In cover cropped Mediterranean vineyards, a major difficulty is to properly manage the two crops with respect with the competition for the soil resources and the variability of climate. These cropping systems should both fulfil the grapevine objectives of performances and provide the ecological services (decrease of runoff, improvement of soil quality, control of grapevine vigor) expected from the cover crop. To better understand the water dynamics of these systems and evaluate water stress during the grapevine producting cycle, a simple model of water balance was adapted to intercropped vineyards. The soil was partitioned in two compartments corresponding to the different root systems of the two crops. Cover crop takes up water in the soil surface compartment only, whereas grapevine takes up water in the two compartments. The model was calibrated and evaluated with a 3-year experiment (2004-2006) in Montpellier (South of France) on three treatments (bare soil, permanent and temporary intercropped wineyards). The water balance dynamics was well stimulated by the model for all treatments despite the contasted water regimes observed over the three years.