Meteorological drought and long-term trends and spatial variability of rainfall in the Niger River Basin, Nigeria

In sub-Saharan Africa, rainfall is crucial for the livelihood of the population. This study aims to assess meteorological drought and long-term trends and spatial variability of rainfall in the Niger River Basin, Nigeria. This study employed the Bayesian estimator of abrupt change, seasonality, and trend (BEAST), Mann‒Kendall (MK), modified Mann‒Kendall (MMK) test, seasonal Mann‒Kendall (SMK) test, and innovative trend analysis (ITA) to analyze seasonal and annual rainfall trends in the Niger River Basin (NRB). Rainfall variability was assessed using the coefficient of variation (CV) and precipitation concentration index (PCI), while meteorological drought was assessed using the standardized precipitation index (SPI). The PCI results revealed that the rainfall concentration ranged from low to high. The BEAST revealed nonsignificant changes in most parts of the NRB. The MK, MMK, SMK, and ITA methods all show comparable increasing trends in annual rainfall, with ITA detecting significant trends at four out of five stations. Seasonal rainfall showed high variability, marked by significantly decreasing rainfall in the MAM but increasing rainfall in the SON season. The increasing annual rainfall indicates an overall trend toward wetter conditions, which might improve agricultural productivity in areas dependent on rain-fed farming. Additionally, it could result in greater recharging of groundwater resources, potentially boosting water supply to people and agriculture. The study also revealed that severe drought events occurred across the NRB, with the highest severity recorded in the 1970s and 1980s. The study's findings can inform policies aimed at enhancing food security by investing in irrigation and drought-resistant crops.