Taking Care of Lake Five 

Northwest Montana Lakes Network (NMLN) is an organization dedicated to the care of Montana’s lakes and waterways. The NMLN is a partnership between Montana Fish, Wildlife & Parks and the Whitefish Lake Institute. Many organizations seek information about water quality for a variety of reasons related to early detection of AIS, education, water quality research, planning, and regulatory purposes. NMLN strives to provide this information. 

Established in 2011, NMLN trains local volunteers to monitor the quality of their waterways. These monitoring programs provide baseline data and record changes in the water that may have otherwise gone unnoticed. 

Volunteers collect and record lake data measurements pertaining to physical conditions and visual observations. Among the most important parameters monitored by the volunteers are temperature, Secchi disk depth, and the presence/absence of aquatic invasive species (AIS). Qualitative atmospheric and water condition data are also recorded. Volunteers sample their assigned location twice per month, at roughly two-week intervals at a mid-lake site. Midday (11am – 3pm) is the best time to insure optimum sunlight penetration, regardless of cloud cover. 

The project coordinator from Whitefish Lake Institute, Cynthia Ingelfinger, visits each program lake between mid-July and mid-August to ensure data consistency and to obtain additional data addressing the question of whether nutrients are on the rise due to anthropogenic activity around the lakes. AIS early detection monitoring is also conducted at this time. 

A. Temperature of the water: Using a thermometer attached to a float and a string, the volunteer drops the thermometer into the water to a depth of 18 inches to obtain his bi-weekly temperature information. The once-a- summer test by Cynthia Ingelfinger checks in addition to the temperature, many physical parameters to include dissolved oxygen, salinity, PH and chlorophyll of the water column from the surface to the lake bottom using a Hydrolab. On this day of testing, August 9, 2021 the results for Lake Five were: 73 degrees on the surface and 46.6 degrees at the bottom of the lake. 

B. Transparency of the water: A Secchi disk, an 8-inch (20 cm) disk with alternating black and white quadrants, is lowered into the water of a lake until it can no longer be seen by the observer. This depth of disappearance, called the Secchi depth, is a measure of the transparency of the water. Transparency indicates the impact of human activity on the land surrounding the lake. If transparency is measured through the season and from year to year, trends in transparency may be observed. Transparency can serve as an early 

warning that activities on the land are influencing a lake. The Secchi disk clarity was 17.10 feet down on August 9th. 

C. Trophic status of the water: The trophic status of a lake is determined by the amount of nutrients (nitrogen and phosphorus). Lakes are classified as either oligotrophic, mesotrophic or eutrophic. Eutrophic lakes are high in nutrients and plant growth, whereas oligotrophic lakes have relatively low levels of nutrients. Mesotrophic lakes fall somewhere between the eutrophic and oligotrophic range. Most of the lakes in the NMLN are oligotrophic thus having good water quality, clarity and lower nutrient levels. 

There are many sources of nutrient supply. Nutrients can come from geologic bedrock, soils, and vegetation. Anthropogenic sources of nutrients include fertilizer, agricultural runoff and wastewater effluent. As human interaction with lakes grows in terms of use and development, water quality tends to decline. 

D. Aquatic Invasive Species: 

On her annual visits to local lakes Cynthia Ingelfinger uses a plankton net to collect microscopic samples for analysis by Montana Fish, Wildlife & Parks. Volunteers also watch for the appearance of mussels, snails and clams along with invasive aquatic plants. They compare their found samples with pictures of invasive species found on the NMLN website, reporting their findings in the bi- weekly reports they send back to NMLN. 

E. Lake Five’s Volunteers: 

Mike Kopitzke: 2020, 2021 Ron Ridenour: 2011-2019 

E. More Information: 

To learn more about NMLN visit https://nmln.info/

For information specific to Lake Five visit: http://whitefishlake.org/wp-content/uploads/2020/10/NMLN_2019_Medium-Lakes.pdf

To learn more about Whitefish Lake Institute visit https://whitefishlake.org/
To contact NMLN’s program director e-mail: cynthia@whitefishlake.org or call Cynthia Ingelfinger: ph: 406.862.4327