Meteorological estimates for the water balance of a sparse vine crop growing in semiarid conditions

Estimates are presented for the long-term water balance of a sparse vine crop growing under semiarid conditions. The annual water losses are estimated using a simple soil moisture accounting model combined with a two-component energy combination model representing the separate but coupled evaporation fluxes from plants and bare soil. The models we calibrated using data collected during the European Field Experiment in a Desertification-threatened Area (EFEDA) field experiment in the summer of 1991 in southern Spain. The hourly averaged meteorological conditions required as input to the model were derived both from field observations and using a stochastic model. For the year of the field experiment, the simulations suggested that the plant water consumption was close to the long-term average but that the groundwater recharge was substantially below normal. The sensitivity of this balance was examined using the stochastic model both for current conditions and for various hypothetical changes in the average rainfall, plant spacing and plant species.