Water Quality Overview

For most, the defining characteristic of any lake is its quality of water. Water quality has a direct impact on aesthetics and suitability for recreational activities, as well as habitat for fish and wildlife. Water quality also affects aquatic vegetation growth, which can dramatically impair enjoyment of the lake if left unchecked – especially when invasive species are present. Bay Lake is fortunate to have good water quality supported by an effective program for invasive vegetation management. But protecting the lake requires continual effort and attention from everyone.

The Bay Lake Improvement Association (BLIA) conducts monthly water quality sampling, May through September, each year to quantify the parameters that define the trophic state index (TSI). TSI monitoring for chlorophyll, phosphorus and clarity (Secchi disk) provides a widely recognized and standardized “scorecard” to measure a lake’s health. TSI is a useful tool to compare similar lakes in the same eco-region. The association also measures temperature and oxygen levels at various depths to monitor conditions for fish habitat.

More information on how TSI is measured and used as a tool »


Since all parameters mentioned above can be impacted short-term by sudden or abnormal weather events such as extreme rainfall, drought or extended summer heat waves, the BLIA also conducts through-ice testing every other winter. Sampling though drilled holes while the lake is ice-covered and “resting” (i.e., undisturbed by surface weather and human activity) provides the best information for long-term trend analysis. pH and chloride levels are also included in winter sampling tests.

BLIA contracts with A.W. Research Laboratories (AWRL), an independent, certified water testing laboratory in Brainerd, to conduct sampling and lab analysis. Association volunteers assist AWRL technicians with sampling work to minimize program costs. AWRL summarizes testing results summer TSI sampling annually or winter sampling bi-annually for actions to protect and improve Bay Lake water quality.

Archived AWRL Reports

How can we help maintain and improve water quality?

Click to read 10 Tips for a Healthy Lake

Below are actions we can all do to help improve and protect the water quality of Bay Lake for future generations: 


Keep out chlorides.

Like many lakes in Minnesota, Bay Lake has elevated levels of chlorides (aka salts) which can be harmful to aquatic life. Elevated chlorides are a result of human activity – the two biggest contributors being road or sidewalk deicing salt (runoff into lake) and discharges to septic systems from water softeners. Septic systems do not treat or remove chlorides – they pass directly through the drain field and in many cases make their way to the lake via surface runoff or groundwater flow. Chlorides do not naturally degrade so once they are in the lake, they remain essentially forever. Chloride levels could fall as they are slowly flushed away, but only if the introduction of new chlorides to the lake is reduced or stopped.  

“Hold the Salt” – learn more on the problem of chlorides in Minnesota lakes.


Keep out phosphorus.

Phosphorus acts as a fertilizer to aquatic plants and algae. You can tell there are high levels of phosphorus when a lake or pond that is pea-soup green and weed-choked in the summer. Phosphorus is introduced from both natural and human activity, so lakeshore property management is the key to controlling it.

  • Minimize or discontinue fertilizer use on shoreline areas that runoff to lake. While phosphorus was banned from most commercial fertilizers years ago, individual grass fertilization and more frequent grass clipping release phosphorus which can get into the lake from surface runoff.
  • Irrigate prudently. Unnecessary or excess yard watering exacerbates the problem by increasing yard runoff from saturated soils, flushing more contaminants into the lake
  • Maintain a shoreline buffer strip. A buffer strip of natural vegetation along your shoreline will help mitigate this problem by slowing down surface water flow, trapping grass clipping, leaves and debris, and taking up some of the phosphorus for shoreline plant growth in the vegetation strip. See the Minnesota DNR guide to shoreline buffer strips
  • Keep leaves out of the lake. Like grass clippings, tree leaves release phosphorus when they biodegrade. While it’s impossible to keep any leaves from getting into the lake, it’s worth the effort to collect leaves from your shoreline during fall cleanup and dispose of them from the lakeshore. Dumping leaves into the lake as a disposal method is never acceptable.
  • Minimize disturbance to shorelines, vegetation and sediments. Large wakes from watercraft can cause shoreline erosion and propwash in shallow areas can tear up vegetation and stir up sediments. Both scenarios release contaminants, like phosphorous, to the lake water column that were previously bound up and contained via natural physical and chemical processes. It’s important to operate your boat in a responsible manner. Read recent studies on the impact of boat wakes and prop-wash