Evaporation of water from a saturated soil surface with ample free water is known as potential evaporation, PE, and the associated physical processes are quite well understood. However, evaporation of water from an unsaturated soil surface is known as actual evaporation, AE, and the associated physical processes are more complex and less understood. The calculation of actual evaporation is important for many geotechnical engineering applications. Soil suction and the corresponding water content at which the AE rate begins to depart from the PE rate during a drying process are re-assessed using a series of laboratory tests (i.e., thin soil section drying tests and soil column drying tests).Laboratory results show that the suction at which the actual rate of evaporation begins to depart from PE rate for soil columns (or thick soil layers) may be different than for thin soil layers. The suction at the "evaporation-rate reduction point", (ERRP) appears to be approximately 3,000 kPa for thin soil layers, but is between the air-entry value and residual soil suction for thick soil layers or soil columns. The analyses presented in this paper have resulted in the development of a methodology for the estimation of the suction corresponding to the ERRP in soil columns. Equations are also proposed to calculate the

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Potential Evaporation, PE, from soils is defined as the water loss through evaporation from a saturated soil surface with ample water. The calculation of Actual Evaporation, AE, is required when calculating water balance for near-ground-surface engineered situations. AE can be less than PE for a number of reasons. It has been noted that the rate of evaporation begins to depart from the potential rate of evaporation during drying process at distinct soil suction values that are related to the soil-water characteristic curve, SWCC. This paper mainly focuses on re-assessment of soil suction and the corresponding water content at which the actual rate of evaporation begins to depart from potential rate of evaporation during drying process using a series of the laboratory data collected from the research literature. It is found that the value of suction at evaporation-rate reduction point appears to be approximately 3,

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