Water rights - your roof, your tank, your water, right?

In Western Australia, current legislation, namely the Rights in Water and Irrigation Act 1914, is silent on rights to water collected by roofs. Under proposed legislation, the state government will claim that a person’s roof is “land” whereby water collected by roofs is “overland flow” water the rights to which are vested in the state. To clarify this position, the Minister for Water Resources, John Kobelke, was asked, “Does a roof collect rain falling from the sky?” He declined to provide an answer, on the grounds that the term “overland flow” is not yet defined.

In Tasmania, the state government claims that a person’s roof is land and water that falls on a person’s roof is dispersed surface water, the rights to which are vested in the state.

So in summary, three states - New South Wales, Victoria and Queensland - advise that a person’s roof is not the surface of the ground, while the other three states advise that it is.

However, there is an even more fundamental issue at hand. Whereas governments happily spend tens of millions of taxpayers’ dollars on unnecessary rainwater tank subsidies, they are unwilling to explore ways of achieving rainwater supply for every house in Australia at an affordable cost.

Is it because rainwater tanks are privately-owned water supply?

Or, perhaps it is because rainwater supply is the lowest cost source of additional water supply?