Diurnal Soil‐Water Evaporation: Comparison of Measured and Calculated Soil‐Water Fluxes

The Philip and DeVries theory and the “isothermal” theory were used to predict diurnal soil water fluxes near the soil surface. The predicted values were compared with those obtained by measurements of soil‐water content, soil temperature, and evaporation. Previously measured soil‐water diffusivities were used in the theoretical calculations. The thermal vapor diffusivities were calculated using both the “simple” and the “complete” theory of Philip and DeVries. Comparison of measured and calculated fluxes indicated that the theory of Philip and DeVries predicts the measured values better at intermediate water contents, but the “isothermal” theory predicts values better at high and very low water contents.