In Los Angeles, new commercial development is required to deal with its own runoff and not dump it into the storm drain system.
That can include rain barrels and cisterns to collect water for later irrigation, but it mostly consists of having planters, swales and detention basins that let the water soak into the ground rather than run off.
Also, here in LA, collecting local rain for almost any purpose that displaces the use of tap water is a net win, since most of our tap water is imported. (We can’t use much of our most important local aquifer, because it was contaminated in the process of building about half of the air armada that destroyed Nazi Germany.)
But even if the aquifer is undrinkable, using rainwater for landscape irrigation is a Good Thing here. LA is NOT a desert, and we don’t need landscapers trying to turn it into one. We’ve already paved over far too much of the local biome.
