Analysis of rainfall variability and extreme events in South-Western Nigeria: implications for water resource management and climate resilience

Abstract Rainfall variability and extreme events significantly impact agriculture, water resource management, and urban planning in South-Western Nigeria, a region characterized by distinct wet and dry seasons. The study aims to analyse rainfall patterns, quantify extreme rainfall events, and estimate return periods using statistical models to address the challenges posed by these variations. Forty years of rainfall data (1983–2023) were analysed to capture seasonal and inter-annual variability. Extreme rainfall events were modelled using Gumbel and generalized extreme value (GEV) distributions, with the latter providing a superior fit, as validated by Kolmogorov–Smirnov (K–S) and Anderson–Darling (A–D) tests. The results show a bimodal rainfall pattern with peaks in June–July and September–October and an "August break". Annual variability highlighted high-rainfall years like 1995, 2009, and 2019 and low-rainfall years such as 2000 and 2015, influenced by climate drivers like ENSO and AMO. Rainfall intensities for return periods of 2, 10, and 100 years were estimated at 1463 mm, 1647 mm, and 1733 mm, respectively, based on the GEV model. The findings emphasize the need for adaptive strategies, including improved water storage systems, flood control infrastructure, and climate-resilient agricultural practices. Future research should integrate climate projections to anticipate trends under changing climatic conditions, supporting sustainable development and disaster resilience in the region.