Radon-to-thoron ratios as well as radon and thoron activity concentrations in different underground water samples belonging to different aquifers in the Moroccan Middle Atlas area have been evaluated by LR-115 and CR-39 solid state nuclear track detectors (SSNTD) using a new calibration method. The radon isotope (222Rn) was used as a tracer for studying the water exchange between different aquifers of the area studied. The influence of the lithological and hydrogeological parameters of the aquifers on radon emanation were investigated.