Stewart Lake Causation Study

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Muskoka's residents and District Council care about water quality. This important topic impacts the environment, economy, and desirability of the District as both a place to call home and a destination. In an effort to enhance water quality and resident/visitor experience in Muskoka, the District is undertaking causation studies on lakes considered as vulnerable from a water quality perspective. One of these causation studies will be on Stewart Lake.

Stewart Lake is 1.52km2 in size and is located in the Township of Georgian Bay and Township of Muskoka Lakes. The lake experienced blue-green algae blooms in 2010 and 2011. This led to the lake being classified as vulnerable in Schedule E2 of the Muskoka Official Plan (MOP). As outlined in the MOP, when a lake is listed as vulnerable, a waterbody-wide causation study should be initiated to determine the causes and relative contributing factors which lead to the identified water quality indicator, as well as to produce recommendations and mitigative actions that can be taken by stakeholders, the District, and others to ensure water quality may be enhanced in the long-term.

To receive project updates and to stay informed of the outcomes of the Stewart Lake Causation Study Project, enter your email address in the "Stay Informed" tool (located at the top right-hand corner of this page on your desktop or scroll down on your mobile device) and click the subscribe button.

Muskoka's residents and District Council care about water quality. This important topic impacts the environment, economy, and desirability of the District as both a place to call home and a destination. In an effort to enhance water quality and resident/visitor experience in Muskoka, the District is undertaking causation studies on lakes considered as vulnerable from a water quality perspective. One of these causation studies will be on Stewart Lake.

Stewart Lake is 1.52km2 in size and is located in the Township of Georgian Bay and Township of Muskoka Lakes. The lake experienced blue-green algae blooms in 2010 and 2011. This led to the lake being classified as vulnerable in Schedule E2 of the Muskoka Official Plan (MOP). As outlined in the MOP, when a lake is listed as vulnerable, a waterbody-wide causation study should be initiated to determine the causes and relative contributing factors which lead to the identified water quality indicator, as well as to produce recommendations and mitigative actions that can be taken by stakeholders, the District, and others to ensure water quality may be enhanced in the long-term.

To receive project updates and to stay informed of the outcomes of the Stewart Lake Causation Study Project, enter your email address in the "Stay Informed" tool (located at the top right-hand corner of this page on your desktop or scroll down on your mobile device) and click the subscribe button.

  • Causation Study Update for Stewart Lake

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    The District Municipality of Muskoka and project consultants have now completed the Causation Studies initiated in 2021 at the direction of Muskoka District Council. The final report for Stewart Lake can be viewed here:

    Steward Lake Final Report

    Below are answers to some common questions:

    Is my lake still subject to Enhanced Protection Policies?

    No. The Causation Studies have confirmed that development was not the cause of the reported water quality indicators on these five waterbodies. As such, all five waterbodies are now considered to be removed from Schedule E2 and are not subject to the Enhanced Protection Policies, as outlined in Section C2.6.6. of the Muskoka Official Plan (MOP).

    What happens if my lake experiences another blue-green algae bloom this summer?

    The scope of each Causation Study is to determine the cause of one specific blue-green algae bloom and are intended to provide an in-depth review of a snapshot in time to determine why a bloom occurred. However, the results of each report indicate that the primary cause of the reported bloom is climate change.

    If you suspect a blue-green algae bloom, call the Pollution Hotline at 1-866-663-8477.

    If my lake experiences another blue-green algae bloom, will another Causation Study be initiated?

    While the Muskoka Official Plan currently envisions causation studies to be undertaken on all lakes that experience a confirmed blue-green algae bloom, the District is currently embarking on a follow-up study to determine the effectiveness of the existing lake system health policy set and the value in conducting future causation studies.

    I have additional feedback I want to provide – is it possible to do so?

    While we welcome additional feedback, the reports are now final and no further amendments/revisions will be occurring. The District is undertaking a review of the applicable policies contained in the MOP, and a public consultation process will occur through that initiative, which all are welcome to contribute to.

    What are your next steps?

    The District is in the process of retaining a consultant to conduct a follow-up study to determine the effectiveness of the existing lake system health policies contained in the MOP, and the value of conducting future causation studies. Any changes to the existing policies will be undertaken as a public process and anyone who is interested in contributing their comments/concerns will be able to do so through the public meeting process that will be initiated – likely in the fall.

    I have more questions. Who do I contact?

    Please feel free to reach out to Elizabeth Purcell, Manager of Planning, if you have any questions about the Causation Studies. You can email her at Elizabeth.purcell@muskoka.on.ca(External link)(External link).

  • Extended Comment Period for Stakeholder Meeting and Draft Report

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    Due to high stakeholder engagement, the project team has extended the comment period for the draft report and the recorded stakeholder meeting.

