I do quite a bit of work in hydrology, and I can tell you that water laws are more regional, illogical, and convoluted than alcoholic beverage laws, and that is saying a LOT. I just found it interesting that in some places the rain that falls on your roof belongs to someone else. Guess I'd be sending them a roofing bill for damage done by their precipitation.
Here on Hawaii Island, about 65,000 of us depend on rainwater catchment for our household water. I never worry about wasting water because, #1 we get around 180" of rain per year here at my house, and #2 I just intercept it on its way of going to ground, to make it do a bit of work, before it goes to ground. I use a little recycled sunshine to add pressure, put it to use, and then send it on its way.
And have no doubt, EVERY level of government has a say in what happens with water. If I had a nickle for every hour I've spent reading water related laws I'd be part of the 1%.