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<p>Despite increasing concerns over climate variability, limited research has examined the spatiotemporal dynamics and long-term trends of extreme rainfall events in southeastern Ethiopia at the watershed scale. Understanding rainfall extremes is crucial for guiding adaptation strategies and resilience planning. This study investigates the variability and trends of rainfall extremes in the Welmel watershed, southeastern Ethiopia, for the period 1991–2020, using ground-based data from the National Meteorological Institute of Ethiopia. The Mann–Kendall test was applied to detect trends at seven stations, and Sen’s slope estimator determined the magnitude of change. Selected rainfall extreme indices were calculated using the RClimDex 1.1 tool, while spatial patterns were analyzed with the Inverse Distance Weighted method. Results revealed both upward and downward trends in annual rainfall. Significant positive trends were observed at Angetu, Bidire, Meda Walabu, and Melka Amana, whereas Rira and Haro showed insignificant declines. Seasonal analysis indicated increased rainfall during September–November at 85.7% of stations, but decreased rainfall during December–February at 71.4%. Extreme rainfall indices showed mixed patterns: one-day (Rx1day) and five-day (Rx5day) maximum rainfall increased significantly at Angetu and Melka Amana but declined at Bidire and Delo Menna. Heavy (R10mm) and very heavy (R20mm) rainfall days rose at Angetu and Meda Walabu, while consecutive wet days (CWD) decreased and consecutive dry days (CDD) increased across stations. Analysis of standardized rainfall and anomaly indices reveals high interannual variability, characterized by severe meteorological droughts and extreme wet years that pose significant risks to regional agriculture and hydropower infrastructure. Furthermore, the Precipitation Concentration Index and intensity metrics indicate a trend toward increasingly irregular, high-intensity rainfall events, signaling heightened threats of flash floods and soil erosion that necessitate adaptive water management strategies. These changes in rainfall extremes threaten agriculture, water resources, and ecosystems, underscoring the need for area-specific adaptive strategies to strengthen climate resilience and protect rain-fed livelihoods.</p>

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Spatio-temporal analysis of rainfall variability, extremes and trends in Southeastern Ethiopia

  • 期刊论文

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  • 发表日期：

    2026年7月19日

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  • Tesfaye Bogale,
  • Sileshi Degefa,
  • Gemedo Dalle,
  • Gebeyehu Abebe

摘要

Despite increasing concerns over climate variability, limited research has examined the spatiotemporal dynamics and long-term trends of extreme rainfall events in southeastern Ethiopia at the watershed scale. Understanding rainfall extremes is crucial for guiding adaptation strategies and resilience planning. This study investigates the variability and trends of rainfall extremes in the Welmel watershed, southeastern Ethiopia, for the period 1991–2020, using ground-based data from the National Meteorological Institute of Ethiopia. The Mann–Kendall test was applied to detect trends at seven stations, and Sen’s slope estimator determined the magnitude of change. Selected rainfall extreme indices were calculated using the RClimDex 1.1 tool, while spatial patterns were analyzed with the Inverse Distance Weighted method. Results revealed both upward and downward trends in annual rainfall. Significant positive trends were observed at Angetu, Bidire, Meda Walabu, and Melka Amana, whereas Rira and Haro showed insignificant declines. Seasonal analysis indicated increased rainfall during September–November at 85.7% of stations, but decreased rainfall during December–February at 71.4%. Extreme rainfall indices showed mixed patterns: one-day (Rx1day) and five-day (Rx5day) maximum rainfall increased significantly at Angetu and Melka Amana but declined at Bidire and Delo Menna. Heavy (R10mm) and very heavy (R20mm) rainfall days rose at Angetu and Meda Walabu, while consecutive wet days (CWD) decreased and consecutive dry days (CDD) increased across stations. Analysis of standardized rainfall and anomaly indices reveals high interannual variability, characterized by severe meteorological droughts and extreme wet years that pose significant risks to regional agriculture and hydropower infrastructure. Furthermore, the Precipitation Concentration Index and intensity metrics indicate a trend toward increasingly irregular, high-intensity rainfall events, signaling heightened threats of flash floods and soil erosion that necessitate adaptive water management strategies. These changes in rainfall extremes threaten agriculture, water resources, and ecosystems, underscoring the need for area-specific adaptive strategies to strengthen climate resilience and protect rain-fed livelihoods.