The Changing Rainfall Resources of Sudan

Rainfall is one of the key resources of Sudan. This requires detailed measurement and monitoring of rainfall availability to enable its effective management. The changing nature of rainfall supply in Sudan during the twentieth century is examined using historical annual, monthly and daily data back to 1900. Rainfall depletion has been most severe in semi-arid central Sudan where between 1921-50 and 1956-85 annual rainfall has declined by 15 per cent, the length of the wet season has contracted by three weeks, and rainfall zones have migrated southwards by between 50 km and 100 km. This depletion has been due more to a reduction in the frequency of rain events rather than to a reduced rainfall yield per rain event. Effective resource management requires timely and accurate information about the current and future state of the resource. Three aspects of Sudan rainfall information availability are discussed in the light of recent developments: historical archived data, automatic, near real-time rainfall monitoring, and both seasonal and decadal rainfall forecasting. The measurement and monitoring of rainfall are not ends in themselves and it is important that such information is used in the climate management process.