Analysis of rainfall and discharge regime characteristics of a segment of river Benue in Adamawa state, Nigeria

River discharge regime refers to the seasonal variation in the volume of water flowing through a river system between wet and dry seasons. This study examined the rainfall and discharge regimes of a section of the River Benue in Yola, Adamawa State, Nigeria. Specifically, the study assessed the characteristics of rainfall and river discharge, investigated their temporal trends, examined the relationship between rainfall and discharge, and developed a regression model to determine the influence of rainfall on river discharge. The study utilized 40 years of rainfall and discharge records covering the period from 1986 to 2025 for Yola and Numan meteorological stations. The data were obtained from the Upper Benue River Basin Development Authority (UBRBDA), Yola. The Mann–Kendall test was employed to determine the presence and significance of trends in annual rainfall and discharge, while the Kendall correlation coefficient was used to assess the strength and direction of the relationship between the two variables. Linear regression analysis and ANOVA were further applied to model the relationship between rainfall and discharge and assess the statistical significance of the model. The results of the Mann–Kendall test revealed a statistically significant decreasing trend in mean annual discharge, with a Z-value of −2.8687 and a p-value of 0.004122, indicating strong evidence against the null hypothesis of no monotonic trend. In contrast, annual rainfall exhibited no statistically significant trend, with a Z-value of 0.42604 and a p-value of 0.6701, suggesting insufficient evidence to reject the null hypothesis. The correlation analysis produced a Kendall’s tau-b coefficient of −0.045, indicating a very weak negative association between mean annual discharge and total annual rainfall. However, the relationship was not statistically significant, as demonstrated by the p-value of 0.701. Similarly, the regression analysis showed that total annual rainfall was not a statistically significant predictor of mean annual discharge, with an ANOVA p-value of 0.470. The findings therefore indicate that the observed decline in river discharge over the study period cannot be adequately explained by variations in annual rainfall alone, suggesting the possible influence of other climatic, hydrological, or anthropogenic factors on the discharge regime of the River Benue.