Impacts of climate change on environmental flows in West Africa's Upper Niger Basin and the Inner Niger Delta

Abstract

Modified water regimes due to climate change are likely to be a major cause of freshwater ecosystem alteration. General Circulation Model (GCM)-related uncertainty in environmental flows at 12 gauging stations in the Upper Niger Basin and flooding within the Inner Niger Delta is assessed using the Ecological Risk due to the Flow Alteration method and a hydrological model forced with projections from 12 GCM groups for RCP 4.5 in the 2050s and 2080s. Risk varies between GCM groups and stations. It increases into the future and is larger for changes in low flows compared to high flows. For the ensemble mean, a small minority of GCM groups projects no risk for high flows in the 2050s (low risk otherwise). This reverses for the 2080s. For low flows, no risk is limited to three stations in the 2050s and one station in the 2080s, the other experience either low or medium risk. There is greater consistency in the risk of change in flood extent, especially in the dry season (medium risk for all groups and the ensemble mean). Some (low or medium) risk of change in peak annual inundation is projected for most groups. Changing flood patterns have implications for wetland ecology and ecosystem services. HIGHLIGHTS Projected river discharge in the Upper Niger for 12 GCM groups is combined with the Ecological Risk due to Flow Alteration (ERFA) environmental flow method.; ERFA is also applied to projected flood extent within the Inner Niger Delta.; Risk of river flow change varies between GCM groups and stations. It increases into the future and is larger for low flows than high flows.; Risk for flood extent is more consistent especially in the dry season (medium risk).;

Keywords

• climate change
• environmental flows
• inner niger delta