Introduction

The drought which has ravaged most Sahelian countries during the 1970 and 1980 decades is unprecedented in recent records. The objective of this chapter is to compare the recent sequence of low Nile floods with past historical evidence of droughts in Egypt; an attempt to put this century's flows in an historical context.

The major question facing engineers, planners and politicians alike is whether this drought will continue; whether this persistence of low rainfall years in the Sahel is just further evidence of the natural ‘Hurst Phenomena’, whereby sequences of low Nile flows and large Nile floods tend to occur together, or whether it is man-made, possibly a manifestation of global warming representing a permanent or semi-permanent change in the general circulation of the atmosphere influencing the continental climate of Africa.

The Sahel is a region with steep rainfall gradients with annual rainfall decreasing rapidly from 600 mm to less than 200 mm in a few hundred kilometres. Slight shifts in the circulation can cause major problems which would go unnoticed in other climatic zones.

The Nile is the birth place of hydrology. No other river provides such a wealth of information. Available records reach back to before 3000 BC. The heavy dependence of Egyptian civilisation on the size of Nile floods, leading to years of famine or plenty, and the ability of Egyptian dynastic society to record evidence for posterity provides a unique opportunity to investigate historical river flows.