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.

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Purpose: New innovative ways of communicating agrometeorological information are needed to help farmers, especially subsistence/small-scale farmers, to cope with the high climate variability experienced in most parts of southern Africa. Design/methodology/approach: The article introduces an early warning system for farmers. It utilizes short messaging system (SMS) to convey weather information and basic agronomic advice to 12 small-scale farmers in Makhado Municipality, Limpopo Province, South Africa. This case study demonstrates the usefulness of incorporating weather information on day-to-day farm management activities. Coded rainfall forecasts for light (0Á5mm), medium (5Á20mm) and heavy rainfall (20mm) were distributed three times a week to individual farmers and extension officers. Accompanying the forecasts were possible agricultural activities for the week. Findings: Extensive training of the farmers and extension officers is a pre-requisite for full comprehension of the coded SMS early warning system. The recommendations on farming conditions are not always adhered to due to farmers' indigenous knowledge and other factors like access to labour. Practical implications: Weather and climate information distributed to farmers has the potential to add value to the farming methods employed, hence positively impacting on rural food security. Originality/value: The article demonstrates that agrometeorological information must be packaged in such a way as to assist farmers and should be disseminated timeously and appropriately to maximize its utility or adoption.

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