Can you combine a natural swimming pool with a rainwater harvesting garden?
I don't have specific details yet but we would like to build a swimming pool on a newly aquired 4 acre property and we like the idea of a more natural type of pool (no chlorine). We also want to grow some crops and harvest rain water and water from a small creek running through our property. I can't see why a natural swimming pool and a rainwater harvesting garden / system cannot be combined into one area.
If you mean feeding rainwater into your natural pool from roof runoff, I would see no problem doing that with a metal roof, but shingles, particlularly older ones, may deposit toxic debris in it. This page would be great place for you to start reading -
How to Build a Natural Swimming Pool