Please check this info from a Kolar farmer for inspiration about growing Papaya on only rain water:
He is practicing natural farming in depending only on rain water.
He grows, Ragi, pegionpea, orse gram, sericulture, tamrind, banana, legums, chicken,ashgaurd etc.
Results was good, except the taste of papaya, he confirmed good taste of our papaya after consuming papaya gifted by me to him.
He is good in utilising locally available materials to enhance farm production