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Assessment of hydraulic conductivity in the multi-layered aquifer system of the Bengal Basin, Bangladesh, by performing slug tests

Abstract

Various studies have described upon importance of the performance of multilevel slug tests to assess hydraulic conductivity of aquifer sediment. For this study, slug tests were performed at 33 locations in 107 numbers of observation wells under six physiographic divisions in the Bengal Basin, Bangladesh. The objective of this paper is to evaluate the potential of multilevel slug tests to determine depth distribution and vertical variations of hydraulic conductivity in layered aquifer systems of the Bengal Basin that can be utilized for resource assessment. The studied aquifer sediments are dominated by unconsolidated fine and very fine sand with lenses of clay and silty clay aquitards. The hydraulic conductivity values commonly correspond with the lithology and their settlements. The unconsolidated sand in the Active and Tidal Delta contains high hydraulic conductivity values of up to 24.4 m/day. Older sediments in the Teppera Surface and Coastal Plain show lower average hydraulic conductivity. Very low hydraulic conductivities in few wells indicate the heterogeneities as well as poor development of these newly installed wells. Individual layers have relatively uniform grain size with well sorted sands, and their hydraulic conductivity values have a small variation, while sediments from multiple layers have variations in grain size with anisotropic signature and their hydraulic conductivity values, in many cases, vary by orders of magnitude. However, multilevel slug tests can provide considerable information about vertical variations in hydraulic conductivity under the right conditions. Although the slug tests were performed with precaution, unknown uncertainties in the well during the operation may influence the values of hydraulic conductivity. A more accurate values of the conductivity variations can be achieved by placing thin, low-conductivity layers in the sand pack that reduces vertical flow. Selection of drilling procedure and the techniques of measurement and analysis are also important to get good results. Factors like leakage and partial penetration should also be minimal for optimum results

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Data availability

Data and materials have been generated under the above mentioned research and knowledge management project of the Bangladesh Water Development Board, leaded by the first author Dr. Anwar Zahid, Director, Ground Water Hydrology, Bangladesh Water Development Board.

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Acknowledgements

Bangladesh Water Development Board (BWDB), Ministry of Water Resources and Bangladesh Climate Change Trust (BCCT), Ministry of Environment, Forest and Climate Change are highly acknowledged for supporting the study under Climate Change Trust Fund project to assess coastal water resources. Aminur Rahman, M. Jahangir Alam, Nur Ahmed, and all other hydrogeologists of the project team are acknowledged for their participation in the slug test activities. Farzana Bashar is acknowledged for editing literature of the manuscript.

Funding

Funding for this project of Bangladesh Water Development Board has been provided by the Bangladesh Climate Change Trust, Ministry of Environment, Forest and Climate change of the Bangladesh Government.

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Authors and Affiliations

Authors

Contributions

Anwar Zahid leaded, guided, and actively participated the research activities as well as prepared the manuscript. Sara Nowreen and M. Jakir Hossain were engaged to review the manuscript. M. Kamrul Islam, M. Rashedul Hasan, and Salah Uddin Abbassi participated in the field research activities and analyzed the slug test data using appropriate software.

Corresponding author

Correspondence to Anwar Zahid.

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Conflict of interest

The authors declare no competing interests.

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Zahid, A., Nowreen, S., Islam, M.K. et al. Assessment of hydraulic conductivity in the multi-layered aquifer system of the Bengal Basin, Bangladesh, by performing slug tests. Bull Eng Geol Environ 80, 5941–5955 (2021). https://doi.org/10.1007/s10064-021-02294-3

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  • DOI: https://doi.org/10.1007/s10064-021-02294-3

Keywords

  • Hydraulic conductivity
  • Slug test
  • Bengal Basin
  • Multi-layered aquifers