SUMMARY
In this study, we use the hydrological model: rain flow Zygos that is integrated in the Hydrognomom software. The aim is to estimate the fraction of rain supplying the groundwater. The latter is composed of several parameters that represent the infiltration and flow process. Data outputs, namely percolation and evaporation, are deduced after automatic calibration between the measured flow rate at the outlet and the calculated flow rate. The input parameter: “mean monthly rainfall estimate”, was carried out by two ways: the first is isohyets; the second is that of the arithmetic mean. Numerical simulations show that the first method gives a very good result. On the other side, the second reveals a bad timing. Finely, it is shown that, for an average annual rainfall of 425.2 mm intake, percolation represents only 10 % of the precipitation.