05/21/2026
What is Turbidity?
The Lake Windermere Ambassadors have been collecting turbidity measurements from 3 sites on Lake Windermere since 2011!
There has been a lot of recent discussion in our community about turbidity and what may influence it in the lake. Because there is a mix of accurate and inaccurate information circulating, we wanted to share a simple science-based overview of what turbidity is and what can affect it.
Turbidity is a measure of clarity; how cloudy or murky water appears due to tiny particles suspended in the water. These particles can include:
• fine sediments such as silt or mud,
• algae and plankton,
• organic matter,
• and disturbed material from the lake bottom.
Clear water has low turbidity, while cloudier water has higher turbidity.
Scientists commonly measure turbidity using light-based instruments that detect suspended particles in the water. Results are often reported in NTU (Nephelometric Turbidity Units). Water clarity can also be assessed using a Secchi disk.
Turbidity levels are dynamic and can be influenced by many factors.
Natural influences can include:
• spring runoff and freshet,
• heavy rainfall and inflowing streams,
• wind and wave action,
• shoreline erosion,
• and storms that disturb bottom sediments.
Human-related influences can include:
• shoreline disturbance,
• land clearing or construction near waterways,
• propeller wash and wave action from boats,
• and sediment disturbance in shallow-water areas.
Because Lake Windermere is a relatively shallow lake, sediments on the lake bottom can be more easily disturbed and suspended into the water column under certain conditions. Scientific studies from shallow lakes have shown that recreational boating — particularly activities that generate larger wakes or propeller turbulence in shallow areas — can contribute to temporary increases in turbidity by resuspending bottom sediments.
At the same time, boating is only one of several factors that can influence turbidity levels. Weather conditions, seasonal runoff, inflowing rivers and streams, shoreline erosion, and overall watershed conditions can also play significant roles.
Higher turbidity can reduce light pe*******on in the water, generate algae blooms, affect aquatic plants and fish habitat, and move beneficial and harmful nutrients and sediments through the lake ecosystem.
Understanding lake health requires ongoing and long-term monitoring, good data, and respectful discussion grounded in science. As a community, continuing to learn from evidence-based monitoring helps support informed decisions about protecting the long-term health of the lake.
