EFFECT OF THE ENSO PHASES ON RAINFALL VARIABILITY OVER THE NORTHERN HIGHLANDS OF ETHIOPIA

Abstract

This study investigates the effects of the El Niño-Southern Oscillation (ENSO) phases on rainfall variability over the Northern Highlands of Ethiopia, focusing on four key stations—Debre Birhan, Kombolcha, Woldia, and Lalibela—from 2011 to 2020. Utilizing descriptive statistics, Mann-Kendall trend tests, Sen’s slope estimator, and correlation analyses, the research evaluates seasonal (Belg, Kiremt, and Bega) and monthly rainfall patterns in relation to ENSO events. The results reveal significant regional variability in rainfall responses to ENSO phases. During El Niño years, Belg rainfall decreases notably in Woldia (-31.3%) but increases in Lalibela (+40.4%), while Kiremt rainfall declines in Debre Birhan (-8.1%). Conversely, La Niña years enhance Belg rainfall across all stations, with Woldia experiencing a 32.7% increase. Time series analysis indicates upward rainfall trends in Debre Birhan (+8.6 mm/year) and Lalibela (+10.5 mm/year), linked to intensified Kiremt rains, whereas Woldia faces declining Belg rainfall (-14.2 mm/year), threatening earlyseason agriculture. The study underscores ENSO’s critical role in modulating rainfall variability, with implications for agriculture and water resource management. Positive trends in Lalibela and Debre Birhan suggest opportunities for improved crop yields, while Woldia’s rainfall decline highlights vulnerabilities requiring adaptive strategies such as drought-resistant crops. These findings advocate for localized climate adaptation policies to mitigate ENSO-induced risks and leverage favorable rainfall patterns in Ethiopia’s highlands.