Phosphorus and the Kawartha Lakes - Lakefield Herald

Conclusion
The majority of the archived data and subsequent analyses used in this chapter
suggest that phosphorus levels have declined in the Kawartha Lakes watershed, which is
congruent with the finding of Robillard and Fox (2006); however, the results should be
interpreted cautiously. There is evidence that phosphorus levels are closely linked with
precipitation patterns, where wet years have higher phosphorus concentrations than dry
years (Novotny and Olem, 1994). According to Environment Canada the Kawartha
Lakes area had a much higher average rainfall in 1972 than it did in either 1976 or 2005.
Similarly, 1976 had a higher average rainfall in 1976 than it did in 2005; however, it is
ostensible that phosphorus levels have been decreasing over time. Fortunately, the datum
from Sturgeon Lake was collected annually and demonstrates a clear decreasing trend in
phosphorus concentrations over time (Figure 5.3). It would appear that phosphorus
concentrations have remained relatively stable in Sturgeon Lake from 1988 through to
2005 at approximately 17 µg/l.
Finally, the results authenticate that lake phosphorus concentrations increase as
water flows East through the lake continuum from Balsam Lake to Lovesick Lake. The
increasing logistic pattern is then disrupted as phosphorus poor water enters the system
from Upper Stony Lake and dilutes the phosphorus rich water of Lovesick Lake below
Burleigh Falls in Lower Stony Lake. The lakes’ phosphorus concentrations continue to
increase after dilution at Lower Stony Lake as demonstrated by the successively higher
phosphorus concentrations in Clear and Katchewanooka Lakes.
Take Home Message
Phosphorus levels have declined approximately 7 µg/l over the past 20 years and
are currently around 14 µg/l. Phosphorus concentrations are known to increase in wet
years and decrease in dry years: 2005 was a dry year. Phosphorus concentrations
increase as water flows from Balsam Lake along the Trent Severn Waterway to Rice
Lake. There is a slight dilution and resultant reduction in phosphorus concentration as
phosphorus poor water enters the system from Upper Stony Lake via Lower Stony Lake
(Figure 5.4).
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