A method is described for determining water consumption of trees by transpiration considering the ecoclimatic factors of the environment. The trees are studied in a situation where they have accenss to as much water as they need. The tree species being studied are transplanted to large plastic containers in which, by means of special system, the subsurface water is maintained at a constant level. Whenever there is a decrease in the level of surface water, the special mechanism, which registers accumulated water in the study system, automatically restores the water to its initial level by the addition of more water