Dehydration can cause impaction colics. Horses should drink at least a gallon of water per 100 pounds of body weight. This translates into about 10 gallons of water per day for an average-sized horse just hanging around the pasture. If your horse is exercising hard on a humid summer day, she could need 4 times that amount.
Dehydration-caused impaction colic is more common in winter because horses don't like ice-cold water. Use a stock tank heater
When traveling, bring water from home if possible. Horses can be picky about strange water and, combined with the stress of travel, can set the stage for colic.
Know the signs and symptoms of equine dehydration. In mild cases, careful cool down and equine electrolyte supplementation