The idea that a megalitre of water is the amount in an Olympic swimming pool has been repeated endlessly. Here’s what happened when someone actually checked.

Leaving aside the fact that Olympic swimming pools vary in depth and width, I find the metaphor almost useless. The old acre-foot (about 1.1 ML) at least gave an idea of how a given volume of water might be used in practice. You can do the same the fact that 1ML will supply 10cm of irrigation water to 1 hectare of land.

While I’m on this topic, my piece in today’s Fin (subscription required) is about the Murray, but regular readers will have already seen most of it in bits and pieces on the blog. Thanks to all who helped me sort out my thoughts on this