Usage of carbon isotopes in characterizing groundwater age, flow direction, flow velocity and recharge area

Carbon-13 and Carbon-14 isotopes were utilized in this study to determine the age, flow direction, flow velocity and recharge area of groundwater in the two main aquifers of Kuwait. For this purpose 20 groundwater samples were collected from the Kuwait group aquifer and lower Dammam formation aquifer. The collected groundwater samples were analyzed for C-14 activity and C-13 activity. C-14 activity was measured using accelerator mass spectrometry (AMS) and expressed as percentage modern carbon (pmc) while C-13 was measured using an isotope ratio mass spectrometer (IRMS) and expressed as permil (parts per thousand) in the form of CO2 gas. The interpretation of the analysis results of carbon isotopes data indicated that the general groundwater flow direction is towards north east and the estimated groundwater velocities are 11 to 30 m/a for Kuwait group aquifer and 12 to 21 m/a for Dammam formation aquifer. Based on the estimated groundwater velocities, the approximate location of the recharge areas of these aquifers was identified. The groundwater ages calculated for Kuwait group aquifer varied from 800 a B.P for modern ground water in the northern part to 22500 a B.P for very old groundwater in the northeastern part, while the age of Dammam formation groundwater is 26000 to 36000 a B.P. (C) 2015 The Authors. Published by Elsevier B.V.