Human-water relations are the subject of this spartan, well-traveled documentary by filmmaker Jennifer Baichwal and photographer Edward Burtynsky, whose takeaway is that relations aren’t great. Actually, they knew that going in. Baichwal and Burtynsky make the most of big-screen proportions, shooting in magnificent ultra-high-definition video — and presuming each of their hyper-rich pictures to be worth even more than a thousand words. For all the grand fluidity of its imagery, the film has a treacherous drought of context. It is at least more poised than other nonfiction films developed from pleading environmental concerns. There’s some time-lapse footage of a dam basin flooding, but more attention is paid, generally, to the gradual pace of stuff drying up. At its best, Watermark seems to have been rendered in a sort of geologic time; otherwise it’s so jammed with slo-mo that you suspect the whole thing played at normal speed might only total about half an hour. But it gets around, from hot springs to rice fields; from the decadent fountains of Las Vegas to the sublimely crowded shores of the Ganges; from an inviting watershed in British Columbia to a repulsive tannery in Bangladesh. “Nothing happens without chemicals at any stage of tanning,” says a worker at the latter, over ominous shots of polluted river sludge. A similar effect is achieved in China, when someone says, “Xiluodu Dam’s capacity will be about six times that of the Hoover’s,” and the mood put across by accompanying visuals make it seem like what’s being discussed is a weapon of mass destruction. There’s also a hint of what it took to build the Los Angeles Aqueduct, but only a hint. For more — maybe too much — information on that horror story, see Chinatown. Although mostly in unfortunate ways, Watermark does finally reveal what it’s like for a substance to seem ample yet spread thin.