Measuring and simulating of water movement and solute transport in layered soils

The precise simulation of water and solute transfer in porous media is very important in soil and water studies. The purpose of this study was to measure and simulate water movement and solutes transfer of layered soils. In this study, the effect of soil bulk density changes and different soil layering on water and solute movement were measured and simulated with HYDRUS-1D model in 5 treatments and two replications. For this purpose, 10 columns of PVC with a height of 105 cm and an inner diameter of 31.5 cm, and three soil textures including loamy sand, sandy-clay loam and clay loam were used. The columns were irrigated with irrigation water and saline water with salinity of 0.67 and 4.46 ds/m, respectively. During the experiment, moisture content (using TDR moisture meter) and salinity (by saturated mud extraction method) were measured at depths of 10, 20, 30, 40 and 60 cm. The results of the study showed that the water movement in the soil is affected by the position of the layers with the least permeability and when the fine texture layer is placed on top, the time of water exit is the highest. Also, the results showed that in all columns the EC value was the highest in the upper layer and decreased from top to bottom regardless of the order of the arrangement of the layers. The survey of the nRMSE index indicates the high accuracy of the HYDRUS model in simulating the movement of water and solute in the layered soil. The lowest error in simulation was in homogeneous soil.