Your dog needs to drink plenty of water for the same reasons we do - simple biology. Sometimes he's just thirsty and needs hydration, but just as importantly, your dog needs water to properly digest his food.
Without proper water, your dog's digestive system will be stressed and he will be highly uncomfortable.
Water should be made available to your dog at all times of the day and should be kept fresh and not left out in the sun too long. Warm water does not help to cool down a dog who's essentially wearing a fur coat. Keep an eye on the water level and make sure there is plenty to drink, especially if you have an active dog who may need a little extra after a good run.
Dogs have a finely tuned sense of knowing when they need water and how much water to drink. Therefore, there is no reason to worry about your dog over drinking as this is extremely rare.
(information provided by Long Tail Pet Products, Marketer of the Dog Pause Bowl