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Sharp drop

It is widely accepted nowadays that climate change affects water supply. After all, it plays havoc with rainy seasons, melts glaciers, and causes drought in normally humid regions. 

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 (forthcoming), Water Resources Allocation: Sharing Risks and Opportunities, OECD Publishing.

©OECD Observer No 302 April 2015

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7th World Water Forum 2015