Observational trend analysis reveals widespread rainfall increases across weather stations, suggesting critical shifts in seasonal water availability.
Key Points
To assess long-term annual and seasonal rainfall variability and trend dynamics across the Upper Blue Nile Basin using complementary statistical trend detection methods.
Analyzed historical rainfall data spanning 1981 to 2024 from 41 stations using National Meteorology Agency records supplemented with CHIRPS data for gap-filling.
Controlled for multiple testing and spatial dependence across stations using Benjamini–Hochberg false discovery rate (FDR) testing.
Approximately 75% of stations exhibited increasing annual rainfall, with significant rises at Asendabo (9.22 mm/yr) and Nekemte (7.35 mm/yr), and significant declines at Mota (−4.11 mm/yr) and Debre Tsige (−2.55 mm/yr).
Summer and autumn precipitation primarily showed increasing trends, while winter precipitation decreased across approximately 65% of stations.
Significant change points occurred at 34% of stations clustered around 2002–2005 and 2011–2012; FDR testing confirmed annual and autumn increases as field-significant, whereas widespread spring increases failed multiple testing correction.