This study was based, firstly, on observations and analysis of water table level variations in the Plio-Quaternary and Hauterivian aquifers, Oualidia (Morocco), and secondly, on comparing this behavior to oceanic tidal variations. Recordings were made in the well located at 1318 m from the coast, where the two aquifers are in direct contact. This investigation was subdivided into two periods of 4 months each. Results showed a tidal influence on water table level within the well during semi-diurnal and monthly periods. Water table fluctuation periods were equal to 12 h 25 min identical to oceanic tide propagation period, while time lag between water levels was equal to 3 h 24 min. Moreover, results allowed aquifer diffusivity calculation through a confined aquifer model, which was equal to 6.20 m(2) s(-1) calculated from average value of water amplitude and to 40.6 m(2) s(-1) calculated from average value of time lag. In addition, tidal wave amplitude attenuation occurred exponentially with distance from ocean, which disappeared completely after 2000 m from coast.
Keywords: Costal aquifers; Hydraulic diffusivity; Morocco; Oceanic tide; Oualidia.