A documentary by Greg MacGillivray. Rated G. Now playing at the Omnimax Theatre

In the childhoods of most of us over 40, many places, events, and ideas appeared permanent, immutable—carved in stone, as it were. Today, however, the world seems a far less stable place, with the most majestic locations subject to drastic and frightening changes.

Case in point is a geographical spot that virtually defines the notion of majesty: the Grand Canyon. As amazing as the mile-deep system of chasms, gullies, dams, and switchbacks remains, the loss of water flowing through it, as part of the once-unstoppable Colorado River—should be setting off alarm bells everywhere in North America. With the U.S. still in the grip of people who think killing polar bears will solve their energy problems, it is naturally left to Robert Redford to narrate this tale, which carries the burden of responsibility to the viewer.

The gorgeous lensing in Grand Canyon Adventure: River at Risk, with plenty of great underwater stuff, soaring bird’s-eye views, and some cool historical images, is compelling. And the tone is lightened by the presence of rootsy music by Dave Matthews, a master of the almost-good song. Director Greg MacGillivray makes the story personal by centring things on a single trip down the river by two men, environmental activist Robert F. Kennedy Jr. and B.C. ethnobotanist Wade Davis, along with their college-age daughters.

Also on hand in this latest IMAX documentary are gentle-voiced Shana Watahomigie (just the first Native American, rather shockingly, to become a park service river guide) and her own child. The emphasis here, pitched at a family audience, is less on thrills than on thoughts of the future and how best to keep it from drying up.