Hydro-salinity dynamics in a semi-arid agricultural plain: implications for sustainable land management

• Groundwater mineralization controls deep salinization. • Evaporation and precipitation leaching control surface salinization. • Capillary flux is the main mechanism of salt accumulation in semi-arid areas. • Groundwater flow patterns significantly shape the soil water–salinity gradient. Soil salinization drives degradation in semi-arid agro-ecosystems and has far-reaching effects on the sustainable use of water resources, agricultural productivity, and ecological security. Although the severity of soil salinization has been increasing, especially with intensifying environmental issues, the spatial distribution of groundwater and soil salinity and the associated multiscale driving mechanisms remain unclear. The aim of this study was to understand these aspects in a typical semi-arid agricultural plain. The spatial dynamics of groundwater and soil salinity and the dominant driver were analyzed based on remote sensing data, groundwater monitoring, and high-precision spatial modeling. Groundwater dynamics (depth and mineralization), topography (elevation), vegetation cover, and climatic factors were identified as key drivers of soil salinity distribution. Groundwater depth negatively correlated (p < 0.01) and groundwater mineralization positively correlated (p < 0.001) with soil salinity.​​ Capillary flux due to groundwater recharge–evaporation was the dominant mechanism underlying soil salinity accumulation, explaining 48.65 % of salinity variance in discharge zones. Groundwater depth, elevation, and normalized difference vegetation index negatively correlated (p < 0.01), whereas groundwater mineralization and each of the major ions (Cl-, Na + , and SO 4 2 -) showed positive correlations with salinity (p < 0.01). The standardized precipitation evapotranspiration index positively correlated with soil salinity (p < 0.05) in GWR analysis. Groundwater flow shaped the soil water–salinity gradient markedly, with the discharge zone showing the highest soil salinity. The findings offer theoretical support and practical guidance for sustainable land management in semi-arid regions, contributing to the mitigation of soil salinization and enhancement of ecological security.