Every week, scholars, governments, ecological activists, and hydrologists produce thick reports about water scarcity and its relationship to irrigation, urban decay, and human health. Perhaps no one is more prolific or authoritative than Gleick, whose biennial report, “The World’s Water,” is a selective encyclopedia of the world’s aquatic resources. Gleick is a reserved, tweedy-looking man with thinning hair, a short, graying beard, and, behind his circular wire-rimmed glasses, the searching eyes of an East Bay idealist. Although he received a Ph.D. in hydrology from Berkeley and studied engineering as an undergraduate at Yale, he knew by the end of his senior year that he didn’t want to build dams for a living. He has spent his professional life searching through obscure collections of data for patterns of water use. He lectures frequently, and can cite dreary statistics, evidence of governmental inaction, and worrisome trends with great rhetorical force. But his central message, which is often ignored by both planners and environmentalists, is surprisingly hopeful. “It is a little-known fact that the United States today uses far less water per person, and less water in total, than we did twenty-five years ago,’’ he said. “It’s a shocker. People don’t believe it, but it’s true. This is an indication that things are not the way people think they are. It is not really because we are trying to cut our water use, although that is true in some regions of the United States, and particularly in the West. But we have changed the nature of our economy, and we have become more efficient at doing what we want to do.’’

The amount of water that Americans used for nearly all purposes rose steadily from the beginning of the twentieth century, through the Second World War, and into the seventies. Every projection indicated that the growth would continue. Yet, in 1980, the amount of water we withdrew from rivers, lakes, and reservoirs reached its peak and then began to subside. Despite increases in wealth, industrial productivity, and the size of the American population, the decline has accelerated.

There are several methods to assess the way we use water. Withdrawals measure how much we actually take from the earth. Some of the water used in factories or homes can be recycled. On the other hand, once water is consumed by agriculture or polluting industries, it is gone—at least until it rises to the clouds, evaporates, and returns as rain or snow. In the United States, total water withdrawals now stand at levels not seen since the end of the fifties; per-capita withdrawals—the amount each of us uses every day—have fallen by twenty-five per cent. This is true even though the population has grown by more than a hundred million. Among the reasons are higher energy costs, which force consumers and industries to become more efficient in their use of water. (More freshwater is used to produce electricity than for any purpose other than farming.) Environmental laws, enacted in the seventies, forced factories to cut back on the amount of wastewater they discharged into American rivers. Many industries quickly realized that the cheapest way to meet the new requirements was to use less water. Conservation is another reason for the changes; federal and state laws now require efficiency improvements for many American appliances. (Toilets, for instance, use more water than any other domestic appliance. Over the past decade, the average amount of water in a standard flush has fallen from six gallons to 1.6.) Most important, perhaps, growing pressure on water resources—particularly for farmers in the West—has forced dramatic improvements in how much food we are able to grow with every gallon of water.

Finland, parts of Australia, much of Europe, and even Hong Kong also have experienced decreases in per-capita water consumption. As countries become more industrialized, pollution and economic inequality increase—often dramatically—and so does the use and abuse of natural resources. Eventually, though, as the gross domestic product of a nation rises, technologies mature, efficiency improves, and so does the amount of attention paid to human welfare and the environment. (This general phenomenon is known as the Kuznets Curve, after the Nobel Prize-winning economist Simon Kuznets.) In 1965, Japan needed fifty million litres of water to produce a million dollars’ worth of goods. By 1989, the figure, after adjusting for inflation, had dropped to thirteen million litres. Such statistics suggest a fundamental change in how people live, and Gleick, among others, has argued that, in order to abandon what he calls the “hard path,” planners, economists, and public officials must begin to address water use in an entirely new way. “The hard path treats our water problems as a simple issue of getting more from the environment, of finding new ways to take water from rivers and lakes and aquifers and move it farther and farther and farther away, completely independent of any analysis of how we are moving that water or how we are using it,’’ Gleick said. “That is what the World Bank guys and traditional water engineers were trained to do. That is what we did in the twentieth century. It brought great benefits, but it has not solved all our water problems, and it is not going to.

“People who build dams don’t understand the concept of efficiency, and neither do water managers,’’ he continued. “I am a hydrologist. I was taught how to satisfy the needs of a hundred thousand people by making a dam. I can design a dam on a virgin river to meet those needs. I was never taught in engineering school to think about how people actually use water.”

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Since the nineteen-seventies, nearly all water-demand forecasts issued by governments and international agencies have grossly overestimated future needs. This has led engineers and planners to continue pushing for giant public-works projects. “These are the nuclear people from the seventies, the big-dam people from the sixties, and now they are the desalination people,’’ Gleick said, stressing that, in theory, he was opposed to none of them. “All these people seek large magic bullets to solve the world’s problems. They all have this very strong belief that there is one solution out there and if only we could build enough of it or find it our problems would be over. It drives me crazy.”

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“I would argue that almost everything we do on earth we could do with less water,’’ Gleick told me. “And that is the soft path. This is a different way of thinking than in the twentieth century, when the simple answer to every demand was ‘Let’s go get some water.’ That is what led to the destruction of the Aral Sea, the dewatering of the Colorado River basin in Mexico and the Yellow River, in China.” He stopped for a moment and stared at his hands. “This is really good news, you know. Because it means we can do better. We don’t need to run out of water. We just need to think more seriously about how we can avoid using it.”