Recharge and mineralization of groundwater of the Upper Cretaceous aquifer in Orontes basin, Syria

Chemical and isotopic data of groundwater of the Upper Cretaceous aquifer in the Orontes basin, Syria, have been used to assess the groundwater geochemistry, the origin of groundwater recharge and groundwater residence time.The chemical data indicate that dissolution of evaporite minerals is the main process controlling groundwater mineralization.The composition of stable isotopes 18 O and 2 H, together with 14 C activity, reflect the existence of three different groups: (a) groundwater in the Coastal Mountains with 18 O of -6.65, quite similar to modern-day precipitation, and high 14 C (>50 pmC); (b) groundwater in the unconfined aquifer of the Hama Uplift, which has 18 O of -5.52 and 14 C near 20 pmC, and is recharged locally; and (c) groundwater from the confined aquifer of the Homs Depression, which is characterized by more depleted 18 O" -8.01, and low 14 C (<7 pmC), and might be recharged in the northern piedmont of the Anti-Lebanon Mountains.The distinctive isotope signatures of the latter two groups indicate different recharge elevations and palaeoclimatic effects.The low recharge rate of the groundwater in the Hama Uplift aquifer, and the even slower recharge rate in the Homs Depression aquifer, are reflected by groundwater 14 C residence times of 5 and over 22 Ka BP, respectively.