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Experimental investigation of the diameter and length effects of the dendritic, bottomless, extended structure on reservoir sediment removal efficiency by flushing 树枝状、无底、延伸结构的直径和长度对水库冲沙效率影响的实验研究
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-11-01 DOI: 10.1016/j.jher.2022.09.002
Hadi Haghjouei , Majid Rahimpour , Kourosh Qaderi , Sameh A. Kantoush , Sepideh Beiramipour

Sedimentation in front of a dam is the main obstacle against reservoir sustainability. Due to the limited availability of suitable new dam sites, the ramifications of inefficient sediment management are associated with socio-economic concerns and environmental issues. Most of the existing sediment management techniques are unfavorable for arid and semi-arid regions due to their impacts on available water storage and power generation. Therefore, pressure flushing is an economical desilting method as it releases little water through the bottom outlet. However, one of the main disadvantages of pressurized flushing is limited sediment removal near the bottom outlet. In this paper, the impacts of a dendritic, bottomless, and extended (DBE) structure were investigated to develop the scour cone to a broader area. Several experiments were carried out with four different diameters (125, 160, 200, and 250 mm), four different lengths (30, 50, 80, and 110 cm), and three discharge rates (12.5, 15, and 18 L/s), to identify the dimensions of the extended structure with the most efficient operation. The results indicated that the DBE structure with a length dimensionless index of LDBE/Do=10, a diameter dimensionless index of DDBE/Do=1.14, and an outflow discharge dimensionless index of Fro=1.82, yielded a 36.55-fold increase in the sediment flushing cone dimensions and sediment removal efficiency compared to a reference test. Finally, a dimensionless equation is presented for calculating the sediment flushing cone dimensions, according to a statistical analysis of the results. Two diagrams are provided to illustrate the interrelationship between the distance limits of scour, length, and diameter of the structure and outlet discharges.

大坝前的沉积是水库可持续性的主要障碍。由于合适的新水坝地点有限,沉积物管理效率低下的后果与社会经济问题和环境问题有关。现有的泥沙治理技术对干旱半干旱区的有效蓄水量和发电能力影响较大,不利于干旱半干旱区的治理。因此,压力冲洗是一种经济的除淤方法,因为它通过底部出口释放的水很少。然而,加压冲洗的主要缺点之一是底部出口附近的沉积物去除有限。本文研究了树枝状无底延伸结构(DBE)对扩展冲刷锥的影响。在4种不同直径(125、160、200和250 mm)、4种不同长度(30、50、80和110 cm)和3种流量(12.5、15和18 L/s)的情况下进行了多次实验,以确定最有效运行的扩展结构尺寸。结果表明:长度无量纲指数为LDBE/Do=10,直径无量纲指数为DDBE/Do=1.14,流出流量无量纲指数为Fro=1.82的DBE结构,冲沙锥尺寸和除沙效率比参考试验提高了36.55倍。最后,通过对结果的统计分析,提出了计算冲沙锥尺寸的无因次方程。提供了两个图来说明冲刷距离限制、结构长度和直径与出口流量之间的相互关系。
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引用次数: 3
Monitoring water level and volume changes of lakes and reservoirs in the Yellow River Basin using ICESat-2 laser altimetry and Google Earth Engine 利用ICESat-2激光测高和谷歌地球发动机监测黄河流域湖泊水库水位和体积变化
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.07.005
Cong Liu , Ronghai Hu , Yanfen Wang , Hengli Lin , Hong Zeng , Dongli Wu , Zhigang Liu , Yi Dai , Xiaoning Song , Changliang Shao

