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If you’re in New Zealand, you cannot have failed to be aware of the legal wranglings over the ownership of water. Who owns or has rights to the water in our rivers? The raising of this question is a not-so-subtle attempt from one half of the political spectrum to delay (or stop) the sale of state-owned-enterprises (notably hydroelectricity companies) by the other half of the political spectrum. Basically, if the water isn’t the government’s, then it can’t sell it, so it isn’t able to privatise the hydro companies – at least that’s the argument in hopelessly over-simplified terms.

There’s one issue regarding this that I haven’t heard at all in all the debate that is happening. What is it that the government is actually trying to sell?  It isn’t the water.  Hydro power does not involve the removal of water from the rivers. What flows into the station flows out again. So it isn’t water that is the asset that is being sold here. Rather, it’s electrical energy that the hydro-company sells. The energy is gravitational potential energy, as a result of gravity – a litre of water at a height is able to give up energy as it falls – e.g. into kinetic or movement energy. This kinetic energy is then transferred by the turbines in the power station into electrical energy. The water doesn’t vanish in the process; it simply loses height, and with it energy.

It’s similar to the way that electrical current isn’t ‘used up’ by a heater, light bulb or other device. You have two wires (discounting any earth wire) connected to the device. Current flows in one, and the same current flows out of the other. (Indeed, in a domestic supply, it reverses its direction 50 times a second.) How come then you get an electricity bill if what flows in flows out again? It’s because you are being billed for the energy that is transferred through this process. Putting that current through the device leads to transfer of energy from the power grid to the device, just like turning on the water flow through a turbine leads to energy being taken from the water.

So the question shouldn’t be over who owns the water. It should be over who has the right to do something useful with that water.