Design of earthen vegetated open channels

Modified formulas for Manning's equation are developed for use in the design of earthen open channels with submerged aquatic weeds. The proposed relations have their basis in field and experimental data. A multiple regression analysis was used to develop a relationship between the mean velocity, hydraulic radius, and water surface slope. The new formulas are dependent on the distribution of weeds along the channel's wetted perimeter and the percentage of vegetation density with respect to the cross-section area of the waterway.Notation A cross-section area - A _w area of weeds - B ₁ top width of channel flow - g acceleration of gravity - h height of roughness element - n Manning's coefficient - Q discharge of flow - R hydraulic radius - S water surface slope - S ₀ bed surface slope - V mean flow velocity     

Estimation of Clark’s Instantaneous Unit Hydrograph Parameters and Development of Direct Surface Runoff Hydrograph

We present a method to estimate Time of Concentration (T _c) and Storage Coefficient (R) to develop Clark’s Instantaneous Unit Hydrograph (CIUH). T _c is estimated from Time Area Diagram of the catchment and R is determined using optimization approach based on Downhill Simplex technique (code written in FORTRAN). Four different objective functions are used in optimization to determine R. The sum of least squares objective function is used in a novel way by relating it to slope of a linear regression best fit line drawn between observed and simulated peak discharge values to find R. Physical parameters (delineation, land slope, stream lengths and associated drainage areas) of the catchment are derived from SPOT satellite imageries of the basin using ERDAS: Arc GIS is used for geographic data processing. Ten randomly selected rainfall–runoff events are used for calibration and five for validation. Using CIUH, a Direct surface runoff hydrograph (DSRH) is developed. Kaha catchment (5,598 km²), part of Indus river system, located in semi-arid region of Pakistan and dominated by hill torrent flows is used to demonstrate the applicability of proposed approach. Model results during validation are very good with model efficiency of more than 95% and root mean square error of less than 6%. Impact of variation in model parameters T _c and R on DSRH is investigated. It is identified that DSRH is more sensitive to R compared to T _c. Relatively equal values of R and T _c reveal that shape of DSRH for a large catchment depends on both runoff diffusion and translation flow effects. The runoff diffusion effect is found to be dominant.     

Strength and deformation characteristics of concrete of the vilyui III hydroelectric station

Conclusions  

Assessing morphologic complexity and diversity in river systems using three‐dimensional asymmetry indices for bed elements,bedforms and bar units

Geomorphologists are becoming increasingly interested in assessing morphologic structure and the diversity and/or complexity in morphologic structure across multiple scales within river systems. Unfortunately, many of our existing tools/variables are unsuitable for this task because they do not work across multiple scales or with changing discharges. Asymmetry is one variable that can be used to either include or exclude variations in flow stage and that can be assessed across multiple scales. Existing asymmetry indices, however, are limited in scope and largely focus on only cross‐sectional form. This study examines three existing asymmetry indices in the cross‐stream and downstream planes (for cross‐sections and riffle or pools, respectively) and develops nine new asymmetry indices that incorporate vertical, cross‐stream and downstream asymmetry for bed elements (e.g. riffle crests, pool troughs, riffle entrance slope), bedforms (pools or riffles) and bar units (pool‐riffle sequences) to investigate the utility of asymmetry as a measure of morphologic structure and diversity in fluvial systems. These 12 indices are field tested on the Embarras River in East Central Illinois, USA. The results of this study indicate that there is considerable morphologic diversity in bed elements, bedforms and bar units both at bankfull and also with varying flow stage. This multi‐scale, multidimensional, multistage variability in morphologic structure highlights the complexity of natural river systems. The highly variable nature of fluvial form within a reach has important implications for river restoration and/or assessments of physical habitat or river health especially in instances where pools, riffles or pool‐riffle sequences are the focus of study. In general the most robust and useful combination of asymmetry indices for most applications includes A* and A_L1 for bed elements and bedforms and A_L3, A_W and A_H for bar units. Copyright © 2008 John Wiley & Sons, Ltd.     

