  The studies realized in INRNE (Institute for Nuclear Research and Nuclear
Energy) particulary in cosmic rays detection and construction of Muonic
Cerenkov Telescope in University of Blagoevgrad [1] shows the need to develop a
theoretical model based on observed phenomenon and to refine it for the
detection system optimisation. The effect was introduced in EGS4 code system.
The first simulations were consecrated to different geometry of water tank in
total reflection. The model was compared with experimental data realised with
gamma source using the telescope. A simple atmospheric model is introduced in
EGS4. The comparison between CORSIKA and EGS4 codes was realised.
