Water use by an irrigated almond orchard

The evapotranspiration rate of a high-yielding (4.3 t/ha) almond orchard was measured by the eddy covariance technique. The site was subject to advection (LE/Rn > 1) for one-third of the mid-season. The slope of energy balance equation calculated from half-hourly flux data was 0.87. Flux data were transformed by forcing closure of the energy balance to give a seasonal ET of 1,450 mm (ETo 1,257 mm). This value could be reconciled with ancillary measures of soil salinity and water content, and plant water status. The mid-phase crop coefficient was 1.1 which was 0.1 higher than a recently published value. Use of the transformed value of ET in calculations of field application efficiency and annual drainage gives values of 98% and 24 mm, respectively.