Monitoring the water level and volume changes of lakes and reservoirs is essential for deepening our understanding of the temporal and spatial dynamics of water resources in the Yellow River Basin, with a view to better utilizing and managing water resources. In recent years, there have been many studies on monitoring water level and volume changes in inland waters, but they were mainly focused on radar altimetry and the full waveform LiDAR ICESat, which was retired in 2010. Few studies based on the latest photon-counting LiDAR ICESat-2 have been reported. Compared with previous sensors, ICESat-2 has great advantages in footprint size, transmitting frequency, pulse number, etc, but its performance in monitoring water level and volume changes in inland waters has not been fully explored. Here we investigated the spatial distribution of water level and volume changes of 11 lakes and 8 reservoirs in the Yellow River Basin based on ICESat-2 and Google Earth Engine, and analyzed the factors affecting the measurement uncertainties. In-situ validation of lake level in Lake Qinghai indicates that the Root Mean Square Error (RMSE) of our result is only 7 cm after the reference coordinate system conversion. We found that the water level trend of the natural lake shows significant seasonal variations, while the water level trend of the reservoir shows a sharp rise and fall. In addition, precipitation plays a decisive role in the changes in natural lake levels and indirectly affects the artificial control of reservoirs’ water discharges. The uncertainty of water volume change monitoring is mainly affected by water level measurement uncertainty for lakes, while for reservoirs, that is affected by the combination of water level and area measurement uncertainties. The stability of lake level measurement increases with the increase in photon counts. The introduction of ICESat-2 ATL13 Significant Wave Height might lead larger standard deviation in water level measurement. According to the law of propagation of uncertainty, the uncertainty of the water volume change estimation by the combination of ICESat-2 and GEE is less than 9 %.

对黄河流域湖泊水库水位和水量变化进行监测,对于深入认识黄河流域水资源的时空动态,更好地利用和管理水资源具有重要意义。近年来,对内陆水域水位和体积变化监测的研究较多,但主要集中在雷达测高和全波形LiDAR ICESat,该卫星已于2010年退役。基于最新的光子计数激光雷达ICESat-2的研究报道很少。与以往的传感器相比,ICESat-2在足迹尺寸、发射频率、脉冲数等方面具有很大的优势,但其在监测内陆水域水位和体积变化方面的性能还没有得到充分的探索。基于ICESat-2和谷歌地球引擎对黄河流域11个湖泊和8个水库的水位和体积变化进行了空间分布研究,并分析了影响测量不确定性的因素。青海湖实测水位验证结果表明,参考坐标系转换后所得结果的均方根误差(RMSE)仅为7 cm。研究发现,天然湖泊水位趋势具有明显的季节变化特征,而水库水位趋势具有明显的上升和下降趋势。此外,降水对湖泊自然水位的变化起决定性作用,并间接影响水库水量的人工控制。水量变化监测的不确定度主要受湖泊水位测量不确定度的影响,而水库则受水位和面积测量不确定度的综合影响。湖泊水位测量的稳定性随光子数的增加而增加。引入ICESat-2 ATL13有效波高可能导致水位测量的标准偏差较大。根据不确定度传播规律,ICESat-2与GEE联合估算水量变化的不确定度小于9%。
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引用次数: 7
Flow distribution and mass removal in floating treatment wetlands arranged in series and spanning the channel width 跨越河道宽度、串联布置的浮式处理湿地的流量分布和质量去除
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.07.001
Taís N. Yamasaki , Christopher Walker , Johannes G. Janzen , Heidi Nepf

Floating treatment wetlands (FTWs) use plants’ roots for water quality improvement. The plants are supported by a buoyant structure deployed at the water surface. The roots form a porous zone beneath the structure and remove pollutants carried in suspension through filtering, absorption and uptake. This paper used CFD simulation to model FTWs arranged in series and spanning the channel width and to study the effects of root length and spacing between FTWs on flow distribution and mass removal. The root zone was modelled as a porous media, and removal was computed using first-order decay, for which a range of removal constants was tested. Longer roots increased the reactive volume of the root zone, which increased the fraction of pollutant inflow entering the FTWs. Increasing the distance between FTWs allowed greater mixing between water that went through and beneath the upstream FTW. This increased the concentration entering each FTW, which enhanced mass removal per FTW. However, a larger distance between FTWs reduced the number of FTWs in the channel, reducing the reactive volume. In the tradeoff between mixing and reactive volume, the reactive volume was more important, such that total removal in the channel increased with longer roots and more units of FTW (shorter gap distance). However, removing the gap entirely was detrimental, as FTWs in series removed more mass than a continuous FTW of same volume. This study points to two design recommendations for FTWs in series. First, if resources for building FTWs are not limiting, but the channel length is, it is preferable to prioritize higher reactive volume (shorter gap distance) to achieve maximum removal per channel length. Second, if resources for FTWs are limiting, but channel length is not, it is better to place the FTWs with a longer gap distance, preferably along enough to allow mixing over the full depth between FTWs, as this will achieve maximum removal per FTW.

