Numerical simulation of water and salt transport during the re-injection process of farmland drainage

The strategic reuse of agricultural drainage water presents a viable solution to address the growing disparity between water supply and demand in irrigated regions, with Soil Aquifer Treatment (SAT) systems demonstrating significant potential for water quality enhancement. However, the operational efficacy of SAT during drainage water recharge may be compromised by two principal factors stemming from compositional complexity: system clogging risks associated with improper management protocols or potential groundwater contamination through pollutant migration pathways. Through controlled laboratory experiments and systematic data analysis, this study revealed solute transport mechanisms in SAT simulated soil columns. Complementary HYDRUS-1D modeling further quantified the impacts of soil texture gradations and initial infiltration salinity on recharge system performance and subsurface environmental safety. The experimental results demonstrate that: (1) Media with fine-coarse particle gradation exhibited peak solute retention efficiency, and showed positive correlation with infiltration salinity. (2) Optimal gradation configuration requires salinity threshold control ≤ 1.3 g/L.