Quantitative analysis of water, heat, and salinity dynamics during bare soil evaporation

In arid and semi-arid regions, significant evaporation intensifies water scarcities and soil salinization, imposing severe challenges to agricultural productivity and economic advancement. This study quantitatively assesses the impact of varying soil salinity levels (0 to 1 wt%) and their distribution within the soil column on water, heat, and salt transport dynamics during evaporation. With a series of eleven experiments, we have studied how different salinity concentrations and distributions across the soil section affect soil moisture, temperature profiles, and salinity distribution. Our findings reveal that moderate salinity levels delay the decline in soil saturation, reduce evaporation rates, and increase soil temperature due to reduced evaporative cooling and salt crust formation. Notably, a strong polynomial correlation was identified between salinity and the duration of the initial stage of saturation before declining. However, at salinity levels above 0.5 wt%, soil temperature starts to decrease as a thick salt layer forms that increases the soil's albedo and reflecting the sunlight. Additionally, a coupled water-heat-salt transport model was applied to simulate and validate the observed experimental data. Understanding these interactions is crucial for improving the coupled model to optimize water usage, enhance crop growth, and mitigate soil salinization in arid and semi-arid regions.