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<p>The Nile River serves as the primary freshwater source and ecological lifeline for eastern and northern Africa, exhibiting pronounced multi-scale streamflow variability. However, the climatic drivers of this variability across different timescales and sub-basins remain poorly quantified. To address this gap, we developed a three-tiered attribution framework linking large-scale climate modes to sub-basin precipitation and downstream flow across multiple timescales. Over the past 80 years, streamflow at Aswan has exhibited significant interannual variability and a decadal-scale positive–negative–positive phase transition. This multi-timescale variability is primarily governed by precipitation in the White and Blue Nile sub-basins, with temperature variability playing a relatively minor role. Quantitatively, PDO-related precipitation variability in the White Nile Basin dominates the decadal-scale variation of lower Nile streamflow, explaining 69% (CI [62.0%, 77.1%]) of the total variance. In contrast, ENSO-related precipitation anomalies in the Blue Nile Basin account for 67% (CI [61.3%, 71.4%]) of interannual discharge fluctuations. Mechanistically, sea surface temperature anomalies in the eastern equatorial Pacific induce a seesaw pattern in wind field divergence and moisture flux between the tropical Pacific and the Asian–African region. These moisture flux anomalies modulate precipitation over the Nile River Basin, thereby driving streamflow variability. By providing stepwise quantification across multiple timescales and source regions, this hierarchical attribution framework offers deeper insight into the climate–hydrology nexus compared to previous studies.</p>

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Unraveling Nile streamflow variability and its response to climate across timescales

  • 期刊论文

  • 发表日期：

    2026年7月29日

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  • Fang Huang,
  • Zhongfeng Xu,
  • Ping Wang,
  • Ahmed M. El Kenawy,
  • Mohamed Magdy Abdel-Wahab

摘要

The Nile River serves as the primary freshwater source and ecological lifeline for eastern and northern Africa, exhibiting pronounced multi-scale streamflow variability. However, the climatic drivers of this variability across different timescales and sub-basins remain poorly quantified. To address this gap, we developed a three-tiered attribution framework linking large-scale climate modes to sub-basin precipitation and downstream flow across multiple timescales. Over the past 80 years, streamflow at Aswan has exhibited significant interannual variability and a decadal-scale positive–negative–positive phase transition. This multi-timescale variability is primarily governed by precipitation in the White and Blue Nile sub-basins, with temperature variability playing a relatively minor role. Quantitatively, PDO-related precipitation variability in the White Nile Basin dominates the decadal-scale variation of lower Nile streamflow, explaining 69% (CI [62.0%, 77.1%]) of the total variance. In contrast, ENSO-related precipitation anomalies in the Blue Nile Basin account for 67% (CI [61.3%, 71.4%]) of interannual discharge fluctuations. Mechanistically, sea surface temperature anomalies in the eastern equatorial Pacific induce a seesaw pattern in wind field divergence and moisture flux between the tropical Pacific and the Asian–African region. These moisture flux anomalies modulate precipitation over the Nile River Basin, thereby driving streamflow variability. By providing stepwise quantification across multiple timescales and source regions, this hierarchical attribution framework offers deeper insight into the climate–hydrology nexus compared to previous studies.