We have been interested in the study of the nitrogen pollution of MÂnasraÂs water table. This one is located in the Gharb region in Morocco where 145 000 people live. It ensures the development of a dynamic irrigation over an area of about 38 000 Ha in which more than 50% of lands are sandy soils that are very permeable.We have carried out 80 campaigns of measurement in different periods with a quite important time interval between these periods. This water table constitutes the unique non-available resource of groundwater for this region. Agricultural industries are highly represented in this region where nitrogen fertilizers and pesticides are used at a large scale. The results of the statistical analysis have shown a mutation of the nitric and the ammoniacal pollution in the region. This reveals that 87 % of observed wells do not respect the World Health Organization (WHO)Moreover, the spatial analysis has confirmed an area of 2 285 Ha and 19 885 Ha in which the water table has known respectively a nitric and a ammoniacal pollution between 1993 and 2008.