Thanks to heavy precipitation and an intense snowmelt from April into June, communities in the Osoyoos Lake region, located on the border of Washington and British Columbia, contended with serious springtime flooding which indirectly led into an increased risk of wildfires from plant growth.
The winter snowpack upstream around Okanagan Lake was relatively low in the early part of the year, according to Brian Symonds, Canadian section member of the International Osoyoos Lake Board of Control, and the board expected a fairly standard spring season at its early March meeting. Snowfall in the mountains afterward increased the amount of snow to more normal levels into April, alongside a rainy period that ran from March through May elsewhere in the watershed.
“If you look at someplace like Penticton (British Columbia) where they have measured precipitation going back to 1909, this was the wettest March through May period on record,” said Symonds, also retired director of the British Columbia Ministry of Forest, Lands and Natural Resources (MFLNR).
Warm weather in May contributed to a rapid snow melt, bringing more water into the system, Symonds said; that melt was largely completed by the end of the first week of June.
The melt sent water into the Okanagan Lake system and south to the Okanagan River into Osoyoos Lake, said Sue McKortoff, Canadian section board member and mayor of the town of Osoyoos. Zosel Dam, located downstream of Osoyoos Lake, can help control the lake’s water levels, but as of the start of May all the gates were open and water was flowing through as well as it could.
For the towns around the Osoyoos and Okanagan Lakes, the flood required government responses. McKortoff said the Emergency Operations Center provided bags and sand for residents closer to the waterfront, and British Columbia’s Emergency Management Department coordinated the delivery and disposal of sandbags. The British Columbia MFLNR sent a crew with a sandbag filling machine to help. The town staff helped elderly residents by bringing sandbags to their homes, though most people were able to fill and take their own as needed. The municipal waste contractors agreed to pick up the sandbags and dispose of them in useful ways, such as to make new roads in the area’s nearby landfill.
At the water’s peak flood stage, the town also closed its boat launches and ran a campaign asking people to be aware of how power boat usage could cause wave damage in flood zones, she added.
Osoyoos Lake peaked at 914.8 feet (278.8 meters) above sea level around June 2-3, Symonds said, above a more normal summer range closer to 911.5 to 921 feet (277.8 to 280.7 meters) above sea level.
The precipitation had a side effect that played out during the summer with subsequent lack of precipitation, bringing the threat of wildfires. Symonds said the wet spring caused a lot of lush grassy undergrowth. With practically no rainfall from July into September, that undergrowth dried out and provided additional fuel, increasing the risk of fire.
McKortoff said Osoyoos town staff have shifted from dealing with the floods to focus on preventing fires from spreading out of control. Water restrictions were implemented in 2016 to make sure resources are available in case of a blaze, and have continued this year. So far, no major fires have started in in the south Okanagan basin, McKortoff said, though there has been a lot of smoke from fires in the Caribou region.
“We’ve gone from one extreme to another,” she said.