Whitefish Lake is known to fluctuate throughout the year dropping in winter, but a recent measurement of the lake’s water level show it approaching the record all-time low level.
The lake was 0.3 inches from the lowest recorded level in late December, according to the Whitefish Lake Institute. The lake was recorded at 2,996.26 feet.
Mike Koopal, executive director of WLI, said the last four years have all showed at or near record low elevations.
“The record low elevation set in 1967 stood for a long time until the new record set in 2015,” he said.
The lowest recorded level of the lake was set in 2015 when the lake dropped to 2,996.03 feet. The previous record low was in 1967 at 2,996.28 feet.
In 2016 the lake was recorded at 2,996.52 feet and in 2017 it dipped to 2,996.15 feet.
The low water elevations in the past few years have all been below the low mean water elevation for the 58-year-time period of records held by the institute. The mean high water elevation for the lake is 3,000.63 feet.
Koopal notes that the data is the best available, but “certainly doesn’t exclude lower or higher elevations that may not have been captured based on the survey date.”
The recent years of low lake elevations can be attributed, Koopal says, to three primary variables — lack of ice on the lake, flash droughts in summer and climate change impacting spring runoff.
“People don’t think about it, but decreased ice cover and ice duration are important drivers of lake elevation,” he said. “The lake will lose a significant amount of elevation due to evaporation. This winter evaporation can affect lake elevations much more than people would think.”
Koopal notes that less ice cover on the lake also means that lake warms more quickly in the summer, which also can exacerbate the rate of evaporation.
The second variable, he says, is even though snowpack has been near average, there has been flash droughts during summer with decreased precipitation.
The snowpack for the Flathead Basin this week was sitting at 90 percent of average. In January 2018 the snowpack was 119 percent of normal, and in January 2017 the snowpack was 96 percent of normal.
Precipitation in 2015 through 2018 for the months of June, July and August was below average as measured in Kalispell, according to the U.S. Department of Agriculture. The average precipitation between 1980 and 2010 for those months combined is 5 inches. In 2018, those months saw a combined 2.42 inches of precipitation, in 2017 there was 1.71 inches, in 2016 there was 3.93 inches and 2015 had just 1.09 inches for the same months.
Lastly, Koopal noted that climate change is driving the timing and magnitude of runoff from the mountains.
“We’re getting more volume loading to the lake from streams earlier in the year, but base stream flows in summer are decreasing,” he said. “Once again, water evaporation from the lake plays a key role.”
The city of Whitefish does draw some of its municipal water supply from the lake particularly in the summer months to supplement what it gets from Haskill Basin. Whitefish Lake Golf Club and Mountain Harbor also have water rights to pump from the lake.
However, Koopal says while city and other water users draw from the lake, his calculations are consistent with those of engineers that show water draws from those sources are not nearly as significant as evaporation in impacting lake levels.