Water Quality for Irrigation Purposes in the Middle Tafna Watershed (NW, Algeria)

Abstract

Irrigation water quality in semiarid areas of North Algeria is degrading because of contaminants originating from anthropogenic sources. Among these harmful contaminants, nitrate and phosphate ions are the most common. In this context, this study was carried out to assess the contamination degree of irrigation water, with a particular emphasis on nitrate and phosphate enrichment in the groundwater of Hennaya alluvial aquifer and surface water of Sikkak wadi. Surface and groundwater samples were collected, during April and November in 2017 and analyzed. The concerned physicochemical parameters were pH, Temperature (T), Electrical conductivity (EC), Total Dissolved Solids (TDS), Chloride (Cl⁻), Nitrate (${{\text{NO}}_{3}}^{ - }$) and Phosphate (${{\text{PO}}_{4}}^{3 - }$). The obtained results were compared to irrigation water quality guidelines. All groundwater samples showed that nitrate concentrations were distinctly higher (up to 98 mg/L) than the guideline values of irrigation water quality (30 mg/L). Phosphate contents were observed in 3 wells in which they attained the maximal value of 0.42 mg/L. These high concentrations in nutrients (Nitrate and phosphate) originated from an excessive use of agrochemicals, when penetrating the soil and reaching the groundwater.