If California were not already so famous for Sillicon Valley  and Hollywood, it might be well-known for the groups of water-technology firms in its San Diego County. The reverse-osmosis (RO) spiral module, the technique that supports turning seawater and waste-water into drinkable stuff, began in San Diego in 1964. Today dozens of firms in the area supply many of the world's approximately 13,000 RO plants in places from the Persian Gulf and Israel to Australia and China. Southern California itself, however, has not so far been a big user of its own technology. This is surprising, given that the whole American south-west faces a water problem. But now as the climate gets warmer and the population increases, there is more agreement that the existing infrastructure, consisting of vast pipes that carry water from the Sacramento Delta in the north and the Colorado River in the east, will not be enough. In places such as San Diego, which has inadequate and salty groundwater and currently imports 90% or its water, the answers must be greater conservation, reusing as much water as possible, and getting most of the rest from the sea. The first part, conservation, has been widely accepted by the public. San Diego today uses less water with a larger population than it did in 1989, the year water consumption peaked. The second part, water recycling has been a hard sell, because of an unpleasant factor. Americans still use the term "toilet-to-tap" for recycling, even though properly treated waste-water is nowadays completely clean. Singapore made its programme acceptable in part by renaming it as NEWater. This is where desalination comes in, which means taking the salt out of salt water. A firm called Poseidon Resources is now close to building the biggest desalination plant in America behind a power station by the beach in Carlsbad. The power plant sucks in 304m gallons of seawater a day for cooling, so Poseidon plans to change 104m gallons a day by using the RO spiral module. Lots of people like the idea. Once fully running in 2015, the plant could produce 10% of the region's water. And there are plans for more desalination plants. Many places would need to take much less water from the endangered Colorado River. But a few people hate it a lot. Joe Geever, an expert in biology, says desalination uses too much energy and that Poseidon plant would kill too much sea life. He understands that there is a role for desalination, he says, but would rather not have it right there, right now, and on this scale. How many solutions to the water problem in San Diego are mentioned in the article?
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