Deepen the pool - we had people suggesting that when our dams were nearly empty. Civil engineers explained our dams have a clay seal - so ‘dig it deeper’ will destroy that seal.
Desalination is also on the Cape Town menu, but then the sludge (not just salt but all our pollution) is tipped back in the ocean, causing fresh problems to marine life.
Extracting water from the air. Is what our fynbos does using the Tablecloth (cloud on Table Mountain) It is why Cape Town was originally founded, its first name Camissa - place of sweet water. And why we have ‘nature’ reserves, protecting the mountain catchment which supplies water to urban populations and agricultural irrigation. Camissa - where I was born, and where my heart lives, in the shadow of our mountain rising from the sea 
We have a pilot project to harvest methane from landfill. Teaching people to compost would be a far better solution. If only.