Numerical simulation of the influence of management alternatives of a projected reservoir on a small alluvial aquifer affected by seawater intrusion (Almuñécar, Spain)

The present study concerns the application of a numerical approach to describe the influence of anthropogenic modifications in surface flows (operation of a projected reservoir) on the freshwater-seawater relationships in a downstream coastal aquifer which has seasonal seawater intrusion problems (River Verde alluvial aquifer, Almuñécar, southern Spain). A steady-state finite element solution to the partial differential equation governing the regional motion of a phreatic surface and the resulting sharp interface between fresh water and salt water was used to predict the regional behavior of the River Verde aquifer under actual surface flow conditions. The present model approximates, with simple triangular elements, the regional behavior of a coastal aquifer under appropriate sinks, sources, Neumann and open boundary conditions. A steady-state solution to this numerical approach has been shown to precisely calculate freshwater heads, saltwater thicknesses, and freshwater discharges along steeply sloping coasts. Hence, the adequate treatment and interpretation of the hydrogeological data which are available for the River Verde aquifer have been of main concern in satisfactorily applying the proposed numerical model. Present simulated conditions consider steady-state yearly averaged amounts of external supplies of fresh water in order to determine the influences of the projected Otívar reservoir on the further behavior of the River Verde coastal aquifer. When recharges occur at the coastline, essentially because of freshwater deficits due to groundwater overexploitation, a hypothesis of mixing for the freshwater-saltwater transition zone is made in order to still allow the model to continue calculating groundwater heads under the sea level, and, as a consequence, the resulting seawater intrusion and recharges of saltwater from the sea. Simulations show that a considerable advance in seawater intrusion would be expected in the coastal aquifer if current rates of groundwater pumping continue and a significant part of the runoff from the River Verde is channeled from the Otívar reservoir for irrigation purposes.     

Identification of suitable sites for open and bore well using ground magnetic survey

The study aims to identify a suitable site for open and bore well in a farmhouseusing ground magnetic survey in south India. It also aims to define depth to granitoid and structural elements which traverse the selected area. Magnetic data(n=84) measured, processed and interpreted as qualitative and quantitatively. The results of total magnetic intensities indicate that the area is composed of linear magnetic lows trending NE-SW direction and circular to semi-circular causative bodies. The magnetic values ranged from -137 nT to 2 345 nT with a mean of 465 nT. Reduction to equator shows significant shifting of causative bodies in the southern and northern directions. Analytical signal map shows exact boundary of granitic bodies. Cosine directional filter has brought out structural element trending NE-SW direction.Results of individual profile brought to light structurally weak zone between 90 m and 100 m in all the profile lines. Sudden decrease of magnetic values from 2 042 nT to 126 nT noticed in profile line 6 between 20 m and 30 m indicates fault occurrence. Magnetic breaks obtained from these maps were visualized,interpreted and identified two suitable sites for open and bore well. Radially averaged power spectrum estimates depth of shallow and deep sources in 5 m and 50 m, respectively. Euler method has also been applied to estimate depth of granitoid and structural elements using structural indexes 0, 1, 2, and 3 and found depth ranges from 10 m to 90 m. Study indicates magnetic method is one of the geophysical methods suitable for groundwater exploration and site selection for open and borewells.     

Geospatial web services pave new ways for server-based on-demand access and processing of Big Earth Data

ABSTRACT

Big Earth Data has experienced a considerable increase in volume in recent years due to improved sensing technologies and improvement of numerical-weather prediction models. The traditional geospatial data analysis workflow hinders the use of large volumes of geospatial data due to limited disc space and computing capacity. Geospatial web service technologies bring new opportunities to access large volumes of Big Earth Data via the Internet and to process them at server-side. Four practical examples are presented from the marine, climate, planetary and earth observation science communities to show how the standard interface Web Coverage Service and its processing extension can be integrated into the traditional geospatial data workflow. Web service technologies offer a time- and cost-effective way to access multi-dimensional data in a user-tailored format and allow for rapid application development or time-series extraction. Data transport is minimised and enhanced processing capabilities are offered. More research is required to investigate web service implementations in an operational mode and large data centres have to become more progressive towards the adoption of geo-data standard interfaces. At the same time, data users have to become aware of the advantages of web services and be trained how to benefit from them most.     

