How much do you know about Xeriscaping?
Xeriscaping reduces watering and maximizes the use of natural precipitation. It is both similar and totally different from a Rain Garden. However, they have so much in common that I think I'll move right to Xeriscaping from Rain Gardens. For this I might suggest that you do a bit of reading about it. Here's the Amazon link where you can check out some books that give you a more detailed version.