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.

Comparative Assessment of Standard Precipitation Index and Standard Precipitation Evapotranspiration Index as Drought Evaluation Tools in Coastal Winneba-Ghana

“…In summary, both SPI and SPEI are better indices to be employed in drought severity and extreme assessment as has been confirmed in studies such as [8,18,30,31,62,63,64]. In this study, SPEI was able to identify clearer extreme and severe droughts over Winneba than SPI.…”

“…This study has detected decadal extreme and severe droughts occurrence in the 1980s, 1990s, 2000s and 2010s over Winneba. This result can be compared with other drought studies in Ghana (e.g., [26,27,30]. [26] has utilized the SPI index to mild to extreme drought in coastal Ghana.…”

“…[27] has also employed the SPI index to identify drought in the Volta Basin of Ghana. [30] further utilized the SPI index to detect drought in the Volta Region of Ghana.…”

“…There exist several pieces of evidence on drought occurrences in Ghana [27,28,29,30,31,32,33]. Many of these studies have either analysed drought occurrences for the whole Ghana or for the Volta basin zones [27,30,31,33]. However, data for these studies are either analysed for the whole country or whole agro-ecological zone.…”

Spatiotemporal variability and change in rainfall in the Oti River Basin, West Africa

“…This shows a low variation of rainfall for RCP4.5 and RCP8.5 scenarios. Although almost all stations revealed a low to moderate variation in rainfall amount for the understudied periods, studies such as Nyatuame & Agodzo (2017), Ayanlade et al (2018) and Alemu & Bawoke (2019) have stated that such variations can adversely impact agriculture and water management. The spatial distribution of CV for annual rainfall is given in Figure 8.…”