Self Sufficiency: hydro = license requried?

I was talking to somebody the other day and they said that if you are using a little hydro turbine on a stream or a river, you need a license because you are "diverting the flow". How true is this? This is in the UK, but still interested to hear from others. I know you need some kind of license to discharge stuff into a water course (e.g. waste).

 

no sure how things are in the UK but almost universally the diverting of a waterway is a no no without some sort of approval

 

Bit surprised really, nobody seems to have mentioned it in any of the articles I've look at online, and a few local peeps were in two minds about it.

Ultimatly though if a communal dwelling doesn't have planning permission then a license for hooking up a hydro device probably isn't going to be high on the list for that sort of commune!