The first question you should have asked is, does this include only chemically free water? It does not. Geology 101 will tell you that a lot of water is chemi

The first question you should have asked is, does this include only chemically free water? It does not. Geology 101 will tell you that a lot of water is chemically bound in rocks. The accessibility of said "water" is... questionable. These aren't necessarily hydrates either; if it has oxygen and hydrogen, then you can extract water from it.