Yoram Cohen argues for more desalination:
Critics contend that reverse osmosis desalination requires large amounts of energy. But so do our home refrigerators, air conditioners, and washing machines. The real issue is the cost of water desalination relative to other available sources. For example, bottled water costs range from $1 to $3 per liter in the U.S., depending on the brand and location of purchase. In comparison, seawater desalination costs can be as high as about $0.45 per 100 liters and about $1.50-$2.00 per 1,000 liters for large-scale production. Of course, the above cost does not include conveyance of the water to the customer.
Over the years, intensive research and development efforts have been devoted to lowering the energy cost of reverse osmosis seawater desalination with tremendous success. Since about 1990, energy costs have decreased by nearly 75 percent for large-capacity plants.
But Eric Holthaus instead recommends recycled water:
While it’s not quite correct that every glass of water contains dinosaur pee, it is true that every source of fresh water on Earth (rainfall, lakes, rivers, and aquifers) is part of a planetary-scale water cycle that passes through every living thing at one point or another. In a very real way, each and every day we are already drinking one another’s urine. …
Barring a miracle, desalination is among the least desirable options. There are significant economic, environmental, energy, and political barriers. Desalination is the Alberta tar sands of water resources. When you look closely at the choices, it’s clear the future of Western water supplies is toilet water.