Author(s)

Nasir Ahmed¹, Manzoor Ahamad Choudhry², Mohammed Khaliquzzaman^3*, Arif Ahamed³, Mohammad Abdul Quaiyum Bhuiyan¹, Nipa Deb¹, Tasrina Rabia Choudhury⁴, Mohammad Masud Karim¹, Sheikh Mohammad Mahbubur Rahman⁵, Mohammad Murshed Alam⁵, Abul Khair Mohammed Fazlullah⁶, Mohammed Ariful Islam⁶

¹Isotope Hydrology Division, Institute of Nuclear Science and Technology, Bangladesh Atomic Energy Commission, Dhaka, Bangladesh.
²Isotope Hydrology Section, International Atomic Energy Agency, Vienna, Austria.
³The World Bank, Dhaka, Bangladesh.
⁴Chemistry Division, Atomic Energy Centre, Dhaka, Bangladesh.
⁵Institute of Water Modelling, Dhaka, Bangladesh.
⁶Chattogram Water Supply and Sewerage Authority, Chattogram, Bangladesh.

The study was undertaken for understanding the potential of deep aquifers as a source of safe drinking water and for assessing the status of groundwater aquifer near Madunaghat area, Chattogram. The specific issues are salinity, interconnectivity of the shallow and deep aquifers, mixing of groundwater with the adjacent Halda river water, recharge condition and groundwater age. The isotopic data suggest that most of the groundwater results from a mixture between recent recharge and an older component recharge under climatic conditions cooler than at present. The interconnectivity between shallow aquifers and river waters are mostly found in the line wells installed particularly in shallow depth (16 m) close to Halda river as evidenced from the similar tritium values of sampled line well water with that of the Halda river water. The groundwater in Madunaghat well field area is not affected by salinity, as it is evidenced by higher values of Na/Cl ratio of the groundwater samples compared to the sea water fresh water mixing line. The geochemistry of intermediate and deep groundwater is dominated by Na-Mg-HCO₃ and Na-HCO₃ type waters. Even the relationship between chloride and oxygen-18 (Cl-δ¹⁸O) depicts that the waters from the deep, intermediate and shallow wells do not fall on the seawater mixing line. The Carbon-14 contents of intermediate to deep groundwater samples vary from 16.2 to 59.3 pMC indicating the residence time in the range of 4300 to 15,000 years BP, i.e., the sourced water recharged the aquifers a long time ago. The intermediate and deep wells have water with arsenic concentrations less than the detection limit of 3.0 μg/L. Only a few shallow wells have arsenic concentrations greater than the detection limit varying from 13.7 - 47.4 μg/L, which is less than the DoE permissible limit (50 μg/L) implying that the groundwater at Madunaghat area is not affected by Arsenic contamination.

Stable Isotope, Tritium, Carbon-14, Salinity, Chloride, Recharge, Residence Time

Ahmed, N. , Choudhry, M. , Khaliquzzaman, M. , Ahamed, A. , Bhuiyan, M. , Deb, N. , Choudhury, T. , Karim, M. , Rahman, S. , Alam, M. , Fazlullah, A. and Islam, M. (2021) An Assessment of Aquifer Potential in and around a Proposed Well Field Area near Madunaghat, Chattogram Using Isotopic Techniques. Journal of Water Resource and Protection, 13, 395-418. doi: 10.4236/jwarp.2021.136024.