Modeling salinity and sodicity risks under long-term irrigation with medium salinity water: Kinneret catchment as a case study

Climate change is intensifying droughts and reducing freshwater availability in arid, semi-arid, and Mediterranean regions. Agricultural areas within the Lake Kinneret basin (Israel) are currently irrigated with high-quality Dan Spring water; however, climate projections indicate an approximately 20 % reduction in spring discharge by 2050, prompting consideration of Kinneret water (EC ≈ 1.3 dS m⁻¹) as an alternative irrigation source. This study evaluates the long-term (25 years) effects of Kinneret water irrigation on soil salinity and sodicity using HYDRUS-1D coupled with the geochemical module UNSATCHEM. Field data were collected from a silty clay maize field during one growing season under three irrigation treatments: Kinneret water (EC ≈ 1.3 dS m⁻¹), Mixed water (EC ≈ 0.7 dS m⁻¹), and Dan Spring water (EC < 0.1 dS m⁻¹). Model calibration was performed using an inverse approach, with soil heterogeneity represented through the 95 % prediction uncertainty (95PPU) of hydraulic parameters. The calibrated model adequately reproduced soil water and solute dynamics, with most observations falling within the 95PPU range. Simulation results indicated that irrigation with Kinneret and Mixed water led to increased salinity and sodicity compared to Dan water. Soil water salinity (ECsw) exhibited pronounced seasonal dynamics, preventing long-term salt accumulation in the root zone, whereas sodicity increased gradually over time. After 20 years of Kinneret irrigation, the sodium adsorption ratio (SAR) increased from < 1 to ∼7, and the exchangeable sodium percentage (ESP) from < 1–9. Uncertainty analyses under Kinneret water, incorporating 95PPU and variable Gapon constants showed that salinity and sodicity indices could reach ECsw > 8 dS m⁻¹ , SAR ≈ 9, and ESP ≈ 13 within the root zone. Although SAR and ESP remained below standard sodicity thresholds, uncertainty analyses revealed that values could approach levels that impair soil hydraulic properties in clay-rich soils, especially under repeated wetting–drying cycles, posing long-term risks to soil health and agricultural sustainability. This modeling framework provides valuable insight into salinity and sodicity processes in Mediterranean agro- systems under conditions of water scarcity. • Long-term impacts of Lake Kinneret irrigation on soil salinity and sodicity were evaluated using HYDRUS-1D. • Kinneret irrigation increased salinity and sodicity over time, mainly in the 20–50 cm root zone. • Additional irrigation reduced salinity but did not prevent sodium accumulation. • Field-scale soil heterogeneity had a noticeable effect on salinity and sodicity risk under Kinneret water irrigation. • Irrigation management with marginal water should focus on reducing SAR and accounting for field-scale soil heterogeneity.