I dunno. Water doesn't sound right for supplying water to a city. You can water an animal or your lawn or the crops, but it doesn't really work for anything else. I say just go with my original suggestion. You don't always need a single word for some concept. And coming up with some word special for the occasion just doesn't work if you expect your language to communicate. Use it and someone is just going to ask you what it means. You'll probably say, "supply water to the city."