When we bought our first home, the builder neglected to mention that it was built upon a river. Of course a river at the bottom of a garden is a charming sight. Something that seeps up through the cellar is less attractive, and so, in due course, the builder was called back to install a sump pump. Our young sons were fascinated by the hole in the basement floor and the coppery water that flowed at the bottom and wondered whether, with the help of makeshift fishing poles, it could yield some fish.