Change Detection in Land Degradation and Environmental Hazards Sensitivity in Some Soils of Siwa Oasis

SOME selected soils of Siwa Oasis were characterized, classified and …. evaluated for land degradation. Soil samples from pedogenic horizons were analyzed. The total investigated area is 126166.7 (529.9 km²). The study revealed seven major physiographic units in the area: sand sheets, hummocks, alkali flats, overflow basins, decantation basins, mountain footslopes and hill footslopes. One soil profile was taken from each of the physiographic units. Since cultivation started in Siwa, several problems have arisen including wind erosion, soil salinity, sodicity, drought, water-logging and expansion of the water bodies. Wind erosion hazard status ranged from none to very severe hazards. Salinity hazard ranged from slight to very severe hazards, 85.70% of the total area showed increased salinity (27610.01 ha). Sodicity hazards ranged from slight to very severe, 71.31 % of the total area showed increased sodicity (22970.05ha). Waterlogging hazards ranged from moderate to severe; 70.60 % of the total area showed a rise in water table level (22740.05 ha). There are changes between land cover feature in between 1999 and year 2014. The increment of agricultural area with 14616 ha. Enlargement of area of lakes and ponds increased by 3190 ha.  The soils which altered to salinity in area 94 ha and the area of wetlands decreased 187 ha.