Agricultural Drought Indices - US Department of Agriculture

Agricultural Drought Indices in the
Greater Horn of Africa (GHA) Countries
P.A. Omondi
IGAD Climate Prediction and Applications Centre (ICPAC), Nairobi, Kenya
Abstract
This chapter highlights some of the practical applications of agricultural drought monitoring over
the Greater Horn of Africa based on the experiences gained and lessons learned on regional and
national scales. The paper draws upon the longstanding and sustained efforts by the IGAD
Climate Prediction and Applications Centre (ICPAC) with the drought monitoring system that has
been in operation since 1989, when the Centre was established. ICPAC is a specialized institution
of the Intergovernmental Authority for Development (IGAD), dealing in climate applications and
disaster-related issues in the Greater Horn of Africa region. This drought monitoring system helps
in detecting, early and easily, where and when a drought has occurred, and how the drought
situation is slowly creeping into the sub-region. The onset and withdrawal dates of a drought can
be defined clearly by this system. Also, it is useful for detecting changes in the rainfall regime.
The Standardized Precipitation Index (SPI), which is an intensive measure that considers rainfall
accumulation with the weighting function of time, is used on operational basis in the IGAD subregion.
Introduction
The Horn of Africa is prone to extreme climatic events such as droughts and floods, with severe
negative impacts on the key socio-economic sectors. Natural resources (such as water,
vegetation, wildlife, general flora and fauna, and biodiversity) that determine the livelihood of
communities are impacted by temperature and rainfall. Thus climate variability has far-reaching
implications for the livelihoods of most of the rural communities in the region. The IPCC Fourth
Assessment Report (IPCC 2007a) has shown that any change in climate will have more adverse
socio-economic impacts in Africa than in other parts of the world, because of the vulnerability of
society and the sensitivity of the environment. Hazards such as floods, droughts, desertification,
locust infestation, infectious diseases, epidemics, and resources-based armed conflicts continue to
inflict loss of property, injury, death, food insecurity, health hazards, environmental degradation,
poor economic performance, displacement of people, environmental refugees, and other miseries.
In comparison to weather-related natural hazards such as floods and windstorm events, droughts
develop slowly (Wilhite 2000). However, they are often more widespread and cause more
extensive damage to the Greater Horn of Africa’s population than any other hazard. Climate
change is projected to increase the risk of drought over many parts of Africa in the 21st century
(IPCC 2007b), partly through altering the frequency of El Niño events. Drought impacts are often
aggravated by poor policies, or, alternatively, conflicts over limited water, food, and grazing
resources. Therefore, drought particularly affects societies that have little resilience and
preparedness. Here, the effects can linger for years after the drought event.
The Intergovernmental Authority on Development (IGAD) Climate Prediction and Applications
Centre (ICPAC) is a specialized institution of the seven IGAD countries (Figure 1a) in the Greater
Horn of Africa plus Tanzania, Burundi, and Rwanda (Figure 1b). ICPAC is charged with the
responsibility of climate monitoring, prediction, early warning, and applications for the reduction of
climate-related risks in its member countries. This is in support of specific sector applications for
the mitigation of climate variability impacts, alleviation of poverty, management of the environment,
and sustainable development over the IGAD sub-region.
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