Computerized streamflow measurement using slug injection

Using current meters to estimate flows in fast mountain streams is difficult and inaccurate. The salt dilution method offers an easier and more accurate alternative. The method has been used for many years but is time consuming and messy because of the need to mix chemical solutions and measure chemical concentrations in the field. A computer program has been developed which uses a laptop computer to calculate the mixing length and the mass of salt needed. The program controls the conductivity measurements and calculates the streamflow directly in the field. The development of this program is described and examples are presented of the application of the method in the Rocky Mountains of Alberta and British Columbia.     

Effect of image segmentation & voxel size on micro-CT computed effective transport & elastic properties

Digital rock technology is rapidly evolving interdisciplinary field with many promises, including fast turnaround times for core analysis, repeatable analysis, and multiphysics simulation. We study the impact of the image segmentation threshold and image voxel size on image-computed permeability, elastic moduli, and electrical conductivity. Improved quantitative understanding of such effects is critically important when comparing laboratory-measured rock properties with those computed on digital images of rocks. We analyze properties of over 500 binary microstructures (each of size 1024³ voxels) segmented using different segmentation algorithms. We find that uncertainty in computed rock properties, induced due to the choice of segmentation threshold, increases with coarsening of image voxels. Segmentation of the same rock, acquired with different voxels sizes, lead to small variations in porosity but induces relatively large variation in flow and electrical rock properties. This uncertainty is larger for rocks of lower porosity. We find that coarsening of image voxels also leads to rounding and smoothing of pore throats and a sharp decline in specific surface area which results in an increase in computed permeability. We propose simple models to remove the bias in rock properties when image-derived porosity is either overestimated or underestimated due to the choice of the segmentation threshold. This approach is particularly useful when comparing laboratory-measured rock properties to those derived from digital rocks since often the image calculated porosity and the laboratory-measured porosity are not the same. Even after such corrections, the impact of finite image voxel size would still need to be compensated.     

酸雨观测异常数据的试验分析和处理方法

本文就酸雨观测仪器在测量操作中出现的异常状态进行了试验和分析,且对校错电极常数、测温系统故障、"后测K值"3种异常状态, 结合酸雨观测业务实践进行了试验、分析和讨论。推导出校错电极常数的电导率订正公式;制定了仪器测温系统故障的应急观测方案;指出"后测K值"会导致数据严重失真, 测量中必须严格遵循 "先测K值"规程;并建议在《酸雨观测业务规范》修订时, 增加本文有关的分析和处理方法。     

偏硼酸锂溶液物种分布和物化性质

测量了不同浓度LiBO2溶液分别在298.15和323.15 K的密度、电导和pH,通过测得的pH和硼酸根离子化学平衡常数计算得到溶液中硼酸根离子的物种分布。根据获得的物种分布结果,推测溶液中各硼酸根离子之间的相互转化过程,并分别用偏摩尔体积公式和Onsager方程对溶液偏摩尔体积及摩尔电导率进行计算并拟合。对计算得到偏摩尔体积值和极限摩尔电导率值与文献报道的数据进行对比,计算结果与文献报道值吻合较好。     

Extension spatiale de la salinisation des ressources en eau et modèle conceptuel des sources salées dans la plaine des Triffa (Maroc nord-oriental)

The succession of drought years and excessive abstraction in the plain of Triffa caused deterioration in water quality and endangers future exploitation of groundwater resources. A combination of geophysical surveys, including electrical resistivity and hydrochemical data has been used to identify the geographical extension of salinization and identify its origin. Electrical conductivity measurements are used to show the history of salinization in space and time. In this paper, a first conceptual model of the brackish springs has been established. To cite this article: M. Boughriba et al., C. R. Geoscience 338 (2006).     

Comments on “Steady- and transient-state inversion in hydrogeology by successive flux estimation” by P. Pasquier and D. Marcotte

Pasquier and Marcotte [Pasquier P, Marcotte D. Steady- and transient-state inversion in hydrogeology by successive flux estimation. Adv Wat Res 2006;29:1934–52] propose some modifications to the Comparison Model Method (CMM), in order to apply it to transient 3D ground water flow data for conductivity identification. We present some remarks on that paper to improve the comprehension of the basic features of the CMM and of the real value of the novelties introduced by Pasquier and Marcotte.     

