Combination of sensitivity and uncertainty analyses for sediment transport modeling in sewer pipes

Mitigation of sediment deposition in lined open channels is an essential issue in hydraulic engineering practice.Hence,the limiting velocity should be determined to keep the channel bottom clean from sediment deposits.Recently,sediment transport modeling using various artificial intelligence(AI) techniques has attracted the interest of many researchers.The current integrated study highlights unique insight for modeling of sediment transport in sewer and urban drainage systems.A novel methodology based on the combination of sensitivity and uncertainty analyses with a machine learning technique is proposed as a tool for selection of the best input combination for modeling process at non-deposition conditions of sediment transport.Utilizing one to seven dimensionless parameters,127 models are developed in the current study.In order to evaluate the different parameter co mbinations and select the training and te sting data,four strategies are considered.Considering the densimetric Froude number(Fr) as the dependent parameter,a model with independent parameters of volumetric sediment concentration(C_V) and relative particle size(d/R) gave the best results with a mean absolute relative error(MARE) of 0.1 and a root means square error(RMSE) of 0.67.Uncertainty analysis is applied with a machine learning technique to investigate the credibility of the proposed methods.The percentage of the observed sample data bracketed by95% predicted uncertainty bound(95 PPU) is computed to assess the uncertainty of the best models.     

基于GMS软件对某矿区松散层孔隙水污染的数值模拟研究

以云南某矿区为研究对象,在详细调查区域水文地质条件和已有资料的基础上,结合调查区监测井,利用GMS软件建立研究区域地下水水流场模型和溶质运移模型。模型计算了在合理误差范围内的水流场模型并预测了硫酸盐在持续泄漏730d、180d后切断泄漏源,硫酸盐的迁移过程。研究结果表明:随着持续泄漏时间的增加,调查区域北部边界附近受到污染的浓度越高、污染范围越广,超标的污染物在北部边界区域进入岩溶含水层,遇到岩溶带会加速污染物向下游运移,破坏下游水质、危及下游村庄饮用水安全。     

Internal-wave-induced and double-diffusive nutrient fluxes to the nutrient-consuming surface layer in the oligotrophic subtropical North Atlantic

In the literature, an inconsistency exists between estimates of biotically-effected carbon export inferred from large-scale geochemical studies (Jenkins 1982; 47 gC m^–2 a^–1) and local measurements of turbulent nutrient supply (Lewis et al. 1986; 4 gC m^–2 a^–1) in the eastern subtropical North Atlantic. Nutrient supply to the upper ocean by turbulent mixing is reexamined using local standard oceanographic measurements and high-resolution vertical profiles of nutrients averaged over a large region directly comparable to that investigated by Jenkins (1982).Responsible Editor: Franciscus Colijn     

Observations of several characteristics of aeolian sand movement in the Taklimakan Desert

With both sides of the Taklimakan Desert highway line as the study area, three typical aeolian sand landforms, i.e. complex dune ridge, barchan dune and flat sand land, were selected as sand beds for the observation, analysis and research of the characteristics of aeolian sand movement such as aeolian sand stream structure, sand transport intensity, etc. in the Taklimakan Desert. The results show that there is a linear relation between the height and the log of sand transport rate over transverse dune chain, longitudinal dune ridge and flat sand land, i.e. the sand transport percentage decreases exponentially with increasing height. Sand transport rate within the 10 cm height above the bed surface accounts for 80%-95% of the total sand transport rate of the observed height (40 cm), while the sand transport rate in 20 cm occupies 98% of the total amount. Sand transport rate (g·cm-1·min-1) differs greatly with respect to different landform types and different topographic positions. Based on the investig     

A participatory approach to integrated aquifer management: The case of Guanajuato State,Mexico

Guanajuato State, located in central Mexico, with less than 2% of the countrys area, has almost 17,000 deep water wells, from which nearly 4,000 cubic hectometers (hm³) per year are being extracted, more than 1,000 hm³ over the estimated renewable yield. Since, in Mexico, water is administered under federal jurisdiction by the National Water Commission (CNA, for its Spanish acronym), the state government faces the challenge of ensuring its populations economic development without formal means of intervention. Being thus limited to apply mandatory policies and measures, the state water program has focused on the implementation of a two-sided strategy. First, basic hydrogeological studies and mathematical groundwater hydrodynamic models were developed upon a comprehensive survey of existing wells and a general revision of the states geological framework. Second, a structure for water users participation in water management actions was promoted (from the dissemination of information to the implementation of pilot efficient water use projects) with financial, technical and political support from the state. Simultaneously, a coordinated effort towards the completion of the water users registry was performed with the federal authority along with other supporting measures such as training and monitoring programs. In this paper, a general overview of the projects achievements and challenges is presented.To make direct contact with the water-user associations mentioned in this paper, please write to Eng. Aurelio Navarrete of the State Water Council at: cehgto@prodigy.net.mx.     

