10. Run-of-river power (Water current creates electric current)

We all know water wheels on mills. People have been using the energy of flowing water for a very long time. Since the invention of turbines connected with power generators, flowing water can also be used to generate electricity.

Water power, people and fish

Make a guess: how many households in the district of Lörrach can be powered with electricity from run-of-river power stations?
And what are the consequences of this use of water power for fish, such as salmon or trout, which have to swim up-river once a year?