This doesn't answer the actual question, but...
I hear that the desperate need to chew ice means you are low on iron. Can anyone confirm this?
As far as the amount of water in ice... if you fill up let's say an 8 oz glass with water
AND ice and you drink & chew the whole thing, then you have taken in exactly 8 oz of water, no more. The ice does not take up more "space" because it's frozen.
Now, if you just chew a cup full of ice (without water), that's another thing. No telling how much water it is unless it melts first.
Make sense?