Growing Season Rainfall Trends, Alterations and Drought Intensities in the Guinea Savanna Belt of Nigeria: Implications on Agriculture

This paper examined the growing season rainfall trends, alterations and drought intensities in the Guinea Savanna belt of Nigeria using monthly rainfall data of 1941-2010 from eight synoptic weather stations (Ilorin, Minna, Bida, Lokoja, Enugu, Makurdi, Jos and Kaduna). Simple linear regression and second order polynomial were used to investigate the rainfall trend of the synoptic weather stations. The rainfall data were partitioned into two periods (1941-1975 and 1976-2010). Simple percentage and t-test statistics were used to examine to monthly and growing season changes in rainfall while the drought intensities for the growing season were computed as percentage deviation below the mean (PDBM). The results revealed upward trends in Bida, Lokoja and Enugu during the 1941-2010 period with that of Lokoja being sharpest while Ilorin, Minna, Makurdi, Jos and Kaduna experienced downward trend with that of Jos being the sharpest. Rainfall in Minna, Lokoja, Enugu, Makurdi and Kaduna exhibited curvilinear attribute while Ilorin, Bida and Jos exhibit linear pattern. Only Makurdi and Jos revealed significant difference between the 1941-1975 and 1976-2010 periods. While Makurdi witnessed the highest percentage change in growing season rainfall, Bida experienced the lowest. Alterations of rainfall among the selected synoptic stations reveal mixed variations while the droughts were of slight and moderate intensities with the exception of Enugu which witnessed severe drought in 1966. The paper concludes that the change in growing season rainfall, especially in Makurdi and Jos, as well as the drought incidences could pose negative implications on Nigeria’s food security if measures such as irrigation, cultivation of drought resistant varieties as well as alignment of cropping schedules with unfolding climatic patterns are not adopted. Keywords: Growing season, rainfall, drought, Guinea Savanna, Nigeri