Well, Jim. The water has to come from somewhere. If there's a big head of water, it needs to be taken from a good way above the site of the generator. The smaller the flow, the bigger the head needed for a useful output. So either the user of the power needs to own all the land from the water take off point to the generator, or he needs to have kind neighbours who will let him cross their land with his pipe. They also need to be forebearing about the loss of water in their bit of the stream, which might also damage local woldlife (stet, I like that word).

It was in fact such a scheme that we looked at for our village, and the stream is just too small for worthwhile power, even if we could get everyone to agree. And this stream ran at least 4 mills in the 18th century, which just goes to show how our demand for power has changed. The mills can't have been more than a few hundred watts each (though perhaps mining and opencast working has disrupted the water flows so the stream is smaller).