Water Quality of Medjerda Wadi Used for Irrigation Purpose (Eastern Algeria)

Abstract

Waters of Medjerda wadi catchment (eastern Algeria) are one of the most important resources in Algeria. In this basin, waters are used for irrigation purposes. However, they collect domestic and industrial sewages and irrigation effluents exposing surface and groundwater to significant pollution. In this study water quality monitoring in Medjerda wadi has been completed. Longitudinal profiles of water quality were completed using the data from 14 sites. All sewages from agricultural and industrial discharges were included. The water samples were analysed for nutrients (${\rm{NO}}_{3}^{\\-}$, ${\rm{NO}}_{2}^{\\-}$, ${\rm{NH}}_{4}^{\\+}$ and ${\rm{PO}}_{4}^{\\3-}$), biochemical oxygen demand (BOD₅) after 5 days and dissolved oxygen (DO). Chemical composition showed the waters in the Medjerda wadi are extremely polluted, especially, at the confluence with domestic releases of Souk Ahras city and downstream of industrial discharges and therefore present a serious risk for irrigation. This pollution is characterized by an increase in indicators of pollution (BOD₅, ${\rm{NO}}_{2}^{\\-}$, ${\rm{NO}}_{2}^{\\-}$, ${\rm{NH}}_{4}^{\\+}$ and ${\rm{PO}}_{4}^{\\3-}$), a very low rate of dissolved oxygen and high concentrations of heavy metals particularly iron.