SUMMARY
The intensive exploitation of groundwater resources in the region of Hodna has greatly influenced the hydrochemical functioning of the Mio-Plio-Quaternary aquifer located in the northern part of the basin of Hodna M'Sila, south eastern Algeria. This has resulted in a general decline of the piezometric level of the groundwater level. The objective of this study is to define the main factors governing water chemistry wide plain with 54 groundwater samples. The initial facies on the limits as well as infiltration areas is carbonate. In the southern part of the plain water becomes charged with SO4, Cl and in connection with the dissolution of salt formations and salt lake. The presence of nitrates is related to agricultural activity. The multivariate statistical techniques such as principal component analysis and hierarchical clustering were applied to data on the groundwater quality of the aquifer. Thesestatistical techniqueshave shownthepresenceofthreesalinitygroupsIt gradually changes from upstream to downstream (North-South) of unsalted water to a heavily salted water near the Chott. Water infiltration in group 1 is mixed gradually along the groundwater flow to achieve a higher water charge to group 3 in the zone of discharge.