Bio station dives into data to explain low lake levels

The Flathead Watershed has confronted several significant climate-related challenges in recent years—severe drought conditions, beetle infestations, and increased wildfire activity among them.

Yet in spite of these challenges, the one thing the region has been able to depend on has been consistent and reliable conditions in our pristine freshwater rivers and lakes.

But that all changed this summer, when Flathead Lake (and more recently, Whitefish Lake) began experiencing notably low water levels that impact our recreational opportunities and local economies. As the water dropped, concern began to rise, and there are now many narratives attempting to make sense of this summer’s low water levels.

So, the question for many remains: What’s going on with lake levels in northwest Montana?

After diving into preliminary data, the Flathead Lake Biological Station (FLBS) Director Jim Elser and fellow FLBS scientists are now able to communicate the Bio Station’s perspective on the hydrological and water management situation at hand.

The story behind the low lake levels begins with the winter of 2022-2023 being a low snow year.

“Across the upper Flathead drainage, water stored in snow during the winter of 2022-23 was only 80% of the long-term average,” said Elser at the Bio Station’s annual Open House on August 4. “Most importantly, however, with spring’s arrival, the snow that did accumulate melted exceptionally fast due to warm temperatures and rain in May.”

Typically, snowmelt in the Flathead persists through June and into July. In 2023, snowmelt had all but ceased by the start of June.

When Elser examined the total annual discharge of the mainstem Flathead River at Kalispell from January 1, 2023 to August 6, 2023, he found the 2023 discharge was only 60% of the 50-year (1969-2023) median discharge during those same months. This means that, relative to the median, the volume of the absent snowmelt water from January 1 through August 6 would have been enough to raise the level of Flathead Lake by one foot at least 17 times.

Diving deeper into the data, Elser found that Flathead Lake’s positive water balance (when the water flowing into the lake from its rivers is greater than the water leaving the lake) increased sharply at the end of April as the snow pack began its extremely rapid melt. This led to lake level rising rapidly during the month of May, and near full pool was reached on June 13.

But during early June, Flathead Lake inflows dropped considerably—so much so, that the water coming into the lake was less than the mandated minimum amount of water the dam operators are supposed to release per the Seliš Ksanka Qispe (SKQ) Dam’s operating license. These mandates are in place to protect ecosystems, economies, and industries dependent upon Flathead’s waters further downstream.

Elser’s calculations show that, from the start of April through June 12, which is the period when Flathead Lake is normally filling, inflows were 78% of the median. However, from June 13 through August 6, inflows were only 34% of the median. Once the river inflow rates had declined to levels below the mandated minimum discharge at the dam, SKQ Dam operators had no capacity to maintain the lake level.

These low flow conditions are consistent with the severe drought that northwestern Montana has been experiencing in recent years, per data from the U.S. Drought Monitor. According to analysis from the U.S. Environmental Protection Agency, the low snow conditions are part of a longer-term and likely ongoing decline in snowpack in western Montana. Unfortunately, this means that we should be prepared for more summers with low lake levels moving forward.

From a management standpoint, it’s important to recognize that Flathead Lake and the rivers that feed it are part of the Columbia River drainage—a vast network of free and regulated rivers and lakes that includes a network of dams and other water control structures. These dams and structures are governed by a complex system of statutory, regulatory, and contractual arrangements involving federal, state, tribal and private entities.

Short-term changes in operations by any individual entity within this system are very challenging to implement, and no dramatic changes in operations can be made without prior approval by an interagency technical team. As a result, water management plans are assembled well in advance of seasonal transitions, and regional water managers depend on medium and long-range climate forecasts when plans are made.

In February 2023, the National Oceanic and Atmospheric Association (NOAA) predicted that our region would come out of drought during March, April, and May but this did not occur. NOAA later adjusted its forecasts to include continued drought conditions in subsequent communications, but it’s possible that the initial forecast of higher precipitation during the spring had an impact on the winter and spring decision-making in the Columbia Basin.

However, while it’s conceivable that SKQ Dam operators could have held more water in the lake during May (although their ability to do so is constrained by flood avoidance requirements), this only would have filled the lake faster.

Holding more water in May would not have avoided lake level decline after June 13, which is when river inflows declined to levels below the mandated minimum discharge.

When down-ramping of dam discharge began at the beginning of July, the negative water balance began to moderate and the rate of lake level decline slowed. By the end of July, inflows and discharge came into approximate balance.

One silver lining of the lake level issue: FLBS scientists do not anticipate any major ecological or water quality impacts in the main body of the lake. Even with the current low levels, Flathead Lake remains within the normal annual range of lake level fluctuation. The absent water represents only 0.8% of the lake’s maximum depth and 2% of its average depth. FLBS researchers will consult the ongoing, decades-long monitoring record and provide a more comprehensive assessment once the entire summer’s monitoring data are assembled.

Until then, Elser stresses the necessity of collaboration and informed communication among community leaders, managers, and residents to best address the lake level challenges.

“In light of these challenging limnological, hydrological, and climatic conditions,” said Elser, “we at FLBS recommend that water managers, political leaders, and community members engage in constructive conversations about adjustments in operations, infrastructure, expectations, and attitudes to best cope with the possibility that the difficult situation we are experiencing in 2023 may happen again in the coming years.”

For more information, or to view more in-depth analysis, data, and figures explaining northwest Montana’s low lake levels, visit the FLBS website at https://flbs.umt.edu/newflbs/outreach/news-blog/posts/2023-flathead-lake-level-data.