Water is an extremely important nutrient that contributes to overall health in every living creature.  Couple this with the fact that cats do not have a very strong thirst drive when compared to other species, and you will understand why it is critical for them to ingest a water-rich diet. The cat’s lack of a strong thirst drive can lead to low-level, chronic dehydration when dry food makes up the bulk of their diet especially if they have any level of kidney insufficiency.  A cat’s normal prey contains approximately 70 – 75 percent water.  Dry food only contains 5-10 percent water whereas canned foods contain  approximately 78 percent water.  Canned foods therefore more closely approximate the natural diet of the cat and are better suited to meet the cat’s water needs. Source: Catinfo