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The Limpopo River Basin
 Introduction
Geography
Climate and Weather
 Principles of Climate and Weather
 Climate of the Limpopo Basin
 The Regional Climate
 Climatic Patterns
 Climatic Variability
 Climatic Classification
 Water Scarcity
Drought
 Cyclones
 Climate Change
Hydrology
Water Quality
Ecology and Biodiversity
Sub-basin Summaries
 References

 



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Climate of the Limpopo River Basin: Drought  

Drought is the most common and devastating of all environmental affecting the Limpopo basin, with impacts felt in economic, social and environmental terms (Leira et al 2002; FAO 2004).  Variable and erratic rainfall means that the rainy season often does not start when expected and can be episodic, with an entire season’s rainfall occurring in the space of a few days.

Drought Hazard Index

One measure of drought risk is Drought Hazard Index (DHI), which focuses on the probability of crop failure combined with the degree of rainfall variability.  Relative DHI for the Limpopo River basin is illustrated in the map below.  Low DHI indicates a relatively low chance of crop failure, and High indicates an increased probability of crop failure, due mainly to rainfall variability. 

The northern bank of the Limpopo River in Botswana, Zimbabwe and Mozambique, appears to be more susceptible than the northern bank in the South African portion.

Relative Drought Hazard Index for the Limpopo River basin.
Source: Leira et al. 2002
( click to enlarge )

Drought Vulnerability in the Limpopo River basin

IFAD (1996) and Benson et al. (1997) suggest that approximately 60 % of the southern African region is vulnerable to drought, with 30 % highly vulnerable. The Leira et al 2002 for Disaster Preparedness and Response in the Limpopo Basin (Leira et al 2002) suggests that droughts in the region occur every 7 to 11 years.  FAO (2004) states that extreme droughts occur in the basin every 10 to 20 years.

The drought of 1991–92 was the most severe in recent history, affecting the entire southern Africa region including the Limpopo River basin. Although there are strong indications that drought occurs cyclically in southern Africa, it is not yet possible to predict these events with a high degree of certainty. Scientists have discovered a relationship between the El Niño Southern Oscillation (ENSO) and drought in southern Africa, but the correlation is not strong. In terms of hydrological drought, a mixed positive and negative correlation between the warm ENSO events and the quarterly seasonal river runoff in southern African Rivers has been reported (Alemaw and Chaoka 2006).

Recent studies have shown that the occurrence of droughts is closely linked to the see-saw of El-Niño events and La- Niña conditions over southern Africa from December to February.  These changes are illustrated in the diagram below.  In most, but not all cases, El Niño events cause unusually dry and warm conditions in southern Africa during the December to February months, whereas La Niña events bring unusually wet and cool conditions to the region for the same period.

El Niño and La Niña events from December to February in southern Africa.
Source: after INGC/ FEWS NET Mind (2003)
( click to enlarge )

Impacts of Drought

Drought is often seen as simply an agricultural and food supply issue (FAO 2004), but studies have shown (Benson and Clay 1998; Vogel, Laing and Monnik 1999) that the impacts of droughts are far-reaching, with signficant economic, environmental and social impacts. The table below, adapted from Vogel, Laing and Monnik (1999), summarises the impacts of drought in South Africa, but FAO (2004) assert that these issues are relevant to drought vulnerable areas across all of southern Africa.

Impacts of drought in southern Africa.

Primary impacts

Secondary impacts

Social

Disrupted distribution of water resources

Migration, resettlement, conflicts between
water users

Increased quest for water

Increased conflicts between water users

Marginal lands become unsustainable

Poverty, unemployment

Reduced grazing quality and crop yields

Overstocking; reduced quality of living

Employment lay-offs

Reduced or no income

Increased food insecurity

Malnutrition and famine; civil strife and conflict

Increased pollutant concentrations

Public health risks

Inequitable drought relief

Social unrest, distrust

Increased forest and range fires

Increased threat to human and
animal life

Increased urbanization Social pressure,
reduced safety

 

Environmental

Increased damage to natural habitats

Loss of biodiversity

Reduced forest, crop, and range land
productivity

Reduced income and food shortages

Reduced water levels

Lower accessibility to water

Reduced cloud cover

Plant scorching

Increased daytime temperature

Increased fire hazard

Increased evapotranspiration

Crop withering and dying

More dust and sandstorms

Increased soil erosion; increased air
pollution

Decreased soil productivity

Desertification and soil degradation
(topsoil erosion)

Decreased water resources

Lack of water for feeding and drinking

Reduced water quality

More waterborne diseases

Economic

Reduced business with retailers

Increased prices for farming commodities

Food and energy shortages

Drastic price increases; expensive
imports/substitutes

Loss of crops for food and income

Increased expense of buying food, loss of income

Reduction of livestock quality

Sale of livestock at reduced market price

Water scarcity

Increased transport costs

Loss of jobs, income and property

Deepening poverty; increased unemployment

Less income from tourism and recreation

Increased capital shortfall

Forced financial loans

Increased debt; increased credit risk
for financial institutions

Source: FAO 2004, adapted from Vogel, Laing and Monnik (1999)

 



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