SUMMARY
Watershed Agneby is located southeast of the Côte d’Ivoire. This basin has a vulnerability to climate change manifested by an increased sensitivity to extreme situations (floods and drought) since 70’s. This natural determinism seems to be reinforced by population increasing whose economic activities are based on water resources. View this problem which challenge is to satisfy water demand; we proposed to model the flows for an immediate assessment of the water balance. To achieve this, data of precipitation, evapotranspiration and runoff discharge collected over the 1984-2009 period were ejected in GR4J model to assess its performance in runoff simulating. The results gave satisfactory wedging in Nash values (60-80%). In addition, the comparison of observed and simulated hydrographs showed that the flow dynamics is well respected and floods are reproduced in calibration and validation. All these results have shown a good performance of GR4J model to reproduce the flows in the basin. Thus, the calculated water balance showed that 75% of the annual average rainfall estimated at 1168 mm for the period 1984 to 2009 has evaporated. The runoff is about 2%, while infiltration is about of 23%.