Clearwater Lakes Alliance (CLA) Information
Disclaimer: For a general intro to lake ecology and a list of terms used below, check out the CLA home page.
~ Placid Lake ~
View of Placid Lake from the eastern shore. Photo by Emily McGuirt.
About Placid Lake
Figure 1: Location of Placid Lake within the Clearwater Watershed
Located southwest of Seeley Lake, Placid Lake is one of the most popular lakes in our watershed, known for its trout fishing, wildlife viewing, smooth water, and natural beauty (Figure 1). Best explored by kayak or motorboat, Placid Lake is around 1,300 acres, with a maximum depth of just over 90 feet.
The land surrounding the lake is a mixture of state and private lands, including a popular state park with a public boat launch. Due to the history of intensive forest management and fires in recent years, Placid Lake’s water quality is of concern. Placid Lake also has one of the most developed shorelines in the Clearwater Valley, which likely further contributes to the addition of excess nutrients and pollutants into the water.
Past Monitoring
Overall, the Secchi depth measurements taken by Adopt-a-Lake volunteers over more than ten years place Placid Lake in the meso-oligotrophic range (middle-to-good water quality) with little variation seen from year to year (Figures 2 and 3). This is not surprising, as lake trends generally change slowly over time. However, in the last three years, volunteers have commented on noticeable shoreline “blue green algae” (scientifically known as cyanobacteria) accumulation in the fall, similar to what has been documented in Salmon Lake. This increased productivity could be a result of increased nutrient loading from both anthropogenic and natural sources.
Figure 2: Secchi depths recorded at 2 sites on Placid Lake from 2009 through 2020.
Figure 3: Secchi depths recorded at 15 sites on 8 lakes in the Clearwater Watershed, 2009 through 2020. The red and green lines represent the bounds for transparencies considered indicative of eutrophic and oligotrophic conditions, respectively. Note that as of 2020, Clearwater and Rainy Lakes were omitted from monitoring.
Figure 4: Dissolved oxygen depth profiles in Placid Lake in 1974, 2008, and 2020.
Dissolved oxygen (DO) has been monitored on Placid Lake sporadically over the past few decades. From this data it is evident that Placid Lake has historically shown an oxygen deficit at its deepest depths, but this trend is more pronounced in recent years (2008 and 2020) as compared to historical data (1974) (Figure 4). In 2020, CRC undertook DO monitoring on Placid Lake to give us a better idea of current conditions and whether water quality is further declining. In addition to Placid Lake, DO profiles was taken on 5 other lakes in our watershed (Salmon, Seeley, Big Sky, Alva, and Inez) on a monthly basis throughout 2020 to establish a baseline DO dataset.
Figure 5: Dissolved oxygen (mg/L) profile recorded at two sites in Placid Lake, from May through September 2020.
Figure 6: Temperature (°C) profile recorded at two sites in Placid Lake, from May through September 2020.
Although DO readings did not begin until July for most of the lakes, one May reading was taken on Placid Lake (Figure 5 and 6). From the 2020 profile, it is evident that before air and water temperatures peaked mid-summer, the water was still mixing not well stratified, and a thermocline (the depth where dramatic change in temperature occurs) was not well defined. As a result, this DO profile contained some of the highest readings through the water column, with the least amount of change as depth increased. As the water became more stratified in July-September, DO decreased more through the water column in all of the lakes.
Once the thermocline formed in Placid Lake, it remained at about 8 meters through the summer, consistent with the other lakes. In general, DO was lower at site 2 (the north arm) than site 1 (mid-lake), especially in August and September. There is likely more mixing mid-lake throughout the year, which would increase DO through aeration. Additionally, a potentially toxic algae bloom of the genus anabaena was confirmed in the north arm of Placid Lake in September of 2020, which could have decreased DO through the respiration of microorganisms consuming this large algae bloom, as discussed in the introduction. The oxygen in Placid Lake decreased quickly through the water column after May which could be cause for concern for larger organisms living in the lake.
Current and Future Monitoring
Figure 7: Dissolved oxygen monitoring on Placid Lake, May 2020
Water Quality
Drawing conclusions based upon the sporadic data that currently exists prior to 2020 is difficult, and more consistent measurements are needed to better assess the status of each lake in the Valley. In 2021, CRC is collecting data on DO, conductivity, algae, nutrient, and pH conditions on Placid Lake (as well as Alva, Inez, Big Sky, Salmon, and Seeley) in order to continue establishing baseline data to aid in future water quality analyses. We will also be analyzing data to evaluate the health of our aquatic ecosystems in the Valley. This includes looking for trends in Nitrogen and Phosphorous levels, presence of E. coli bacteria, evidence of oxygen depletion, growth of potentially toxic algae, and other changes to the waterbodies in the Clearwater Watershed.
