• Lake McDonald has fairly clear water, with moderate nutrient concentrations and algal growth.
• Long-term trends suggest that water quality in Lake McDonald has been improving over time, with decreasing nitrogen and chlorophyll concentrations.
• Chlorophyll concentrations in 1996-2000 were substantially higher than those observed from 2001 onwards. This trend is not described in the table above, since the estimates for the amount and percent of change assume a constant, linear trend – but the chlorophyll trend is distinctly non-linear. In the water-quality plots above, note that the red dashed trend line (the estimate of constant, linear change) is a poor fit for the actual data.
• No algal blooms were reported for toxin testing in 2023.
This bathymetric map shows contour lines of equal depth, similar to a topographic map would for mountains and valleys. The red 'X' marks the location where water quality samples are taken.
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).
