The man in the shirt and tie with thin-rimmed glasses, a graying beard, and slightly tousled hair spoke with confidence and carefully chosen words. He was being interviewed on “Inside Story,” a TV news program on Al-Jazeera America, at its San Francisco studio. The segment, called “Poor People’s Water,” aired in late January and focused on the unfolding water crisis in Flint, Michigan.

Lead contamination from corroded pipes had polluted the main drinking supply, and the beleaguered city was still reeling. How on Earth could this have happened? The expert on camera pointed to major economic, technological, scientific, and political mistakes that directly led to this harrowing situation. The speaker was Peter Gleick, water policy guru, and he succinctly summed it up: “We have a great water system in the United States, but it doesn’t take much to screw things up and lose people’s trust.” He forcefully criticized those with anti-government sentiment and Michigan politicians who withdrew funding from the water system’s infrastructure problems, warning that “there will be more Flints if we don’t tackle this.”

Following nearly three decades of leading the Pacific Institute, a nonprofit environmental think tank in Oakland, California focusing on water conservation, Gleick knows what he’s talking about. As of July 1, 2016, he will step down from his position, but he will continue to play a major role as president emeritus and chief scientist.

“He’s definitely a go-to person in the national and international community,” says Frances Spivy-Weber, vice chair of the California State Water Resources Control Board. “Peter has been very helpful, because he’s been able to get lessons learned in California out to the world.”

The American Southwest has always been plagued by water problems, with ever growing demands on the Colorado River and groundwater aquifers. California in particular—a populous, prosperous and diverse state with complex geography—struggles to find enough water to fulfill all of its urban, industrial and agricultural needs. (Recall the movie “Chinatown.”) Now in the middle of a historic drought, with depleted groundwater reserves measurable by NASA satellites, the parched state has been experiencing water scarcity like never before, and people are scrambling for more sustainable long-term solutions.

But water policy issues have become incredibly difficult to untangle, with frequent debates about water rights, water pricing schemes, agricultural irrigation, water storage, desalination, and water quality and recycling. Over the years, as a science and policy wonk, Gleick gained a reputation among scientists, policymakers and journalists as an authority and clear communicator. He has served as a much needed guide in navigating these complex problems, with a persistent emphasis on doing more with less water, minimizing waste, and exploiting currently available tools. Water issues cannot be solved merely with engineering ingenuity or technological innovation, he argues, as they are fundamentally social, economic and political in nature. Says Gleick, “Water is not rocket science; it’s a lot harder!”

Growing up with Silent Spring

The Pacific Institute is housed in a 110-year-old Victorian-style home in Oakland’s Preservation Park. Inside, the building is filled with beautiful desks and other antique furniture, and the wooden floors squeak under people’s footsteps. A typical day for Gleick is crammed with multiple media interviews, meetings with staff and calls from policymakers. He squeezed in the interview for this story by answering a wide range of water-related questions while scarfing down a burrito and keeping a surreptitious eye on the clock.

Preservation Park is a very different place than where Gleick grew up, in Manhattan. When he was a boy, he managed to connect with nature and the environment in the city of skyscrapers and high finance, often going on birdwatching adventures with his lawyer-father. “Many people don’t know this, but during spring migration, Central Park is a real hotspot for birds,” says Gleick. He still takes his binoculars with him everywhere and goes birding whenever he can.

As his older brother, the writer and journalist James Gleick, put it, “If you’re the kind of person who spends a lot of time in the woods or the marshes doing nothing but listening or looking for birds and wildlife, you must have some gut appreciation of nature.”

Peter Gleick went to college at Yale, where he majored in engineering and applied science. This was the 1970s, after the publication of Rachel Carson’s Silent Spring and during the blossoming of the environmental movement, which witnessed the birth of the Environmental Protection Agency. At the same time, global energy crises shook the U.S. and other major industrial countries, which faced major oil shortages and price fluctuations. “I grew up at a time when environmental issues were increasingly urgent and important,” he says.

He moved to California nearly four decades ago to study climatology and hydrology in the energy and resources group at UC Berkeley. In his dissertation, he was among the first people to identify impacts of climate change—which scientists were just starting to measure—on water systems. In particular, he discovered that Sierra Nevada snowpack, upon which central California depends for water, was at risk as temperatures rise. “He was one of the pioneers on that,” says Bob Wilkinson, a colleague and professor of water policy at UC Santa Barbara.

Upon earning his doctorate in 1986, he first considered pursuing teaching jobs but decided to follow his more interdisciplinary leanings. He and two fellow graduate students persuaded a foundation in San Francisco to give them a small, $37,000 grant. It turned out to be the first of many.

They used the initial money to establish the first manifestation of the Pacific Institute in a little two-room office in downtown Berkeley and started putting together a water-focused research agenda. “I don’t think if you’d asked us at the time where we’d be in 28 years, anybody would’ve had a clue,” says Gleick, now 59.

His grad student friends later returned to academia and became professors, while Gleick became the institute’s president. Since then, the research center has dramatically expanded beyond its humble origins, with a staff today of about 20 people and an annual budget of $2.3 million from grants, contracts and donations. The Pacific Institute now includes a large water program, as well as programs involving corporate sustainability, water security, and community engagement.

