Using 14C and 3H to delineate a recharge 'window' into the Perth Basin aquifers, North Gnangara groundwater system, Western Australia

► Isotopic variations in the Gnangara System are controlled by different lithologies. ► Carbonate dissolution provides 'dead' carbon to the groundwaters making them appear older. ► A recharge 'window' into the confined aquifers of the Perth Basin was delineated. ► Understanding aquifer interaction is needed for sustainable water management.