Soil Water Evaporation • Stage 1. For soils saturated to the surface, the evaporation rate is similar to surface water evaporation. • Stage 2. As the surface dries out, evaporation slows to a rate dependent on the capillary conductivity of the soil. • Stage 3. Once pore spaces dry, water loss occurs in the form of vapor diffusion. Vapor diffusion requires more energy input than capillary conduction and is much, much, slower. Note that for soils under a forest canopy, R net , vapor pressure deficit, and turbulent transport (wind) are lower than for exposed soils.