The country’s largest desalination plant is in the ground at Carlsbad and its water is in our pipes, but the debate over whether it was a wise or economical investment continues.The ability to turn salty ocean water into drinking water creates a dependable water supply for 3 million people in San Diego County. Even without a drought continuing across California, the ability to constantly sip from the ocean seems like an obvious plus. There are downsides, though: The desalination process is energy-intensive and its water is currently far more expensive than our other water supplies.