If You Do Have Electricity
If you DO have electricity to your coop and run area, you have a few more options. Heated waterer bases are available commercially, but they are expensive and don't seem to last more than one or two seasons.
There are tons of instructions online on how to make your own heated base out of a cookie tin, but the waterer can easily slide off the slick metal surface of the tin. Even scarier, we've had several people tell us theirs caught on fire, and one guy, in the comments below this post actually had a chicken electrocuted. Not good. And anyway, I prefer to store cookies in my cookie tins! So just say NO to the DIY cookie tin heater. Instead why not try....
Lightbulb in a Cinder Block - This idea is brilliant. You clamp a light bulb inside a cinder block and cover it with a stepping stone. Your waterer sets on top of it. The rough surface prevents slipping and this couldn't be easier or safer in your run in winter.