Drought frequency in the Volta Basin of West Africa

Abstract

According to various reports, climate change is responsible for the change in rainfall amount and pattern accompanied by the various degrees of extreme events in Sahelian West Africa in recent years. Other reports also suggest that there has been a ''recovery'' of the rainy season (Nicholson 2005). In this study, temporal characteristics of meteorological droughts in the Volta basin, a semi-arid region in West Africa, are investigated in order to provide a guide for sustainable water resource management. For this purpose, drought intensity, areal extent and recurrence frequency is analysed using the standardised precipitation index (SPI) for a time series between 1961 and 2005 from 52 meteorology stations across the Volta basin. Using this analysis the severity of the historical droughts of 1961, 1970, 1983, 1992 and 2001 that occurred in the region are assessed and their intensity, areal extent and return periods are obtained. The drought intensity is lower than -2.0 over nearly 75% of the region, meaning that a major part of the region was under extreme drought conditions during this year. The drought of 1983/1984 has a probability of occurrence of up to 0.1 from records spanning 44 years. The areal extent of extreme drought conditions is about 90% during this drought period.

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

“…This revelation implies that the extreme climatic events are rare though drought frequency in general is on the ascendancy. In a related study by Kasei et al [21] on the drought frequency in the Volta basin of Ghana they found out that 1983/84 drought affected the whole region of Ghana. In that study, the authors revealed that the drought intensity was lower than −2.0 for that particular year and affected about 75% of Ghana suggesting that a major part of the Ghana was under extreme drought conditions.…”

A review of droughts on the African continent: a geospatial and long-term perspective

“…Dai, 2011Dai, , 2013 as well as by most of the regional and country level studies (e.g. Ouassou et al, 2007;Touchan et al, 2008, Elagib and Elhang, 2008Kasei et al, 2010;Manatsa et al, 2008;Richard et al, 2001). The available data (though limited in temporal coverage) from EM-DAT also supports this observation (Table 2).…”

“…The evidence presented in the previous section pointed out to the increased aridity and intensification of droughts, especially during the second half of the 20th century (e.g. Dai, 2011;Elagib and Elhang, 2008;Kasei et al, 2010;Ouassou et al, 2007;Manatsa et al, 2008;Touchan et al, 2008Touchan et al, , 2011Richard et al, 2001). Dai (2013) predicted the likelihood of increased droughts and aridity over central and southern Africa during the 21st century.…”

“…Clarke et al, 2012;Cornforth, 2013;Dube and Jury, 2000Green, 1993;Jager et al, 1998;Manatsa et al, 2008;O'Meagher et al, 1998;Richard et al, 2001;Unganai and Kogan, 1998;Vogel et al, 2010), Sahel (western Africa) (e.g. Giannini et al, 2008;Govaerts and Lattanzio, 2008;Kasei et al, 2010;Lebel et al, 2009;Lodoun et al, 2013;Traore and Fontane, 2007;Zeng, 2003), eastern Africa (Horn of Africa) (e.g. Anderson et al, 2012;Syroka and Nucifora, 2010) and northwestern Africa (e.g.…”

Water resources assessment of the Volta River Basin

“…A study by Owusu et al (2008) also concluded that total rainfall input to the Volta Basin has declined since the early 1970s, and this low frequency reduction in annual input has been more intense in the drier Sahelian, unimodal northern basin than in the more humid, bimodal, forest and Guinea savannah South. Kasei et al (2010), who investigated temporal characteristics of meteorological droughts in the Volta Basin, also found that the frequency of droughts has increased from the 1970s onward. The results of a study conducted by McCartney et al (2012) also showed that reductions in rainfall, and increases in temperature and potential evapotranspiration, anticipated in certain climate change scenarios, would affect both river flow and groundwater recharge in the Volta Basin.…”