We visited Loch Ken in southern Scotland. It's 9 miles long and part of it is a bird reserve.
A display board on the reserve explained that the loch was created by damming in 1937.
The dam actually looked more like a weir. I seemed to be possible to raise and lower it. You'll have to look hard to spot the top of the structure in this picture. The display board said that the actual power station fed by the loch is at Tongland. This is quite a few miles away. Wikipedia says that it is part of the Galloway Hydro scheme from the 1930s. They did it then because the National Grid had just been invented. Before that, all electricity generation was local; every town had its own power station and there would not have been the population to justify a scheme like this in Galloway. The power station is quoted at 33MW and it says that the water falls 106 feet. It also claims that these power stations were some of the least costly ever built in terms of £ per kW. http://en.wikipedia.org/wiki/Galloway_Hydro_Electric_Scheme
