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

Julian R Thompson,Michael C Acreman,Cédric L R Laizé,Andrew Crawley,Daniel G Kingston

doi:10.2166/nh.2021.041

Julian R Thompson, Michael C Acreman + Show 3 more

Open Access

https://doi.org/10.2166/nh.2021.041

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Abstract

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

Hydrological conditions within rivers exert critical controls upon aquatic ecosystems
This study demonstrates the application of Ecological Risk due to Flow Alteration (ERFA), an environmental flow method developed by Laizé et al (2014) and modified by Thompson et al (2014) and Laizé & Thompson (2019)
Increases and decreases in mean annual precipitation are projected by different General Circulation Model (GCM) groups and over different sub-catchments (Supplementary Material, Figure S3)

Summary

Introduction

Hydrological conditions within rivers exert critical controls upon aquatic ecosystems. This influence is implicit within the natural flow paradigm (Poff et al 1997) that recognises that a river’s regime, characterised by variability, magnitude, frequency, duration, timing and rate of change of discharge, is central to sustaining ecosystem integrity. Indirect influences include the important role of high flows in controlling connections between rivers, floodplains and riparian wetlands. The resulting wetland hydrological conditions, water-level/inundation regimes, are a dominant influence upon vegetation, animals and biochemical processes that support numerous ecosystem services Modifications to river regimes and floodplain inundation can potentially impact wetland ecosystem service delivery (Acreman et al 2014)

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