Question

How Can We Ensure That We Continue To Have Adequate Supplies Of Fresh Water To Meet Our Needs?

Answer 1

-- Conserve.  Don't use more than we need.  There isn't any more of it.

-- Conserve.  Don't pollute what we have.  There isn't any more of it.

Of course, what we REALLY need to do is convince great numbers of people to go along with these suggestions.  Otherwise it won't work.