• In 2024, the TSI values were in the mesotrophic range. Mesotrophic lakes (TSI 40–50) have fairly clear water and moderate nutrient concentrations and algal growth.
• Nitrogen-to-phosphorus (N:P) ratios were below 25 for much of the monitoring season. This indicates the potential for algal blooms to be dominated by cyanobacteria (which have the ability to produce toxins).
• No algal blooms were reported for toxin testing in 2024.
• Long-term trends suggest that water quality in Forbes Lake has been improving over time, with decreasing nitrogen and chlorophyll-a concentrations and deeper Secchi depths (clearer water).
Bathymetry map unavailable
This map shows the area of the watershed relative to the area of the lake. Generally speaking, the larger a watershed is relative to a lake, the greater the influence land use practices on lake water quality.
The average of these three TSI indicators during the growing season can be used
to place lakes in one of three broad categories:
<40 = oligotrophic (low productivity),
40 to 50 = mesotrophic (moderate productivity)
>50 = eutrophic (highly productive).
