Top tides

Various points in the Bay of Fundy, Canada, claim to have the world's highest tides. This undignified squabble is mostly about dragging in tourists. My favourite river, the Mersey in England, has a tidal range of about 4m, which is pretty spectacular. Anywhere in Fundy has a range of over 12m, which would be a worthwhile sight, whatever the warring town-ships claim.

There is little doubt that the biggest total tidal range – the variation in water level from the lowest low tide to the highest high – in the Bay of Fundy is about 15m.This beats a number of close contenders including Bristol on the River Severn in the UK (14.6m), Mont St Michel in France (12.3m). Puerto Gallegos in Argentina (13.2m) and Bhaunagan, India (12.2m).

Also noteworthy is Derby, Western Australia, which is home to the biggest tides in Oz (11.8m), and whose town website is the source of these numbers (visit www.derbytourism.com.au and choose “Tides'from the “Derby” menu). There is so much energy in tides that it seems a shame not to capture and use some of it. A tidal power station at La Ranсe in France has been doing so for thirty years, and there are others around the world. Some very large tidal power schemes, such as a plan for a massive barrier across the Severn between England and Wales, would have very severe environmental effects and have yet to happen, but there is fresh interest in the tides as a form of renewable solar and lunar energy.