    The commenting period now closes on January 13, 2023.

    Please see the News Feed post below for more details.

  • Stakeholder Meeting and Draft Report open for comment

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    The final stakeholder meeting for the Stewart Lake causation study took place on Monday, November 28, 2022 via Zoom - thank you to those who were able to participate in the live meeting!

    If you were not able to join the live meeting, we have made the video recording of the meeting available below. The draft report is also posted in the “Related Documents” section of this page (located to the right).

    I have feedback that I want to provide. How do I submit comments?

    The Muskoka Official Plan contains Lake System Health policies. Within these policies, a lake is considered vulnerable if a lake experiences a water quality indicator (i.e. blue green algae bloom). The purpose of a Causation Study is to determine if shoreline or watershed development contributed to the bloom and what additional studies or actions may be warranted by stakeholders to ensure water quality is enhanced in the long term.

    You can email your comments directly to Cassie Emms, Planner at cassie.emms@muskoka.on.ca.

    While we appreciate the ongoing data collection by stakeholders, for the purpose of the causation study, the data analysis is complete and new data will not be incorporated.

    The commenting period closes on January 13, 2023.

    Next Steps

    The project team will review and consider the stakeholder comments provided at the meetings as well as those submitted in writing. It was originally anticipated that the final reports would be posted by end of 2022, however given high stakeholder interest and amount of comments to date, the final reports will be published in early 2023.

    District staff will review individual causation study results, as well as identify any trends, patterns, or themes across all five concurrent studies. Ultimately, the results of causation studies will not only identify the cause of the water quality indicator on a specific lake, but will also inform the Muskoka Official Plan Lake System Health Policies. These policies are continually updated based on the best available science to protect water quality and overall lake health.

    District staff will review the results of these five causation studies, and provide policy update recommendations to the District’s Community and Planning Services Committee for consideration in early 2023.

    Learn more and Stay Informed!

    To learn more about causation studies, visit our Engage Muskoka platform at: www.engagemuskoka.ca/protecting-muskokas-vulnerable-lakes-causation-studies

    To stay informed of the causation studies that are of interest to you, including a notification of when the final reports are published, subscribe to the Engage Muskoka project page.


  • Upcoming Public Meeting

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    A public meeting for the Stewart Lake Causation Study is scheduled for Monday, November 28 from 10:00 am – 12:00 pm via the virtual platform Zoom.

    Please contact Cassie Emms at cassie.emms@muskoka.on.ca to receive the details for this meeting.

    The purpose of this meeting is for the consulting team to share the results of the Stewart Lake Causation Study, for stakeholders to ask questions, and provide any information or insights that may be helpful as the consulting team prepares the final report.

    If you cannot attend the meeting, it will be recorded and posted on the Engage Muskoka webpage. The public is welcome to provide feedback following the meeting.

  • Causation Study Update

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    Posted on August 24, 2022

    The District Municipality of Muskoka and project consultants have experienced unexpected delays with respect to external data collection required for these projects. This has resulted in an overall delay for all causation studies.

    The required data has recently become available, and the analysis portion of the studies is now underway.

    When will the next stakeholder meetings be?

    The next stakeholder meetings will occur in late Fall 2022. At these meetings, the draft report for each subject lake, including project results, will be shared and discussed. Stakeholder and public comments are welcome and encouraged. You can stay informed on the future meeting dates by subscribing to the Engage Muskoka Page. To subscribe, enter your email address in the “Stay Informed” tool.

    When will the final report be published?

    Following the public consultation on the draft report in late Fall 2022, the final report is anticipated to be published in late 2022 and brought forward to the District’s Community Services and Planning Committee in early 2023.

    Is my lake still subject to Enhanced Protection Policies?

    Yes. Until a causation study is completed and any recommendations adopted by Muskoka District Council, the enhanced protection policies will continue to apply to development on vulnerable lakes, as outlined in Section C2.6.6. of the Muskoka Official Plan (MOP).

    What happens if my lake experiences another blue-green algae bloom this summer?

    The scope of each Causation Study is to determine the cause of one specific blue-green algae bloom and are intended to provide an in-depth review of a snapshot in time to determine why a bloom occurred. For that reason, blue-green algae blooms in subsequent years will not be a part of the current/underway Causation Study. Further, if current Causation Studies did include new blooms, the project would be delayed due to more data collection and analysis requirements.

    If you suspect a blue-green algae bloom, call the Pollution Hotline at 1-866-663-8477.

    If my lake experiences another blue-green algae bloom, will another Causation Study be initiated?

