Future river flows and flood extent in the Upper Niger and Inner Niger Delta: GCM-related uncertainty using the CMIP5 ensemble

Julian R Thompson,Andrew Crawley,Daniel G Kingston

doi:10.1080/02626667.2017.1383608

Julian R Thompson, Andrew Crawley + Show 1 more

Open Access

https://doi.org/10.1080/02626667.2017.1383608

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Abstract

ABSTRACTA semi-distributed hydrological model of the Upper Niger and the Inner Niger Delta is used to investigate the RCP 4.5 scenario for 41 CMIP5 GCMs in the 2050s and 2080s. In percentage terms, the range of change in precipitation is around four times as large as for potential evapotranspiration, which increases for most GCMs over most sub-catchments. Almost equal numbers of sub-catchment–GCM combinations experience positive and negative precipitation change. River discharge changes are equally uncertain. Inter-GCM range in mean discharge exceeds that of precipitation by three times in percentage terms. Declining seasonal flooding within the Inner Delta is dominant; 78 and 68% of GCMs project declines in October and November for the 2050s and 2080s, respectively. The 10- and 90-percentile changes in mean annual peak inundation range from −6136 km2 (−43%) to +987 km2 (+7%) for the 2050s and −6176 km2 (−43%) to +1165 km2 (+8.2%) for the 2080s.

Highlights

Hydrological processes are key drivers within wetland environments (e.g. Baker et al 2009)
Whilst the vast majority of subcatchment–General Circulation Models (GCMs) combinations are associated with increases in potential evapotranspiration (PET), both increases and decreases in mean annual precipitation are projected by different GCMs in both studies
The much larger percentage ranges of change in annual precipitation for the current study (Fig. 2, Fig. 9 for the GCM groups) echo those of Thompson et al (2016), in which the mean range of change in annual precipitation exceeded that of PET by over five times

Summary

Introduction

Hydrological processes are key drivers within wetland environments (e.g. Baker et al 2009). The ecosystem services provided by wetlands are conditioned by the interplay between hydrological, biophysical and ecological processes (Maltby et al 2011). In some locations these wetland ecosystem services are central to the livelihoods of large human populations, a role that is clearly demonstrated in Africa’s floodplains. Africa’s floodplains typify the ecological, economic and social significance of “wetlands in drylands” (Scoones 1991) Despite this significance, many African floodplains have experienced changes in flooding patterns due to water resource developments, in particular dams. Many African floodplains have experienced changes in flooding patterns due to water resource developments, in particular dams These changes have in turn impacted the provision of ecosystem services and the people that depend upon them Further modifications to the hydro-ecological conditions of Africa’s floodplain wetlands are likely to result from climate change

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