Rainfall and Water Resources Variability in Sub-Saharan Africa during the Twentieth Century

Abstract

River basin rainfall series and extensive river flow records are used to characterize and improve understanding of spatial and temporal variability in sub-Saharan African water resources during the last century. Nine major international river basins were chosen for examination primarily for their extensive, good quality flow records. A range of statistical descriptors highlight the substantial variability in rainfall and river flows [e.g., differences in rainfall (flows) of up to −14% (−51%) between 1931–60 and 1961–90 in West Africa], the marked regional differences, and the modest intraregional differences. On decadal time scales, sub-Saharan Africa exhibits drying across the Sahel after the early 1970s, relative stability punctuated by extreme wet years in East Africa, and periodic behavior underlying high interannual variability in southern Africa. Central Africa shows very modest decadal variability, with some similarities to the Sahel in the adjoining basins. No consistent signals in rainfall and river flows emerge across the whole of the region. An analysis of rainfall–runoff relationships reveals varying behavior including strong but nonstationary relationships (particularly in West Africa); many basins with marked variations (temporal and spatial) in strength; weak, almost random behavior (particularly in southern Africa); and very few strong, temporally stable relationships. Twenty-year running correlations between rainfall and river flow tend to be higher during periods of greater rainfall station density; however, there are situations in which weak (strong) relationships exist even with reasonable (poor) station coverage. The authors conclude for sub-Saharan Africa that robust identification and attribution of hydrological change is severely limited by data availability, conflicting behavior across basins/regions, low signal-to-noise ratios, sometimes weak rainfall–runoff relationships, and limited quantification of the magnitude and effects of land use change.

Climate and southern Africa's water–energy–food nexus

“…Multiyear rainfall variability in southern Africa is higher than in many other parts of the world 31,32 . Interannual variability, expressed as the coefficient of variation (COV), is not particularly high on national scales: <20% for most countries, except for Botswana and Namibia, the driest two countries (Fig.…”

Adaptation to climate change in international river basins in Africa: a review / Adaptation au changement climatique dans les bassins fluviaux internationaux en Afrique: une revue

“…Per capita indicators of water scarcity tend to be lower in areas with high population density and high water use. Many of these areas also experience high inter-annual variability, and surface flows show high sensitivity to climatic perturbations (Vörösmarty et al, 2005;Conway et al, 2009). It is these areas (much of southern and northern Africa) where climate change is most likely to exacerbate the challenge of achieving sustainable and equitable water resource management.…”

“…In addition much of the groundwater resources are located in an estimated 40 aquifer systems that are shared by several countries (Scheumann & Alker, 2009). The hydrological monitoring network for surface water in Africa is more developed than that for groundwater, but has generally sparse coverage and short fragmentary records, although some reliable long records exist for parts of the Nile basin and on major rivers in West Africa (Conway et al, 2009). Soil water is not generally monitored.…”

“…The high levels of variability in rainfall and river flows in Africa across a range of spatial and temporal scales have important consequences for the management of water resource systems (Peel et al, 2004;Conway et al, 2009). Throughout Africa, this variability brings significant implications for society and causes widespread acute human suffering and economic damage .…”

Análisis de series temporales de precipitación y vegetación para la detección de anomalías en la producción de alimentos en el Cuerno de África. El caso de Lower Shabelle (Somalia)

“…Según la bibliografía consultada, actualmente los recursos naturales del Cuerno de África están sufriendo una continua degradación como consecuencia de las actividades humanas y del cambio climático (Kassahun et al, 2008;Conway et al, 2009;Flintan et al, 2014;Dutra et al, 2013). Además, en el futuro próximo la situación va a continuar agravándose, dado que es una zona sin las medidas de adaptación suficientes a los efectos generados por el cambio climático.…”