top of page
  • JA

Lake Simcoe Phosphorus Reduction Study

Updated: Apr 12

Last month I attended a conference for the Lake Simcoe Phosphorus Reduction Study. The amount of phosphorus in Lake Simcoe is much higher than is desired so the federal and provincial governments have committed $16 million and $24 million respectively to develop projects to capture the mineral before it makes its way into the lake through the Holland Marsh basin. Among other things, the study is reviewing what the final project will look like and whether is is capturing plant or a hybrid solution that includes both a plant and wetlands. The conference was a chance for everyone involved – including Holland Marsh farmers - to better understand the purpose and scope of the study.


Aside from its many other important attributes, Lake Simcoe provides drinking water for eight surrounding municipalities, so its water quality is critical. This quality, however, is being affected by the large amount of phosphorous in the lake. Phosphorus comes from a variety of sources including urban runoff, fertilizer, sewage, septic systems, etc. As it is an essential plant nutrient, the extra amount is artificially increasing the weed and algae population which negatively impacts biodiversity. When lake plants die and sink to the bottom, they use up oxygen in the process of decomposing. Fish live at the bottom of the lake over the winter but aren’t able to survive because of the reduced amount of oxygen. High levels of phosphorus can also lead to algae blooms that produce algal toxins which can be harmful to human and animal health.


Following are two great links to learn more about the issue:


Significant efforts have been made over the last 25 years to decrease phosphorous loads in Lake Simcoe. In the 80s and 90s, Lake Simcoe averaged well over 100 tonnes of phosphorous per year which has been decreased to an average of 83 tonnes per year since 2000. The LSRCA’s goal, however, is 44 tonnes/year which will take considerable effort to achieve.


The majority of the phosphorous comes from the many tributaries that feed into the lake, with other sources including Sewage Treatment Plants (STPs), septic systems, the atmosphere (pollen, fossil fuels, dust, etc.) and polders (aka marshes). You will note that phosphorus levels have decreased in recent years which is attributed to invasive species such as Zebra and Quagga mussels which eat the plants. The trouble with relying on these species to manage phosphorous is that they eventually die. When that happens the plants will thrive an all the excess phosphorous which would lead to a significant decreased in oxygen.

As the chart shows, phosphorous enters the lake from a variety of sources, and experts explain that it is easiest to capture the phosphorus at a specific source. For example, the 15 Sewage Treatment Plants (STPs) in the Lake Simcoe watershed all discharge either directly or indirectly into Lake Simcoe and have had caps on their phosphorous load since the late 80s. It is interesting to note that the caps are significant and limit the phosphorus load to 98 parts per billion in the Lake Simcoe watershed as compared to 1,000 parts per billion permitted in other parts of Ontario.  


The Holland Marsh Drainage System is another example of a specific source and offers an ideal opportunity to capture an estimated 2.5 of the 4.3 tonnes of phosphorus the polders contribute.

Water for the Holland Marsh Drainage System is drawn from the North and South Canals as well as the Central River all of which drain into the Inner Canal. The runoff from the Inner Canal is collected at the Art Janse Pumping Station (AJPS) which drains into the Holland River and Lake Simcoe.

Possible project locations are being considered as part of the current study, but somewhere in proximity to the Holland Marsh would be necessary and may also offer some benefits to farmers. The Holland Marsh is maintained by six pumping stations as the level of the water in the canals that edge the marsh is higher than the level of the fertile soil inside where the vegetables are grown. The Art Janse Pumping Station is the main pumping station and can remove about 1.5” of rainfall from the marsh in a 24-hour period. This capacity used to be sufficient, but over the last several years the Marsh has experienced more intense storms delivering 3” of rain in a short time frame which then takes 48 hours to pump off. As some crops don’t tolerate wet conditions for that long, the Marsh would benefit from a secondary system to help remove water faster. In addition, the quality of the irrigation water is not the best so the secondary system would be a chance to improve water quality which would help food production.


At first, I was shocked that $40million was being spent to recover just 2.5 tonnes of phosphorous, especially since it’s such a small part of how much needs to reduced overall. Then I learned that whatever solution is finally approved will likely cost much more than the $40 million allocated - one estimate I heard was closer to $100 million. It will be interesting to see whether the federal and provincial governments will allocate more funds to support this project when the actual price is revealed.

The challenge is that capturing phosphorous is very expensive. Consider that Barrie has spent 10 years and tens of millions of dollars optimizing its water treatment facility which has led to a reduction from 1 tonne of phosphorous in 2009 to 400 kg in 2020. Another example is the Lake Simcoe Regional Conservation Association (LSRCA) which has complete 867 reduction projects over the last 10 years at a cost of about $20 million which has reduced the phosphorous load by 3.9 tonnes.


Aside from the cost of construction, one of the other contentious aspects of this project is who is going to pay to operate the new project estimated to cost $1 million annually. The study, being conducted by the Ontario Clean Water Agency, will advise the province on design options, cost estimates, site locations, and cost recovery mechanisms among other things.


There was some initial concern from farmers in the Holland Marsh that they would be expected to foot the bill for maintaining the new project as it will likely tie in with the Holland Marsh Drainage System (HMDS) which they pay to maintain. Further, many farmers have already invested in several improvements to their properties to reduce phosphorus including restricting fertilizer use, companion cropping to reduce wind erosion, bank stabilization, and irrigation management. During the conference, however, I felt that the general sentiment was that residents of all eight municipalities in the watershed who will benefit from the phosphorous reduction should share the cost of the annual maintenance.





36 views0 comments

Recent Posts

See All


bottom of page