In order to monitor the spatial and temporal variability of the water quality of Oued Za on its passage from the town of Taourirt, eleven physicochemical descriptors were repeatedly measured over time (the four Seasons of the year 2015) in four stations located upstream and downstream of the agglomeration. To study the temporal stability of the spatial structure, and to measure the interaction between dates and stations, in the four mesological tables obtained, we used inter and intra-class PCA. The study of the spatial structure of the obtained results showed that, whatever the sampling season, S2 and S3 stations located downstream of the domestic and industrial wastewater discharges of Taourirt city are still opposed to the other two stations, showing that these stations remain polluted throughout the year. The peak of pollution is reported in autumn, during massive trituration of olives. This pollution is attenuated at the level of the S4 station, thanks to the self-purifying power of the water before throwing in the Moulouya River.