Study of groundwater recharge and movement in shallow and deep aquifers in Saudi Arabia with stable isotopes and salinity data

The connection between major aquifers and their source of recharge has been studied by means of the 18O content and the salinity and chemistry of the groundwater. In the Wadi Miyah region the chemistry of groundwater has shown that no leakage was taking place from the Umm-Er-Radhuma aquifer to the overlying Alat and Khobar aquifers that have a similar 18O content. In the same region isotope and salinity data indicate that the groundwater in the Neogene aquifer has its source in the Alat and Khobar aquifers. Along the coast of the Arabian Gulf both the 18O content of the groundwater and its salinity show that the Alat, Khobar and Umm-Er-Radhuma aquifers are connected. In the Al Hassa region the origin of water in large karstic springs has been investigated using piezometric, chemical, isotopic data and the temperature of the springs. Results indicate that the water of the springs and the groundwater in the Neogene aquifer consists of water originating from the Umm-Er-Radhuma aquifer, and that there is mixing of waters that have been subject to atmospheric contamination with uncontaminated and more recent waters. In the Harad region the 18O content of groundwater indicates old groundwater and no substantial recharge taking place. Finally, the 18O content and salinity of groundwater in the alluvial aquifer of Wadi Bishah indicate that isotopic enrichment and higher salinity of the groundwater in the irrigated areas is most probably due to the recirculation of the irrigation water. (author)