The recharge process in alluvial strip aquifers in arid Namibia and implication for artificial recharge

Alluvial strip aquifers associated with ephemeral rivers are important groundwater supply sources that sustain numerous settlements and ecological systems in arid Namibia. More than 70 % of the population in the nation’s western and southern regions depend on alluvial aquifers associated with ephemeral rivers. Under natural conditions, recharge occurs through infiltration during flood events. Due to the characteristic spatial and temporal variability of rainfall in arid regions, recharge is irregular making the aquifers challenging to manage sustainably and they are often overexploited. This condition is likely to become more acute with increasing water demand and climate change, and artificial recharge has been projected as the apparent means of increasing reliability of supply. The article explores, through a case study and numerical simulation, the processes controlling infiltration, significance of surface water and groundwater losses, and possible artificial recharge options. It is concluded that recharge processes in arid alluvial aquifers differ significantly from those processes in subhumid systems and viability of artificial recharge requires assessment through an understanding of the natural recharge process and losses from the aquifer. It is also established that in arid-region catchments, infiltration through the streambed occurs at rates dependent on factors such as antecedent conditions, flow rate, flow duration, channel morphology, and sediment texture and composition. The study provides an important reference for sustainable management of alluvial aquifer systems in similar regions.     

硬土-软岩的厘定及其判别分类

结合我国大量工程实践和作者的研究积累,证明在中国岩石和土两种工程类型之间,确实存在着难以"一刀切"的过渡类型(即硬土-软岩),并根据其地质成因和分布规律进行了初步分类.     

江苏沙洲电厂一期工程循环泵房施工阶段沉降监测

江苏沙洲电厂一期工程循环泵房沉井位于天然软地基上,特殊的施工工艺和负载过程必将导致建筑物的沉降并可能危机泵房的安全.为解决监测中的核心问题——沉降幅度及各监测点沉降的一致性,监测中提出了针对性的实施方案和数据处理技术,通过长期监测,成功的给出泵房不同时期的沉降变化规律,确保了泵房施工和负载工程的顺利完成.     

Use of terrain variables for mapping gully erosion susceptibility in Lebanon

This paper predicts the geographic distribution and size of gullies across central Lebanon using a geographic information system (GIS) and terrain analysis. Eleven primary (elevation; upslope contributing area; aspect; slope; plan, profile and tangential curvature; flow direction; flow width; flow path length; rate of change of specific catchment area along the direction of flow) and three secondary (steady‐state; quasi‐dynamic topographic wetness; sediment transport capacity) topographic variables were generated and used along with digital data collected from other sources (soil, geology) to statistically explain gully erosion field measurements. Three tree‐based regression models were developed using (1) all variables, (2) primary topographic variables only and (3) different pairs of variables. The best regression tree model combined the steady‐state topographic wetness and sediment transport capacity indices and explained 80% of the variability in field gully measurements. This model proved to be simple, quick, realistic and practical, and it can be applied to other areas of the Mediterranean region with similar environmental conditions, thereby providing a tool to help with the implementation of plans for soil conservation and sustainable management. Copyright © 2007 John Wiley & Sons, Ltd.     

Magnetic properties and paleoclimatic implications of loess-paleosol

Detailed rock magnetic investigations and X-ray diffraction (XRD)were carried out on loess-paleosol sequences of the last interglacial-glacial at Znojmo section in Czech Republic. The results indicate that pedogenesis causes susceptibility enhancement in the paleosols, which is similar to that observed in the Chinese Loess Plateau. k-T curves, IRM, and XRD show that magnetite is the dominant magnetic mineral in the loess-paleosol sequences at the Znojmo section, while maghemite, hematite, and pyrite/pyrrhotite are minor minerals. Measurements of anisotropy of magnetic susceptibility (AMS) indicate that the magnetic lineation is smaller than the foliation. The susceptibility ellipsoids are oblate and the directions of the maximum principal axes (Kmax) are distributed randomly, and cannot be used to determine the paleo-wind direction.     

四川省大渡河下游峨眉山玄武岩夹层中绿鳞石的研究

产于四川省铜街子电站玄武岩沉积夹层中的绿鳞石,具有二八面体1M云母结构,与海绿石结构相似,但以其八面体层中的高Mg含量与海绿石相区别。该绿鳞石是玄武岩两次喷发间断中,凝灰物质沉积后经蚀变而成。     

关于土与土体工程地质研究的新进展

作者在简要回顾近两年国内土及土体研究及会议的基础上,详细论述了本次大会在土与土体工程地质研究的进展,最后指出了5个有待加强研究的问题。     

地电台站观测环境干扰源探讨

随着我国经济建设的发展，一些地电台站的的观测受到大面积施工破坏形成大面积干扰源，给地电为干扰，文中对地电台站观测环境干扰 的影响作了一定的理论推导，对其引起的干扰电位进行了计算；同时对干扰电位与观测电流关系，环境保护距离等进行了探讨。