Reference condition approach to restoration planning

Ecosystem restoration planning requires quantitative rigor to evaluate alternatives, define end states, report progress and perform environmental benefits analysis (EBA). Unfortunately, existing planning frameworks are, at best, semi‐quantitative. In this paper, we: (1) describe a quantitative restoration planning approach based on a comprehensive, but simple mathematical framework that can be used to effectively apply knowledge and evaluate alternatives, (2) use the approach to derive a simple but precisely defined lexicon based on the reference condition concept and allied terms and (3) illustrate the approach with an example from the Upper Mississippi River System (UMRS) using hydrologic indicators. The approach supports the development of a scaleable restoration strategy that, in theory, can be expanded to ecosystem characteristics such as hydraulics, geomorphology, habitat and biodiversity. We identify three reference condition types, best achievable condition (A _BAC), measured magnitude (MM_i which can be determined at one or many times and places) and desired future condition (A_DFC) that, when used with the mathematical framework, provide a complete system of accounts useful for goal‐oriented system‐level management and restoration. Published in 2010 by John Wiley & Sons, Ltd.     

芦苇占优势农田溪流营养盐滞留能力分析与评估

2014年9月—2015年4月,在合肥地区二十埠河流域的某一典型农田源头溪流段,选择以Na Cl为保守示踪剂,NH4Cl和KH2PO4为添加营养盐,采用恒速连续投加的方式,开展了7次野外现场示踪试验。在此基础上,利用OTIS模型和营养螺旋原理,从机制层面分析和评估芦苇占优势农田源头溪流氮磷营养盐滞留能力和滞留特征。结果表明,该芦苇占优势渠段的比值As/A明显超过一般源头溪流水体,暂态存储对于营养盐滞留有较大影响;NH4+和SRP的暂态存储区营养盐一阶吸收系数都较主流区高一个数量级,且所有吸收系数均为正值,表明芦苇占优势渠段具有氮、磷"汇"的功能;NH4+吸收长度明显低于SRP,特别是冬季和初春,意味着溪流对于NH4+的滞留能力超过SRP;NH4+和SRP的总滞留率分别为14.46%和10.73%,生物滞留率平均值分别为9.17%和3.67%;主流区流动水体和暂态存储区对于NH4+滞留的平均贡献率分别为43.12%、56.88%;对于SRP滞留的平均贡献率分别50.13%、49.87%。     

Spectral‐ALS data fusion for different roughness parameterizations of forested floodplains

Natural river floodplains and adjacent wetlands grow typically a diverse and heterogeneous combination of herbs, shrubs and trees, which play an essential role in determining the total flow resistance. Hydrodynamic effects of trees in forested floodplains can provide the majority of flow resistance during flood events. Nevertheless, ground‐based techniques to acquire vegetation parameters are expensive and difficult to apply over long reaches. This paper presents a novel method of automated roughness parameterization of riparian woody vegetation by fusion of Quickbird multi‐spectral image with airborne laser scanning (ALS) data. The data fusion approach includes: individual tree detection and estimation of vegetation metrics from light detection and ranging (LiDAR) data, assessment of predictive models for the vegetation parameters and spatial mapping of the vegetation parameters for the forest plants in the riparian corridor. The proposed method focuses on estimation of plant density (d), crown diameters (D_C), tree height (h), stem diameter (D_S), crown base height (cbh) and leaf area index (LAI). The procedure is tested along a 14‐km reach of the Sieve River (Tuscany, Italy) characterized by high woody plant density. Due to the complex study area, the data fusion approach explains with variable reliability the local vegetation properties (R²(D_C) = 0.14, R²(h) = 0.84, R²(D_S) = 0.25, R²(cbh) = 0.66). The generated structural parameter maps represent spatially explicit data layers that can be used as inputs to hydrodynamic models used to analyse flow resistance effects in different submergence conditions of vegetation. A simple flow resistance model was applied over a test area comparing the results of the proposed method and a traditional ground‐based approach. The modelling results showed that the new method is able to provide accurate output data to describe the interaction between water levels and bio‐mechanical characteristics of vegetation. The proposed methodology provides a fast, repeatable and accurate way of obtaining floodplain roughness, which enables regular updating of vegetation characteristics. Copyright © 2010 John Wiley & Sons, Ltd.     

Hydraulic operating conditions of an eddy tunnel outlet with an inclined shaft

Model studies of the hydraulic operating conditions of an eddy tunnel outlet with an inclined shaft showed that:

基于碾压波速的堆石坝压实质量实时监测指标的研究

已有的连续压实质量评价指标在评估堆石坝料的压实质量时仍存在评价精度低、表征压实效果复杂以及结果易受压实材料属性影响等缺点.为给堆石坝施工质量的连续控制提供有效指标,本文采用数据延拓式相关的相位差求解方法来间接获取碾压波速(VR),提出了以实时监测的VR作为堆石坝料压实状态的表征指标.从定性分析角度考虑碾压参数对VR的影...     

