Southern Californians have become used to thinking about water use â" minutes in the shower, full loads of laundry, checking for leaky sprinklers.
Most, however, are unaware of how much water it takes to produce clothes, food, electronics and other goods, water industry officials said.
The amount of water consumed in the production of goods and services is called a footprint. That measurement is increasingly being used to help people understand the value of a resource that is becoming more precious every day, said Maurice Hall, California Water Program director for The Nature Conservancy in Arlington, Va.
âThereâs only so much water to go around, and we all need clean drinking water. Practically everything we use also requires water to manufacture it or grow it,â he said. âIn a (dry) place like Southern California, when you use water for one purpose basically it means water isnât available for other purposes.â
The biggest drain, even more than an overwatered lawn, is beef. Because of the water-intensive feed needed to raise cattle, one pound of beef takes a whopping 1,799 gallons of water to produce. That includes the water used to grow the grain and grass the cows eat.
Most of Californiaâs water footprint comes from the production of goods that are imported into the state and consumed here, according to a study released this month by the Oakland-based Pacific Institute, a nonprofit environmental think tank. It was the first-ever assessment of Californiaâs water footprint.
The stateâs total water footprint is about 64 million acre-feet per year, or 20 trillion gallons, which is more than double the annual average combined flows of the stateâs two largest rivers, the Sacramento and San Joaquin, the study found.
Lead author Julian Fulton, acknowledging Californiaâs huge agricultural industry, said he was surprised that more than half of the stateâs water footprint is from goods imported from other states and countries. The state uses 38 million acre-feet of water to produce goods and services, half of which are exported. About 44 million acre-feet from outside the state is used for goods and services imported to California.
That imbalance can be both positive and negative, he said.
âIt means the water that supports our way of life is vulnerable to issues in other places, like the drought in the Midwest,â Fulton said. âOn the other hand it makes us a little more resilient because if thereâs a drought in California it wonât affect us as much.â
The water footprint, similar to the concept of a carbon footprint long used to measure the output of greenhouse gas emissions, is becoming an important tool as competition for limited water resources intensifies. Much of the water used in the production of goods is lost to evaporation and transpiration during the production process, he said.
He used the examples of a cup of coffee, which takes an average of 35 gallons of water to produce, including the water required to grow the coffee crop.
UC Riverside biochemistry professor Daniel Galllie has been developing crops that use less water.
He and his colleagues have patented two methods that could lower the water footprint of plants. One alters vitamin C levels in plants, allowing leaves to more readily close their pores and conserve moisture; the other technology decreases the hormone ethylene, stimulating plants to respond better to drought.
âBoth of these technologies reduce the amount of water that crops would need to grow,â Gallie said. âIn a state like California, where we can precisely control the amount of water through irrigation that crops use, this would allow farmers to use less of state water resources for their agricultural needs. Since agriculture consumes the vast majority of water in the state, it would prove to be substantially beneficial.â
The average Californian has a footprint of 1,500 gallons per day, less than the nationwide average of 1,600 gallons, but more than residents in other developed nations. Residential water usage accounts for only one-tenth of an average personâs footprint. Items used throughout the day account for most of it â" to grow the cotton for one T-shirt, which requires 713 gallons, or example, or produce a sheet of paper, 1,321 gallons, or grow the ingredients for a bowl of breakfast cereal, which takes 34 gallons, not including the water needed to produce the milk.
There has been talk about companies labeling products with information about their water footprint. Fulton said the information may help consumers make choices between products in what essentially has become a global water economy.
They may choose to patronize companies that use water most efficiently or eat less meat and dairy products, which make up 47 percent of the stateâs footprint, Fulton said. Other agricultural products account for 46 percent of the stateâs water footprint. By comparison, about 4 percent is used in homes, and 3 percent goes into industrial products such as clothing and electronics.
Fulton said he hopes that if people are aware of the information they will âthink about the impacts that our consumption habits have on other places around the world.â Eleven percent of the water in Californiaâs footprint is associated with water use in Mexico, Canada and China, the study shows.
âTraditionally water has been thought of as a local or regional issue, but as globalization has forged increasing interconnectedness among people and economies, better understanding is needed of the ways in which observed impacts to water systems have important global dimensions,â said Fulton, who co-authored the report with Peter Gleick and Heather Cooley.