Drought and desertification

Mechanisms of destruction

Lack of water affects health of crops, trees, livestock, humans: land becomes subject to erosion and flooding; effects are gradual but if not checked, crops and trees and livestock die, people lose livelihood, are forced to move, and may starve if aid is not provided: then buildings and infrastructure are abandoned and decay and cultural artifacts are lost.

Parameters of severity

Rainfall level, rainfall deficit (mm), period of drought; extent of loss of soil cover, extent of desert climatic zone.

Causes

Drought mainly caused by short-term periodic fluctuations in rainfall level; possibly by long-term climatic changes; desertification caused by loss of vegetation and subsequent land erosion caused by combination of drought, overgrazing and poor land management.

Hazard assessment and mapping techniques

Rainfall map indicating areas of desert and semi-desert climatic conditions; mapping of erosion rates and desertification.

Potential for reducing hazard

Drought is uncontrollable; desertification can be reduced by improved land management practices, forest management, infiltration dams, irrigation and range management (control of land use and animal grazing patterns).

Onset and warning

Slow onset, period of years, many warnings by rainfall levels, river, well and reservoir levels, human and animal health indicators. Onset of severe drought, causes death of livestock, rise in infant mortality, migration.

Elements most at risk

Crops and forests; human and animal health, all economic activities dependent on continuous water supply; entire human settlements if drought is prolonged.

Main mitigation strategies

Water rationing; conserving or replacing failing water supply by watershed management, construction of dams, pipelines or aqueducts; conserving soil and reducing erosion rates by checking dams, levelling, planting, herd management; reducing firewood cutting by improved fuel stoves, introduction of flexible farming and cropping patterns; population control; education and training programs.

Community participation

Construction of check dams, reservoirs, wells, water tanks, planting and afforestation; changing cropping patterns; introducing water conservation policies; changing livestock management practices; development of alternative non-agricultural industries.