The UK is surrounded by water- the trick is to remove the salt.
We put 1m of vacuum on the water, and even ice will turn into water vapour, The water will boil – losing all salt and contaminants.
All farmers on the cost do this, and sell the water to the water grid: in the same way people sell excess power to the electricity grid. So 40W in the noonday sun. 40,000L of water vapour,
So we sell 40L of pure water to the national water grid. So 8.7 million farmers on a river or sea coast. 34.8 million litres of water a day. The UK annual demand is 9 billion litres. Farmers can supply 12.7 billion.
So no need for reservoirs. The UK can use a 1m3 solar panel on each farm to supply MORE water than we can ever use.
And farmers make a lot of money. OK, ONLY 80 pounds a year, at 2p/L. So they never get a water bill, they get an annual cheque. They set up 1,000 pumps, and get 80,000 a year.
And the set up cost them 60 UK pounds.