Trend and Spatial Distribution of Rainfall: A Case Study of Edo State, Southern Nigeria from 1983 – 2023

Abstract

Understanding rainfall patterns and geographical distribution is critical for sustainable water resource management, agriculture, and disaster preparedness. This study analyzed rainfall trends and patterns in Edo State, Nigeria, from 1983 - 2023 using data from the Climate Hazards Group Infrared Precipitation with Station Data (CHIRPS). Rainfall records were analyzed using the non-parametric Mann-Kendall (MK) test and Sen's slope estimator. Results show that the mean annual rainfall ranged from 1425 mm in the year 1983 to 1892 mm in the year 2023, with the highest average recorded in the year 1995 at 2242 mm. Spatial maps revealed consistently lower rainfall in northeastern LGAs like Akoko-Edo, Esan Central, and Esan North-East, while southwestern LGAs such as Egor, Ikpoba-Okha, and Oredo experienced higher rainfall. Despite the observed variability, no statistically significant trend (p > 0.05) was detected over the 41-year period. These findings highlight the region's dynamic rainfall patterns, providing valuable insights for climate adaptation strategies and informed decision-making in water resource management.