Profile Soil Moisture from Surface Measurements

A method is presented for predicting the volumetric soil moisture of the soil profile from the surface layer soil moisture measurement and information on the soil properties of the profile under bare soil conditions. This method is based upon soil physics relationships and the assumption of hydraulic potential equilibrium throughout the profile. This procedure was tested using data generated with a soil-moisture-simulation model for a variety of situations involving bare soils. Results indicated that this procedure can be used to predict profile soil moisture within acceptable error bounds under some conditions. However, the surface layer measurements should be made during predawn period. The optimal surface layer thickness inferred from the analyses was about 0.1 m (4 in). These results provide some guidelines for developing remote sensing methods for soil-moisture determination.