Floating vegetated island mystery solved: BC Hydro locates 140-metre island in Williston Reservoir

BC Hydro has solved the mystery of a large vegetated floating island that vanished from Williston Reservoir in northeastern British Columbia. The island, approximately 70 metres wide and 140 metres long — roughly the size of two football fields — drifted about 30 kilometres northwest from where it was first discovered near Finlay Bay before settling against the shoreline in the Ospika Arm of the reservoir, approximately 30 kilometres northwest of where it was first discovered near Finlay Bay and farther away from the W.A.C. Bennett Dam.

BC Hydro first became aware of the island on Aug. 13 after receiving photos and video believed to be taken around July 21. After the island reportedly disappeared from view, the mystery was solved Monday, Aug. 31 when BC Hydro confirmed its location using satellite imagery dated Aug. 15. The island drifted its full 30 kilometres in just 15 days before coming to rest.

"When we first received photos and video of a floating island covered in trees, we weren't entirely convinced," said Bob Gammer, BC Hydro's community relations manager. "In the age of AI, it's important to verify unusual reports before drawing conclusions."

Once confirmed through satellite imagery, the island quickly captured the public imagination. CBC first reported on the discovery Aug. 29, after which the story generated headlines from the BBC, The New York Times, TMZ, and National Geographic. The island has sparked interest among scientists studying how floating vegetated islands form and move.

One possible explanation is that the island formed from logs and woody debris that accumulated in a sheltered area over many years. As the material gradually decomposed, vegetation may have taken root, creating a stable mass of interconnected debris and plant growth. Floating vegetated islands of this size are uncommon but can occur in large reservoirs.

"Finding the island has answered one question, but it has raised several others," Gammer said. "While we're pleased to have confirmed the island's location, there is still more to learn about how it formed and how it came to drift across the reservoir."

BC Hydro says people are welcome to approach the island by boat or drone to photograph it, but the utility is cautioning that the island is composed of logs and decaying woody debris, making it unstable and unsafe to land on or climb onto. BC Hydro does not expect any operational impacts from the island's presence.