Assessment of Mid-Century Climate Change Impacts in Mono River’s Downstream Inflows

Abstract

In the current context of global climate change and variability, it is important to undertake river flow projection in order to improve watershed management. This is needed to put in place relevant actions in order to improve communities’ security. Hence, this study aims at assessing the impact of the mid-century climate change on Mono River downstream inflows at Athiémé (Benin). The projections from the regional climate model REMO, under the scenarios RCP 4.5 and RCP 8.5 were used to force the hydrological model HBV-light. Within the period 2018-2050, temperature will increase and seasonal cycle of rainfall will change throughout the watershed: in the south, the second rainfall peak which normally occurs in September will be extended to October with a higher value; in central and northern parts, there will be late unset of rainfall, shorter rainy season and higher peaks. Consequently, the mean hydrograph will shift rightward, increase in amplitude and the period of high flow will be shortened. Under RCP 4.5, the lowest maximum flow will be recorded in 2031 (116 m3/s) whereas the highest is expected in 2024 (1236 m3/s). Flood prone areas vary between 6.2% to 20.1% of Athieme’s land surface. For RCP 8.5 the lowest maximum flow is projected for 2033 (123 m3/s) and the highest for 2034 (1150 m3/s), with flood prone areas ranging from 6.4% to 19.2%. Thus, it is recommended to undertake thorough risk assessment on one hand, and to account for both high and low flow situations in Mono watershed management strategies.