Its widely known that you can lead a horse to water but you can't make them drink.  This time of year, water intake by your horse can be overlooked.  In the summer, everyone automatically thinks of water because the heat of the day makes us all thirsty.  In the winter, lack of water intake is a leading cause of colic.  As the temperature drops, many horses don't drink as much water as they need.

Supplementing your horse's diet with salt will increase their water consumption.  You can either provide them with a salt block or add it to their daily grain.