A floating island that disappeared after being spotted on Williston Reservoir in British Columbia, Canada, has been found around 30km from its first documented location.
The vegetated mass, measuring approximately 140m long and 70m wide, has come to rest against the shoreline of the reservoir’s Ospika Arm. Its current position is farther away from BC Hydro’s W.A.C. Bennett Dam than where it was initially identified near Finlay Bay.
BC Hydro said it does not expect the island, which covers an estimated 9800m², to affect reservoir or dam operations. However, the unusual event has attracted interest from geologists, ecologists and researchers studying how floating vegetated islands form and move.
The island was located through a combination of satellite imagery, observations from small aircraft and reports from boaters. Available information indicates that it travelled approximately 30km over 15 days before settling against the shoreline.
“When we first received photos and video of a floating island covered in trees, we weren’t entirely convinced,” said BC Hydro Community Relations Manager Bob Gammer. “In the age of AI, it’s important to verify unusual reports before drawing conclusions.
“Once we confirmed the island through satellite imagery and other observations, it quickly captured the imagination of the public and the media and sparked interest among scientists studying how floating vegetated islands form and move.”
Tracking the island
Williston Reservoir is located in northeastern British Columbia, about 300km north of Prince George and close to the community of Mackenzie. Formed by the construction of the W.A.C. Bennett Dam across the Peace River, the reservoir began filling in 1968.
It covers approximately 1773km² at full pool and is the largest reservoir in British Columbia. According to BC Hydro, it is also the seventh largest reservoir in the world by volume.
The floating island was first documented west of Finlay Bay in satellite imagery dated 21 July 2026. BC Hydro became aware of it on 13 August after receiving photographs and video from local boaters, believed to have been recorded on or around 21 July.
By the middle of August, however, the island was no longer visible at its reported location. Its disappearance prompted efforts to establish whether the mass had broken apart, moved elsewhere on the reservoir or been incorrectly identified.
Satellite imagery captured on 15 August subsequently showed the island near the Ospika Arm. BC Hydro reviewed the imagery alongside other observations and confirmed its new location on 31 August.
The utility announced the discovery on 2 September, ending a search that had attracted international media attention.
The delay between the image being captured and its use to locate the island reflects the fact that satellite imagery is not available in real time. Material may only become accessible for analysis several days or weeks after it has been recorded.
An unusual formation
The island appears to have remained intact during its journey across the reservoir. It supports established vegetation, including trees, and is approximately the size of two football fields.
Although floating vegetated islands of this scale are uncommon, BC Hydro said they can occur in large reservoirs. The precise origins of the Williston island have not yet been established, but the utility has put forward one possible explanation.
Logs and other woody debris may have accumulated over many years in a sheltered area of the reservoir. As this material gradually decomposed, plants could have taken root on its surface, creating a relatively stable and interconnected mass of debris, vegetation and root systems.
Changes in water level, wind or other reservoir conditions may then have caused the island to break free and begin drifting. BC Hydro has not drawn a firm conclusion about what triggered its movement or the route it followed between Finlay Bay and the Ospika Arm.
The event could nevertheless provide researchers with useful observations about the development, stability and movement of large floating islands in 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.
“We’ll continue monitoring the island and learning more about its origins and movement as the story unfolds. Stay tuned.”
Safety warning
Although the island appears solid and carries mature vegetation, BC Hydro has warned that it is unstable. Its structure is believed to consist largely of logs and decaying woody material, presenting a risk to anyone attempting to walk or climb on it.
Members of the public may approach by boat or use drones to photograph the formation, but the utility has asked people not to land on the island itself.
For BC Hydro, its current position offers some reassurance. The island is lodged against the Ospika Arm shoreline and is farther from W.A.C. Bennett Dam than when it was first documented.
No operational impacts are expected, although continued monitoring should help the utility determine whether the island remains in place and provide further evidence about how one of Williston Reservoir’s more unusual features came into existence.
