Assessment and mapping of the agro-ecological risk in the Mina plain (northwestern Algeria): Soil salinity and irrigation water quality

Abstract

Abstract The objective of this study is to contribute in assessing and mapping of the salinity risks level of soil and groundwater for irrigation in the Mina plain. The experimentation was carried out on a surface area of 4000 ha. Electromagnetic conductivity (EM) measurements and soil and well water samples were taken and analysed. The results showed an important spatial variability of the electrical conductivity (EC) of saturated paste extracts (ECe), which varied between 1.35 and 28.8 dS/m. The isovalues map of ECe was estimated by the regression equation and interpolated by the ordinary kriging (OK) method which showed that the area of saline soils (ECe > 4 dS/m) represented 90% of the study area. The results also showed poor to unsuitable well water quality. To find the risk of salinity and sodium, the water points were classified as C3S3 (2.5%), C4S2 (5%), C4S3 (30%) and C4S4 (62.5%). Spatial distribution maps of total dissolved solids (TDS), electrical conductivity of water (ECw) and sodium adsorption ratio (SAR) interpolated by inverse distance weighting (IDW) showed too high risk levels of ECw (>5000 μS/cm) and TDS (>3000 mg/l) occupying a large wellfield (70%); with regard to SAR (>18), 36% of the groundwater had a high risk of sodium. These results showed that the choice of tolerant crops, redevelopment of drainage systems and irrigation with less saline water should be designed for the sustainability of soil productivity and agro-ecosystems.