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.

Increasing Risk of Ecological Change to Major Rivers of the World With Global Warming

“…Some ecological responses are likely to be the same whether MFRIs increase or decrease (e.g., lower or higher magnitude of high flows or low flows may alter assemblages and reduce diversity; Poff & Zimmerman, 2010) whilst others may vary with the direction of change. By identify the relative risks of change in different regions including, for example, the identification of hotspots, it is possible to then undertake more detailed assessments of the nature of projected changes in river regimes and their implications for individual species and ecosystem services (e.g., Thompson et al, 2021).…”

“…Investigations of how environmental flows and aquatic habitat conditions may be impacted by future climate change has largely been conducted at the basin scale (Ahn et al, 2018;González-Villela et al, 2018;Thompson et al, 2021) or for smaller individual sites (House et al, 2016(House et al, , 2017Thompson et al, 2017). Global-scale or even regional studies are comparatively rare (Döll & Zhang, 2010;Laizé et al, 2014;Pastor et al, 2019).…”

Analysing rainfall and runoff patterns over the Niger River in Mali, West Africa

“…Many authors (Olivry et al, 2005;Andersen et al, 2005;Mahé et al, 2009;Roudier and Mahe, 2010;Liersch et al, 2019;Thompson et al, 2021) have conducted their studies on the Niger River basin, and most of the outputs show a decline not only in the river stage but also in the groundwater level. For example, Roudier and Mahe (2010) studied drought events using the standard precipitation index in the Bani Bani, the main subbasin of the Niger River in Mali and found an increasing trend in the total dry days.…”