Accessibility of fresh water, the nature's gift wheels the foremost part of the world economy. The sufficient supplies of water are essential for agriculture, human intake, industry as well as regeneration. The Oued Righ region is located in Algeria's South-East, specifically in the NorthEast of the Sahara, on the Northern edge of the Grand Erg Oriental and the Southern border of the Aures massif. This area appears as a lower Sahara synclinal basin and is part of a broad North-South trending ditch. It is famous for its date palms, the development of the date culture in this region is attributed not only to the population’s efforts, but above all to the particular climatic conditions, the favorable soil characteristics and the existence of significant groundwater. The aim of this study is to understand the results obtained from using different approaches of water hydrodynamics in the Complex Terminal aquifer. The aquifer’s hydrodynamic characterization was carried out using hydrodynamic parameters and piezometry. As a result, the transmissivity and permeability obtained data using traditional Cooper-Jacob method showed that the flow capacities of the aquifer environment and the productivities of the structures are important in the studied zone where, the highest value of transmissivity equal 2.36× 102-m 2 /sis found in the central part of the study area in El-Meghair. The establishment of piezometric maps reveals a flow direction oriented toward the chott.

The studied area, so called Chott El Gharbi shelters a multilayer aquifer system. The hydro-chemical tool shows that the results of the groundwater analyzes of the aquifer system of the Chott El Gharbi region revealed that they are sulphated-calcium and magnesian. Water infiltrated at the Bajo-Bathonian and Mio-Plio-Quaternary carbonate formations is enriched with HCO3- and SiO2 along its underground route. Also, the presence of a Triassic evaporitic formation or the Cenomano- Turonian argilo-gypsum formation enriches these waters with SO4 2- , Cl- , K+ , Mg2+, Na+ and Ca2+ . Thermodynamics has shown that these waters are under saturated evaporitic elements, which gives them a greater power of dissolution than that of carbonates which are in equilibrium or sometimes even supersaturated and tend to precipitate.

This paper was made in the region of M’daourouch-Dréa which is part of the high plains of northeastern Algeria, located southwest of the Souk-ahras Wilaya in eastern Algeria. It is a plain with agricultural vocation which requires for its development more water. Knowing that the rainfall is low (465mm/year) and not enough to meet the needs of farmers, the use of groundwater then becomes the only alternative to fill this lack of resources. Among the aquifers identified in this region is that contained in fissured limestones of lower Maestrichian age. In order to satisfy farmers and citizens in water it is necessary to have a good characterization of this aquifer. The objective of this paper is to improve the knowledge on the morphology and the extension of this aquifer and to locate its roof in space to help operators choose areas favorable to exploitation, so direct them to the nearest areas of the surface thus minimizing the cost of the drilling operation. To achieve this goal, we have exploited by exploiting several tools (geological map, logs of boreholes and geophysics survey), whose combination gave an idea on the geometry of the aquifer as well as the depth of its roof in different regions of the plain and shows by the occasion, the affectation of these limestones by several tectonic accidents generating thus a structure in collapsed blocks from where the very variable depth of the roof of these limestones of a place of the plain to other.

The hydrochemical and multivariate statistical techniques such as the principal component analysis (PCA) and the cluster analysis (CA) were used to identify the hydrochemical processes and their relation with groundwater quality and also to get an insight into the hydrochemical Zana aquifer groundwater chemistry evaluation. Twenty-four samples during the wet season and even during the dry season are analyzed. The Piper diagram showed that water facies are magnesium bicarbonate on the sides of the western reliefs and magnesium chloride-sulfated at the north and the center of the plain. The PCA carried out on three factors revealed that on the factorial design F1-F3, nitrates negatively determine factor 3, indicating the presence of an agriculture pollution. On the factorial design F1-F2, HCO3− positively determine the factor 2, indicating the carbonated origin. However, the CA, based on variables, showed that the waters in the region can be classified into three groups according to flow direction while the CA, based on major ion contents, defined three groups, reflecting the same hydrochemical facies. The first group with dry residue varying between 360 and 1700 mg/l and characterized by Mg2+ and Cl−, HCO3−. Samples of this group are mostly located in the north and northeastern part of the region. The second group with highest dry residue (2080 to 3820 mg/l) characterized by Mg2+ and SO4−, Cl− is located near the Northwestern and western outcrops. The third group coincides with the central part, the lowest of the plain, with heightened dry residue (4140 to 13,950 mg/l), characterized by Mg2+ and SO4−. The hydrochemical study made it possible to allot the evaporitic origin to the elements Na+, Mg2+, K+, Cl−, and SO4−, while for element HCO3−, it results from the carbonated formations. These results showed that the presence of nitrates in the studied area is closely linked to the agricultural activity.