ETUDE DES EAUX SOUTERRAINES DE LA PLAINE D’HENAYA (BASSIN DE LA TAFNA - NW ALGERIEN)

Abstract

The plain of Henaya is located to the north of Tlemcen city in Tafna basin. This plain is characterized by a semi-arid climate and intensive farming activities. The high demand in water for agricultural purposes has resulted in an overexploitation of this resource as well as the use of non-conventional waters for irrigation. Thus, in addition to intensive uses of agricultural inputs the groundwater is exposed to risks of pollution. The physico-chemical characterization of waters of various supply points analyzed in the plain has shown two types of facies with high mineralization. A bicarbonated facies which would probably comes from the conglomerates represents 75% of the analyzed samples. The second one is a chlorinated facies which is likely due to the contact with the saline helvétien marls or to the infiltration of non-conventional waters used for the irrigation. The analyses have also revealed levels of nitrates exceeding the water quality standards which make these waters improper to human consummation. The former are recognized to be indicators of diffuse pollutions from an agricultural origin in the area. It was also noticed that the alkalinity of all analyzed water points is greater than 200 mg / l of CaCO3  hence largely exceeding the standards of the irrigation water quality. As a result, water is encrusting causing high risks of clogging. It also appears that the ground waters for irrigation are classified C3 - S1 in theRiversidediagram with a characteristic that make them suitable for crops with a good tolerance to salt.