Analysis of Annual Maximum Daily Rainfall at Selected Locations in Central Nigeria.

Abstract

In recent times, there has been an intensification in the occurrence of extreme rainfall events, necessitating the need for a deeper understanding of the behaviour of these extreme events. Using the Generalised Extreme Value distribution, this study analysed the probability of occurrence and behaviour of annual maximum daily rainfall at Abuja, Lafia, and Lokoja in the central region of Nigeria between 1989 and 2023. The parameters of the Generalised Extreme Value distribution were estimated using the maximum likelihood method, and the return levels were computed 2, 5, 10 and, 25, 50, 100 and 200 years return period. The results of the Mann-Kendall trend test and Sen’s slope estimator revealed significant declining and increasing trends of 1.1 mm/yr and 2.0 mm/yr at Abuja and Lafia, respectively and no trend at Lokoja. The Augmented Dickey-Fuller test indicated non-stationarity in the time series of annual maximum daily rainfall at Abuja and Lafia, while stationarity was accepted for Lokoja. The results of the distribution fitting showed that the Weibull distribution was the best fit distribution for Abuja, while the Fréchet distribution was the most appropriate for Lafia, and Lokoja. Relative to the return periods, the estimated return level for the 2-year return varied between 75.4 mm and 103.3 mm of rainfall, while the 200-year return period varied between 168.3 mm and 224.8 mm of rainfall. These findings emphasize the need for further deepening of the understanding of extreme rainfall events to improve community resilience to hydrometeorological hazards such as flooding.