Hydroclimatic variability and surface water resources in the Volta River basin in Benin (West Africa)

The occurrence of surface water and its management depends on climate variability in the Benin part of the Volta River basin. Calculation of the quartiles, frequencies analysis, discontinuity detection, calculation of water deficit index (WDI), base flow index (BFI), seasonal irregularity index (SII) and of the drying up coefficient helped in the analysis of hydrological variability. Since 1975, the basin has experienced persistent dryness, induced by a rainfall decrease of about 10%. Consequently, the river flows dropped about 30-40%, characterized by low base flow index of 0.55% at Porga compared with 0.64% over the wetter period 1961-1975, and a very marked seasonal irregularity. The part of the Volta Basin in Benin also experienced a fast drying of the river water and more frequent occurrence of extreme hydrometeorological events which impact surface water availability and management.