1 Combating desert encroachment by guiding people, wind and sand

In central Sudan, desert encroachment is a creeping phenomena of which it is even not monitored whether it fluctuates in intensity with the expansion and retraction of the Sahara that has been most recently claimed to occur. The primary source of the sand that invades irrigation canals and degrades cropland is the Libyan desert. The endangered land parts are at the edges of the more than one million hectares Gezira irrigation scheme between the White Nile and the Blue Nile south of Khartoum, where they merge into the Nile flowing to Egypt. Our soil surveys and interpretations of historical remote sensing pictures revealed an average desertification rate in the secondary source area of something as 35 km/year between 1970 and 1985. Our sand catcher measurements indicated a sand flow of something like 50.000 kg over a width of 100 m in one month at the height of the season. The origin of the irrigation water is the Blue Nile with its sources mainly on the Ethiopian plateau. The main protection against the sand blown into the area from the south-west, the desertified area of north Kordofan, is the White Nile, or so we thought