This summer could be a particularly bad year for wildfires in the Okanagan as a result of an exceptionally warm and dry spring.
“We’re already off to a pretty scary start to the fire year,” Ray Crampton, the Vernon-based district manager with the ministry of Forests, Lands and Natural Resource Operations (FLNRO) told a webinar last week about water supply in the Okanagan.
The webinar last Friday brought together experts on water, climate and fire preparedness to discuss the impacts of the warm, dry and early spring this year. It was organized by the Okanagan Basin Water Board (OBWB).
This year much of the province, especially the Okanagan-Similkameen, was affected by low precipitation, warmer temperatures and an early melting of the snowpack.
There is still plenty of water in the upper Okanagan Lakes and conditions for an official drought year have not yet been met, but that can change. The declaration of a drought year would allow Osoyoos Lake to be maintained at a higher level over the summer to conserve water.
For a drought to be declared, water flows and levels must fall below thresholds on both the Similkameen and Okanagan river systems. Currently, the Similkameen meets the criteria for a drought year, but the Okanagan system is forecasted to remain above the threshold.
The critical factor will be rainfalls in the “monsoon” period of mid-May to early July, normally the rainiest time of the year, said Doug Lundquist, warning preparedness meteorologist with Environment Canada based in Kelowna.
“It’s not looking good at this point,” Lundquist warned, citing long-range forecasts of continued dry, warm weather.
If there’s insufficient rain in this “monsoon” period, it will be hard to catch up over the summer, he said.
One of the major factors contributing to abnormal weather, Lundquist said, is the exceptionally warm ocean temperatures off Vancouver Island, which are, “way above range.”
Although El Niño is more of a winter phenomenon, it has definitely had an impact on temperatures, he said. And because ocean temperatures don’t change quickly, the impact is likely to persist.
The result has been an exceptionally warm spring that melted the snowpack early.
Most locations in the Okanagan saw temperatures about two degrees warmer than average in the February to April period. In Osoyoos, the average temperature was 8.5 degrees Celsius compared to a normal average of 6.3 degrees.
The higher temperatures are resulting in quicker evaporation, and there was less precipitation to begin with, he said.
Dave Campbell, section head with the B.C. River Forecast Centre, discussed snowpacks, which on May 1 were at 57 per cent of normal in the Okanagan, a record low since they have been recorded in 1985. The Similkameen is also breaking records at just 37 per cent of normal.
As early as the March 1 snowpack report, it was noted that warmer temperatures were causing precipitation to fall as rain instead of snow.
As of May 12, snow was found only at the highest mountain levels, Campbell said.
The combination of lower precipitation and earlier than usual melts is highly unusual, if not unprecedented, he said.
Shaun Reimer, who oversees Okanagan River and upper reservoirs for FLNRO in Penticton, observed that much of the early snowmelt has been retained by dams at the outflows of major Okanagan lakes.
There is some flexibility to release less water if drought conditions continue and to release more if rains bring water levels up, he said.
Reimer’s office manages all the dams except the Zosel, which controls the level of Osoyoos Lake and is in Oroville in Washington State. The operation of the Zosel Dam by Washington is based on orders from the International Joint Commission (IJC), which has a rule curve governing when lake levels are raised and lowered.
Gwyn Graham, of the International Osoyoos Lake Board of Control, said that outside of the freshet period when water levels can’t be controlled, Washington tries to maintain the level of Osoyoos Lake at 911.5 feet above sea level during the summer, although the state is allowed to raise it to 912 feet.
In a drought year, the lake level can be raised as high as 912.5 feet in order to retain more water for the late summer and fall.
“Right now we’re not in a position to declare drought,” Graham said, noting that the forecasted level of Okanagan Lake and the April to June net inflow into that lake are both above the threshold for a drought declaration.
The Similkameen River, however, is likely to be significantly below its threshold of 1 million acre-feet in April to July, meaning that this measure meets the criteria for a drought year.
Crampton, of FLNRO, observed that high fire seasons tend to come in four-to-five year cycles. The worst years recently were the 2003-4 and 2009-10 periods.
In 2014, wildfires burned 360,000 hectares of land, the third highest in the province’s history, he said.
Already in 2015, March had about twice as many fires as average. Since April 1, there have been 20 fires covering 137 hectares.
Richard McGuire
Special to the Chronicle
