Once the contamination is recognized, it may last for many centuries ahead even if the contamination practice is stopped. This wide RTD suggests that any recent contamination that may have entered the system could progress slowly within the entire aquifer but would be unnoticed in the early period because of the dilution effect of uncontaminated past recharge waters. The residence time distribution (RTD) indicates a groundwater transport system that is fed by recharges extending back to past several hundred years. Excess crustal and mantle helium flux hindered the use of tritiogenic helium-3 as a potential tracer. The CFC-11 and CFC-12 MRTs are in agreement with tritium-based MRT, after correcting for excess air effect. This suggests an active transport volume of 71 billion cubic meters for the aquifer, a value that is coherent with the estimated void volume of karst aquifer based on the mass of associated travertine deposits. Based on tritium observations between 19, the springs revealed a mean residence time (MRT) of 120 years. Lumped parameter modeling of environmental tracer (tritium, CFCs and tritiogenic helium-3) transport in the Kirkgoz karst springs (Antalya-Turkey) appears to be a useful tool for assessing the vulnerability to contamination. Residence time distribution in the Kirkgoz karst springs (Antalya-Turkey) as a tool for contamination vulnerability assessment Residence time distribution in the Kirkgoz karst springs (Antalya-Turkey) as a tool for.