Application of electrical resistivity to map the stratigraphy and salinity of fluvio- deltaic aquifers: case studies from Bangladesh reveal benefits and pitfalls.


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Created: Jan 06, 2021 at 1:18 a.m.
Last updated: Mar 01, 2021 at 3:17 p.m.
DOI: 10.4211/hs.cf3c2633962b4121a231110d4be0d7a5
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Abstract

Fluvio-deltaic aquifers are the primary source of drinking water for the people of Bangladesh. Such aquifers, which comprise the Ganges-Brahmaputra-Meghna Delta, are extremely hydrogeologically heterogeneous. Because of widespread groundwater quality issues in Bangladesh, it is crucial to know the hydrostratigraphic architecture and hydrochemistry of the aquifers as some units are contaminated whereas others are safe. Geophysical methods provide a potentially effective and non-invasive method for extensive characterization of these aquifers. Here we report the application and investigate the limitations of using electrical resistivity imaging (ERI) for mapping the hydrostratigraphy and salinity of an aquifer-aquitard system adjacent to the Meghna River. In some ER sections we observed excellent correlation between resistivity and grain size. These show that ERI is a powerful tool for mapping internal aquifer architecture and their boundaries with finer-grained aquitards which clearly appear as low ER zones. However, in parts of some ER sections, variations in electrical properties were determined by porewater resistivity. In these cases, low ER was indicative of brine and did not indicate the presence of finer-grained materials such as silt or clay. Accordingly, the following hydrostratigraphic zones with different resistivities were detected: (1) aquifers saturated with fresh ground water, (2) a regional silt/clay aquitard, and (3) a deeper brine-saturated formation. In addition, shallow silt/clay pockets were detected close to the river and below the vadose zone. ERI is thus a promising technique for mapping aquifers versus aquitards. However, the observations are easily confounded by porewater salinity. In such cases, borehole information and groundwater salinity measurements are necessary for ground-truthing.

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This resource was created using funding from the following sources:
Agency Name Award Title Award Number
National Science Foundation EAR-1940772
National Science Foundation EAR-1852652
National Science Foundation EAR-1852653

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People or Organizations that contributed technically, materially, financially, or provided general support for the creation of the resource's content but are not considered authors.

Name Organization Address Phone Author Identifiers
M. Bayani Cardenas University of Texas at Austin

How to Cite

Pedrazas, M. N., M. B. Cardenas, A. Hosain, C. Demir, K. M. Ahmed, P. Knappett, S. Datta, S. H. Akhter, L. Wang (2021). Application of electrical resistivity to map the stratigraphy and salinity of fluvio- deltaic aquifers: case studies from Bangladesh reveal benefits and pitfalls., HydroShare, https://doi.org/10.4211/hs.cf3c2633962b4121a231110d4be0d7a5

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