Impact of Slope Inclination on Salt Accumulation Due to Bare Soil Evaporation

While studies on salt precipitation over porous media due to evaporation have typically focused on horizontal and flat evaporating surface conditions, in reality, many evaporating surfaces are far from horizontal. In natural systems, agricultural environments, manmade structures and many other setups, evaporation from inclined surfaces is very common. Herein, the nature of solute transport and salt precipitation on inclined surfaces is discussed, and field measurements and laboratory experiments shed new light on the complex processes of salt dynamics over inclined, evaporating surfaces. Inclination of the evaporating surface was found to affect the location of the salt precipitation and the degree of salinity along the slope. For slopes of low-inclination, salt precipitation was uniform along the slope; as inclination increased, the lower parts of the slope remained relatively free of salt, while salt precipitation occurred in its upper parts. This was explained by a conceptual model suggesting that changes in slope inclination result in different pressure-head gradients along the slope, leading to different flow paths and velocities of the capillary water parallel to the evaporation front. Consequently, different solute-transport processes develop over slopes with different inclinations.