Figure 8: Water quality monitoring sites on Placid Lake in 2021.
A new addition to the monitoring process this year is a multiparameter water quality monitoring instrument. This new piece of equipment was recently purchased thanks to a Bureau of Reclamation WaterSMART grant. It uses sensors to accurately read and record levels of conductivity, algae, and pH as deep as 30 meters (~100 feet) in our lakes. Such data is integral to determining the health of our lakes here in the Clearwater Watershed and can aid in detecting harmful algal blooms and habitat degradation.
Check back in the winter for results and findings from our monitoring season!
Algae
One concern that is being watched for on a yearly basis is the appearance of toxic blue green algae. This has been found occasionally in the past, with the most recent observation in October 2020. Read the October 22, Seeley Swan Pathfinder article, “Algae bloom observed at Placid Lake” to learn more.
The cause of harmful algal blooms is still unknown, however certain water conditions such as high nutrient levels, warm temperatures, and decreased water flow can increase the frequency of toxic algae growth. Toxic blooms can occur naturally, but the number of blooms has been increasing globally in recent years due to human impacts on aquatic ecosystems. Additional information on toxic algae blooms can be found at:
Harmful Algae Blooms (CRC webpage)
Toxic Algae in Montana (FAQ data sheet by MT DPHHS website & MT DEQ)
Freshwater Harmful Algal Blooms 101 (Natural Resources Defense Council, NRDC website)
Figure 9: Aging dam on Owl Creek
Aquatic Invasive Species (AIS)
Northern Pike
Another area of concern on Placid Lake is the potential for invasive species to access the lake via the aging dam on Owl Creek, which flows south towards Salmon Lake. As of May 8, 2020, biologists from the Montana Fish, Wildlife, and Parks discovered a single non-native northern pike in Placid Lake, a species known to wreak havoc on native fish populations. The extent of the problem is still to be determined. However, if the Owl Creek dam is breached during high water years, this could lead to more unwanted invaders entering Placid Lake.
Zebra and Quagga Mussels
Figure 10: 11 lakes in the Swan, Clearwater, and Blackfoot drainage basins were monitored for AIS in 2020. In order, as labeled, these lakes include: Holland, Lindbergh, Alva, Inez, Seeley, Placid, Big Sky, Salmon, Upsata, Coopers, and Browns.
CRC has been monitoring for invasive species in the Clearwater Watershed throughout the summers since 2009 on each of the major lakes in the Valley (Alva, Inez, Seeley, Salmon, Placid and Big Sky). One of the biggest threats to Montana’s waterways is the introduction of zebra and quagga mussels, collectively referred to as dreissenid mussels. The purpose of our AIS program is to monitor for the presence of veligers in the lakes by straining large volumes of lake water through a fine mesh net to collect planktonic and microscopic materials in the lake water, including mussel veligers, if present. Veligers are the free-swimming, microscopic juveniles of zebra and quagga mussels. Over the course of the 2020 field season, 62 total sites, spread out over 11 lakes (Figure 10), were sampled each round, totaling 310 samples.
We are happy to report that zebra and quagga mussel veligers were undetected in all of the samples collected and analyzed in 2020. We will continue to monitor for zebra and quagga mussel veligers throughout 2021 on the six major lakes in the Valley.
Fragrant Waterlilies
Another problematic invasive species in the Clearwater Watershed is the non-native Fragrant Waterlily. The Fragrant Waterlily was likely introduced to the region as an ornamental plant, but has since experienced exponential population growth. The mats of these waterlilies are detrimental to aquatic habitat and outcompete native plant species. Fragrant waterlilies can also cause oxygen depletion, which negatively affects native fish and amphibian species. In 2020, the Missoula County Weed District mapped the waterlilies on the major lakes in the Clearwater, recording a total of 15.7 acres of the species on Placid Lake.
In 2020, CRC’s first annual Make-the-Cut event took place on Placid and Salmon Lakes. 2021, CRC held lily digging and cutting events at various locations on Seeley Lake in an effort to remove the invasive species. We hope to hold events such as these at more lakes in the Clearwater Valley in upcoming years.
Through the Clearwater Lakes Alliance (CLA), we hope to involve more residents in our citizen science Adopt-a-Lake program to expand the parameters we monitor and increase our monitoring frequency. CLA will also help us to take steps to actively improve the water quality of the lakes, which over time will hopefully be evident through the monitoring data we collect.
Establishing baseline monitoring data through our Adopt-a-Lake program is only the start. Contact CRC’s Dave Torell, (email: dave.torell@crcmt.org ) to learn more about current efforts and/or how you can get involved.
Return to Clearwater Lakes Alliance main page.
Last updated September 2021