I'm giving you a logical account for how I would arrive at my viewpoint.

If you want to quick and dirty, I told you my viewpoint. The government wants to publicly control rainwater so they can leverage private control of drinking water because that would mean by extension that the banks privately control our drinking water. The elite faction that owns this government does not want such a precious resource like water being distributed freely around the country because that means less for them. All must be collected, contained and price-tagged to ensure the rich can buy what they need. Everything must be expropriated from the poor to maintain their poverty so they cannot live in more a sustainable fashion and crowd the rich. That's my viewpoint. It has nothing to do with intrinsic legal properties of water use. I brought up Laissez Faire to discuss what these properties might be, were I living in a country where the law is meant to deliver the greatest good.