People with a river or sea boundary have access to unlimited water. Just brown or salt water. The trick is to use a polar pump, or little wind turbine to get at power.
In emergency, power from a generator will do just fine – and we only want 10 W: the power you use climbing 1 floor of stairs.
We drive a vacuum pump, and as the water rises up, it boils! Even ice will form water vapour at 1m of vacuum head. Losing all salts or contaminants – we get desalinated, pure water.
We use a chain or vacuum pimps to transfer the water vapour to reservoir or holding tank. As we vent the vapour, it condenses into a fine mist – which fills the reservoir, as the drops combine and sink.
So for farmers no water charges: we can actually sell water to the local water users – and generate a nice income. It is cheaper than running a reservoir – so the water companies will use vacuum desalination as a source of cheap water – selling off the reservoir to build on.
Reservoirs are no longer needed.