We're in the mountains of northern Vermont so a similar climate to where you probably are in Maine.
We have running spring water which use 1" black plastic pipe to go from one trough to another down the side of the mountain. By having the troughs in series it requires little water to flow. Put the troughs in a slight greenhouse or den and it provides a warmer microclimate. Sink a 65 gallon barrel deep in the ground to make the trough and it gets earth heat.
I would love to heat the water, the pigs and chickens will drink more if it is warm, but it is not practical to do. I've come up with all sorts of schemes for solar heating it but not yet found perfection.
If you can't having a running spring then I would hand carry the water or use a hose to feed their water trough. I would suggest minimizing the use of electricity, pumps and auto-valves. These are all too failure prone in our harsh winters. I do have heat tape wrapped on the valves of our big whey tanks inside an insulating sleeve but even with that they can freeze up in the worst weather. Beware that in very cold weather valves and handles break easily. See:
site:sugarmtnfarm.com winter water - Google Search
site:sugarmtnfarm.com heat tape - Google Search
I would also recommend having two, count them two (2), sources of water and checking them twice a day ideally.
Cheers,
-Walter Jeffries
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont
Sugar Mountain Farm | All Natural Pastured Pigs, Poultry, Sheep, Dogs and Kids in the mountains of Vermont