Water & Power: A California Heist, a feature documentary from award-winning filmmakers Marina Zenovich and Alex Gibney, premieres Tuesday 9/8c on National Geographic.

It’s an icon of American cinema: the 1974 neo-noir Chinatown shone a gritty light on the California Water Wars of the early 20th century, when politicians of a parched Los Angeles schemed to divert water used by ranchers and farmers in the Owens Valley. Spoiler alert: at the end of the movie, almost everyone’s kicked the bucket, leaving Jack Nicholson’s wearied gumshoe to ponder the bleak lesson that power stays with those in power and nothing really changes.

Not exactly a hopeful ending. But for Marina Zenovich, director of the new documentary Water and Power: A California Heist, the power of Chinatown’s fictional account was a way in to the contemporary Golden State’s all-too-real water woes. (Read more about water wars around the world.)

Zenovich, an Emmy-winning director who’s produced some of this decade’s most talked-about documentaries, took some time from the press circuit to talk with National Geographic about gatecrashing, snooping, and the surprisingly sinister world of water policy.

Water & Power: A California Heist Trailer From Marina Zenovich and Alex Gibney, this feature doc uncovers the exploitation of California's water supply. WATER & POWER premieres March 14 on National Geographic.

How did you familiarize yourself with California's complicated water policy?

I didn't know that much about water when I first started, not water law or water rights or water projects or anything. I think either you know a lot about that or you don't, and most people don't. I was lucky enough in working with Jigsaw that we had a big research team that did a lot of research ahead of time, so I just pored through all the documents.

You just have to dive in at some point. And bit by bit, you interview people, you gain more knowledge, and you piece things together. It's like that on every film—baby steps. You immerse yourself in a subject and try to understand what it's all about.

Why is film a good way to learn about critical issues?

I've been making documentaries for a long time. When I made a film about Roman Polanski and his legal case, his lawyer said to me: "I don't understand why you want to make this film, everything is in the court file downtown." And I said, "That's exactly why I want to make the film!" Because no one's going to go downtown and look through the court file, because they'd have to look at microfiche and what have you.

Documentary filmmaking is a way to engage people with stories, causes, lives—it's a way to get people interested in something. It's wonderful that documentary filmmaking has become so popular. I can't begin to tell you how many people are saying to me, "I love documentaries! I learn so much from a documentary." I think we live in a visual world, and people learn from watching—hopefully from reading too, but, you know.

View Images Pipeline allegedly owend by Stewart Resnick, bringing water from Dudley Ridge to Lost Hills. Photograph by Ted Gesing, National Geographic Channel

You've said you tend to make films about people, you don't really make issue films. How was your process for this film different?

It's funny—my husband said this is a public service film. I think I like to frame it that way instead of as an “issue” film because it's almost like it's my duty, as someone who makes films, to bring a topic like this up for the world to digest and learn about and form opinions on and figure out what can be done to help.

It's really about finding a way in, and the way in for this for me was "Chinatown: The Documentary." This is the real-life version of Chinatown, which is happening right now, in your state, with your water. That intrigued me and got me interested in exploring the issue. Once I saw it in that framework, it became something much more interesting, and now I'm fascinated by it. I’m trying to learn more about it even though I spent a year immersed in it. But it's a very dense, intricate, complicated topic.

What was it like to get people on board with participating in this project?

I've made a career of making films in which people don't want to be interviewed, so much so that it's almost like I specialize in them. With documentary, you always end up in a better position when you're thrown these curve balls that make it harder.

For this film, the only people who didn’t want to be interviewed were the Resnicks [Stewart and Lynda Resnick, founders of the Wonderful Company], who we reached out to several times. They didn't want to be interviewed, so we wanted to talk to someone else from their organization, but no one in the organization wanted to talk to us.

You work around it. We have a quote in the film from the Wonderful Company, something from their website, so we tried to get their voice in there, and say that they didn't want to be interviewed.

View Images A California Heist will premiere at the Sundance Film Festival on Jan. 23, 2017, and air globally on National Geographic in 171 countries and 45 languages this spring. Photograph by Ted Gesing, National Geographic Channel

What was your most memorable experience during filming?

[laughs] Well, we tried to get into an event that the Wonderful Company had in Visalia [in the San Joaquin Valley]. We considered ourselves press—I mean, we were making a documentary—and no one was getting back to us. We tried several times. And so we happened to be in the area and just decided to crash the event. [laughs] And we got thrown out. We didn't film, we were just trying to get to people to interview, and they didn't want us there. They did have press there, so I think they just didn't want us in particular to be there. So that was an interesting moment.

The water world is a small world, there are only about 200 people in the state who really know about it, and it was striking how much people don't want you to know about it…once you kind of penetrate a world, people know about it. This world in particular is so dense and complicated that in an interview, people could talk circles around you—boring circular stuff, policy stuff.

It's a very specialized field. We were lucky to have the people that we follow in the film: Mark Arax, the journalist, who's been covering water for a long time and is writing a book; and Adam Keats, the environmental lawyer who is involved in the litigation with the Monterey Amendments. If this is “Chinatown: The Documentary,” they are the character of Jake Gittes, the Jack Nicholson character who's kind of snooping around. They allowed us to snoop with them.

When I first called Mark Arax and told him what I was doing, he just started laughing. He's like "There's no way that you can wrap your head around this whole topic in a year." And it is very complicated, but we tried. We were trying to figure out everyone's agenda.

Investigating Shadiness Hired by Public Citizen, John Gibler investigates a tip about shady water deals in California.

Did growing up in California impact the way you accessed this story?

I'm from the Central Valley. I left Fresno after high school, but my father was a politician in the Central Valley for 20 years, and California is really my home. My dad died a few years ago and this was a great way to traverse the state and kind of be close to him. Fresno and the Central Valley meant a lot to my dad. I knew Mark Arax’s brother. In interviewing [California governor] Jerry Brown, it helped that my dad had served under both him and [his father] Pat Brown. We've known the Browns for a long time.

A lot of people in Sacramento know who my dad is, though it's from a different time, so I'm always happy to meet the people who remember. People move on, which is kind of disheartening.

What do you think will happen next for California’s water?

Adam is still fighting to have the Kern Water Bank returned to the State of California. I don't know what's going to happen next. I hope people will see the film, and I think the film makes people angry—hopefully there'll be some policy change. That kind of thing takes time, but hopefully the film will excite people. It's always kind of like, "What can we do?" (Read about what’s being done to save the Colorado River Delta.)

Are there any final thoughts you'd like to share?

Tell your friends to see the movie! I'm proud to have made it. The intention is always just to educate and enlighten, and if something can be done to make things better, then all the better for it. But we're trying to shed a light on what happened in the past and how we can have more transparency in the future.

This interview has been edited for length and clarity.