Independent: As the world faces the incontrovertible truth of climate change, so politicians search for ways of protecting sources of water. In the UK, people could be forgiven for wondering why this is such a big issue in a country which is, after all, surrounded by the stuff. The problem, of course, is that sea water is as useful as a chocolate teapot unless the salt is extracted first. Indeed, President Kennedy was once quoted as saying: “If we could ever competitively, at a cheap rate, get fresh …