A 30-year perspective on rainfall characteristics across 30 meteorological stations in Ethiopia's Amhara region

ABSTRACT

A flowchart summarizing a study of rainfall characteristics and variability in Ethiopia during 1991–2020. Station and ENACTS rainfall data are used as inputs, followed by analysis using the coefficient of variation, Standardized Precipitation Index, Standardized Anomaly Index, Seasonality Index, Mann–Kendall trend test, and Sen's slope estimator. The results are presented as maps of mean annual rainfall and annual seasonality index, along with a time-series graph of annual rainfall anomalies at Bahir Dar station.

This study assessed rainfall variability and trends over 30 years (1991–2020) using observations from 30 meteorological stations distributed throughout Ethiopia’s Amhara region. The region’s varied terrain and strong reliance on rain-fed farming increase its exposure to fluctuating precipitation and climate related risks. Daily rainfall observations obtained from the Ethiopian Meteorological Institute, together with Enhancing National Climate Services datasets, were evaluated through the coefficient of variation, standardized anomaly index, seasonality index, modified Mann–Kendall test, and Sen’s slope estimator. Average annual precipitation reached 1,134 mm, with station values extending from 647.7 to 2,250.3 mm. Kiremt (Summer) contributed 78.5% of the yearly rainfall, highlighting its dominant role in the regional hydrological pattern. Annual and Kiremt precipitation displayed limited variability, whereas Bega and Belg rainfall varied considerably. Statistical assessment identified significant upward changes in annual and Kiremt precipitation at multiple stations. Conversely, Bega (Winter) and Belg (Spring) trends were mostly inconsistent or lacked statistical significance. The results reveal substantial geographic and seasonal differences in rainfall behavior, with consequences for crop production, water resource planning, and climate adaptation. They also offer valuable evidence for promoting drought tolerant farming systems, enhancing water-management strategies, and guiding adaptation policies throughout Amhara, Ethiopia.