This modelling study was conducted in the Okpara catchment at the Kaboua outlet in Benin. The target idea is to assess the availability and annual renewal of the water resources. Aiming at this, the SWAT 2003 model, a semi-distributed watershed model with a GIS interface was selected, calibrated and validated for the study basin. After calibration and validation, it springs out that 1075.8 mm/year of precipitation fall in the watershed. The surface runoff is 106.6 mm/year (10% of precipitation) while the total recharge of aquifers is 225.4 mm/year (21% of precipitation). The actual evapotranspiration is 759.8 mm/year (71% of precipitation) and the change in soil water storage is -21,37mm/year. Regarding erosion, an average value of 7t/ha/year was obtained for the watershed with a maximum value for the croplands (16.85t/ha/a) and a minimum value for the bushed savannahs (0.64t/ha/a). Based on these results, some suggestions were made for a sustainable use of water resources in the Okpara-Kaboua catchment.