Hydrogéologie et pollution des eaux : exemple du bassin versant du Mazafran, Mitidja (Algérie)

Mazafran river basin forms a sublittoral plain of the western Mitidja. The Quaternary mantle is formed with gravels incillding Clay lenses. The impervious bedrock is made of blue plaisancien marls, of miocene marls or of certaceous miocene limestones. We can distinguish two aquifer reservoirs, the sandstone astien reservoir and the quaternary alluvial deposits reservoirs. The river basin receives a 740 mm height of water a year, that is to say an average volume of 1,4 millions of cube meter , of which only 1,4 per cent contributes to feed the underground water. Th. hydrodynamic study shows that the general out flow of waters ls made fram South to North, the Interpretation of the pumping tests allowed to determine the hydrodynamic characteristics. The most likely water you can find in the alluvial reservoir is calcic and bicarbonated, slightly magnesian, though the river waters which feed the western part of the plain infer a calcic sulfated composition in that part of the water table. The main part of the Atlas northern side springs, fed by the clefted schistes of the cretaceous present a bicarbonated magnesian aspect. The astian reservoir waters, very highly mineralized are made of bicarbonated soda. The proportion of certain metallic elements such as (Cu. Zn. Fe. Cd. Cr. Hg) and of nutritions ones (nitrate. Organic matters) revealed the water environment the underground watters locally present serious signs of pollution.