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<p>The Volta River Basin is a vital transboundary watershed in West Africa. It provides surface water and groundwater resources for the basin’s riparian countries particularly Ghana and Burkina Faso. Over the years, the Basin has experienced significant hydroclimatic extremes, including floods and droughts, that have led to considerable socioeconomic impacts. As global temperatures increase, the dynamics of rainfall extremes over the Volta Basin are expected to shift. This study used 20 CORDEX-Africa regional climate projections from 6 RCMs driven by 11 CMIP5 GCMs under RCP4.5 and RCP8.5 emission scenarios, to assess projected changes in 7 precipitation extremes over the Volta Basin, under 1.5&#xa0;°C, 2&#xa0;°C, and 3&#xa0;°C global warming levels (GWLs). The precipitation extremes analysed were Consecutive Dry Days (CDD), Consecutive Wet Days (CWD), Wet Days Rainfall (PRCPTOT), Very Heavy Rainfall Days (R20mm), Extremely Wet Days (R99P), Maximum 5-day rainfall (RX5DAY) and Simple Daily Intensity Index (SDII). Relative to a 30-year control period (1971–2000), the results indicate a marked increase in CDD by up to 6 days over the northern Sahelian zone of the Basin at 3&#xa0;°C warming, accompanied by a reduction in CWD by up to 4 days. Notably, R20MM is projected to increase by up to 4 days and R99P by 25–60%, especially over the Guinea Coast and transitional zones. RX5DAY increases by 10–30&#xa0;mm in the south, and SDII rises by up to 1.5&#xa0;mm/day under higher warming scenarios. These changes suggest projected increases in intense rainfall which could lead to increased frequency of flash floods as well as flooding in low-lying and agricultural areas. Moreover, the prolonged dry periods and reduced wet periods could exacerbate meteorological droughts that may evolve into hydrological droughts under persistent conditions. The spatial heterogeneity and temporal variability of these changes call for localized to sub-regional adaptation strategies to better manage climate change related flood and drought risks.</p>

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Changes in extreme precipitation events in the Volta River Basin under 1.5°C, 2°C and 3°C global warming levels

  • 期刊论文

  • 发表日期：

    2025年7月8日

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  • Emmanuel Obuobie,
  • Jacob Agyekum,
  • Marian Amoakowaah Osei,
  • Martin Addi

摘要

The Volta River Basin is a vital transboundary watershed in West Africa. It provides surface water and groundwater resources for the basin’s riparian countries particularly Ghana and Burkina Faso. Over the years, the Basin has experienced significant hydroclimatic extremes, including floods and droughts, that have led to considerable socioeconomic impacts. As global temperatures increase, the dynamics of rainfall extremes over the Volta Basin are expected to shift. This study used 20 CORDEX-Africa regional climate projections from 6 RCMs driven by 11 CMIP5 GCMs under RCP4.5 and RCP8.5 emission scenarios, to assess projected changes in 7 precipitation extremes over the Volta Basin, under 1.5 °C, 2 °C, and 3 °C global warming levels (GWLs). The precipitation extremes analysed were Consecutive Dry Days (CDD), Consecutive Wet Days (CWD), Wet Days Rainfall (PRCPTOT), Very Heavy Rainfall Days (R20mm), Extremely Wet Days (R99P), Maximum 5-day rainfall (RX5DAY) and Simple Daily Intensity Index (SDII). Relative to a 30-year control period (1971–2000), the results indicate a marked increase in CDD by up to 6 days over the northern Sahelian zone of the Basin at 3 °C warming, accompanied by a reduction in CWD by up to 4 days. Notably, R20MM is projected to increase by up to 4 days and R99P by 25–60%, especially over the Guinea Coast and transitional zones. RX5DAY increases by 10–30 mm in the south, and SDII rises by up to 1.5 mm/day under higher warming scenarios. These changes suggest projected increases in intense rainfall which could lead to increased frequency of flash floods as well as flooding in low-lying and agricultural areas. Moreover, the prolonged dry periods and reduced wet periods could exacerbate meteorological droughts that may evolve into hydrological droughts under persistent conditions. The spatial heterogeneity and temporal variability of these changes call for localized to sub-regional adaptation strategies to better manage climate change related flood and drought risks.