Modelling of meteorological drought using the SPI and SPEI indices in the Volta watershed in Togo

Drought is an insidious scourge that results from a decline in precipitation from levels considered normal. The data used cover a period of 118 years (1901-2019) which ensures a good coverage of the studied region. Two approaches (SPI and SPEI) were applied to assess drought in the Volta bassin in Togo. The results show that there has been a decrease in rainfall in the Volta bassin in Togo in recent years. In terms of SPI, 36 years have indices lower than -0.5 and 4 years lower than -1 in the Dapaong station. The longest periods of drought are observed between 1958-1990 or 33 years and 2010-2019 or 10 years. The SPEI show 9 years with an index lower than -0.5 and only one year (2001) with an index lower than -1. The longest droughts occurred during the period 2009-2019, or 10 years, as for the IPS. This shows a trend of aridification of the climate in this area.