Integrated Geochemical Approach to Assess the Sources of Groundwater Salinization in Cascade Irrigation Systems in Semiarid Agricultural Regions

Thirty‐one water samples were collected from surface sources and shallow and deep wells in the Madderambawa cascade system in the semiarid region of Sri Lanka. Electrical conductivity (EC) values ranging between 398 and 7920 μS/cm were used to indicate salinization. The groundwater consisted mainly of Na‐Cl, followed by Na‐HCO 3 and Ca‐Mg‐Cl types. Some of the water isotope values deviated from the local meteoric water line. Salinization in the cascade system is due to the dissolution of aquifer materials and the contribution of anthropogenic activities as inferred from isotopic evidence, ion ratio plots and the chloro‐alkali index. Salinization processes include the direct percolation of rainwater through saline soils of alkali‐feldspar rocks and mixing with flood water contaminated with fertilizers. The results showed that identifying and quantifying groundwater salinization in semiarid regions is essential for protecting subsurface water resources, as the impact of climate change may worsen the situation.