Adaptation of water resources management to climate change

CLIMATE CHANGE AND VULNERABILITY IN SOUTHERN AFRICAAt the Regional Dialogue on Climate Change, Water and Wetlands in Southern Africa, held in November2002, participants discussed the region’s high sensitivity to current climate variability, particularly drought.Managing water scarcity is the predominant challenge. Long-term observations suggest that temperatureshave increased 0.5°C over the past 100 years, that the seasonality of rainfall is changing, and that annualflows of some rivers such as the Zambezi are declining. Droughts appear to be increasing in frequency andseverity.At the same time, the region is starting to experience intense flooding, a phenomenon that is inconsistentwith the long-term climate of the region. Between 1999 and 2002, the region was hit by a series of intenserainfall episodes including tropical cyclone Connie that produced the worst flood in 50 years. Two weeks later,tropical cyclone Elaine further inundated the region, causing extensive flooding in the Limpopo River Basin.Such an event is supposed to occur only once every thousand years. The overall conclusion is that SouthernAfrica is facing more and more climate variability.These changes are consistent with the climate change projections of the Intergovernmental Panel on ClimateChange. With a projected warming of 1.7°C over the next one hundred years, rainfall in the region is expectedto decrease by 5 to 20% in all the major river basins. Increases in evapo-transpiration are expected to resultin losses of run-off in all the major river basins of the region. The most severe impact are expected in theRuvuma River Basin in Tanzania and Mozambique and the Zambezi River Basin, whose resources are sharedby eight countries - Angola, Botswana, Malawi, Mozambique, Namibia, Tanzania, Zambia and Zimbabwe.With demand for water in the region expected to increase more than 90% by 2020, meeting these needswill require a major investment in resource development and management. When the current and projectedtrends of climate change are added to the equation, the situation appears daunting.its Third Assessment Report published in 2001, the Panel concluded that annual precipitation wouldincrease in high and mid-latitudes and most equatorial regions, but would generally decrease inthe subtropics. The Panel also projected alterations to the seasonal distribution of precipitation,with the likelihood of more rain, less snow, and higher evaporation as temperatures increase.Rainfall intensity and variability is expected to increase in many areas.The impactsThese changes are already having an effect. In many places mountain glaciers are shrinking,and mountain snow cover is decreasing. This is likely to decrease the volume of spring and summerflow in rivers fed by snow and ice melt, and increase the winter flows. River basins where this ishappening include the Rhine and the Rhone in Europe. 3 In tropical regions, such as the Andes andMount Kilimanjaro, a dramatic melting of glaciers has already occurred over recent decades andis likely to affect downstream livelihoods sharply. Since water is more in demand during the growing6