But a common mistake by policymakers is to assume that the impact of climate change on water supply will be gradual, whereas sudden step-changes can occur. For instance, reductions in rainfall can produce even sharper reductions in stream flow.
A study in Jarrahdale, Western Australia, showed that a 14% reduction in rainfall resulted in 48% less stream inflow, and a 20% reduction resulted in 66% less stream inflow. And because sufficient base flows were required before water could be extracted, a small reduction in mean rainfall ultimately led to a massive and disproportionate impact on the volume of water available for use.
©OECD Observer No 302 April 2015