I realize that matter can not be destroyed, it just changes form or location. So I believe we have the same amount of water as when Jesus walked the earth.
However, there is less water in mid-west lakes recently, which makes boating less fun.
I don't know if there are actual cycles, but the continents have changed, flooded and changed again over the eons. Recently, self important man has decided we are reasonable for all these changes.
The one thing I can predict, is that clean water from the tap will become a precious commodity as the years pass.