What have we learned?

A weevil that eats Eurasian milfoil!

Is the tiny milfoil weevil a useful way to control this invasive water plant?  Check out our Weevil Guide.


KLSA was pleased to be awarded a 2010 Trillium Foundation grant to study algae in the Kawarthas.  A two year study by Trent University students resulted in “The Algae of the Kawartha Lakes”, KLSA’s Algae identification guide, which was released in the late summer of 2012. Copies of the printed version are being distributed throughout the area and will be available at the KLSA Spring Meeting and Fall AGM. You can download the pdf version from the link in the Published Material section.

Storm sewer outfall study

In April 2010 KLSA released the surprising results of a study by Fleming College students on Lindsay storm sewer outfalls.  The eight outfalls tested drain into the Scugog River, the source of Lindsay’s drinking water. Some outfalls had E.coli counts so high as to suggest that human sewage is somehow getting into storm sewer pipes. Click here for the full report.

Aquatic plant study and guide

Kawartha residents are seeing a surge in growth of aquatic plants along their shores, including invasive plants such as Eurasian milfoil and curly-leaved pondweed.  They are using many methods to try to control them, legal or not: herbicides, mats on the lake bed, cutters, harvesters, dredgers, and raking, with mixed results.

In 2008, Trent University Masters student Andrea Hicks and her research team collected plenty of data for us on weed management techniques in the Kawarthas, with results that may be surprising. Mats, for example, do seem to control plant growth and make swimming more pleasant in small areas near your shore, but they allow for increased algae growth.  Whether it’s large plants or algae, something is going to feed on those rich nutrients in the water!

Raking controls both plants and algae growth, but it’s hard work and must be kept up all summer. Mechanical cutters are effective and can control large areas, but they’re expensive.

There seems to be no long term, easy, environmentally friendly way to control weeds.  In effect, if your shoreline has the following, then you can expect high plant growth:

  • A gradual slope from shallow to deep water
  • A lake bottom that is mud, silt, sand, or a combination of these
  • Protection from wind and waves, such as a sheltering point or enclosed bay
  • A nearby marsh or swamp

The final report on weed management came out in spring 2009.   You can download the comprehensive, illustrated 2009 Aquatic Plants Guide from the Published Material section.

E coli

E coli levels are generally low throughout the Kawarthas.  Higher levels in some areas are often due to waterfowl, especially Canada Geese, leaky septics, or rain runoff into constricted bays.   KLSA volunteers continue to collect samples for E. coli testing six times per year on many lakes.


Phosphorus is a nutrient that promotes growth of weeds and algae. KLSA volunteers sample for phosphorus six times each year on many lakes.

Phosphorus enters the lakes from many sources:

  • Lawn fertilizers
  • Agricultural runoff
  • Municipal storm sewers
  • Rainwater runoff into the lake, especially where there are no shoreline plants to stop it
  • Sewage treatment plants, which can contribute as much as 15% of the phosphorus in parts of the Kawartha Lakes during low flows in summer
  • Septic systems
  • Feces from farm animals, Canada geese, beaver, and other shore dwellers

Click here to see what we’ve learned about sewage treatment plants in the Kawarthas.

Where are phosphorus levels higher?

  • Phosphorus is generally more concentrated in shallow lakes
  • Phosphorus levels tend to increase as you move downstream (eastward)
  • In July and August, phosphorus levels in lakes in the southern part of the watershed, which borders rich farm land, often approach 20 parts per billion (ppb), the Ministry of the Environment’s “danger point” for algal blooms.
  • The more northerly lakes, which border the Canadian shield, tend to have lower phosphorus levels.
  • We still have much to learn about what causes phosphorus increase and resulting plant growth in our lakes.
  • The relationship between water clarity and phosphorus levels is unclear and is influenced by zebra mussels

What else are we working on? Please click here to see some new projects.


Monitoring and Sustaining the Health of the Kawartha Lakes

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