Use of hydrochemistry and environmental isotopes for evaluation of groundwater in the Paleogene limestone aquifer of the Ras Al-Ain area (Syrian Jezireh)

Atmospheric precipitation and groundwaters from the Paleogene aquifer system in northeastern Syria (Jezireh) have been investigated using major ions and environmental isotope methods to interpret the hydrogeological features characterizing this system. Based on the chemical ratios and isotopic compositions, the groundwater bodies are differentiated into three main groups: (1) fresh, cold, and shallow groundwater; (2) brackish, thermal, and deep groundwater, and (3) an admixed groundwater. The fractions of deep thermal water in the total discharge of admixed groundwaters were estimated and the elevations of recharge zones for the Paleogene aquifer were determined. Based on tritium content in atmospheric precipitation and by adopting a model with exponential time distribution function, the mean residence time of groundwater is evaluated. Radiocarbon groundwater ages were calculated and corrected according to the most commonly used models. The extensive declining of major karst springs discharge in the Ras Al-Ain area is the consequence of a severe groundwater pumping from the Paleogene aquifer. The remaining groundwater resources in this aquifer are subject to be exhausted in the future years, in the absence of any real rational treatment and suitable management strategies.