The general downward trend in rainfall in West Africa since the 1970s has favored long periods of drought. The rainfall decrease has not only caused the depletion of water resources, but has also led to a disruption of the runoff regime of rivers. The objective of this study is to carry out a spatial and temporal characterization of the rainfall regime in the Bagoé watershed over the period from 1928 to 2000 in order to analyze its influence on the rivers runoff to better predict adaptation solutions. Statistical approaches and a GIS were used to characterize the rainfall variability which was then analyzed in relation to the runoff regime of rivers over the period from 1961 to 1986. The average annual precipitation recorded is 1397.04 mm with two dry periods (1928-1949 and 1976-2000) which frame the only wet period (1950-1975). A secondary rainfall rupture in 1949 and a principal rainfall rupture in 1975 were highlighted. The principal rainfall rupture in 1975 suggests a significant drop in precipitation from 1976 to 2000 marked geo-spatially by the predominance of 1100 mm and 1200 mm isohyets during the decade 1991-2000. This drop in rainfall led to a decrease in the water flow of rivers, also due to hydraulic activities in the basin. Adaptation solutions should therefore be found in the planning of development projects.