Spatio-temporal pattern of rainfall distribution over Ilorin metropolis, Nigeria

Abstract

Rainfall varies over time and space and the study of its variability cannot be over emphasized. This paper examines spatio-temporal patterns of rainfall in Ilorin metropolis, Nigeria. 30 years data were collected in 3 locations [Nigeria Meteorological Agency (NIMET), Lower Niger River Basin Development Authority (LNRBDA) and Kwara State Water Corporation (KWWC)]. The analytical procedure includes trend analysis, reduction analysis, and ordinary kriging with Gaussian semivariogam model. The results showed that June and September recorded the highest amount of rainfall in Ilorin across three stations. An upward trend of rainfall of about 0.30mm, 0.40mm and 0.2mm respectively, were recorded in the 3 stations. The reduction pattern analysis revealed the variability and percentage change in the amount of rainfall received in Ilorin over the 30 years of study. Nine regional pattern were also revealed from the kriging analysis, and a variability of 50mm were recorded over the 12km² sized metropolis. The south-western part of Ilorin recorded more rainfall than the other parts. It was concluded that spatial distribution of annual rainfall in Ilorin, varied from one part to the other. The increasing upward trend might increase water supply, increase chances of urban flooding, erosion and sedimentation. The paper recommends that wet season rainfall be properly managed to boost water supply in dry season.

Key words: Rainfall, Variability, Spatio-temporal, Trend, Flood, Water supply, Kriging