A quarter-century ago, San Diego and its suburbs imported 95% of their water supplies. Thanks to investments in desalination and other efforts to boost supplies, that figure has already dropped to 57% and is projected to fall to just 18% sometime in the next two decades.

San Diego has gone from being one of the most vulnerable areas of California during drought to one of the best prepared — and in so doing has become a model for the future of water use in cities.