基于DWGDirect的CAD到GIS数据转换研究

针对CAD数据到GIS数据的转换中大量存在的信息缺失、效率低下、更新困难等诸多问题,提出基于DWGDirect类库,结合ArcEngine实现CAD数据到GIS数据的转换,很大程度上解决了上述各种问题,确保了数据转换的科学性和高效性。     

Characterization of Continental Intercalaire aquifer (CI) in the Tinrhert-East Area-Illizi Basin on the Algerian-Libyan Border

This paper addresses the characterization of the Continental Intercalaire aquifer (CI) in the Tinrhert-East area of Illizi Basin on the Algerian-Libyan border, which belongs to the SASS1 system, one of the biggest transboundary aquifers in the world. This study concerns a superficies of 4 300 km2. On the basis of Mud Logging borehole data conducted in this part of the aquifer, a realistic characterization of the aquifer was done. The thickness of the CI aquifer varies from 300 m in the south to 700 m in the north, and the depth ranges from 180 m to 320 m. The interpretation of the logs showed that the aquifer is characterized by a maximum net thickness in its southwestern part (more than 600 m), the porosity is very high, ranging from 30% in the west to 24% at the Libyan borders, the permeability is low to medium around 10-5 m/s, and the maximum transmissivity values of about 8×10-3 m2/s were recorded at the center of the study area. The depth of water varies from 235 m to 312 m, and the water flows from south to north, in accordance with the general direction observed in the CI aquifer in the Northern Sahara Aquifer System (SASS). The porosity values obtained from the interpretation of the sonic and density logs permit to estimate the water reserves of this aquifer considered fossil, at thresholds much higher than what was considered until now.     

安徽马鞍山高村采场矿坑地下水疏干预测

根据马鞍山高村铁矿露天采场矿区地质及水文地质特征,对矿区的基岩裂隙地下水系统进行概化。结合高村采矿场历史疏干资料和观测孔的地下水动态观测资料,建立了矿区地下水水流模型。然后按照露天采场的开采计划,论证矿坑地下水疏干对策,分别对2个开采规划期进行地下水疏干预测,为安全开采和经济有效地防治地下水提供设计依据。     

Linear and nonlinear irregular waves and forces in a numerical wave tank

A time-domain higher-order boundary element scheme was utilized to simulate the linear and nonlinear irregular waves and diffractions due to a structure. Upon the second-order irregular waves with four Airy wave components being fed through the inflow boundary, the fully nonlinear boundary problem was solved in a time-marching scheme. The open boundary was modeled by combining an absorbing beach and the stretching technique. The proposed numerical scheme was verified by simulating the linear regular and irregular waves. The scheme was further applied to compute the linear and nonlinear irregular wave diffraction forces acting on a vertical truncated circular cylinder. The nonlinear results were also verified by checking the accuracy of the nonlinear simulation.     

开放地质体系中物质迁移质量平衡计算方法介绍

地质体系的开放过程,如交代、蚀变、熔融、风化、渗透、变形等,往往伴随着显著的物质组分(元素)的活动和迁移.研究这些地质过程需要我们深入地了解发生迁移组分的种类和程度.质量平衡计算作为定量限定地质体系开放过程中物质迁入或迁出情况的重要手段,已经被广泛应用到诸多的地质问题研究中.目前,已有许多的学者建立了各种各样的质量平衡计算公式和相应的图解方法,但是这些方法的核心思想和基本原理都是一致的.因此,本文选取了目前国际上几个常用的质量平衡计算方法进行了详细地介绍.这些方法包括成分-体积图解法(Gresens,1967)、Isocon图解法(Grant,1986)、标准化Isocon图解法(Guo et al.,2009)和定量计算法.同时,作者也结合自身的研究经验和实例,对这些方法的应用范围、优缺点和注意事项做了相应地评述.通过这些介绍,希望可以帮助初学者对质量平衡计算方法的基本原理、主要思想及应用过程有一个相对全面的了解.     

基于OSGEarth的城市三维地物模型组织与调度研究

基于OSG开源工程采用可见性裁剪、LOD与动态调度等技术,分别对静态加载模型、静态加载LOD模型、动态加载和结合四叉树动态加载、瓦片式动态加载等进行试验分析,研究了城市三维地物模型的组织与调度方式,实现了基于OSGEarth城市三维场景构建,取得了良好的效果,为城市三维信息服务平台的建设提供空间框架和理论支持。     

基于VC++的梁式桥震害评估软件

震后桥梁结构震害快速评估能够为地震应急救援提供重要参考信息,对减灾工作具有重要价值。为了快速准确地评估遭受地震影响梁式桥的破坏状态,使梁式桥震害评估方法在地震应急中发挥更大作用,基于统计回归模型、神经网络模型和推断模型等三种梁式桥震害评估模型,采用VC++6.0及Access2003数据库软件开发了有关评估软件,并以桥梁震害资料为算例验证了软件的可靠性。