I know this well, it runs within feet of my property. Today, I thought I would have a look at the other end, as I was passing, it would be rude not to.
It runs from Llyn Alwen in North Wales to Birkenhead
As it says:
It's not very wide, but quite high - the lake was showing 86 feet of water
Don't ask what the architectural style of the Dam is (Birkenonic Modern ?)
I think it's quite elegant, especially from the lake side, with the elegant overflow stonework
Of note, are the two concrete cylinders either side, made of what looks like MoD concrete
Possibly, Light AA Gun mounts, or to hold some cables up with camoflage netting during WW2 ?
I also turned up a booklet on the system, from ages ago