Climate change impacts weather and changes in weather is
the single largest factor influencing fluctuations in water
demand. Therefore, it would be natural to expect climate
change to impact on demand. However, most climate
models typically do not produce a single forecast, but rather
produce an ensemble of equally likely scenarios. The high
variation between these projections lead to different
estimates of demand, leaving decision makers with the task
of selecting one projection to use. On the other hand, there
exists no scientific way of doing this, as they are all equally
likely, meaning selecting one would be as good as the other.
This paper describes the way Sydney Water approached the
problem, which was to use a two-staged process. This
meant developing a mathematical solution to integrate the
output of global models with Sydney Water’s demand
forecasting model, and developing an approach based on
the risk tolerance thresholds of the decision it informs to
select the most appropriate output from a climate model.
Figure 1. Annual Demand.
Red CCMA3.1, Green CSIRO-MK 3.0, Blue ECHAM5, Brown-MIRCO3.2 (reproduced from Barker et al (2018b)
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Last updated 23 January 2018