Recharge Regimes of the Saq Aquifer System, Saudi Arabia: Inferences from Geochemical and Isotopic Compositions

Thursday, 18 December 2014
Abdou Abouelmagd1,2, Matthew F McCabe3, M. Clara Castro4, Mohamed Sultan5, Raghavendra B Jana1 and Samir Al-Mashharawi1, (1)King Abdullah University of Science and Technology, Thuwal, Saudi Arabia, (2)Suez Canal University, Geology Department, Ismailia, Egypt, (3)King Abdullah University of Science and Technology, Biological and Environmental Sciences and Engineering, Thuwal, Saudi Arabia, (4)Univ Michigan, Ann Arbor, MI, United States, (5)Western Michigan Univ, Kalamazoo, MI, United States
One of the most valuable groundwater reserves in Saudi Arabia is the Saq aquifer system (SAS), a thick (400−1200 meters) sandstone unit that extends across 300,000 km2 in Saudi Arabia and neighboring Jordan. Due to its high productivity and high water quality, current pumping and overexploitation of the aquifer has significantly lowered the groundwater level over the years. Understanding the recharge regimes of the SAS is critical for the development of sustainable exploitation of water resources in the region and for the establishment of appropriate management practices. In this study, we investigate the hydrologic setting of the SAS and seek to differentiate the degree of paleo versus modern contributions using a range of geochemical approaches. Multiple groundwater samples were collected from deep production wells tapping the SAS at depths between 375−1800 m and across a range of locations. Samples were analyzed for their chemical concentrations, stable isotopic compositions (δ18O and δ2H), and dissolved noble gas concentrations and isotopic ratios. Examining these data identifies unmixed pools of fossil groundwater at deeper depths as well as mixed shallower systems that indicate contributions from modern precipitation. Through isotopic and noble gas analyses, the relative age and timing of these recharge events was examined and show contributions from both glacial and inter-glacial periods, with some modest contributions from modern meteoric sources.