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Unlike other major cities, Singapore can't access land outside the city for water. Instead, the island nation of about 277 square miles has had to get creative over the last decade.

The city gets 30% of its daily needs from recycled water and 25% from desalination plants.

"We take it back, we clean it, we send it back -- like a laundry service," said George Madhavan, a director at the government's water agency. "Then you don't have to pipe water from long distances away."

Meanwhile, the two desalination plants use reverse osmosis to squeeze salt water through a membrane, allowing only water molecules to pass through.

The government is developing more energy-efficient ways to treat saltwater -- for example, putting an electric field across the water that would pull out the salt, much like a strong magnet. Singapore is building a pilot plant to explore whether the technology can be scaled up for wider use.

To ensure water safety and quality, the government has installed over 100 fish tanks -- any unusual behavior could indicate something unsafe in the water. It's even developed a special camera system to monitor signs of fish stress. --Sophia Yan