algerian journal of environmental science and technology
Volume 4, Numéro 1, Pages 671-682
2018-04-30

The Hydrochemical Characterization Of The Underground Waters Of The Plain Of Sidi Bel Abbès (northwestern Algeria).

Authors : Bellaredj A.el-m . Hamidi M. .

Abstract

The population of Sidi Bel Abbèshas become over the years moredependent on the neighboring cities of Tlemcen and Mascara to satisfy its growing needs of potable water. The absence of dams with big storage capacity combined with the semi-arid climate characterizing this region (irregular andlow to medium rainfall rates) is superposed tothe poor knowledge of the underground waters potential inthearea.The Plio-Quaternary aquiferof the Sidi Bel Abbèsplain can however be considered an exception.This unconfined aquifer, whichstretches over 800 km2is by far the most important underground water reservoir in the region. The aquifer is mainly drained by the Mekerra River and is exploited by an impressive number of pumping wells (legal and illegal), destined for their majority to irrigation. The strategic importance of this water resource for the city of Sidi Bel Abbès is thus, immense and its characterization both qualitatively and quantitatively vital.Thehydrochemical study of the Plio-Quaternary aquifer waters shows that they vary from fresh (Total Dissolved Solid < 1 g/l) to extremely saline (Total Dissolved Solid >5 g/l) waters. The results demonstrate that the salinity of the Plio-Quaternary aquifer waters isderived from the combination of a multitude of processes. The anthropogenic activities materialize in the contamination of the aquifer’s waters, both directly by the polluted waters (industrial and domestic water wastes) of the Mekerrariverandseptic fosses (absence/weak coverage of sanitization networks) and indirectly due to the extensive usage of fertilizers and pesticides in farming, which reach by soils leaching the aquifer, during the rainy and irrigation seasons. The hydrochemical results illustratethe important contribution of the evaporation in the salinization process of the Plio-Quaternary aquifer waters, especially East and North of the plain of Sidi Bel Abbes where the aquifer is shallow and its section and thickness small. They also emphasize the major role of the water/rock interaction (dissolution of carbonates, ion exchange processes andsilicates weathering) and its influence on the salinity, hardness and geochemical facies of the Plio-Quaternary aquifer waters.

Keywords

Plio-Quaternary aquifer, Mekerra river, salinity, anthropogenic activities, evaporation, water/rock interactions