%0 Journal Article %T Groundwater residence time in basement aquifers of the Ochi-Narkwa Basin in the Central Region of Ghana %+ University of Ghana %+ Ghana Atomic Energy Commission %+ Université du Ghana %+ Bureau de Recherches Géologiques et Minières (BRGM) (BRGM) %+ Czech Technical University in Prague (CTU) %+ Environment Laboratories (IAEA) %A Ganyaglo, Samuel %A Osae, Shiloh %A Akiti, Tetteh %A Armah, Thomas %A Gourcy, Laurence %A Vitvar, Tomas %A Ito, Mari %A Otoo, Isaac %< avec comité de lecture %@ 1464-343X %J Journal of African Earth Sciences %I Elsevier %V 134 %P 590 - 599 %8 2017-10 %D 2017 %R 10.1016/j.jafrearsci.2017.07.028 %Z Sciences of the Universe [physics]/Earth Sciences %Z Sciences of the Universe [physics]/Earth Sciences/Applied geologyJournal articles %X Groundwaters from basement aquifers in the Ochi-Narkwa basin of the Central Region together with rain and surface waters have been analysed for stable isotopes (delta O-18, delta H-2 and delta C-13) and radioisotopes (H-3 and C-14) to determine sources of recharge, groundwater residence time and flow path. The mechanism of recharge to the groundwaters is by direct infiltration of past local rainfall of mean isotopic composition delta O-18 = -3.8 parts per thousand V-SMOW and delta H-2 = -18 parts per thousand V-SMOW. Tritium in the groundwaters ranged from 0.05 +/- 0.07 to 4.75 +/- 0.16 TU. Tritium data revealed that 85% of the groundwater samples were of modern recharge or young waters. The C-14 content of the groundwaters ranged between 9.50 pMC in borehole CR2-50 at Ekumfi Asokwa to 113.56 pMC in borehole CR3-26 at Onyaadze. Evaluation of H-3 and C-14 data distinguished three groups of water namely (1) waters characterised by high H-3 and high C-14 depicting modern recharge, (2) waters showing a mixture of young and old water due to fractures and (3) waters showing low H-3 and low C-14 contents referred to as very old waters and include borehole CR2-50 at Ekumfi Asokwa. The estimated age or residence time of this older water is 19,459 years BRbased on uncorrected age. The major flow direction is northwest-southeast. The dominant months contributing to recharge in the study area were February, March, April, May, June, August, September and October. Groundwater residence times in the basement aquifers of the Ochi-Narkwa basin showed that groundwater abstraction is sustainable and requires that the recharge areas are protected from contamination. %G English %L hal-01849374 %U https://brgm.hal.science/hal-01849374 %~ BRGM %~ GIP-BE