In sore, we drill down to a magma chamber – located using ground sonar. This water comes up, at 250oC, 8 atmospheres with a limit concentration of gold and heavy metals.
We pass this through a aggrandised Dyson dry cleaner, to extract the heavy metals, and any salts. We sell this dust on, to process into salt, and metal ingots: there is 455 million tonnes of gold, which is dissolved in the geothermal water.
For all his mining, man has extracted only 2,000 tonnes of gold from the deep. The Kruger mines are now using air conditioning to solidify the earth's mantel – so is now mining the core material directly – more gold!
So we get steam at 240oC and 7.8 atmospheres. We use this to generate power. And use some of this power to drive a Carnot heat pump, which loops back 85% of this heat, so the entry steam is heated to over 800oC, using heat liberated to the air today.
We can use this idea from the 18th century, to improve present Fossil Fuels power generation. We get the same power, from 1/9th of the oil or gas burn.
In the desserts, we now have a limitless source of fresh water – we now fill high reservoirs – then it is over to biology, to reintroduce life.
We seed the area with soil, dredged from the sea floor, and washed at river outlets. We will actually need to provide salt licks, for the animals – as we turn dessert beck into lush arable land. We will introduce animals as the grass gets established.
Until then, we will ship animal manure, to fertilise the new grass lands. Liberia still has huge corn fields from the Roman empire – it fed Rome.
The other idea is for farmers that have sea coast, but no fresh water. We use solar panels to drive pumps, and expose the sea water to 1m of vacuum. The water boils.
This is how nature makes fresh water, evaporation from huge areas of the sea. Here we reduce the pressure on the water, and it boils away to fresh steam.
A group of waters invest in more solar pumps, and transport the water inshore. AS we vent the pressure over a reservoir, the steam condenses into mist – that fill the reservoir with liquid water.
The UN and other charities provide subsidised pumps – as it ends global hunger and thirst – which is a lot dearer to manage.
So we turn what is now semi-desert, back into lush farm land. For nearly free. No need for expensive and dangerous high pressure desalination. No filters – just by turning the pumps around. And reducing the power we use.