅｎ（Ｄｅｐｔ．ｏｆＨｙｄｒａｕｌｉｃｓａｎｄＳａｎｉｔａｒｙＥｎｇｉｎｅｅｒｉｎｇ，Ｓｃｈ... 相似文献
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基于等效阻力的植被化复式河道流速分布研究 总被引：1，自引：0，他引：1
天然河道中许多都是具有主槽和滩地的复式河槽,水流漫滩以后,复式河槽的水流结构发生复杂的变化.而天然河道漫滩上常常生长着各种植物,水中植被的存在增加了河床的阻力,如何确定流速分布和流量十分重要.本文基于植被作用下水流阻力的等效平衡原理,提出刚性植被等效附加阻力系数以及植被等效综合阻力系数的计算方法.通过运用SKM方法计算植被作用下的复式河槽垂线平均流速的横向分布,结果表明,本文提出的植被等效综合阻力系数的计算方法是可行的,能较好地确定植被作用下的复式河道垂线平均流速的横向分布. 相似文献
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新型航空海水温度、盐度、深度探头运动特性的计算方法和实验验证 总被引：1，自引：0，他引：1
本文以一原型探头的实验资料为依据成功地设计了一个扩充了功能的、改变尺寸和重量的新型探头,提出了分离摩擦阻力的形状阻力的计算方法,预报了新探头在下沉过程中的运动特性和极限速度。预报结果与新探头的试验数据符合良好,验证了这一方法的合理性。 相似文献
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本文通过由流速分布推求冰期河道冰盖糙率系数,提出了由流速分布推算冰盖及河床糙率的计算方法,同时考虑冰盖影响区与河床的流速分布,确定最大流速位置,阐述了冰盖对水流的阻力是研究河道冰情演变及其运动规律的依据.并对河道冰期形成冰盖,其阻力使河道水位升高、过流能力降低、水位流量关系改变.流速分布推算冰盖及河床糙率的计算方法进行了分析.为北方地区基层测站的冰期测验工作提供参考. 相似文献
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为评估富水区运营公路隧道的排水系统淤堵状态,基于对广东省多座高速公路隧道的调研,总结了公路隧道排水系统病害与淤堵物类型,提出了淤堵状态评价方法,研究结果主要表明:①隧道渗漏水病害在时间上与季节性降雨密切相关,在空间上与岩溶等不良地质的分布紧密相连,排水系统淤堵导致的排水功能下降是隧道水害的重要原因;②公路隧道排水系统的淤堵物类型分为淤泥、砂石、混凝土块或异物、结晶物或结垢物,对淤堵状态提出的评价指标为充盈程度、流动状态、浑浊程度、堆积程度;③基于对淤堵状态评价指标优先级的划分,提出了公路隧道排水系统的淤堵状态评价方法,并将其成功应用于新屋隧道的排水系统整治工程中。研究成果可为公路隧道排水系统的运营养护提供参考。 相似文献
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Large river paradigms suggest that natural flow regimes are critical for maintaining instream habitats and promoting production and growth of native aquatic organisms. Modifications to the Missouri River, Nebraska, within the past 100 years have drastically reduced shallow water habitat, homogenized the flow regime, and contributed to declines in several native species. Despite drastic flow modifications, several metrics of the Missouri River's flow regime still vary across years. We related age‐0 channel catfish growth to environmental conditions in the channelized Missouri River, Nebraska, between 1996 and 2013 using an information theoretic approach. Growth rate was most influenced by growing season duration and duration of discharges below the 25th percentile of 30‐year daily Missouri River discharges. Periods of low water may be important for juvenile growth because of channel modifications that limit critical shallow water habitat during higher within‐bank flows. Exclusion of peak discharge and peak discharge timing in the best model to predict growth is counter to conventional thoughts on river fish responses to hydrological conditions but may be reflective of the general lack of high‐magnitude flooding during the majority of our study. Future efforts to relate juvenile fish growth to environmental conditions can provide guidance for water management in the Missouri River and other regulated North American rivers. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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《Journal of Flood Risk Management》2018,11(Z1):S395-S402
Most urban rivers carry much natural debris, such as vehicles and trees, during extreme flood events, and these large debris, particularly vehicles, can block a local hydraulic structure such as a bridge. Such blockages usually increase the upstream water levels and cause more water to be diverted into adjacent urban areas. A scaled physical river model was constructed in a laboratory flume, consisting of a sketched urban reach with a compound cross‐sectional geometry, and experiments were conducted on three model bridges, blocked by vehicles, with the corresponding hydrodynamic impacts of these vehicles blocking bridges being investigated. The main findings obtained from the investigation show that (i) the upstream water depths in the urban river increased significantly due to the vehicle blockage, for the single opening arch bridge and the straight deck bridge, while the upstream depths increased slightly for the three‐opening straight deck bridge; (ii) the non‐uniformity in the velocity profiles varied along the channel centreline, with the exponents in the power‐law velocity distribution reaching their maximum values around the first two blocked model bridges, while the exponent values changed slightly along the channel for the third model bridge due to the middle opening not being blocked; and (iii) the downstream mean velocity was slightly greater than the upstream velocity for the first two cases, with the minimum value occurring just downstream of the bridge. However, the depth‐averaged velocities just downstream of the bridge were relatively higher for the third case. Therefore, the obstruction caused by vehicle blockage at bridges has significant impacts on the hydrodynamic characteristics in an urban reach, and these impacts depend on the specified bridge type and the blockage mode. 相似文献