基于神经网络的时间域直升机电磁数据电导率深度成像

采用G-S变换以及高斯数值积分法,形成了时间域直升机的航空电磁响应正演样本集,分析了飞机测量过程中吊舱高度变化对电磁响应的影响,并将吊舱高度的变化等效成电导率为零的假层厚度的变化,以去除高度计等的影响.以假层半空间模型为基础,研究了基于人工神经网络的电导率深度成像算法,通过分析两个三层模型的电导率深度成像结果得出,神经网络方法计算时间域航空电磁探测的视电导率精度较高,特别是对高阻层的视电导率计算.     

Field assessment of acid mine drainage contamination in surface and ground water

Both sulfate and conductivity are useful indicators of acid mine drainage (AMD) contamination. Unlike pH, they are both extremely sensitive to AMD even where large dilutions have occurred. The advantage of using sulfate to trace AMD is that unlike other ions it is not removed to any great extent by sorption or precipitation processes, being unaffected by fluctuations in pH. These two parameters are also closely associated as would be expected, as conductivity is especially sensitive to sulfate ions. Therefore, as sulfate analysis is difficult in the field, conductivity can be used to predict sulfate concentration in both AMD and contaminated surface waters using regression analysis. Most accurate predictions are achieved by using equations given for specific conductivity ranges or AMD sources. There is also potential to use conductivity to predict approximate concentrations of key metals when the pH of the water is within their respective solubility ranges.     

A scaled experiment for the verification of the SeaBed Logging method

SeaBed Logging (SBL) is an application of the marine controlled source electromagnetic (CSEM) method that is used to directly detect and characterize possible hydrocarbon-bearing prospects. Although the CSEM method has been used by academia for more than three decades, the application as a direct hydrocarbon indicator was first introduced about five years ago. The central idea of SBL is the guiding of electromagnetic energy in thin resistive layers within conductive sediments. Even if it has been well known for a long time that electromagnetic signals can propagate from a conductive region to another via resistive regions such as air or resistive parts of the lithosphere, the application to hydrocarbon exploration has not been developed until recently. This might be due to the uncertainty of getting any significant response from thin resistive layers such as hydrocarbon reservoirs since electromagnetic energy is highly attenuated in conductive sediments. Thus, during the early development phase of the SBL technique, a scaled laboratory experiment was performed to validate if a thin resistive layer (e.g. hydrocarbons) buried within conductive media (e.g. sediments) could be remotely detected by using electric dipoles as sources and receivers. Data from this experiment were compared to a forward modelling code for layered media, and the comparison showed good agreement between experimental and theoretical results. This suggested that thin resistive layers buried in conductive media are detectable due to the guiding of the electromagnetic field within the resistor. The successful results were vital for realizing the application of marine CSEM as a hydrocarbon exploration technique. We here present the results of the first scaled SBL experiment.     

Two-phase hydrodynamic and sediment transport modeling of wave-generated sheet flow

This numerical investigation was carried out to advance mechanistic understanding of sediment transport under sheet flow conditions. An Euler–Euler coupled two-phase flow model was developed to simulate fluid–sediment oscillatory sheet flow. Since the concentration of sediment particles is high in such flows, the kinematics of the fluid and sediment phases are strongly coupled. This model includes interaction forces, intergranular stresses and turbulent stress closure. Each phase was modeled via the Reynolds-Averaged Navier–Stokes equations, with interphase momentum conservation accounting for the interaction between the phases. The generation and transformation of turbulence was modeled using the two-equation k–ε$k''–''\epsilon$ turbulence model. Concentration and sediment flux profiles were compared with experimental data for sheet flow conditions considering both symmetric and asymmetric oscillatory flows. Sediment and fluid velocity variations, concentration profiles, sediment flux and turbulence parameters of wave-generated sheet flow were studied numerically with a focus on sediment transport characteristics. In all applications, the model predictions compared well with the experimental data. Unlike previous investigations in which the flow is driven by a horizontal pressure gradient, the present model solves the Navier–Stokes equations under propagating waves. The model’s ability to predict sediment transport under oscillatory sheet flow conditions underscores its potential for understanding the evolution of beach morphology.