© 2021 The Authors Hydrology Research Vol 52 No 4, 958 doi: 10.2166/nh.2021.041 Impacts of climate change on environmental flows in West Africa’s Upper Niger Basin and the Inner Niger Delta Julian R. Thompson a,*, Cédric L. R. Laizé b, Michael C. Acreman b, Andrew Crawleya and Daniel G. Kingston c a Wetland Research Unit, UCL Department of Geography, University College London, Gower Street, London WC1E 6BT, UK b UK Centre for Ecology & Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford OX10 8BB, UK c School of Geography, University of Otago, P.O. Box 56, Dunedin, New Zealand *Corresponding author. E-mail:
[email protected] JRT, 0000-0002-8927-6462; CLRL, 0000-0002-7560-7769; MCA, 0000-0002-8946-739X; DGK, 0000-0003-4205-4181 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.