Is a dry earth actually possible?

it's utter rubbish. Environmentaists, particularly those with little or no scientific training like to outdo each other with their catastrophic scenarios. according to some the earth will get wetter weather others dryer, and in a billion years there wont be anything around to care that we could communicate with. water can react with so many things to saturate them and 'lock the water away' but expose them to heat e.g. volcanism and it breaks the bonds and liberates the water. Our bodies, unless you have a medical condition or drink too much too quickly (or the wrong thing) regulate the amount of water in them through cellular osmosis. bigger people have more water in them than smaller people, so if you live off Mcdonalds you will consume more water than you excrete, but overall if you drink more then this you will just get rid of it in the normal ways.