Five radiocarbon analyses were performed on 5 different sources within Soreq Cave, which was used as a model for the Judea Group Aquifer of Israel (pMCq0). The transit time of rainwater through the roof of the cave to sources within it had been determined with tritium. From this information, the year of deposition of rain on the roof of the cave, which later appeared in one of the sources, was estimated and the atmospheric 14C concentration at that time was ascertained (pMCa0). The parameter Q = pMCq0/pMCa0 was found to be Q = 0.60 ± 0.04. This makes it possible to calculate the age of water in any well in the Judea Group Aquifer of Israel by measuring its 14C concentration (pMC qt) by use of the decay equation and applying Q.