The vast area of swamp and wetlands of the Southern Sudan, the Sudd, absorbs and dissipates by evaporation about half the inflow from the upper catchment of the White Nile. Ways and means of reducing these losses by canalisation have been under engineering investigation since the beginning of the twentieth century, the objective being to provide additional water for irrigation and hydro-electric power in Egypt and the northern Sudan. Construction of the Jonglei Canal began in 1977; at the end of 1983 it was halted by civil war, 260 kilometre from its outfall and 100 kilometres short of...