Forest and woodland ecosystems cover approximately 37 % of the earth’s terrestrial surface. Trees and shrubs of these ecosystems are a primarily route by which water re-enters hydrological cycle. Since anthropogenic activities have begun to decrease woody cover over the surface of the globe, it became timely to improve our understanding of the role that particular woody stands play in the ecosystem water balance. In this respect, a mediterranean stand of Pistacia lentiscus has been studied in terms of water exploitation from deep and moist soil pockets. Because mediterranean ecosystems are critically important in the view of global changes, a process-based model which simulates water flux and carbon fixation is tested with data recorded in Sardinia, Italy. The model includes dynamics of CO2 fixation, carbon allocation within shrubs to leaves, stems and roots. The model encompasses the possibility for these shrubs to perform hydraulic lift. This phenomena consists in an uptake of water from deep soil. Water is relocated at nighttime in the upper portion of the profile, via outward flux of water from hydrated roots into dry soil. During daytime transpiration demand increases so that water will be uptake. Water depletion by hydraulic lift has implications not only at the plant level but also at the hydrological scale. The model is used to assess the role of hydraulic lift in supporting transpiration as the dry summer season moves in. Through the simulation we try to quantitatively analyze the pattern of water status and net carbon exchange, their interactions, the impact of climate change on it, and its potential feedback. For the purpose of validation, we measured the diurnal cycle of stomatal conductance, photosynthetic rate and leaf water potential. Changes in soil moisture caused by evapotranspiration and hydraulic lift were hourly recorded. For this purpose we installed six automated time domain reflectometry probes in different points of the evergreen stand. The linkage between the canopy ET and the soil moisture is discussed.