浮动处理湿地(FTWs)利用植物的根来改善水质。这些植物由部署在水面上的浮力结构支撑。根在结构下形成一个多孔区,通过过滤、吸收和吸收去除悬浮中的污染物。本文采用CFD模拟方法,对跨通道宽度串联布置的FTWs进行建模,研究了根长和FTWs间距对水流分布和质量去除的影响。根区被模拟为多孔介质,去除用一阶衰变计算,并对去除常数范围进行了测试。较长的根系增加了根区的反应体积,从而增加了污染物流入FTWs的比例。增加FTW之间的距离可以使上游FTW下面的水之间的混合更大。这增加了进入每个FTW的浓度,从而提高了每个FTW的质量去除。然而,FTWs之间的距离越大,通道中FTWs的数量就会减少,反应体积就会减小。在混合和反应体积之间的权衡中,反应体积更为重要,因此随着根的延长和FTW单位的增加(间隙距离的缩短),通道中的总去除量增加。然而,完全消除间隙是有害的,因为串联的FTW比相同体积的连续FTW减少了更多的质量。本研究提出了两个串联ftw的设计建议。首先,如果用于构建fts的资源不受限制,但通道长度受到限制,则最好优先考虑更高的反应体积(更短的间隙距离),以实现每个通道长度的最大移除。其次,如果FTW的资源有限,但通道长度没有限制,则最好将FTW放置在较长的间隙距离上,最好足够长,以便在FTW之间的整个深度上进行混合,因为这将实现每个FTW的最大去除。
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引用次数: 2
Air flow inside a vertical pipe induced by a free-falling water jet 自由下落水射流诱导垂直管道内的气流
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.07.003
Yiyi Ma , Pengcheng Li , David Z. Zhu , Abdul Khan

The air flow induced by a water jet freely falling inside a vertical pipe with its top and bottom both open to the atmosphere was investigated experimentally and numerically. In the experiments, the radial air velocity distribution and the air pressure variation along the vertical pipe were measured. The air drag of the falling water jet was related to the jet surface disturbance and analyzed by introducing the equivalent friction factor. A predictive model was developed for the air flow inside a 3-m-high pipe based on the momentum equation and its results compared well with the experimental measurements. Numerical simulations were also conducted by approximating the free-falling water jet as a continuous moving solid with diameter and velocity varying in the direction of motion. The effects of pipe size on the air velocity profile and the induced air flow rate were examined. The simulation results showed that the streamwise air velocity profiles inside pipes of different sizes approached the same after a certain traveling distance. The maximum induced air flow rate was found at the pipe diameter of about 20 times of initial water jet diameter.

用实验和数值方法研究了水射流在上下都对大气开放的垂直管道内自由落体所引起的气流。在实验中,测量了沿垂直管道的径向风速分布和气压变化。通过引入等效摩擦系数,分析了水射流的空气阻力与射流表面扰动的关系。基于动量方程建立了3 m高管道内气流的预测模型,其结果与实验测量结果吻合较好。将自由落体水射流近似为直径和速度随运动方向变化的连续运动固体,进行了数值模拟。研究了管道尺寸对气流速度分布和诱导气流流量的影响。模拟结果表明,不同尺寸的管道在经过一定距离后,其流向气流速度分布趋于一致。当管道直径约为初始水射流直径的20倍时,诱导空气流量最大。
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引用次数: 0
Pressure Driven analysis of water distribution systems for preventing siphonic flow 防止虹吸流的配水系统压力驱动分析
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.09.001
Wael Mohamed Hamdy Khadr , Mohammed Magdy Hamed , Mohamed Salem Nashwan

The analysis of the water distribution network is complicated and requires several assumptions to simplify its problem definition. Demand Driven Analysis (DDA) is typically used to analyse the network assuming that all network nodes can deliver the required demand regardless of the available pressure. In the case of analysing an existing network under deficit condition such as pipe breakage or extra demand required for firefighting, assumptions used to simulate the network with DDA is not valid. Node Head Flow Relationship (NHFR) should be considered through Pressure Driven Analysis (PDA) to analyse the network. Most PDA methods assume that the networks are airtight which means that if the pressure at any demand node is negative, delivered demand will be equal to zero and the flow is permitted in the connected pipes (Siphonic flow). This assumption is hydraulically incorrect since the air is allowed to get into the connected pipes and prevent their flow leading to node isolation. In this paper, a new Pressure Driven Analysis to Prevent Siphonic Flow (PDA-SF) approach is proposed to analyze the network under deficit conditions and consider isolating the nodes that show available head less than node elevation. The PDA-SF was tested and compared to previous methods in four case studies under steady state analysis or extended period simulation. The case studies cover also different network conditions whether node isolation is needed or not. The PDA-SF was able to solve different networks where other methods failed to achieve the required demand or service pressure. The new PDA-SF method shall enable peers and modelers to better simulate and analysis water distribution networks.

