Caractérisation géochimique des eaux d’irrigation de la palmeraie d’Oumache (oasis des Ziban, sud-est de l’Algérie) ; Geochemical characterisation of the irrigation waters of the Oumache Palmeray (Ziban oasis, south-east Algeria)

The ancient palm grove of Oumache, located downstream of Zab el Gharbi (west Ziban-Biskra, south-eastern Algeria) shows today a decline mainly due to deficiency of irrigation water and a rise in the level of the saline water table. The presence of a highly endorheic environment has accelerated soil salinization. This work consists in geochemical characterization of water samples (borehole and groundwater) used for irrigation in order to improve water management. The results show that well water presents a very high risk for soil salinization. Salinity type is neutral, calcic- and magnesic-sulfated. However, groundwater is unsuitable for irrigation with very high risks of salinization and soil alkalization. Groundwater evolves towards a neutral saline path of the type chlorinated-sulfated sodium (57% of samples) and sulfated-chlorinated sodium. It is oversaturated with calcite and gypsum, and under saturated with halite and thenardite. In the water table, water flows from the upstream feeding area (considered as recharge area) to the downstream accumulation zone (Chemoura’s sebkha). To remediate the problem, a plan is recommended for sustainable management of water and salinity that includes rehabilitation of the drainage system of this palm to remove saltwater. Finally, the extension of the oasis will have to take into consideration this aspect of preventive management by opting for the Djedi Oued as another natural outlet. ; L’ancienne palmeraie d’Oumache située à l’aval de Zab el Gharbi (ouest de Ziban-Biskra, sud-est de l’Algérie) connait aujourd'hui un déclin dû essentiellement à l’insuffisance de l’eau d’irrigation et à la remontée des eaux trop chargées de la nappe phréatique. De plus, le milieu endoréique très évaporant a accéléré le phénomène de salinisation du sol. Ce travail traite de la caractérisation géochimique des eaux (forage et nappe) utilisées pour l’irrigation en vue d’une meilleure gestion de l’irrigation. Les résultats montrent que l’eau de forage présente un risque élevé de salinisation des ...