Résumé : This study aims to evaluate the abundance of heterotrophic aerobe bacteria (HAB) adhered during the dayperiod and the night to fragments of granite, basalt and migmatite immersed in 2 well water points. Theincubation periods were 12h in day time, 12h at night and 24h (day and night). For the 2 wells the highestabundance of the HAB adhered on granite, basalt and migmatite varied respectively from 11.20 to 11.94, 11.49 to11.54 and from 12.16 to 13.68 (Log (CFU/cm2)) during the day period, respectively from10.92 to 12, 10.40 to11.37 and from 10.20 to 11.79 (Log (CFU/cm2)) during the night period, and respectively from 10.70 to 11.13,10.47 to 10.59, and from 10.56 to 11.17 (Log (CFU/cm2)) during the 24h incubation period. The abioticparameters considered and assessed at 6 am on each sampling day were pH, electrical conductivity, totalsuspended solids, color, turbidity and the water column thickness. The Principal Component Analysis (PCA)showed for each of rock-type, a relative variation with respect to incubation period of the percentage ofinformation contained in each principal axis. This could be due to the substantial influence of incubation periodand some meteorological parameters on hydrological properties of water as well as the bacterial and rockfragmentsurface.