Dogs use water for several purposes, as do people. Dogs need water for body cooling, digestion, and other necessary bodily functions. Dogs exhale water vapors through their lungs more so than humans do, and so water is very important to a dog, perhaps more so than for humans. It is important to carry water with you wherever you go so that your dog is never dehydrated. This is especially true if you are in a desert area, however no matter what climate you experience where you live if you have sunshine. Typically in the sun, the temperature is 10 or 20 degrees hotter than in the shade, depending on wind chill factor. But even in cold weather, you need water available for yourself and your dog. It's necessry to have water available for hikes and bike rides even if the dog isn't peddaling the trike, because the sun is hot. Dogs want and need exercise as much as people. They're healthier and happier when they have regular active exercise, to a greater or lesser extent depending on the breed of dog, but all dogs need some exercise. Most dogs love to run, so why not provide them with the opportunity to do so on a regular basis. It's cheaper than Veternary bills, and much more humane to give them what is needed for their well being.