Evaluation of the Effects of Climate Change and Environmental Parameters on Evaporation and Settlement of Unsaturated Soil

Realistic estimates of evaporation from unsaturated soils, which are important for many geotechnical and geoenvironmental applications, need to be considered in the context of soil settlement, and require thermohydromechanical (THM) analysis. Evaporation also depends on environmental parameters, including air temperature, air relative humidity, net radiation, and wind speed. Therefore, a consideration of atmospheric coupling in predicting evaporation is also necessary. In this study, the two-dimensional model EVAP1––which numerically estimates evaporation from unsaturated soil using THM and employing a soil–atmosphere model––was used to conduct a parametric study in order to investigate the effects of variation in environmental parameters and to study the effects of climate change on potential and actual evaporation and soil settlement. We found that the evaporation rate increased nonlinearly with increases in air temperature, net radiation, and wind speed, but decreases with an increase in relative humidity. However, the effect of a change in wind speed was less than the effect of a change in the three other environmental parameters. In addition, the change in evaporation rate differed in different regions with different air temperatures. For example, the temperature change had more of an effect on the evaporation rate at higher temperatures. In addition, neglecting soil settlement led to an overestimation of evaporation, albeit the amount of evaporation was almost the same whether soil settlement was considered or not, both at the beginning of the evaporation process, when potential evaporation was dominant, and at the end, when the water content in both cases had decreased almost to the residual water content, and the evaporation was minimized. The difference in the amount of evaporation was greater in the middle of the evaporation process, when actual evaporation dominated.