Can canals be used as reservoirs?

>Here in Manchester the Ashton canal runs within a few hundred metres of Audenshaw reservoir. I'm in Stockport. Current canal closures in Greater Manchester: **Ashton Canal from Lock 1 in Manchester city centre to Lock 18 in Droylsden** Rochdale Canal from Lock 92 in Manchester city centre to Lock 48 in Littleborough The Marple and Bosley lock flights on the Peak Forest Canal The Huddersfield Narrow Canal from Lock 1 West in Ashton-under-Lyne to Lock 1 East in Huddersfield, West Yorkshire These are all due to lack of water. This is one of the flaws in your problem: the canals and their balancing ponds, reservoirs etc are just as reliant on rain as the other stuff. Another flaw is the canals and their associated network aren't linked with the domestic/commercial network: you identify one place where they're close, and there are plenty of others, but even when we had the Green Goddesses to bridge that gap we would not have had anywhere near enough (a few hundred metres is actually a vast amount of water too). Another issue what do you do about people affected by the canals being drained? I applaud the idea and have supported a 'national water grid' as a concept for years (I've never thought too much about how it would work). Canals have a role to play in the UK more generally but I don't think this would work in the way you envisage with the current network, although I could envision the development of a National Water Grid that involved new canals.