Water quality

Water quality

Invasive species

Our first defense against invasive species in our water is to use a self-wash power spray located at the DNR’s boat ramp on Little Glen.

Our invasive species prevention helps prevent the introduction of the quagga mussel, coltsfoot, the spiney water flea, the fishhook water flea, the round goby, the rusty crayfish, viral hemorrhagic septicemia (VHS), Eurasian watermilfoil, starry stonewort, and hydrilla to mention a few.



Coltsfoot (Tusilago farfara), a vicious foreign invader, was first found on the shores of Big Glen Lake in 2008. Since then, it has spread rapidly along the shoreline and now is found throughout the shoreline from Brooks Lake to Inspiration Point-a four-mile area. It quickly wipes out native herbaceous plants as it invades shorelines, lawns, and neighboring fields. It’s easiest to identify in early spring when a bright yellow flower appears atop of plant stems as seen in the picture to the left.  It may poke its head up through snow as early as mid-March. Deadheading these blossoms is the first line of defense and helps prevent further spread of the plant through seed heads easily carried on wind to new locations.

Mid-summer leaves as shown to the right are large, up to 7 inches wide, hoof-shaped with angular teeth on the margins. The creeping, underground rootstalks may lurk as deep as 10 feet. They preserve their vitality for a very long period and a small piece may send up foliage after many silent years underground. Attempting to eradicate by digging is not encouraged.


PFAS- What Are They?

The GLA has been doing its part to stay up to date on this emerging water/health issue.
Please use the following links for information.
PFAS What you need to know
PFAS Info Sheet PDF
Learn more about PFAS here

Shoreline Management

Our Shoreline Management program is organized by the Water Quality Committee. The purpose is to protect our beautiful lake and has three major segments to its focus:

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  • Property Maintenance – Suggestions on how to maintain your lake front property, so as not to damage the lake;
  • Cladophora Studies — Measuring the extent of damage to the lake by pollutants entering into the lake from surrounding surfaces;
  • Shoreline Surveys — Analysis of individual pieces of property to reduce/eliminate contaminate intrusion into the lake, by making suggestions on alternations in landscaping as well as septic maintenance.
  • Fertilizer — The Glen Lake Association has recommendations (in order of importance) for riparians who wish to add nutrients to their lawns and landscape.

The Glen Lake Association is a member of the Cooperative Lakes Monitoring Program (CLMP) which is a volunteer inland lakes water quality monitoring program. Every week during the summer volunteers measure water clarity (secchi disk visibility depth) and at various specified dates sample for phosphorus and Chlorophyll. We measure and sample on Big and Little Glen, Brooks, and Big Fisher lakes.

The CLMP website has data on Big Glen data going back to 1979 for secchi depths and to 2001 for chlorophyll and phosphorus. Water clarity has been improving on Big and Little Glen giving it that look of the blue Mediterranean. You might think this is a good thing, but maybe not Clarity is affected by suspended solids and algae. We believe clarity is increasing due to the removal of zooplankton and algae by zebra or quagga mussels. This means less food for small fish and greater depth where aquatic plants can grow. Our lakes have a lot of mussels. When we do our yearly invasive aquatic plant survey, we often bring up small mussels attached to the plants.

The following chart shows the numbers.

Phosphorus levels for Big Glen are averaging about 4 parts per billion over the last 18 years, dropping slightly. This is very good, indicating that we don’t have a lot of fertilizer or septic runoff into the lake. Some phosphorus is essential for plant and algae growth which is food for fish. Our level is very low.

Chlorophyll is the pigment that allows plants (including algae) to use sunlight to convert simple molecules into organic compounds via the process of photosynthesis. Measuring chlorophyll concentrations in water is a surrogate for actually measuring algae biomass. The chlorophyll has been steady at less than 1 part per billion for 18 years. These are very low levels which indicates little fertilizer and septic runoff.

In some lakes, as septic systems get older and homes are upsized and lived in for more of the year, phosphorus and chlorophyll levels ramp up. This has not happened to Big Glen. The same is true for Little Glen, Brooks and Big Fisher lakes.

Score your own shoreline using this survey.