Delineating alluvial aquifer heterogeneity using resistivity and GPR data
Delineating alluvial aquifer heterogeneity using resistivity and GPR data
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DOI：
10.1111/j.1745-6584.2005.00103.x
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发表时间：
2005-11-01
期刊：
影响因子：
2.6
通讯作者：
Zheng, CM
中科院分区：
文献类型：
--
作者：
Bowling, JC;Rodriguez, AB;Zheng, CM
基于地球物理数据的概念性地质模型可以阐明含水层在米和更小尺度上的结构和非均质性，从而可以更好地预测优先流动路径。宏观弥散实验(MADE)场地获得了>；2000的水力传导性测量，并进行了三次示踪剂测试，是检验河流含水层地下水流特征与地球物理属性之间关系的理想自然实验室。渗透系数测量的空间变化表明场地具有很大程度的非均质性。为了评价地球物理方法在更好地圈定河流含水层非均质性和优先流动路径分布方面的有效性，收集了二维探地雷达(GPR)和直流(DC)电阻率数据的表面网格。根据这些数据建立了一个地质模型，它描绘了四个具有不同电性和雷达特性的地层单位，包括(从上到下)(1)曲流河体系(MFS)；(2)辫状河体系(BFS)；(3)细粒砂体；(4)富含粘土的区段。利用直流电阻率和探地雷达数据，在MFS中绘制了一条古河道，这是其他作者推断的影响水流的因素。这条水道有2到4米深，根据电阻率值，主要是粘土和粉砂。将已有的导水率测量和示踪剂羽流迁移模式与地质模型进行比较，结果表明水流主要发生在边界层内，绘制在边界层内的河道对羽流迁移模式没有影响。
Conceptual geological models based on geophysical data can elucidate aquifer architecture and heterogeneity at meter and smaller scales, which can lead to better predictions of preferential flow pathways. The macrodispersion experiment (MADE) site, with >2000 measurements of hydraulic conductivity obtained and three tracer tests conducted, serves as an ideal natural laboratory for examining relationships between subsurface flow characteristics and geophysical attributes in fluvial aquifers. The spatial variation of hydraulic conductivity measurements indicates a large degree of site heterogeneity. To evaluate the usefulness of geophysical methods for better delineating fluvial aquifer heterogeneities and distribution of preferential flow paths, a surface grid of two-dimensional ground penetrating radar (GPR) and direct current (DC) resistivity data were collected. A geological model was developed from these data that delineate four stratigraphic units with distinct electrical and radar properties including (from top to bottom) (1) a meandering fluvial system (MFS); (2) a braided fluvial system (BFS); (3) fine-grained sands; and (4) a clay-rich interval. A paleochannel, inferred by other authors to affect flow, was mapped in the MFS with both DC resistivity and GPR data. The channel is 2 to 4 m deep and, based on resistivity values, is predominantly filled with clay and silt. Comparing previously collected hydraulic conductivity measurements and tracer-plume migration patterns to the geological model indicates that flow primarily occurs in the BFS and that the channel mapped in the MFS has no influence on plume migration patterns.