配水管网的分析是复杂的,需要几个假设来简化其问题定义。需求驱动分析(DDA)通常用于分析网络,假设所有网络节点都可以提供所需的需求,而不管可用的压力如何。在分析现有管网亏损情况(如管道破裂或消防所需的额外需求)时,使用DDA模拟管网的假设是无效的。通过压力驱动分析(PDA),考虑节点水头流量关系(NHFR)对网络进行分析。大多数PDA方法假设网络是密封的,这意味着如果任何需求节点的压力为负,交付的需求将等于零,并且连接的管道(虹吸流)允许流量。这种假设在水力上是不正确的,因为空气被允许进入连接的管道,并阻止它们的流动导致节点隔离。本文提出了一种新的压力驱动分析方法来防止虹吸流(PDA-SF),该方法分析了亏损条件下的网络,并考虑隔离可用水头小于节点高程的节点。在稳态分析或长周期模拟的四个案例研究中,对PDA-SF进行了测试和比较。案例研究还涵盖了不同的网络条件,无论是否需要节点隔离。PDA-SF能够解决其他方法无法达到所需需求或业务压力的不同网络。新的PDA-SF方法将使同行和建模者能够更好地模拟和分析配水网络。
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引用次数: 2
A statistical approach to multisite downscaling of daily extreme temperature series: A case study using data in Bangladesh 日极端温度序列多站点降尺度的统计方法:使用孟加拉国数据的案例研究
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.07.006
Mahzabeen Rahman, Van Thanh Van Nguyen

Downscaling techniques are required to describe the linkages between Global Climate Model outputs at coarse-grid resolutions to surface hydrologic variables at relevant finer scales for climate change impact and adaptation studies. In particular, several statistical methods have been proposed in many previous studies for downscaling of extreme temperature series for a single local site without taking into account the observed spatial dependence of these series between different locations. The present study proposes therefore an improved statistical approach to downscaling of daily maximum (Tmax) and minimum (Tmin) temperature series located at many different sites concurrently. This new multisite multivariate statistical downscaling (MMSD) method was based on a combination of the modeling of the linkages between local daily temperature extremes and global climate predictors by a multiple linear regression model; and the modeling of its stochastic components by the combined singular value decomposition and multivariate autoregressive (SVD-MAR) model to represent more effectively and more accurately the space-time variabilities of these extreme daily temperature series. Results of an illustrative application using daily extreme temperature data from a network of four weather stations in Bangladesh and two different NCEP/NCAR reanalysis datasets have indicated the effectiveness and accuracy of the proposed approach. In particular, this new approach was found to be able to reproduce accurately the basic statistical properties of the Tmax and Tmin at a single site as well as the spatial variability of temperature extremes between different locations. In addition, it has been demonstrated that the proposed method can produce better results than those given by the widely-used single-site downscaling SDSM procedure, especially in preserving the observed inter-site correlations.

在气候变化影响和适应研究中,需要降尺度技术来描述粗网格分辨率的全球气候模式输出与相关细尺度的地表水文变量之间的联系。特别是,以前的许多研究提出了几种统计方法来降低单个局地极端温度序列的尺度,而不考虑这些序列在不同地点之间的空间依赖性。因此,本研究提出了一种改进的统计方法来降低同时位于许多不同站点的日最高(Tmax)和最低(Tmin)温度序列的尺度。多站点多元统计降尺度(MMSD)方法是利用多元线性回归模型综合模拟局地极端日温度与全球气候因子之间的联系;结合奇异值分解和多元自回归(SVD-MAR)模型对其随机分量进行建模,更有效、更准确地表征极端日温度序列的时空变化。利用孟加拉国四个气象站网络的每日极端温度数据和两个不同的NCEP/NCAR再分析数据集的说白性应用结果表明了所提出方法的有效性和准确性。特别是,这种新方法能够准确地再现单个站点的Tmax和Tmin的基本统计特性,以及不同地点之间极端温度的空间变异性。此外,研究表明,该方法比广泛使用的单位点降尺度SDSM方法产生更好的结果,特别是在保留观测到的位点间相关性方面。
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引用次数: 0
Mapping of coastal surface chlorophyll-a concentration by multispectral reflectance measurement from unmanned aerial vehicles 无人机多光谱反射测量海岸带表层叶绿素-a浓度的制图
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.08.003
S.N. Chan, Y.W. Fan , X.H. Yao