An ardent conservationist

Gleick and his staff invest considerable effort in assessing and advocating for water conservation measures. Traditionally, policymakers often focused on finding and exploiting dwindling water sources, such as by building dams and pipelines, and now, desalination plants that remove salt from seawater. But Gleick argues that such approaches overlook how much water can be saved by merely using existing supplies more efficiently.

He has built his case point by point, examining how each person, industry, and part of the economy could save water. “Peter is very thorough,” says Wilkinson. “He’s very good at finding the key points of an issue to address, breaking down problems into key parts.”

For instance, in a recent book co-authored with Juliet Christian-Smith, then a senior research associate at the Pacific Institute, Gleick points out that water usage per person in the U.S. dropped in the 1980s, which “demonstrate[s] that the old assumption that total water use is inextricably tied to population and economic growth is false.” This bolsters his argument that, since new and affordable sources of water are hard to come by, especially in California, the most effective solution is conservation and efficiency—“doing better with the water we already have,” he says. “Our analysis suggests it’s the cheapest and fastest and most common sense thing to do.

In a 2003 study called “Waste Not, Want Not,” he and his colleagues conclude that, with existing technology, it’s possible to cut urban water use by one third. Their research has also found that California’s farmers could grow the same amount of food on a given amount of land while cutting water use by 15 percent, such as by putting in drip irrigation systems and scheduling irrigation to more precisely meet the water needs of crops. Since agriculture takes up four fifths of California’s water, these upgrades would save even more.

In practice, however, carrying out these changes has proven difficult as water managers lacked necessary information about who is using all that irrigated water and when they’re using it. Christian-Smith, now at the Union of Concerned Scientists’ Oakland office, describes how she and Gleick sought to persuade the State Water Resources Control Board to require that water irrigation districts and farmers’ groups start reporting their water usage as part of the Agricultural Water Management Planning Act of 2009. State officials initially resisted the request, saying it was enough to trust the farmers to comply. “Peter was very quick-witted, and he immediately responded, ‘Trust but verify, Ronald Reagan’s words.’” The officials adopted his advice.

When he occasionally disagrees with other water policy experts, such as about where to focus California’s water management efforts—or about his view that desalination is a risky and expensive undertaking—he makes his opinion or criticisms known. For instance, some experts observed that efficiency improvements can backfire, resulting in people using more water rather than holding onto their savings, a phenomenon known as the “rebound effect.” When asked about this argument, Gleick bluntly responds, “I don’t buy it!” Then he clarifies that one must distinguish between the concepts of efficiency and productivity: If farmers have water savings but use them to grow more food (rather than keeping the saved water in the ground), then they nonetheless improved their water productivity. He concludes, “I think there may be some rebound effect, but it’s absolutely not an argument for not doing efficiency.”

Tangled path to saving water

Gleick’s water research also looks beyond California to much bigger questions. Since the 1990s, he has studied international water security and conflicts around the world. From Syria to India to Ethiopia, control of water resources and systems have driven or influenced disputes, and sometimes wars. In 2010, Gleick also first proposed the influential concept of “peak water”—analogous to the specter of “peak oil”—which pointed to the limits of renewable and nonrenewable water sources.

And in a popular book titled Bottled & Sold, Gleick argued persuasively that the U.S. tap water system is more regulated and usually safer to drink than bottled water. But Americans spend billions annually on Dasani and Aquafina, which produce massive profits for Coca-Cola and PepsiCo. When asked about the public obsession with bottled water, Gleick raises three issues: People are worried about their tap water (remember Flint); bottled water companies have huge advertising campaigns while public agencies don’t; and it’s becoming harder and harder to find public water fountains.

“He has a gift for communication,” says Christian-Smith. “He can take a very complex topic and distill it down to something at a lot of people can relate to.”

Perhaps the most contentious arena Gleick has stepped into has been the investigation of myriad connections between water, energy, and climate change. “The science about climate change is very strong,” he explains, “but there is a small well-funded group of deniers, and I tangle with them.”

His persistence resulted in a highly publicized incident in 2012, in which he assumed a false identity to obtain documents from a public policy think tank, Heartland Institute, and uncovered that it had a program to pay scientists to challenge the findings of the Intergovernmental Panel on Climate Change. He also revealed that their funders include the Charles Koch Foundation and many corporations. “I chose to confront these guys, and there were some interesting debates about my methods,” Gleick says. He took a three-month leave of absence from the Pacific Institute during an independent investigation, which ultimately supported his position.

He withstood some criticism following the affair, but he received considerable support as well, helping him recover. Gleick returned to his post and tirelessly continues his water conservation struggles. “He forces other people to think, and he’s an important voice,” says Steve Macaulay, former chief deputy director of the state’s Department of Water Resources and head of California Urban Water Agencies. “If it wasn’t for the fact that he keeps pushing, sometimes more with advocacy than with science, we wouldn’t be thinking about things like this. I give him a huge amount of credit for pushing the envelope on thinking about the consequences of our actions.”

When he isn’t tacking the perennial problems of water management and conservation, Gleick takes his own lessons on efficiency to heart at his home in Berkeley. He and his family have installed efficient toilets, showers, washing machine and dishwasher. “My water use is probably less than half the average of homeowners of California. And we have a beautiful garden, but no lawn,” he said. Then he paused, adding, “You could always do more.”

[Thanks to Ingfei Chen and my UC Santa Cruz colleagues for help with editing this story.]