How much water do you use to wash your jeans?

Levi Strauss figured out that 45 percent of the water used in the life of a pair of 501 jeans – including growing cotton and transporting goods – is spent on washing the denim. That's out of the 3,480 liters of water used during the life of the jeans, said Michael Kobori, vice president of supply chain social and environmental sustainability at the clothing company. Nearly half of the water used – or 49 percent – goes into growing cotton. Five percent is used for making that pair of jeans, Kobori said.

Kobori appeared on a panel at the one-day conference in San Francisco to talk about how paying attention to water use can improve corporate image and enable companies to figure out new ways to make money.

For example, Levi has teamed up with detergent maker Proctor and Gamble and Wal-Mart to tout a particular new line of jeans that can be washed with cold water, thus saving the heating cost. Washing and drying clothes account for six percent of the home energy bill.

Energy efficiency has become a corporate and political buzzword, but attention has largely been focused on electricity and fuel consumption. More attention should be paid to the use water in different aspects of a business operation, said Jason Morrison, another panelist. Morrison is the director of economic globalization and environmental program at the Pacific Institute, a nonprofit in Oakland, Calif., that works on water issues.

"There are an amazing number of Fortune 500 companies that don't understand the depth of their exposure. Very few have given thought to their indirect water use," Morrison said. That will make those companies appear to be poor stewards of natural resources, especially as water becomes an even more precious commodity, he added.

About 900 million people in the world today don't have access to potable water, Morrison pointed out. About a third of the world's population live in places with scarce water supplies, according to a United Nations-sponsored study.

Frito-Lay has efforts in place to reduce water use at its manufacturing plants, said Al Halvorsen, director of environmental sustainability at the food company.

Halvorsen, another panelist, said the company set a goal back in 1999 to reduce water use by 50 percent per pound of product. The company isn't there yet, but it has cut overall water consumption by 1.5 billion gallons, he said. The company's plant in Casa Grande, Ariz., recycles water used for washing vegetables and makes use of renewable energy, he added.

A new focus on water as a precious source of energy could lead to new opportunities for tech companies. There already are a growing number of companies developing electronics and software to measure electricity use. How about more and better devices to measure and analyze water use?

Perhaps in the near future water credits can be created for trading, much like the billion-dollar business that exist today for trading carbon emission allowances.