In subtropical coastal waters, the explosive growth of phytoplankton under favorable conditions can lead to water discolouration and massive fish kills. Manual field sampling and laboratory analysis of chlorophyll-a concentration (Chl-a) as an indicator to algal biomass, is resources intensive and time consuming, delaying responses to disastrous harmful algal blooms. Cloudy weather often precludes the use of satellite images for water quality and algal bloom monitoring. This study aims at developing an estimator algorithm for quantitative mapping of surface Chl-a for coastal waters, based on surface reflectance measurement from an Unmanned Aerial Vehicle (UAV) with a five-band multispectral camera. The surface reflectance is obtained from calibrated multispectral images which are radiometric-corrected against incoming solar radiation. It is found that Chl-a has an inverse correlation with the Normalized Green-Red Difference Index (NGRDI). A regression estimator model for Chl-a from NGRDI is developed, showing excellent performance for fish farms in coastal waters with different characteristics. The technology is demonstrated for mapping the spatial and temporal variation of Chl-a during an algal bloom, offering a useful complement to traditional field monitoring for fisheries management and emergency response.

在亚热带沿海水域,浮游植物在有利条件下的爆炸性生长可能导致水体变色和大量鱼类死亡。人工实地取样和实验室分析作为藻类生物量指标的叶绿素-a浓度(Chl-a)是资源密集型和耗时的,延迟了对灾难性有害藻华的反应。多云天气常常妨碍使用卫星图像监测水质和藻华。本研究旨在基于搭载五波段多光谱相机的无人机(UAV)表面反射率测量,开发一种用于沿海水域表面Chl-a定量制图的估计算法。表面反射率是由经过校准的多光谱图像获得的,这些图像是根据入射的太阳辐射进行辐射校正的。结果表明,Chl-a与归一化绿红差指数(NGRDI)呈负相关。建立了基于NGRDI的Chl-a回归估计模型,该模型对不同特征的沿海水域养鱼场具有良好的性能。该技术用于绘制藻华期间Chl-a的时空变化,为渔业管理和应急响应的传统现场监测提供了有益的补充。
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引用次数: 2
Flow over embankment gabion weirs in free flow conditions 自由流动条件下的路堤石笼堰流量
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.08.001
Roya Biabani , Farzin Salmasi , Meysam Nouri , John Abraham

In this study, a series of laboratory tests were performed to investigate the effects of side ramp slope, crest length, and porous media properties on the flow regimes, water-surface profiles, discharge coefficients, and energy dissipation in embankment gabion weirs with upstream and downstream slopes. 24 physical models of solid and gabion weirs with three different upstream/downstream slopes (90°, 45° and 26.5°) were created. To investigate the complexity of flow over the porous-fluid interface and through the porous material, three-dimensional (3D) numerical simulations were developed. In numerical simulation, the standard k-ε turbulence model was utilized. A structured mesh domain was used to simulate the physical model. Water surface profiles above the porous weirs were used for comparison between the numerical simulations and measured data. These comparisons helped determine variables in the numerical simulations. Numerical simulation enables visualization of streamlines around and through the gabion weirs. In addition, mean stream wise velocity profiles above and within the porous structures were obtained. Numerical simulations showed that a reduction in the slope of the upstream face leads to an increased curvature of streamlines and the velocity distribution exhibits a non-uniform wavy shape due to the geometrical properties of the weirs. As the velocity profiles move downstream, the velocity distribution within the porous structures were more affected by the presence of the pores. The experimental results show that decreasing upstream slopes, from 90° to 26.5°, leads to decreased discharge coefficients. However, in all cases, gabion weirs lead to greater discharge coefficients than those of similar solid weirs. For milder side slopes, discharge ratios (flow passing through all faces of the gabion weirs over the inlet discharge) decreased nonlinearly. Moreover, with increasing the inlet discharge, relative energy dissipation was reduced up to 45% in gabion weirs.

