Desalination removes salt from seawater or brackish water to produce fresh supply, first at scale through multi-stage flash distillation from the 1950s and later, more efficiently, through reverse-osmosis membranes developed in the 1960s. The technology gave arid coastal regions a water source independent of rainfall and rivers. It underpinned the explosive growth of Gulf cities such as Dubai, Abu Dhabi and Jeddah, and supports drought-prone places from Israel to south-eastern Australia and California. Plants are energy-intensive and discharge concentrated brine.
Desalination lifted the natural water ceiling on coastal arid cities, enabling metropolitan growth in places that rainfall alone could never sustain.
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