A dog’s head shows that it is a carnivore, not only by its teeth and jaws (a dog can only pinch, bite and tear), but by the fact that he is not really able to drink.
Herbivores must also live from plants beyond the summer months, and these are then hydrated by nature. Only in the summer do plants keep up a lot of moisture.
For a horse, cow, deer or rabbit, for instance, this is not a problem, as they can by almost completely closing their lips, turn their mouth into a kind of funnel enabling them to suck up water. This works well, and big herbivores are quickly able to drink litres of water within a very short period of time.
Dogs and cats are hunters by nature and must be able to open their mouth very wide to catch a prey; that is why the corners of their mouth lie very deep and they cannot close their lips to drink.
In nature they don’t need to. Their food (prey) consists in winter and summer of 70% moisture and in the couple of hundred years of domestication, evolution hasn’t changed this at all.
So dogs that eat dry food should not only drink because of thirst, but also to replenish the moisture missing in dry food. They must turn their tongue into a kind of little spoon to ladle and throw in all that extra moisture. The result is that everything that is close to the water bowl is splashed with water.
Water is not the same as meat moisture! Meat moisture is liquid consisting partly of water. To digest its food a dog must bring its stomach acid from +/- 5 pH down to 2 pH.
With natural food this is not a problem because the basis for this is fresh meat and as we saw earlier meat consists for 70% of moisture. This moisture is natural and neutral, it does not contain calcium and is absorbed in a solid substance, i.e. the meat!