Rainwater tanks can provide the lowest cost source of additional water supply in Australia - cheaper than desalinated seawater and recycled sewerage. Based on 85 per cent mean annual rainfall for the next 30 years, rainwater tanks can yield 80 kilolitres a year in Sydney costing the house owner $1.20 a kilolitre. In Melbourne and Brisbane, the yield can be 70 kilolitres a year costing $1.40 a kilolitre. The average household uses 150 kilolitres of water indoors each year.
Every house in Australia can be using lowest cost rainwater supply within 10 years. Payment of government subsidies costing taxpayers tens of millions of dollars is unnecessary. This outcome is achievable under a national program that generates economies of scale in production and installation. It uses compact tanks (less than one kilolitre) connected to most house downpipes.
The yield and cost estimates, above, are based on four 670 litre tanks (linked by 25mm water pipe) collecting water from four downpipes or 175 square metres of roof.
A national program requires a national policy. National water policy is embodied in the National Water Initiative Agreement. Clause 2 of the Agreement says, “In Australia, water is vested in governments that allow other parties to access and use water for a variety of purposes”. The Federal Government claims that rainwater falling on roofs is vested in governments. This claim is not supported by three state governments- New South Wales, Victoria and Queensland. Therefore, the National Water Initiative Agreement may not be interpreted to mean that all water is vested in governments.
Additionally, state governments have abolished common law rights to “naturally occurring” water. However, no state government claims that rain falling from the sky is “naturally occurring” water. Only when water is on or below the surface of the ground, may it be considered to be “naturally occurring”.
The policy questions are:
- is water that falls on a person’s roof “naturally occurring” water - in other words, is a person’s roof the surface of the ground? and
- does a person own the water that falls on their own roof?
The Victorian Government’s position is that the water that falls on a person’s roof in Victoria is the property of that person. The Victorian Government has advised that the state’s right to the use, flow and control of water extends to all water in a waterway and groundwater. The terms "waterway" and "groundwater" are defined in the Water Act 1989. If water falls on a person's roof, it may, after it has left that roof, become water in a waterway or groundwater. For the period that the water remains on the roof, it is not water in a waterway or groundwater. In other words, a person’s roof is not the surface of the ground in Victoria.
On March 14, 2007, the New South Wales Premier, Morris Iemma, was asked, “Do you know who owns the water that falls on a person’s roof in NSW”? The reply provided on the Premier’s behalf on March 20 was, “The water that falls on a person’s roof is considered the property of that person”. Under section 392 of the Water Management Act 2000, the state’s rights to water extend to the control, use and flow of all water occurring naturally on or below the surface of the ground, all water in rivers, lakes and aquifers, and all water conserved by any works that are under the control or management of the minister. In other words, a person’s roof is not the surface of the ground in New South Wales.
In Queensland, the state government has advised that, based on the meaning of water in the Water Act 2000, water collected in rainwater tanks does not fall within the ownership of the state. Under section 19 of the Act, “All rights to the use flow and control of all water in Queensland are vested in the State”. Also under the Act, “water collected from roofs for rainwater tanks” is not included in the meaning of overland flow water. In other words, a person’s roof is not the surface of the ground in Queensland, and rights to water collected from roofs for rainwater tanks are not vested in the state.
In South Australia, the state government claims that a person’s roof is the same thing as “land”. Under section 124 of the Natural Resources Management Act 2004, water flowing over land is surface water, and rights to surface water are vested in the state. The State Government advises that surface water is not owned by anyone, including the state.
To clarify this position, on June 14, 2007, the state government was asked, “Does a roof collect rain falling from the sky?” If the answer given is “yes”, this means that the water being collected is not surface water. If the answer given is “no”, the question becomes, does an enclosed rainwater tank collect rain falling from the sky? On February 27, 2007, the state government released its “runoff policy” for surface water in surface water prescribed areas. A “water user” capturing rainwater in excess of 500 kilolitres requires a water licence, and then may be eligible to pay a water based levy if that water is used for commercial purposes. The policy applies to rainwater tanks, on the presumption that water collected from roofs for rainwater tanks in South Australia is “surface water”.