When the waters of the Similkameen River peaked during the flooding on Nov. 15, enough water was moving to turn the Okanagan River backwards into Osoyoos Lake.

The combination of the atmospheric river and melting snow sent the river into near-record conditions at many monitoring stations along the way. South of the border, the Nighthawk station recorded a peak of water flowing at a rate of 762 cubic metres a second, which is shy of the all-time record during the spring of 2018 when the station recorded 883 cm/s.

Muddy water from the Similkameen River that flowed upstream into the Okanogan River contrasts with clear water in Osoyoos Lake. The aerial photograph was taken at 11:15 a.m. on Nov. 17 by Colville Tribal Fisheries Biologist Mary Davisson, at the outlet of Osoyoos Lake to the Okanogan River near Oroville. (Mary Davisson photo/CCT Fisheries)

At the monitoring station near Hedley, the Similkameen River recorded provisional flow levels of 1,110 cubic metres a second, enough to fill an Olympic swimming pool every 2.25 seconds.

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According to the International Osoyoos Lake Board of Control, the record high autumn discharge combined with low lake levels caused the Okanogan River south of the border to reverse flow on Nov. 15.

By 2 p.m. on Nov. 16, the water had crested the spillway on the Zosel Dam and began to flow up the channel towards Osoyoos Lake.

Over Nov. 28, the waters rose again to around 350 cubic metres before beginning to drop again.

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