    Currently, there are 9 lakes in Muskoka on Schedule E2 of the Muskoka Official Plan as a result of a confirmed blue-green algae bloom. While the Muskoka Official Plan envisions causation studies to be undertaken on all lakes that experience a confirmed blue-green algae bloom, it does not provide guidance on a priority order for the vulnerable lakes to be studied. For the current lakes undergoing a Causation Study, they were recommended by staff to District Council based on development potential, historical water monitoring and stewardship activities, stakeholder impact, and engagement between the District and the lake association.

    Once the current causation studies are complete, District staff will once again review the vulnerable lakes and provide options for the consideration of District Council..

    I have more questions. Who do I contact?

    Please feel free to reach out to Cassie Emms, Planner, if you have any questions about the Causation Studies. You can email her at cassie.emms@muskoka.on.ca.

  • Public Survey Results Now Posted

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    Thank you to all who participated in the Stewart Lake Causation Study Survey this spring. A summary of the survey results is now available and posted to this page at the following link: Stewart Lake Survey Results.

    Other key aspects of the public consultation process will be summarized in the study’s final report.


    Next steps in the study:

    • The Terms of Reference (TOR) for the study will be shared with stakeholders by August 2021. We will post the TOR to this page and send a newsletter to advise that this document has been posted.
    • Data collection and field work will continue into the fall, after which, the consultant will analyze the data and prepare the draft report for the study.
    • Once the draft report is ready, a stakeholder meeting will be scheduled where you can ask questions to better understand the report findings and recommendations and provide feedback.
    • The timing of the draft report may be affected by late fall blooms but is expected to be prepared for early 2022.
    • After the stakeholder meeting, the report will be revised (if needed), finalized, and presented to the District’s Community and Planning Services Committee.


    Please continue to be our eyes on the lake over the summer and fall seasons and report any sightings of potential blue-green algae blooms to the Ministry of the Environment, Conservation, and Parks’ Spills Action Centre at 1-866-663-8477.

    If you have any additional data or information you would like to share with the consulting team, please send it to jacquie.evans@muskoka.on.ca. We will be accepting submissions from lake stakeholders until October 31, 2021.

  • Stewart Lake Public Survey

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    Stewart Lake Causation Study Survey Now Open!

    The goal of the survey is to gather information on lake use and observations of water quality, and how it has changed over time. We are seeking input from members of the lake association, those who live or work on or near the lake, those who use the lake for recreational purposes, and others with knowledge about the lake to help inform the causation study. We know that these stakeholders have data, information, and observations to share which is critical to our current and historical understand of the lake.

    Anyone with specific knowledge about Stewart Lake, factors that could contribute to algae blooms, and overall water quality on the lake is asked to complete the survey to share this information with us. The survey can be accessed at the link below and will be available until May 27th, 2021.

    Take the survey now!

  • Public Meeting Video Recording

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    The first public meeting for the Stewart Lake causation study took place on Monday, April 19, 2021 via Zoom - thank you for those who were able to participate in the live meeting!

    If you were not able to participate with us, we have made a video recording of the meeting available below. If you have any questions or comments about the presentation or the study process, or if you have information or data to contribute to the study, please contact Jacquie Evans, Planning Policy and Programs Coordinator, at jacquie.evans@muskoka.on.ca or 705-645-2100 ext 4114.

    Thanks again for your interest in the Stewart Lake Causation Study!


  • Upcoming Public Meeting

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    A public meeting for the Stewart Lake Causation Study is scheduled for Monday, April 19, 2021 from 10:00 am – 11:30 am via the virtual platform Zoom.

    Please RSVP to Jacquie Evans at jacquie.evans@muskoka.on.ca to receive the details for this meeting. Please note that the consultant’s presentation from this meeting will be recorded and posted to this project page at a later date.

    The purpose of this meeting is to provide stakeholders with the opportunity to understand the consultant’s approach to the study, to ask questions of the consulting team, and to provide any information or insights that may be helpful to the project. Please help us spread the word!

    For those unable to attend in person or wishing to provide additional details, an online survey will be conducted and will be posted to the this project page when available.

    Stay tuned for more project updates in the coming weeks!


  • Consultant Selected

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    Through the Request for Proposal (RFP) process, the District Municipality of Muskoka has selected Hutchinson Environmental Sciences Ltd. (HESL) as the successful proponent for the Stewart Lake Causation Study. Using a multi-disciplinary approach, HESL has partnered with Eco-Vue Consulting, a firm which specializes in public consultation, to ensure both the scientific and engagement components of the project are thoroughly performed.

    A start-up meeting between the District and the consultants have recently taken place and the consultation plan is currently underway.

    Please be sure to subscribe to the Stewart Lake project page to receive information regarding upcoming meeting dates, consultation opportunities and important project updates.

    Thank you for your interest in the Stewart Lake Causation Study!

Page last updated: 05 Jul 2023, 09:25 AM