Mahmoud S. Alyamani

Using Geochemical and Environmental Isotopes Composition to Study the Possible Leakage between Two Major Aquifers, Eastern Saudi Arabia@@@استخدام التركيب الكيميائي والنظائر البيئية لدراسة احتمال التسرب بين خزانين مائيين رئيسين ، شرق المملكة العربية السعودية

Major ion analyses of 156 fresh and mineral groundwater samples from Umm Er Radhuma aquifer (UER) in eastern part of Saudi Arabia reveal a consistent pattern of variation in the sedimentary basin. The piezometric data shows a broad pattern of regional flow from west to east towards the Arabian Gulf coast. The groundwater chemistry is highly variable, where TDS ranged between 220 and 15815 mg/l; with an average of about 2257 mg/l. The chemical and isotopical composi- tions of the groundwater of UER aquifer show that the water is pro- gressively enriched in Na+ , Ca 2+ , Mg 2+ , Cl - and SO 4 while iso- topically (δ 18 O and δD) depleted in the direction of flow. The isotopic contents of the groundwater of UER, measurements of the piezometric level and stratification of groundwater chemistry with depth suggest that the UER aquifer receives a considerable amount of water leaking from the overlying Dammam Formation characterized by being young- er and low in TDS. The groundwater chemistry in UER aquifer, there- fore, is mainly controlled by mixing processes besides, the chemical re- actions that take place between water and aquifer materials within the UER aquifer through its movement.