OK, Rain Barrels may not exactly be Water Gardening, but somehow, the concept fits here in my mind. Rain Barrels, Rain Gardens, Swales -- all water catchment and conservation to benefit the garden.
I have to admit the guy lost me about half way down -- I think this is beyond my capability. But I suspect many of you wouldn't think so. Check this out: https://www.emmitsburg.net/gardens/articles/adams/audrey/water_barrel.htm