I keep all my water in old orange juice containers (1500litre) which as it happens sit over what used to be a reservoir for the farm below me. The reservoir is a hollow concrete box of around 6metres cube and the tanks sit over the open top of this. The theory is, and this can be applied almost anywhere, is that the air temperature in a space over the ground is never below 5C so therefore the tanks should never freeze. Now there is something that I haven’t been able to prove, since we are getting warmer winters here in Devon nothing freezes for more than a day and so the volume of water never gets to drop very far any way. So in fact my study here is of little use as to prove anything. However I am confident that air allowed to rise from a rock strata will maintain temperatures above freezing so long as you are not above permafrost. So simply put, build an insulated container over a rock fissure and you should be drinking ice cold fresh water all year round. My water is fine and all I have done is as I said above and then wrapped all the pipework in plastic sheet filled with rockwool insulation which I was given. So far so good. Three winters with no freezing. Mind you we have a few chilly nights to come, but I have complete faith.
Whether this will help I don’t know but you could easily set up a trial with a max min thermometer and a box.