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The El-Meita plateau is situated in the south of the city of Khenchela and it is delimited by the Saharan Atlas to the north and Chott Melghir to the south. The agricultural importance and the high productivity of this region are provided by the aggressive use of chemical fertilizers. For this reason, we have decided to conduct this study, considering that all water bodies � superficial waters and groundwaters � record significant amounts of NO3-, NO2-, NH4-, heavy metals (Pb, Cd, Cu, Zn and Hg) and other major chemical elements. The campaign of collecting the 30 water samples took place in the month of May 2016. The chemical analyses were conducted in the Lacip ain-Mlila laboratory in Algeria. Findings show a contamination of groundwater by nitrates and lead; values exceed the maximum limits approved by World Health Organization (WHO). TDS were also found in high concentrations, which limit the use of water for some agricultural cultures, but which can be admissible for certain salinity-resistant species.

Abstract:The aim of this study is to determine and treat a hierarchical basis of the various mechanisms responsible for the space variation of the water quality in a endoreic semi-arid basin. The water chemistry showed a large variability in space and time. The total dissolved solid (TDS) in water increases from upstream to downstream due to the effect of the arid climate, but also due to the waterrock interactions and the anthropic polution of surface water. The water chemistry changes progressively from bicarbonate calcic upstream to sulphated and chlorinated calcic in the median zone to chlorinate sodic in the Sebkha. Thermodynamic modelling showed the major role of evaporation in the evolution of the water chemistry. The result indicated calcite precipitation then gypsum precipitation as well as cations exchanges reactions. Statistical approach allowed to arrange processes that responsible for the hydrochemical variability according to their important. The increase of water salinity is due mainly to the aridity process. The differentiation between salty surface water (Sebkha) and deeper water (Chott) is the second process. The combined of the geochemical and statistical methods allowed to identify the main variability sources of the water composition and to classify them in this complex system.

Es-Sbikhat El-Mahmel basin, located at the southeastern piedmont of Aures massif (Northeastern Algeria), is characterized by a semi arid condition . The sampling process was realized within 39 boreholes and wells during May 2015. Results of analysis data projected on the PCA (Principal Componet Analysis) plan which express 52.70% of variance has shown a chemical facies evolution from calcium bicarbonate water into calcium chloride water, going through a transition facies marked by calcium-sulfate to magnesium-sulfate water.Thermodynamic analysis corroborated that water rock interaction is the main process that control mineralization (dissolution precipitation, cationic exchange and anthropogenic pollution).

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