Analysis of Extreme Rainfall Events (Drought and Flood) over Tordzie Watershed in the Volta Region of Ghana

Abstract

In regional water resources management and disaster preparedness, the analysis of extreme rainfall events is essential. The need to investigate drought and flood conditions is now heightened within the context of climate change and variability. The Standardised Precipitation Index (SPI) was employed to assess the extreme rainfall event on Tordzie watershed using precipitation data from 1984-2014. The SPI on the time scale of 3, 6, 9 and 12 months were determined using “DrinC” software. The drought was characterised into magnitude, duration, intensity, frequency, commencement and termination at the time scales of SPI-3, SPI-6, SPI-9 and SPI-12. Results indicated that the middle reaches (Kpetoe) of the watershed experienced less severe drought condition compared to the lower reaches (Tordzinu). Mann-Kendall (MK) test and Sen’s slope (SS) revealed general increasing drought trend but insignificant at 95% confidence interval. The SS indicated change in magnitude of 0.016 mm/year, 0.012 mm/year, 0.026 mm/year and 0.016 mm/year respectively at the mentioned time scales at 95% confidence interval at the Tordzinu and that of Kpetoe were 0.006 mm/year, 0.009 mm/year, 0.014 mm/year and 0.003 mm/year. These changes could have implication for agriculture and water resources management and engender food insecurity among smallholder farmers.