黄河流域Budyko方程参数n演变规律及其归因研究

基于移动窗口法、多元逐步回归模型、敏感性系数法和贡献评估法,定量分析黄河流域Budyko水热耦合平衡方程中的参数n在黄河流域的变化规律及其与气候变化和人类活动的相关关系。结果表明,参数n在1956—2000年间呈现上升趋势,其变化与降水(P)、人口状况(Pop)、生产总值(GGDP)和有效灌溉面积(Airr)最为相关。其中,参数n的变化对P最为敏感,敏感系数达到1.169,且P的变化抑制了参数n的增加(贡献率为-20.2%);参数n对Pop、GGDP和Airr的敏感性系数分别为0.795、0.038和-0.152,并随人类活动的加剧而上升,其中Pop的增加对参数n增加的贡献最大(128.7%)。     

A real-time flood forecasting model based on maximum-entropy spectral analysis: II. Application

The MESA-based model, developed in the first paper, for real-time flood forecasting was verified on five watersheds from different regions of the world. The sampling time interval and forecast lead time varied from several minutes to one day. The model was found to be superior to a state-space model for all events where it was difficult to obtain prior information about model parameters. The mathematical form of the model was found to be similar to a bivariate autoregressive (AR) model, and under certain conditions, these two models became equivalent.Notation A _k parameter matrix of the bivariate AR model - B backshift operator in time series analysis - eT forecast error (vector) at timet = T - _t uncorrelated random series (white noise) - F _k forward extension matrix of the entropy model forkth lag - I identity matrix - m order of the entropy model - N number of observations - P order of the AR model - Q _p peak of the direct runoff hydrograph - R correlation matrix - t _p time to peak of the direct runoff hydrograph - ₁ coefficient of variation - ₂ ratio of absolute error to the mean - forecasted runoff - x _i observed runoff - mean of the observed runoff - X ^–1 inverse ofX matrix - X* transpose of theX matrix Abbreviations AIC Akaike information criterion - AR autoregressive (model) - AR(p) autoregressive process of thepth order - ARIMA autoregressive integrated moving average (model) - acf autocorrelation function - ccf cross-correlation function - FLT forecast lead time - MESA maximum entropy spectral analysis - MSE mean square error - STI sampling time interval     

Effects of stream hydraulics and other environmental variables on density of Narapa bonettoi (Oligochaeta) in the Paraná River system

Hydraulic and substratum conditions have been identified as two stream features which affect the benthic community composition, abundance and distribution. However, little attention has been given to the influence of hydraulic variables in large river beds. The aim of this study was to analyse the incidence of the near‐bottom hydraulic conditions and other environmental variables on the density of Narapa bonettoi (Oligochaeta, Narapidae), a typical and dominant species found in sandy bed rivers of diverse hierarchy of the Paraná River basin. A large amount of existing and available benthic data were used. The highest correlations among N. bonettoi densities and environmental variables were obtained with the hydraulic variables of friction Reynolds number (R_*) and shear stress (τ₀); the substratum type (sand, silt and clay) and organic matter content. The results show that N. bonettoi density would be related with the hydraulic variables following a ‘bell‐shaped’ tendency, e.g. with the friction Reynolds number, N. bonettoi would have a preference for transition values of turbulence (～40 < R_* < ～50), which is equivalent to τ₀ between ～0.6 and ～0.8 kg ^?2. Densities show a slight decreasing tendency toward the maximum R_* values, suggesting that the species does not support a completely developed turbulence (R_* > ～70). Significant but negative correlations were reported in the literature between benthic macroinvertebrates typical of smaller and steeper streams and R_* values far beyond the threshold 70 value. N. bonettoi shows a clear preference for a completely sandy substratum and for sand particles sizes around 300 µm. Finally, considering the important role played by the hydraulic variables on the benthic community studied herein, the contagious distribution pattern of N. bonettoi, reported by other authors, would be principally linked with the interactions between current and sediment near the bottom rather than with the mobility of these organisms. Copyright © 2008 John Wiley & Sons, Ltd.     

