I don't think you need to store more water than usual. Just stay alert as when the switch will happen...The work is taking place over 4 months, just checked their website and they plan to start on Tuesday 7th Feb and end some time in June. It's replacing an old pipe but doesn't say exactly when the switchover from old to new pipe will be.
In any case, Stop using water for a while as soon as dirt shows-up. Ask your neighbours hows their supply is going after? then flush your home network.
The time I had the most aquariums in my life was when I had the poorest water supply imaginable. and all these tanks survived January 1998 North American ice storm. 3 weeks without power. All fishes survived with nearly no food given, mini water changes, no filtration and I had to re-cycle all tanks "fish in" afterwards. Also nearly all the plants melted.