Flow: For Love of Water is a troubling and eye-opening documentary about problems with the world’s supply of drinking water.

It’s tempting to glibly dismiss Flow: For Love of Water as this week’s entry in the Environmental Apocalypse agit-doc genre. Like An Inconvenient Truth, The Unforeseen, and other recent documentaries, it wants to terrify us into action, in this case over the privatization of and misuse of our planet’s water supply. Like many of those films, Flow preaches to the choir with a starry-eyed NPR eco-humanism that can set some people’s teeth on edge. For instance: Can we have a moratorium on quotes from wise Native American chieftains on how the earth belongs to all of us? Facts will do just fine, thanks.

When filmmaker Irena Salina does marshal the facts, Flow is an eye-opening, troubling 90 minutes that makes us think twice about an element we take for granted. Turn on the tap, out comes the water, and it belongs to everyone, right? Not in countries where the natural water table has been ruined by industrial development and big agriculture. There, governments have been pressured to contract with Europe-based corporations like Suez and Vivendi, who charge the poor for tap water and whose product isn’t nearly as pure as they promise.

The larger message — that Earth is headed for a crisis of unparalleled proportions as rivers dry up and drinkable water supplies dwindle — is sobering, and the film’s discussion of water problems in the United States is even more so. Here the issues aren’t scarcity and control but contamination and lack of oversight, as a nation flushes its industrial chemicals and prescription medications into the water table. If that unsettles you, eat some of the Texas fish whose tissues are infused with Prozac.

Worried and unfocused, Flow spreads its arguments around, taking on the evils of dams and bottled water, the strong-arm tactics of Coca-Cola in India, Nestle in Michigan, and the World Bank everywhere. Salina’s anti-globalism rhetoric often drives her findings rather than the other way around; the film lectures more than it persuades, and persuasion is what’s needed here.

She’s no Michael Moore either, even though she tries in one wan skit featuring magician-prankster Penn Jillette selling ersatz bottled water to unsuspecting restaurant patrons (the whole segment feels staged). Nor is the movie’s case helped by random clips from The Third Man or the-sky-is-falling pronouncements of author William Marks (The Holy Order of Water), who warns we’re on the verge of another mass extinction. Maybe he’s right, but on camera he comes across as a paranoid crank.

During the closing credits, Flow depicts smaller conservation initiatives like playground pumps in Africa and rainwater collection in Texas. Suddenly, the movie’s missed opportunities crystallize. Salina has spent so much time showing us what mega-corporations are doing wrong that she neglects to show us what some people are doing right, and what the rest of us can do to help.

***Flow

Starring: Maude Barlow, Penn Jillette

Unrated