Physical engineering of an island‐braided river by two riparian tree species: Evidence from aerial images and airborne lidar

Following a review of the European distribution, habitat requirements and life history characteristics of two riparian tree species, Alnus incana (L.) Moench (grey alder, a member of the Betulaceae family) and Populus nigra L. (black poplar, a member of the Salicaceae family), we explore their changing spatial distribution and topographic position within a 7 km, island braided reach of the Tagliamento River, Italy, where Populus nigra dominates the woody vegetation cover. Combining field observations and information extracted from aerial images, airborne lidar data and river flow time series for the period 1986–2017, we investigate (a) the changing spatial distribution of all (P. nigra‐dominated) woody vegetation and of A. incana alone; (b) whether river bed topography can be associated with these changing spatial distributions and (c) we consider whether A. incana displays any particular characteristics in its spatial and topographic distribution that may indicate that it is complementing the physical engineering role of P. nigra. We show that A. incana predominantly grows in lines along channel, island and floodplain edges, bordering wooded areas dominated by P. nigra and that areas supporting A. incana are associated with the topographic development of the river bed. We conclude that A. incana appears to be acting as a complementary physical engineer to P. nigra, suggesting that similar complementary physical engineering of river beds may be achieved by species with different life history traits to influence landform development in other river environments.     

Changes in abiotic and biotic phosphorus uptake across a gradient of stream condition

Degraded streams have been shown to retain fewer nutrients than un‐modified streams. The aim of this project was to investigate the relative importance of abiotic and biotic pathways of phosphorus uptake by epilithic communities in un‐modified and modified streams. This was investigated through a series of filterable reactive phosphorus (FRP)‐uptake experiments in two streams of the Torrens River Catchment, South Australia. Total benthic FRP uptake was assessed as the loss of FRP to un‐sterilized epilithic communities (k_T), abiotic uptake was the loss to sterilized epilithic communities (k_A) and biotic uptake (k_B) was the difference between total and abiotic uptake. It was hypothesized that un‐modified reaches would have higher k_A and k_B than degraded and engineered reaches. Overall, k_T, k_A and k_B were greatest in un‐modified reaches, but this pattern was not consistent across seasons. k_T and k_B were greatest in the un‐modified reaches in autumn–winter and late spring, but not in winter–spring. Differences in k_B were best explained by phosphorus availability in the water column and the period of continuous flow. k_A was greatest in the un‐modified reaches in autumn–winter, greatest in the degraded reaches in winter–spring, but similar in the un‐modified reaches and degraded reaches in late spring. k_A was most dependent upon the background FRP concentration, but also the attached organic matter in the un‐modified reaches. The project demonstrated that several impacts of changes in land‐use can alter the affinity of biotic and abiotic processes for phosphorus, which will have implications for in‐stream nutrient availability and downstream ecosystems. Copyright © 2009 John Wiley & Sons, Ltd.     

Selecting Between One‐Dimensional and Two‐Dimensional Hydrodynamic Models for Ecohydraulic Analysis

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 (R²_mean = 0.98 and R²_median = 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 (R²_mean = 0.75 and R²_median = 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.     

基于修正立方定律对单裂隙辐射流剪切耦合的研究

修正了辐射流立方定律,并研究了裂隙的力学性能和水力特性。进行了不同恒定法向压力和剪切速率下的高液压水头剪切渗流实验。发现峰值剪切强度随剪切速率的增加呈现先增大后减小的趋势。线性系数A和非线性系数B都随剪切位移先增大后减小,且减小后的稳定值小于剪切破坏前的值。但是系数B比系数A大5个数量级,变化幅度更大。临界雷诺数经剪切破坏后大于剪切破坏前的值,流态将变好。此外,剪切过程中的水力特性也表现出与力学性能相似的趋势。     

Coefficients of heat and mass transfer of current-technology sprinklers for process computations of cooling towers

Analysis of formulas for computing coefficients of heat and mass transfer derived on the basis of results of laboratory tests of 22 sprinklers is used to show that the classification of sprinklers into film and drop ones can be based on a physically grounded parameter m, i.e., the exponent in the formula for the evaporation number K _ev = A _pλ^m (or for the Merkel number Me = A _xλ^m). Ageneralized formula describing the dependence of the coefficients of heat and mass transfer on the height of the sprinkler is derived, which makes it possible to determine the optimum sprinkler height in cooling tower design. The accuracy of the formulas for computing the coefficients is confirmed by a comparison of experimental and computed values of the temperature of cooled water in the cooling tower of the Novo-Ryazanskaya cogeneration plant. __________ Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 24–30.     

