that's where the promise of desahlennization comes in. a way to college the growing thirst, by taking the salt out of saltwater. there carlsbad california hope for a future -- in the western hemisphere. when it is completed in 2016, the plant will provide 300,000 san diego residents. peter says it is time to dip our straw into the pacific ocean. it says it is worth it. >> without doing desahlennization, without having another source of supply, we would have shortages of water. >> large plants are already operating in the middle east. but the west has been slow even reluctant to adopt the technology. >> the promise of harvesting water remains very much up for debate. with some water policy saying on the surface, desahlennization sees like a valuable option. there are a number of unresolved issues that must be addressed before we can say pass the salt. >> we would consider it an option of last resort, when you have exhausted all the preferable alternatives. >> that enormous energy demand, and that it's so expensive that it crowds out other