RES-EAU Scholars

Summary of scientific project:
West Africa is one of the regions most vulnerable to extreme events and other impacts caused by climate change. The Sahelian zone, and in particular the city of Niamey, has been exposed in recent decades to a drastic increase in flooding during the rainy season, and in particular to the so-called "red flood" phenomenon. A long-term database on the monitoring of mesoscale convective systems (MCS) based on the MSG in West Africa is used to study the impact of the number and intensity of convective systems on hydrology. This TOOCAN database, developed by Fiolleau and Roca (2013) is used in conjunction with a satellite rainfall estimation product (Imerg) and a hydrological model, to quantify the impact of individual CSMs on the flow of the Niger at Niamey.

Summary of results:
The MGB hydrological model was tested for sensitivity to the Mesoscale Convective Systems (MCS) that feed the Niger River basin during the monsoon season. The rainfall associated with each MCS identified during the 2020 monsoon season was quantified and suppressed, revealing that these MCS are primarily responsible for the rise in water levels in Niamey. Suppressing the rainfall they produce completely eliminates the red flood. 10 particular CSMs were found to be responsible for a drop in flow of over 50%: these are the CSMs associated with the highest volumes of precipitation in the study area. These CSMs are very fast, with large sizes, very cold peaks and long lifetimes. These results highlight the importance of monsoon convective systems in the hydrological balance of the Niger basin.

Perspective at the end of the thesis:

Generate scenarios to analyze in detail the impact of SCMs on the hydrology of the Niger.

Perspective after completion of thesis:

Continue research through post-docs on the issue of hydro-climate intensification in the world's most vulnerable regions.

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