Move over, carbon, the next shoe to drop in the popular awareness of eco-issues is the “water footprint.”

That’s the word in environmental circles these days. Just as the image of a heavy carbon foot made it possible for the masses to grasp the power of carbon-dioxide emissions, water footprint is the phrase now drawing attention to the impact of human behavior regarding water.

“H2O is the next CO2,” says Nicholas Eisenberger, managing principal of GreenOrder, a consulting firm that specializes in sustainable business. As a phrase, water footprint “will probably move more quickly through the public mind as it catches on,” he says, because water is more tangible than carbon.

Measuring how much water an individual, business, or government uses is a concept everyone can viscerally relate to, he adds, “because they put their hands on it every day, which is not the case, necessarily, with carbon.”

Why is “water footprint” coming to the fore now? And why does what is arguably humanity’s most vital resource need what some call a gimmick to connect people with its importance?

“You can’t control what you don’t measure,” says Laura Shenkar, principal of the Artemis Project, a water consulting firm. People take water for granted, she says, but the growing talk about climate change inevitably includes water. And recent droughts in the usually verdant southeastern United States have helped bring the issue to public attention.

But causing people to take action on this issue isn’t necessarily going to be easy. One simple “wake-up” tool is the calculator at the website of the Water Footprint Network. It asks questions about your diet and lifestyle and then churns out eye-popping “prints,” or water consumption estimates in the hundreds of gallons.

These figures include both direct use and indirect, or what’s known as “virtual water,” meaning how much H2O your Big Mac or Toyota Prius required all the way through the production chain – including growing the alfalfa that fed the cow that made the beef patty.

But calculators that return such large numbers that they convince people they’d never be able to live a comfortable lifestyle, “aren’t really helpful,’ says activist Alexandra Cousteau, who adds that she prefers to pursue projects that will “inspire and empower people.”

On June 8, the granddaughter of undersea explorer Jacques-Yves Cousteau will complete a 100-day global journey to expand awareness of the “interconnectedness of our hydrosphere.”

She and her team are chronicling critical water sites on five continents. “Expedition: Blue Planet” delves into crises such as the dwindling River Ganges in India and solutions such as a state-of-the-art Coca-Cola bottling plant in the Palestinian city of Ramallah (It’s the only multinational corporation in the West Bank.)

According to Greg Koch, director of the company’s Global Water Stewardship program, Coca-Cola (whose water brand, Dasani, is a sponsor of Ms. Costeau’s tour) eventually hopes to achieve “water neutrality” at its plants worldwide. (Water neutrality compares the amount of groundwater used with how much is returned to the earth through conservation measures.)

Agriculture uses about 70 percent of the global water footprint, while industry clocks in at around 20 percent.
But individual awareness and behavior is an important starting point in reducing one’s impact on the environment, says Alex Mayer, director of the Center for Water and Society at Michigan Technological University in Houghton.

Even small steps can make a difference. “Maybe even a calculator meter magnet on your fridge, so that every time you open the door or run the faucet, you’re faced with your own behavior,” he says with a laugh.

Nobody has to tell California officials about growing water crises. The state, now in its third year of drought, declared a water emergency in February. Two days after Easter, southern California water agencies announced mandatory cuts for the summer and September rate hikes for the 19 million residents of Los Angeles, Orange, San Diego, Riverside, San Bernardino, and Ventura counties.

“We’re always looking for ways to encourage people to change their ways with water,” says Bob Hayward, general manager of Lincoln Avenue Water Co. in Altadena, a water district of 16,000 users in the heart of Los Angeles. His customers were asked to voluntarily cut their water use by 10 percent last year, which most were able to do.

But now the district is asking customers to cut back an additional 20 percent. “They’re not taking that very well,” Mr. Hayward says with a  sigh. Officials are hoping to inspire residents to switch from water-hungry gardens and lawns to plants that are more suited for arid locales.

What many people may not realize, notes Mr. Hayward, is that nearly 75 percent of residential water use in California goes to outdoor purposes, mostly landscaping.

Across southern California, water districts maintain demonstration gardens that illustrate how to have plants and conserve water at the same time. At one on the edge of the grounds of Santa Monica College, Andrew Villegas, a local high school senior, says he knows about the carbon footprint but hasn’t heard about the water footprint. He likes the alternative garden, which is full of drought-tolerant grasses and water-wise options to shrubs.

Adjacent to the “good” garden, a traditional one grows the thirsty roses and pansies favored by many homeowners in the region. Brochures show the differences in waste, water, and maintenance between the two gardens.

Sitting nearby with her 2-year-old daughter Lucy, Annie Bloom says she likes the water footprint idea and tries hard to keep hers down. When she bathes Lucy, she rarely fills the tub anymore, and sometimes, she adds with a  laugh, she’ll even give her a bath in the kitchen sink. “That takes much less water.”

Even as the water-footprint concept is catching on, some think it’s just a start. “What’s good for water conservation may not be good for energy efficiency, for example,” says Cameron Wilson, a research analyst of environmental and building technologies with Frost & Sullivan, a consulting firm in Toronto.

Ultimately, he would like to see the discussion move beyond individual components in the ecosphere. If it has to be a catchy line, he says, “let’s try an ‘ecological footprint.’ ”