ENB:04:11 [Next] . [Previous] . [Contents]


Habib Zebidi, Programme Specialist in Hydrology, Division of Water Sciences, discussed the effects of desertification on surface water and groundwater systems and on water availability and quality. He began with definitions of desertification and noted the fact that there are 6,100 million hectares of arid lands, home to one-fifth of the world's population, with Africa, the Arabian Peninsula and Australia as the regions most affected. He focussed on the characteristics of these areas. The first characteristic is that rainfall is limited and irregular, with the greatest variability of rainfall found in arid and semi-arid land. High sediment transport is a feature of surface flow, due to run-off fluctuations. Another characteristic is that groundwater is often found in these regions. The availability of water depends on the type of catchment system used. He noted the effects of desertification on groundwater systems. He also discussed surface run-off from flood waters and rain and the collection of this water with dams. He concluded by noting the potential for conflict over water resources in the event of drought and the need for national policies to distribute scare water resources. He also noted the possibilities of more violent flash floods due to the soil's lower retention capacity to absorb irregular rainfall.