在本研究中,进行了一系列实验室试验,以研究边坡、坝顶长度和多孔介质特性对具有上下游边坡的路堤石笼堰的流态、水面剖面、流量系数和能量耗散的影响。建立了具有三种不同上下游坡度(90°、45°和26.5°)的实体堰和石笼堰的24个物理模型。为了研究多孔流体界面和多孔材料流动的复杂性,开发了三维(3D)数值模拟。在数值模拟中,采用了标准的k-ε湍流模型。使用结构化网格域来模拟物理模型。多孔堰上方的水面剖面用于数值模拟和测量数据之间的比较。这些比较有助于确定数值模拟中的变量。数值模拟使石笼堰周围和通过石笼堰的流线可视化。此外,还获得了多孔结构上方和内部的平均流向速度分布。数值模拟表明,由于堰的几何特性,上游面坡度的减小导致流线曲率增加,流速分布呈现出不均匀的波浪形状。随着速度分布向下游移动,多孔结构内的速度分布更受孔隙存在的影响。实验结果表明,上游坡度从90°减小到26.5°,会导致流量系数降低。然而,在所有情况下,石笼堰的流量系数均大于类似固体堰的流量。对于较温和的边坡,流量比(通过石笼堰所有面的流量超过入口流量)呈非线性下降。此外,随着进口流量的增加,石笼堰的相对能量耗散减少了45%。
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引用次数: 0
Mean flow, secondary currents and bed shear stress at a 180-degree laboratory bend with and without enhanced permeable groins as an Eco-friendly river structure 180度实验室弯道的平均流量、二次流和河床剪切应力,作为一种生态友好的河流结构,有或没有增强的渗透性Groins
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.07.004
Manoochehr Shokrian Hajibehzad , Mahmood Shafai Bejestan , Vito Ferro , Rahim Avarand

River restoration aims to apply environmentally-friendly structures for bank protection in meandering rivers to restore their natural habitat. Enhanced Permeable Groin (EPG) is a novel river restoration technique that can improve the fish habitat environment in a river system by creating a series of eco-friendly scour pools. This study reports the results of two groups of 3D velocity measurements in a 180-degree channel bend in cases with and without an EPG for clear water conditions to characterize the mechanisms leading to the primary stages of the scouring phenomenon. The analysis revealed that the presence of an EPG amplified the velocity magnitude in the regions near the tip of the vane and increased its value in the middle of the channel 1.13 times the bend without the structure. In addition, the comparison showed that the EPG reduced the velocity magnitude in the recirculation zone by an average of 38%. Secondary currents including main and outer bank cells were observed in the case without the structure. The presence of the EPG in the flow field effectively increased the outer-bank cell strength by 11 times compared to that without the structure. The low-value contours of the bed shear stresses were observed in the zone downstream of the structure for a distance of 6 times the effective length of the structure. Based on the results of this study, the generation of a recirculation zone with low-velocity and shear stress values can provide suitable conditions for aquatic habitats, deep-bodied fish assemblages, aquatic vegetation, shrub roots, and tree roots along the outer bank.

河流修复的目的是在蜿蜒的河流中应用环境友好型结构来保护河岸,以恢复它们的自然栖息地。增强型渗透性腹股沟(Enhanced Permeable Groin, EPG)是一种新型的河流修复技术,通过创建一系列生态友好型冲刷池来改善河流系统中的鱼类栖息地环境。本研究报告了两组在180度河道弯曲处的三维速度测量结果,在清水条件下,有和没有EPG,以表征导致冲刷现象初级阶段的机制。分析表明,EPG的存在放大了叶片尖端附近区域的速度值,并使通道中部的速度值增加了1.13倍。此外,对比表明,EPG平均降低了再循环区的流速幅度38%。在没有结构的情况下,观察到包括主岸和外岸细胞的二次电流。流场中EPG的存在使外壁细胞强度比不存在EPG的情况下有效提高了11倍。在距构造有效长度6倍的构造下游区域,观察到床层剪应力的低值等值线。根据本研究结果,形成一个低速剪切应力值的再循环带,可以为外岸线的水生生境、深体鱼类群落、水生植被、灌木根系和乔木根系提供适宜的条件。
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引用次数: 2
A modified NRCS-CN method for eliminating abrupt runoff changes induced by the categorical antecedent moisture conditions 一种改进的NRCS-CN方法消除由类别前期水分条件引起的径流突变
IF 2.8 3区 环境科学与生态学 Q2 Engineering Pub Date : 2022-09-01 DOI: 10.1016/j.jher.2022.07.002
Ishan Sharma , S.K. Mishra , Ashish Pandey , S.K. Kumre

