I once successfully cached a gallon or so of water for a year at a remote location that was inaccessible to bears and larger critters but that featured plenty of rats, squirrels, etc. I used a recycled plastic bottle, storing it away from sunlight, but above ground.

Returning a year later, the water was quite palatable. I would recommend using more than one container for your stash in case of leakage. I am positive my stash froze several times over a fairly hard winter.