Abstract: Data on monthly rainfall depths in Owena catchment area were collected and analyzed. The mean monthly rainfall depths were found and these values were plotted against the months of occurrence. Periods of high and low rainfall were found from the graph. The streamflow hydrograph of River Owena was also obtained. A comparison was then made between the graphs. From the study, it was found that seven months experienced intense rainfall while five months of the year experienced rainfall deficit. Similarly, from the hydrograph, it was found that River Owena experienced high flows in seven months and low flows in five months, the months perfectly correlating with the onset and cessation of rainfall in the catchment area. This clearly shows that rainfall is a major contributor to the reservoir build up of River Owena and the major cause for its seasonal stage and discharge variability.