Quantitative Analysis of Rainfall Variability and Extreme Events in Benue State Using Long-Term Climate Records

Abstract

Rainfall variability and extreme events present major challenges to food security and infrastructure in Benue State, Nigeria, where agriculture is predominantly rain-fed. This study analyzed rainfall variability using 1980–2020 records and applied the Standardized Precipitation Index (SPI), Mann–Kendall trend test, Sen’s slope estimator, and Generalized Extreme Value (GEV) distribution. Results showed that moderate to severe droughts occurred in about 21% of study years, with 1983, 1992, 2004, and 2011 identified as prolonged drought years. The Mann–Kendall test indicated a significant decreasing trend in annual rainfall at –8.3 mm per decade (p < 0.05), while Sen’s slope confirmed consistent declines in early-season rainfall. In contrast, GEV analysis revealed a 12–15% increase in the probability of extreme rainfall events exceeding 100 mm/day, particularly during the August–September peak, contributing to recurrent flooding in the Makurdi floodplain. Spatial assessment showed greater rainfall variability in the southern zones compared to the north. These findings highlight the dual risks of increasing agricultural drought and intensifying flood hazards. The study underscores the need for integrated adaptation measures, including climate-informed agricultural calendars, flood-control infrastructure, and improved early warning systems. By providing robust quantitative evidence, the research supports informed decision-making for climate risk management and sustainable development in Benue State and comparable regions of sub-Saharan Africa.