Why couldn’t “modern” Libya just desalinate ocean water using their oil for the energy? Or even a large solar desalination plant like a superlarge greenhouse?
It would seem like a natural in any country with a lot of waste ground, lots of sun, and access to the sea. It would require a water to water heat exchange system so that the more briny solution that has been giving off evaporation in the heat could be freshened with less briny solution from the sea. It could run off photovoltaics and windmills (not necessarily wind-generated electricity), but fairly low-maintenance, be very low cost, and the condensation process could take place up a hill in a buried tank (actually a series of them) with no vent. It would be extravagant in size for the amount of freshwater made, but cheap as all get-out.