Application of environmental tracers to study groundwater recharge in a semi-arid area of Central Tunisia

Groundwater of the Tertiary-Quaternary Formations in the Jeloula basin (Central Tunisia), together with rain and surface waters, were analysed to investigate the mineralization processes, the origin of the water and its recharge sources. The water samples present a large spatial variability of chemical facies which is related to their interaction with the geological formations. The main sources of the water mineralization are the dissolution of evaporitic and carbonate minerals and cation exchange reactions. Stable isotopes indicate that most groundwater samples originate from infiltration of modern precipitation. Surface water samples from small dam reservoirs show a O-18/H-2 enrichment, which is typical of water exposed to open-surface evaporation in a semi-arid region. Considerable data of H-3 and C-14 allow the qualitative identification of the present-day recharge that is probably supplied by infiltration of recent flood waters in the Wadi El Hamra valley, and by direct infiltration of meteoric water through the local carbonate outcrops. Editor D. Koutsoyiannis; Associate editor S. Faye