'Hoping for normal': Unpredictable weather a concern for freshet impacts on Okanagan Lake

May’s mix of heat waves and rainstorms sending a surge of snowmelt down the mountainside concerns Penticton’s dam manager, even as Okanagan Lake sits two feet below full pool target.

“It's the middle of May, I don't like seeing the 30 C temperatures. And one thing I also don't like seeing is overnight temperatures staying high up in the alpine and up in the higher elevations. If we have a lot of heat during the day, but it still cools down at night, that helps us out a lot in terms of a more gradual melt,” said Shaun Reimer, Okanagan section head and Penticton dam manager.

The BC River Forecast Centre's monthly snowpack survey was released Wednesday, noting the agency’s bulletin was already out of date on the day it was published due to the major uptick in melting last week.

“It's a little bit more difficult to make sense of some of the data because of this rapid snow melt. So in terms of my operations, as it relates to Okanagan Lake and the flows, we're really trying to set ourselves up for a sort of flexible situation,” Reimer added.

“Despite the fact that we have a moderate inflow forecast, and the lake has been quite low, leading up to this point. It's certainly starting to rise now and it's rising at three or four centimetres a day.”

Reimer said there is still a way to go before Okanagan Lake reaches the full pool target, and his operation is likely going to be increasing the outflows starting next week, continuing over the subsequent weeks.

“Of course, as conditions change, we will make those adjustments as well.”

Dave Campbell of the BC River Forecast Centre previously told Castanet this year’s freshet is happening about two to three times quicker than usual thanks to last week’s heat wave.

Reimer said that one of the things that happened over the last weekend was a “tremendous amount of inflow” into Okanagan River.

“While we have fairly moderate outflows coming out of Okanagan Lake, we had pretty high flows actually going into Osoyoos Lake. And that's from all the tributaries between Okanagan and Osoyoos lakes coming in,” he added.

“We're fortunate this year that Okanagan Lake isn't very high, because there have been in some of those years like 2017, 2018, we've actually had to reduce our outflows, which was threatening people around Okanagan Lake in order to moderate that flow, because of all of the creeks flowing into Okanagan River.”

While creeks and rivers receded, the coming heat this weekend could cause them to surge again. An area of concern lies in the South Okanagan. In Osoyoos, Environment Canada’s forecast calls for a high of 28 C on Saturday, followed by a high of 32 C on Sunday.

Reimer said the data that he does have from some of their real-time stations show them getting back toward normal for some of the high-elevation stations in snowpack melt.

“So, that's comforting. And again, it kind of gives a little bit more confidence in our schedule of releases from Okanagan Lake.”

He added that they are hoping for “normal amounts of rain” throughout June because it is in line with their forecasting and planning, which often takes into account normal amounts of rain.

“So when we don't get that rain, or we get too much rain, which either of those situations happened in the last three years, it certainly throws off our operations as well. So I'm always hoping for normal, but we don't always get what we want.”

Reimer and his team are paying close attention to all factors upcoming forecasts, weather events and snowpack data.