B.C.’s new model for predicting runoff into Okanagan Lake has a very different forecast for 2023

The provincial government manages the lake level and has to strike the right balance to ensure there is sufficient water, but not so much it causes flooding.

Each year heading into spring melt, B.C. tries its best to predict how much water will runoff into Okanagan Lake and other water bodies in the province.

It’s important information as the provincial government manages the lake level using a dam in Penticton and has to strike the right balance to ensure sufficient water in the lake to last through the hot and dry summer, but not so much it causes flooding.

Partially in reaction to the 2017 flood, the province developed a new model for making those predictions and its latest forecast is very different from the old method.

The River Forecast Centre’s Feb. 1 update, says the old model is predicting “Okanagan Lake inflows to be near normal…while the updated model forecasts well above normal (>140 per cent) seasonal inflows.”

Jonathan Boyd a hydrologist with the River Forecast Centre explained the old forecasting method only uses data from up to 2010 while the new method includes more recent data.

“That model also incorporates seasonal forecasting, but it is a little more skillful. It actually will take the Environment Canada seasonal forecast for the temperature and precipitation for the upcoming few months and use that to come up with a forecast.”

Shaun Reimer, the provincial employee who is in charge of managing the lake level, said in early February, he is putting more emphasis on the newer forecast model that is predicting a larger volume of runoff.

The province has been letting more water out of the lake to compensate for the expected larger-than-normal runoff. Reimer said the outflow was “more than doubled” last week and will be increased again this week.