The popular Natural Resources Conservation Service Curve Number (NRCS-CN) (earlier known as Soil Conservation Service Curve Number (SCS-CN) method of rainfall-runoff modeling has often faced the criticism of exhibiting quantum jumps in runoff computations because of the sudden jumps appearing in CN-values derived from NEH-4 tables for three antecedent moisture conditions (AMC), viz., AMC-I, AMC-II, and AMC-III valid for dry, normal, and wet conditions, respectively. The variability of antecedent soil moisture within an AMC category is responsible for the abrupt jump and other deficiencies in the CN method for runoff estimation. This paper suggests a novel procedure to account for the antecedent moisture (M), preventing quantum jumps and eliminating deficiencies in determination of CN and, in turn, estimation of direct runoff. Its validity was verified utilizing the observed rainfall (P)-runoff (Q) events from 36 US watersheds, four sub-catchments of the Godavari basin, and small agricultural plots at Roorkee, India. The performance of the proposed model (M5) for runoff prediction was compared with the existing NRCS-CN (M1), Mishra and Singh (2002) (M2), Singh et al. (2015) (M3), and Verma et al. (2021) (M4) model using various performance indices. Using the CNs derived from observed events, model M5 was seen to have performed better than M1-M4 in terms of Nash Sutcliffe Efficiency (NSE), Root Mean Square Error (RMSE), and Percent Bias (PBIAS) for the data of US watersheds, and CN-P correlation improved as the coefficient of determination (R2) enhanced. Similarly, using the RS & GIS-based CNs on natural watersheds of the Godavari basin and considering AMC-I, the performance of M5 was again better than M1-M4 in terms of RMSE, Mean Bias Error (mBIAS), Mean Absolute Error (MAE), and Normalized-Nash Sutcliffe Efficiency (NNSE). Interestingly, there existed a significant (p < 0.05) relationship between the in-situ water content (w) measured for the experimental plots of Roorkee and the model input variable antecedent moisture (M), offering a physical touch to the conceptual model.

流行的自然资源保护服务曲线数(NRCS-CN)(以前称为土壤保持服务曲线数(SCS-CN))降雨径流模型方法经常面临在径流计算中表现出量子跳跃的批评,因为从NEH-4表中得出的cn值出现突然跳跃,分别适用于三种先决湿度条件(AMC),即分别适用于干燥、正常和潮湿条件的AMC- i、AMC- ii和AMC- iii。在AMC类别中,前壤湿度的变异性是CN方法估算径流时出现突发性跳跃和其他缺陷的原因。本文提出了一种新的方法来解释先前的水分(M),防止量子跳跃,消除在CN测定和直接径流估计中的缺陷。利用美国36个流域、哥达瓦里盆地的4个子流域和印度Roorkee的小型农业地块观测到的降雨(P)-径流(Q)事件,验证了其有效性。利用各种性能指标,将所提出的模型(M5)与现有的NRCS-CN (M1)、Mishra和Singh (2002) (M2)、Singh等人(2015)(M3)和Verma等人(2021)(M4)模型的径流预测性能进行了比较。使用从观测事件中获得的神经网络,M5模型在美国流域数据的纳什萨特克里夫效率(NSE)、均方根误差(RMSE)和百分比偏差(PBIAS)方面表现优于M1-M4,并且随着决定系数(R2)的增强,CN-P相关性得到改善。类似地,使用RS &基于gis的Godavari流域自然流域神经网络在考虑AMC-I的情况下,M5在RMSE、平均偏置误差(mBIAS)、平均绝对误差(MAE)和归一化nash Sutcliffe效率(NNSE)方面的表现再次优于M1-M4。有趣的是,存在显著的(p <0.05)实测的Roorkee试验地块的原位含水量(w)与模型输入变量前含水率(M)之间的关系,为概念模型提供了物理接触。
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引用次数: 1
期刊
Journal of Hydro-environment Research
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