As scientists start to view earthquake patterns and the shock wave sent through the earth they are starting to get a better understanding of what our Earth is made out of since the waves travel slower through water they are starting to see vast amounts of rocks that hold untold amounts of water. Remember, we have only drilled down 7.5 miles into the crust and the mantel alone is around 1800 miles thick.

The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust. You can bake a loaf of bread in your oven at 350 degrees Fahrenheit , at 1600 degrees F. rocks begin to melt. Since we lack the technology to drill any farther than we already have, at present times, we might never know how much water is locked inside out planet.

That means that we should take care of the water that is accessible to us. I also love the interest that this question is fostering in the community.