Evaluation de la qualité des eaux souterraines de la Mitidja et leur aptitude a l'irrigation.

Abstract

The water resources in Algeria in particular in the area of Mitidja are limited, vulnerable and unequally distributed on the space level. This delicate situation inevitably requires undertaking new actions in order to exploit these resources in a rational way. This project falls under this context, it has as an of this study of the space variability of certain chemical properties of underground waters of the plain of Mitidja by a traditional statistical approach which is the analysis in principal components (ACP), and by the geostatistic approach (variography and krigeage) in order to being able to evaluate the quality of this water and their aptitude to irrigation during two years 2005 and 2008. The study by using the ACP showed that the prevalent facies during two years is the calcic chlorinated facies, but one also announces the presence of the sulphated facies. Moreover, the salinity of water of the plain varies from average until very strong with restrictions on the use according to two types of classification. It has suddenly announced also that these undergroundl waters run an enormous risk of pollution by nitrates and are likely to be unsuitable for the agricultural use. The estimation by krigeage showed that generally the cations (Ca, Mg, and Na) and the anions (Cl, SO4 and NO3), as well as the SAR and the EC showed a strong variability, and that the geographical repair of these elements is almost similar except for the nitrates whose it’s presence is related to husbandries and the permeability of the lithological layers. And it is proved that the North-eastern part of Mitidja is most vulnerable to salinity owing to the fact that the contents of some elements largely exceed the international standards set by FAO. According to the study, it seems that the quality of water is better for the period of high level of waters of the year of 2008, owing to the fact that the concentrations of some elements decrease compared to the former situations. Thus, this project will constitute a tool of assistance to the policy makers concerning the exploitation of the resource from the quality point of view and risk of contamination that is for the human health or for the agricultural use.