Belaa Fatma ZohraAbboud Chahra Zad2024-02-292024-02-292015-06-13577-017-Mhttp://dspace.univ-khenchela.dz:4000/handle/123456789/2427Through this work, we have started the physical framework in the study region including geographical, geological, hydroclimatic and hydrochemical contexts of the semi-arid zone (El Mahmel Plains), which is nourished mainly by underground waters from well drillings, in order to identify the chemical characteristics of underground waters and their qualities. We have proceeded to the levy of sampling on 02 wells and 07 drillings; these samples have undergone physico-chemical analysis at ADE Khenchela as well at laboratory Science of Earth Institute laboratory in Constantine. The evolution of the chemical elements through time implies that plains water are divided into two families: calcic Bicarbonated Water Family and calcic sulfated waters. The establishment of these characteristics is due to the presence of carbonated formations from Chattaia Mountain and salifere deposits, which is caused, by the presence of trias and carbonated formations and gypsiferes from plains surrounding massives.frThesis