SPATIAL AND TEMPORAL PATTERNS OF NITRIFICATION RATES IN FORESTED FLOODPLAIN WETLAND SOILS OF UPPER MISSISSIPPI RIVER POOL 8

Overbank flooding is thought to be a critical process controlling nitrogen retention and cycling. Yet, studies aimed at quantifying these effects, specifically nitrification, are relatively few. In this study, we investigated the effects of season and flood frequency on soil nitrification rates in forested floodplains of Upper Mississippi River, Pool 8. Samples were collected from three plots within each site in April, August and November 2006. Plots were equally divided among three flood frequency categories as follows: rare, moderate and frequent based on elevation and flood probability model. We found a significant difference in nitrification rates among flood frequency categories as follows: rare > moderate > frequent (F = 4.49, p < 0.01) and over season: spring > summer > autumn (F = 8.88, p < 0.01). Regression for all samples showed that elevation, NH₄‐N, bulk density and soil temperature explained a moderate amount of variation in nitrification rates (R² = 0.29, p < 0.01). Models for moderately flooded, spring, summer and autumn samples improved when analysed individually. The absence of a correlation between nitrification rates and hydrology limits our ability to predict rates based on hydrology alone. The model based on elevation and season allows us to estimate nitrification rates with moderate confidence (R² = 0.27, p < 0.01). A rough calculation of forest floodplain nitrification rates suggests that 473 mt of NO₃‐N are produced annually, about 0.5% of Pool 8 total annual NO₃‐N budget. Copyright © 2013 John Wiley & Sons, Ltd.     

光学与微波数据协同反演植被覆盖区土壤水分

基于LandSat5 TM和ENVISAT-1 ASAR数据,通过水云模型剔除了植被层对雷达后向散射系数的影响,利用AIEM模型对黑河中游植被覆盖地表的土壤水分进行了反演。建立植被含水量(Mveg;水云模型中关键参数)与多种植被指数之间的响应关系,发现比值植被指数(RVI)反演的植被含水量精度较高(R2=0.71);去除植被影响后,利用AIEM模型建立LUT表,基于VV和VH极化的后向散射系数,通过查表法反演研究区的土壤水分。对比野外实测数据与反演结果,发现VV极化数据反演结果较好(R2=0.74)。考虑了植被覆盖层对后向散射系数的影响,该方法更适用于植被覆盖地表的土壤水分反演。     

黄河水滴灌系统灌水器结构-泥沙淤积-堵塞行为的相关关系研究

传统的黄河水沉淀-过滤系统存在沉沙池建设成本高、过滤器频繁反冲洗能耗高等问题,让更多的细颗粒泥沙随水流排出灌水器体外是解决黄河水滴灌系统灌水器堵塞的新思路,而摸清泥沙在黄河水滴灌系统内部的淤积特性以及灌水器结构-淤积泥沙特性-堵塞特性参数间的相关关系是探索其排沙能力的前提和基础。为此,本文在河套灌区开展了黄河水滴灌系统灌水器堵塞原位试验,系统分析了6种内镶贴片式灌水器内部细颗粒泥沙含量及粒径分布动态变化特征,探索了三者间的级联关系。结果表明：进入灌水器内部的泥沙99%以上可以排出体外,淤积在灌水器内部的泥沙以粉粒为主、砂粒次之、黏粒最少。随着灌水器堵塞加剧,内部淤积泥沙的黏粒、粉粒比例相对降低,而砂粒比例相对增加,泥沙进入灌水器后存在聚集等行为,使得灌水器内部淤积泥沙粒径明显高于毛管入口。泥沙比表面积淤积量、粉粒比例、砂粒比例、D₅₀、D₉₅对黄河水滴灌系统Dra、克里斯琴森均匀系数CU影响显著（p<0.05）,不同灌水器淤积泥沙粒径明显不同,D₅₀与灌水器结构无量纲参数（流道宽深比W/D、面积长度比A^1/2/L）及断面平均流速v显著（p<0.05）相关。本研究对引黄滴灌灌水器设计及灌溉系统过滤配置具有指导意义。