Within‐Field Variability of Bare Soil Evaporation Derived from Eddy Covariance Measurements

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Bare soil evaporation was measured with the eddy‐covariance method at the Selhausen field site. The site has a distinct gradient in soil texture, with a considerably higher stone content at the upper part of the field. We investigated the effect of different soil properties in the upper and lower parts of the field on evaporation using eddy covariance (EC) measurements that were combined with a footprint model. Because only one EC station was available, simultaneous evaporation measurements from the two field parts were not available. Therefore, measurements were put into the context of meteorologic and soil hydrologic conditions. Meteorologic conditions were represented by the potential evaporation, i.e., the maximum evaporation that is determined by the energy available for evaporation. The influence of precipitation and soil hydrologic conditions on the actual evaporation rate was represented by a simple soil evaporation model. The amount of water that could be evaporated at the potential rate from the lower part of the field was found to be large and considerably larger than from the upper part of the field. The difference in evaporation led to threefold larger predicted percolation or runoff in the upper than the lower part of the field. Simulations using the Richards equation were able to reproduce the differences in evaporation between the lower and upper parts of the field and relate them to the different groundwater table depths in the two parts of the field.