Giant floating island travels 30 kilometres across B.C. reservoir
A floating vegetated island rests against the shoreline of the Ospika Arm of Williston Reservoir on Aug. 30, 2026. BC Hydro says the mass travelled about 30 kilometres from where it was first documented near Finlay Bay.
Photo: BC Hydro
A tree-covered floating island roughly the size of two football fields has been found after drifting about 30 kilometres across Williston Reservoir in northeastern B.C.
BC Hydro confirmed Aug. 31 that the mass had come to rest along the shoreline of the reservoir’s Ospika Arm, northwest of where it was first documented near Finlay Bay.
The utility said the island is about 140 metres long and 70 metres wide, covering roughly 9,800 square metres. Established vegetation, including trees, is growing on its surface.
BC Hydro was first alerted to the island Aug. 13, when local boaters provided photographs and video believed to have been taken on or around July 21.
Satellite imagery later showed the island west of Finlay Bay on July 21 and near the Ospika Arm on Aug. 15. Based on those observations, BC Hydro estimates the island travelled about 30 kilometres over 15 days before reaching its current location.
The island is now farther from the W.A.C. Bennett Dam than when it was first documented, and BC Hydro said it does not expect it to affect operations.
BC Hydro has not determined exactly how the island formed.
One possibility is that logs and other woody debris accumulated over many years in a sheltered part of the reservoir. As the material decomposed, vegetation may have taken root, eventually creating an interconnected mass capable of floating while supporting established plant growth.
BC Hydro said floating vegetated islands of this size are uncommon but can occur in large reservoirs. The island has also attracted interest from geologists, ecologists and other researchers interested in how floating vegetated islands form and move.
The utility plans to continue monitoring the island and gathering information about its origins and movement.
BC Hydro is warning people not to climb onto the mass.
Although people can approach it by boat or drone to take photographs, BC Hydro says the island consists of logs and decaying woody debris and is unstable and unsafe to land on or climb onto.
Williston Reservoir is located near Mackenzie, about 300 kilometres north of Prince George. Created by construction of the W.A.C. Bennett Dam on the Peace River, it began filling in 1968.
At full pool, the reservoir covers approximately 1,773 square kilometres and is the largest reservoir in British Columbia.
Floating and submerged debris is already a recognized boating hazard on Williston Reservoir. BC Hydro warns that snags and stumps can lie just beneath the surface and that debris may be encountered throughout the reservoir.
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