If you have a dog and have a garden, you may be tempted to leave water out for the dog all day long. After all, dogs can drink from any fountains, lakes, or ponds – as long as it is clean and not contaminated. But the problem with leaving water out all day long is that it can become stagnant.
In time, the water will become moldy and smell stale. And given enough time, your dog may even start to associate the water with illness and disease, and be less likely to drink it when they need to rehydrate.