[en] The study of luquid discharge is based on mechanical and thermodynamical analysises. Unfortunately, they lead to dischange equations which don't describe the phenomenon in unsaturated porous medium, mainly during the first moment of the liquid dischange. We have imagined an experimental system in view to overcome this difficulty. With this system we have measured the flow dischange during the first time of the phenomenon. Owing to the solution of classical equations of liquid dischange, this value is equal to infinity, but in our case we have found that the later is equal to zero. Generally, the underformation of hydrous profiles during filtration is used in order to simplify and resolve classical equation of liquid discharge. But the use of gamma radiation has shown that this hypothesis is not valid