Evaporation from heterogeneous surfaces at the field-plot scale: effect of lateral heat and water fluxes in soil and atmosphere

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Wet patches in agricultural fields may exist due to local variations in soil structure (compacted wheel tracks) or due to local irrigation (drip irrigation). Commonly used approaches to estimate evaporation assume that the lateral extent of the evaporating surface is large so that the lateral advection of heat and vapor in the air stream and in the soil can be neglected. For the scales of patches that are considered in this project, we postulate that lateral heat and mass fluxes in both the soil and the air may influence the evaporation rate from wet patches. In order to investigate these effects, we will carry out experiments at a field plot under outdoor conditions in which we will monitor the surface temperature of wet patches and the evaporation rate of micro-lysimeters with and without patches and which are or are not thermally insulated from the surrounding soil. The experiments will be accompanied by simulation studies in which lateral heat and water fluxes in both the soil and the air flow will be considered. To support other subprojects, infiltration, evaporation and salt tracer experiments will be carried out in an artificially constructed heterogeneous soil tank.