推移质输沙率的非线性研究

目的是从非线性科学角度探讨泥沙运动的规律。通过分析非均匀沙起动的影响因素得到了尖点突变模型的状态变量和控制变量,建立了能描述推移质运动的尖点突变模型。在尖点突变标准方程的基础上,应用尖点突变理论的坐标变换和拓扑变换,导出了输沙强度和水流参数的函数关系式。将输沙强度作为状态变量,水流参数和床沙密实系数作为控制变量。用水槽实验资料和其它推移质输沙率公式进行了对比验证。验证结果表明,计算值与其它推移质输沙率公式和水槽实验结果基本相符,误差一般在-90%～80%之间。说明建立的推移质输沙率公式是合理的,能够反映泥沙的起动和输移规律。     

Solute transport in a single fracture with negligible matrix permeability: 1. fundamental mechanisms

This report describes the fracture-scale mechanisms acting on solute transport in fractured aquifers under natural-flow conditions. It focuses on low-permeability rocks where advection in the matrix is negligible compared with that in fractures. The relevant transport mechanisms detailed have been identified by experimental and theoretical studies over the past 30 years: advection and hydrodynamic dispersion, channeling effects, matrix diffusion, and sorption reactions. This review is intended to emphasize the fundamental concepts and to draw up a reader's guide through an extensive bibliography by linking key problems to key papers. These concepts might be integrated into transport models, but their influence at the large scale, however, remains an open question that is not dealt with in this review.

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Resumen Este informe describe los mecanismos que actúan a escala de fractura en el transporte de solutos en acuíferos fracturados, bajo condiciones de flujo natural. Se centra en rocas de baja permeabilidad en las que la advección en la matriz es despreciable en relación con la advección en las fracturas. Los mecanismos de transporte relevantes han sido identificados mediante estudios experimentales y teóricos realizados en los últimos 30 años. Consisten en advección y dispersión hidrodinámica, influencia de los canales, difusión en la matriz y reacciones de sorción. Esta revisión pretende enfatizar en los conceptos fundamentales y generar una guía para el lector por medio de una bibliografía abundante que relaciona los problemas clave con artículos clave. Estos conceptos podrían ser integrados en modelos de transporte, pero su influencia a gran escala es todavía un tema no resuelto, el cual no se aborda en este trabajo.

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Résumé Ce rapport décrit les mécanismes agissant sur le transport de soluté dans les aquifères fissurés en régime d'écoulement naturel. L'accent est mis sur les roches peu perméables, où le transport par convection dans la matrice est négligeable devant la convection dans les fractures. Les mécanismes de transport sont analysés à l'échelle de la fracture: convection et dispersion hydrodynamique, chenalisation, diffusion dans la matrice et réactions de sorption. L'objectif de ce travail est double: d'une part, mettre en avant les concepts fondamentaux pouvant être intégrés dans les modèles de transport, et d'autre part, établir un "guide" permettant au lecteur de s'orienter à travers une bibliographie abondante, en reliant chaque sujet abordé à quelques articles clés. Notons que l'influence de ces mécanismes sur le transport à grande échelle reste un problème clé qui ne sera pas abordé ici.

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Fluvial process and morphology of the Brahmaputra River in Assam, India

The Brahmaputra River finds its origin in the Chema Yundung glacier of Tibet and flows through India and Bangladesh. The slope of the river decreases suddenly in front of the Himalayas and results in the deposition of sediment and a braided channel pattern. It flows through Assam, India, along a valley comprising its own Recent alluvium. In Assam the basin receives 300 cm mean annual rainfall, 66–85% of which occurs in the monsoon period from June through September. Mean annual discharge at Pandu for 1955–1990 is 16,682.24 m³ s^{− 1}. Average monthly discharge is highest in July (19%) and lowest in February (2%). Most hydrographs exhibit multiple flood peaks occurring at different times from June to September. The mean annual suspended sediment load is 402 million tons and average monthly sediment discharge is highest in June (19.05%) and lowest in January (1.02%). The bed load at Pandu was found to be 5–15% of the total load of the river. Three kinds of major geomorphic units are found in the basin. The river bed of the Brahmaputra shows four topographic levels, with increasing height and vegetation. The single first order primary channels of this braided river split into two or more smaller second order channels separated by bars and islands. The second order channels are of three kinds. The maximum length and width of the bars in the area under study are 18.43 km and 6.17 km, respectively. The Brahmaputra channel is characterised by mid-channel bars, side bars, tributary mouth bars and unit bars. The geometry of meandering tributary rivers shows that the relationship between meander wavelength and bend radius is most linear. The Brahmaputra had been undergoing overall aggradation by about 16 cm during 1971 to 1979. The channel of the Brahmaputra River has been migrating because of channel widening and avulsion. The meandering tributaries change because of neck cut-off and progressive shifting at the meander bends. The braiding index of the Brahmaputra has been increasing from 6.11 in 1912–1928 to 8.33 in 1996. During the twentieth century, the total amount of bank area lost from erosion was 868 km². Maximum rate of shift of the north bank to south resulting in erosion was 227.5 m/year and maximum rate of shift of the south bank to north resulting in accretion was 331.56 m/year. Shear failure of upper bank and liquefaction of clayey-silt materials are two main causes of bank erosion.     

Intelligent Transportation Systems and Travel Behavior in Connecticut

In the past decade, there has been significant investment in Intelligent Transportation Systems (ITS) technologies that provide information to both en‐route and pre‐trip travelers. However, there is no definitive evidence that en‐route travelers actually use the information and alter their travel patterns. Previous research employed surveys that relied on motorists' written or spoken responses to questions involving travel information and hypothetical roadway scenarios. This research examines travel behavior on freeways equipped with ITS technologies in Connecticut using collected real‐time traffic count data from the diversionary roadways. Results find that more travel is occurring on the diversionary routes during periods of variable message sign (VMS) messages than during equivalent periods having no messages, indicating a motorist travel response to these messages.     

克州地区一场特大暴雪天气过程分析

对2003年3月初发生在南疆西部的一次特大暴雪天气进行了天气成因分析。着重从大尺度环流的演变、高低空急流的配置、物理量场的特征入手，探讨了南疆西部大降水形成的物理、动力条件。