Historical and projected meteorological droughts in the Beninese Niger River Basin, Benin

Abstract

Droughts are part of extreme meteorological phenomena that generate serious social, economic and environmental consequences. This study seeks to characterize the historical (1976-2019) and projected (2021-2050) meteorological drought in the Niger River Basin in Benin. To achieve this, the present study used daily rainfall observations and simulations of two regional climate models (RCM) (HIRHAM and REMO) from fifteen (15) rainfall stations installed around the basin. We used standardized precipitation indices (SPI) at 12 and 36 months’ time steps. To have a normal distribution, the data were transformed according to the Gamma distribution. The results revealed that over the historical period (1976-2019), SPI showed increasing trends with near-normal droughts occurring about 90% and the other drought classes around 10%. At the 12- and 36-month SPI scales, there are average durations of 17 and 32 months respectively and peaks of -1.52 and -1.12. In the future, according to the average representative concentration pathway of the RCM, the trends remain very low (1/1000 per decade) with near-normal droughts occurring at about 80 and 20% for the other classes. For SPI-12 and SPI-36 months, there are likely mean drought durations of 19 and 40 months respectively with likely mean peaks of -1.5 and -1.6. The changes assessment shows the decrease in near-normal droughts and the increase in moderate and severe droughts on average compared to the baseline period. Drought durations are also expected to increase with smaller peaks. These changes remain non-significant according to the Student's test.