Anticipating Climate Uncertainty

Abstract

‘Climate’ has always been variable, as it refers to the long-term prevailing weather conditions while ‘weather’ refers to the place-specific atmospheric state at a given point in time. A change in climate typically takes many years to become apparent. Climate change introduces a host of new unknowns in water security, such as the potential rate of change in rainfall and temperature. While it is highly unlikely that weather patterns change completely and permanently over a couple of seasons, the possibility cannot be entirely ruled out. Rainfed dams provide not only the least costly water supply source, but also one in which the Western Cape’s water authorities have decades of management experience. A plethora of information is available on water supply in the region, including extensive rainfall records. The system design historically provided for sufficient security and a 98% level of assurance of supply, all other things being equal. But the uncertainties introduced by climate change have resulted in reduced trust in reconciling demand and supply. Suppressed demand also limits the potential to impose restrictions in future droughts. As long as carbon emissions continue to increase unabated, the impact of climate change on water security will grow and this risk will need to be actively managed.

Thousands have lived without love, not one without water

–WH Auden