From farmers to city dwellers, people in the western United States are very concerned about the supply of water.
It's been a problem in California for several years, said Kevin Wattier, who formerly managed the water department in Long Beach, California. He called the current drought "clearly the worst" in the state's history.
But the American West is not the only place thirsty for water, said oceanographer Jerry Schubel, president of the Aquarium of the Pacific. "More than half of the world's population lives in water-stressed areas and, according to the United Nations, that number will increase to two-thirds by 2025," he said.
The aquarium in Long Beach is displaying photos taken for National Geographic magazine that show how water scarcity is affecting people around the world. They include such images as a sea of people at the Ganges and women in Africa walking to find water.
Camille Lowry of the Annenberg Foundation, which organized the exhibition, said, "The idea that some people can devote their whole life, their whole day to trekking miles to try to find fresh water is something that's inconceivable for us."
The amount of water on Earth has not changed for billions of years, but the division between fresh and saltwater has changed, Schubel said.
"In much of the world," he added, "shortage of fresh water is a looming crisis that will only be exacerbated by climate change and a growing population."
Schubel said most of the world's population lives in countries that share bodies of water, but many of them don't have agreements on how to share the resource.
Scientists say conservation is the first step to solving the crisis. Desalinating seawater is also an option but has a price, Wattier said.
"It would cost at least twice or three times as much to desalinate seawater as it would cost to buy imported water," he said. "You will increase your global carbon footprint when you go to seawater [desalination]."
But Schubel said the problem can be solved if countries work together.