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Climate change and water – connecting the dots

Climate change and water – connecting the dots

Jun 1, 2013

The world’s climate is an extremely complex system, writes Robbie Louw, a director of Promethium Carbon. Attempts to understand it have been based on a study of past experiences and building models to reflect what was observed. 

Climate change, however, presents a discontinuity in the way the weather has behaved. It becomes almost impossible to predict what will happen in the future based on past observations. Climate change has turned the future climate of the planet into uncharted territory.

The most common way of predicting the impact of climate change on future weather patterns is the use of Global Circulation Models (GCM). These models are based on dividing the world’s atmosphere into large blocks and mathematically calculating a number of variables for each block.

This takes into consideration the interaction of these variables on the boundaries between these blocks. They take inputs such as solar radiation and greenhouse gas emissions, apply the laws of physics and chemistry, and produce outputs such as temperature and rainfall.

The outcome of the GCM models is used to predict climate conditions up to the end of this century. In most areas worldwide, there are clear indications of increasing or decreasing precipitation or rainfall patterns. These changes are often presented in graphs showing gradual changes over time.

Interpretation of these results can easily be made in a way that indicates that the water impact of climate changes can be manageable. In one example, an official in the Western Cape concluded that climate change is not a problem to the Western Cape because the predicted reduction in rainfall meant that only one more dam is needed in the province by 2050.

Consumers are, however, seeing a different face of climate change in reality. What is not that clear from GCM models is the increase in extreme weather events. As far as rainfall is concerned, many areas of the country are showing stable total annual rainfall figures. Statistically however users observe significant reductions in the amount of rainfall days and a corresponding increase in the intensity of rainfall during wet periods.

The impact of these observations is that users need to look differently at water security and management than in the past. Variability in weather systems means that users will see more dry periods, more droughts, more wet periods and more floods.

Consumers must not be fooled into thinking that the water impact of climate change is a local impact. Take for example the situation in the USA. During 2011, floods in the Mississippi River caused major disruptions and led to large insurance claims. During 2012 the situation reversed to the point that barge traffic in the river has stopped due to the low water level.

The drought has also had a major impact on the agricultural crop of the US. The impact is so big that the international maize price rose by more than 40% over a six week period. Recent research has linked international rising food prices in 2008 and 2011 to causing events of social unrest in North Africa and the Middle East. It is no coincidence that the labour unrest in South Africa started at the same time as this rapid increase in food prices.

The increase in variability in precipitation patterns has serious implications for planning in water supply and management. Users need to plan for both very dry and very wet conditions. Dry conditions will require more storage and has specific impacts on water quality. Wet periods, on the other hand, will put the infrastructure on risk of floods and has another set of challenges with respect to the management of the quality.

Climate change adaptation presents a unique set of challenges to the water planning requirements of South Africa. Users can never say exactly what lies beyond the horizon. The rules of the past do not apply anymore and consumers need to think creatively about their future.

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