Eight ounces? First I'd say that's a very modest amount of coffee, and second I'd say the liquid measure of the coffee is by itself meaningless. We'd need to know the caffiene content in milligrams before we could begin to make any conclusions regarding the potency of caffiene as a duiretic.
Now reverting back to anecdotal evidence upon which I based my first post, I know that when I use 3 TBs of very finely ground coffee to make about 12 ounces of brewed coffee I'm pissing like a race horse and my mouth is dry as a bone within a few hours.
Wuss all this bidness about?