State of the Lake, 2009

Researchers at the Flathead Lake Biological Station have produced periodic reports that describe water quality in the big lake back to 1899.  The older studies describe the lake as it was before Kerr Dam and other human-caused influences such as flow regulation, lake shore erosion and pollution from sewage treatment plants and diffuse inputs from urban and agricultural lands began to change water quality. 

Starting in 1977, water quality data have been collected routinely by Dr. Bonnie Ellis and FLBS scientist, Jim Craft.  At least 15 times a year, Craft and Ellis are out on the lake in the Station’s research vessel Jessie B, collecting water samples for laboratory analyses and obtaining profiles of temperature, dissolved oxygen, chlorophyll, conductivity, light penetration, water clarity and other measures with sophisticated electronic sensors that are lowered through the water column from the boat.  The Flathead Lake water quality data base is one of the longest and most detailed for large lakes worldwide.  These data have allowed Ellis and colleagues to describe the long-term trends in water quality that are coherent with the expanding population and changing land uses in the Flathead Basin.  Her studies provide a basis for minimizing pollution and maintaining clear, clean water in the crown jewel of the Crown of the Continent.

With help from Dr. Daniel Goodman, an environmental statistician at Montana State University, Dr. Ellis recently reanalyzed all the Flathead Lake data, including all of the fisheries monitoring data collected by the biologists working for the Confederated Salish and Kootenai Tribes and Montana Fish Wildlife and Parks.  The analysis shows that water quality gradually declined as the human footprint in the Flathead Basin increased.  However, the biggest change in the lake was not due to pollution but rather, was clearly and directly related to the introductions of various fish species during the early years and a mysid (“opossum”) shrimp species in early 1980s.  The native fish community, notably bull and cutthroat trout, have almost completely disappeared from Flathead Lake due to food web changes caused by the shrimp and strongly negative interactions with nonnative fishes, especially lake trout that reproduce in the lake.  Juvenile lake trout feed very effectively on the abundant mysids allowing substantial annual recruitment of adult fish that was not possible in the premysid period.  Hybridization with nonnative brook and rainbow trout also is contributing to native fish decline. 

On the other hand, water quality in Flathead Lake, measured in terms of water clarity, algae production and deep water oxygen content, among other key variables, remains remarkably good given the large number of people living around the lake and in the Kalispell Valley.   In fact, Flathead Lake remains among the cleanest of the world’s large lakes owing to two key attributes.  First, the Flathead River dominates the water flux through the lake and the river water is clean, clear and cold because it comes mostly from Glacier National Park and the Bob Marshall Wilderness complex.  Second, water quality management in the lake basin is very good overall.  All of the urban centers have good sewage collection and treatment facilities.  Kalispell’s is among the best in the USA.  Best management practices on forest lands are well established and monitored basin-wide.  But, agricultural activities are poorly monitored and some of the ground water monitoring wells have high nitrate, pesticide and herbicide concentrations.

Not much can be done about the food web changes that Ellis and colleagues have documented.  Bull trout likely cannot hang on in the face of the burgeoning lake trout population that has spread from Flathead Lake to all the big lakes in Glacier National Park where bulls and cuts once were abundant.  Moreover, lake trout have become a popular sport fishery in Flathead Lake.  Ironically, bull and cutthroat trout populations are robust in the South Fork of the Flathead River because Hungry Horse Dam blocked immigration of nonnative species and the reservoir provides adequate rearing habitat.  Perhaps our native fishes can be preserved there in the long term but preventing introductions via bait buckets or illegal planting will be problematic for managers.  Likewise, new introductions into Flathead Lake are a real threat.  Zebra mussels and walleye are likely candidates and a great deal more effort than currently exists will be required to prevent another bad introduction, if it has not already occurred.

Flathead Lake in 2009 is clean and clear and nothing unusual has occurred so far this year in the monitoring record.  However, it does appear that the lake is getting warmer year by year.  Indeed, the volume of the warm upper layers in the lake during has increased substantially since 1990.  The lake has not frozen over since 1988 and persistence of ice in the bays is declining.  Summer surface temperatures routinely exceed 21°C (70°F), too warm for cold-adapted cutthroat trout to grow, thus compounding the food web problem that has pushed cutthroat to the brink of extirpation.  Moreover, pollution algae thrive in warm water as the nutrient supply increases, and Ellis’ analyses show that nitrogen inputs have steadily increased over the last decade.

Managers and the public must be vigilant and proactive to preserve the healthy state of Flathead Lake water quality.  We have adequate laws to protect water quality if the statutes are enforced.  Nonetheless, conversion of ag lands to urban and commercial uses in the Flathead Valley is gradually increasing the diffuse (nonpoint) inputs of pollution to the Flathead River and the lake.  Gravel mining along the Flathead River is reducing the resiliency of the alluvial aquifer to reduce pollutant loads.  Encroachment of human uses into riparian buffer zones along the river and lake increases every year, reducing natural trapping of nitrogen and phosphorus that increase algae production in the lake.  Plans for giant strip mines to remove coal in the Canadian North Fork of the Flathead River are still moving forward in spite of repeated demonstration that negative effects will extend to Flathead Lake in addition to severely negative effects on the Glacier-Waterton International Peace Park and World Heritage Site.

Continuing the Flathead Lake Biological Station monitoring program is essential to keep track of changes in water quality and to stimulate proper management responses.  The monitoring program costs $200,000 per year for the full suite of variables and sites that should be routinely sampled.  Flathead Lake water quality monitoring by the Biological Station is funded by legislative appropriation and EPA clean water dollars that are passed through the Department of Environmental Quality.  Unfortunately, the monitoring program currently is running on a bare bones budget because the Department of Environmental Quality has been unable to maintain their share.  Private contributions to the monitoring program may be made at www.umt.edu/flbs.  What is more important than Flathead Lake?

For more information about current research at the Flathead Lake Biological Station, visit our Research pages or read the most recent version of the Flathead Lake Journal.