You don't want to keep water in the coop in the winter for one reason... FROSTBITE. Putting extra moisture in the coops is the exact opposite of what you want, plenty of humidity builds up from the birds respiration alone. Ventilations would be extremely important for those who keep water in the coop. Chickens eat about 1/4 pound to 1/2 pound of feed each per day, in the winter they eat more because they need the calories to burn for warmth, they are also finding less grass, bugs and things to eat on their own.
I've kept water in the coop for 23 years & never had a problem. Ventilation is the key. How can my birds get up at 2 a.m. and have no water? Can't understand food or water in the run. I like to keep it there away from the critters. Also you won't usually get poop in your water if your coop is large enough to house birds & their food & water.