Rainfall Variability in Sections of the Benin-Owena River Basin, Nigeria, and its Implication for Rain-fed Cultivation
Publication Date : 03-08-2020
Rainfall variability and vulnerability to extreme climatic event of drought and flood peaks in sections of the Benin-Owena River Basin was analyzed using a 50-year (1961-2010) longterm rainfall data. Time series data for 50 years was generated and the numbers of wet and dry years were determined after the double mass curve technique was used to verify the consistency of the rainfall data. Benin had 2300 mm annual rainfall compared with a threshold of 1727 mm while the other stations had less. The study reveals that Benin had the most satisfactory rainfall regime with the station being vulnerable to high flood peak and only two (2) of the 50 years under consideration being vulnerable to drought (1972 and 1977), while Akure was found to be the most vulnerable station to extreme climatic failure of drought events as forty-seven (47) of the 50 years experienced unsatisfactory rainfall events lower than the minimum threshold rainfall value for the area. Ado-Ekiti with the lowest rainfall events had 41 years of unsatisfactory rainfall or failure conditions (drought) and Ondo had 37. Apart from Benin, most of the stations had rainfall below the minimum threshold value. The implication here is that the basin is prone to drought hence too risky for rain-fed agriculture. Akure, Ado-Ekiti and Ondo are located in the northern part of the basin where rainfall reliability is low and the risk for failure or vulnerability to drought is high. The highest rainfall ever of 2827.2 mm was recorded in Benin in 2010 season.
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