On the causes and control of the waterlogging phenomenon, Siwa Oasis, northern Western Desert, Egypt

Siwa Oasis (1000 km(2)) is today suffering an excessive rise in the subsoil water levels. In 1962-1977, the rate of rise was 1.33 cm year(-1) while in 1977-1990 it measured 4.6 cm year(-1). Consequently, the fertile soils are subjected to deterioration and salinization. In the present study, the waterlogging phenomenon is comprehensively evaluated through hydrogeologic survey, shallow ground-water drilling, field measurements and laboratory investigations. The causative factors are discussed. Among these, the non-manageable agricultural expansion, excess irrigation water and deficiency of a drainage system are the most important. To overcome this serious problem a new agricultural strategy is recommended. This strategy is entirely dependent on reliable water management plans. To control the water balance in Siwa, the following are suggested: (i) full utilization of the naturally flowing water, particularly through winter cultivations; (ii) prevention of new ground-water drilling and control water flow from old wells; (iii) usage of drainage water for afforestation projects; (iv) introduction of new plant species having high capability to consume water (biological drainage); and (v) improvement of the present drainage system. (C) 1997 Academic Press Limited.