Sucking 1 litre of water up 1m, causes it to boil. Losing all salts and contaminants. So it is 20 times less expensive than high pressure desalination. And totally safe – high pressures are VERY dangerous.
So we suck river or sea water into pure water, local tot a town or city. So we do not need as remote reservoir, and we pump water vapour a short distance.
So low pressure desalination is 1 5th of the cost of reservoir water. And it does not depend on rain fall.
No rain – the sea is still there totally unaffected. So there can never be a drought for countries like the UK – surrounded by sea water. And endless supply of fresh water.
And low pressure boiling of water was discovered by scientsits in the 18th century – it is old science. No drought. Endless fresh, cheap water. Using this science, the cost of fresh water should fall by a factor of 3.