Assessing Resiliency to Climate Change for the Elgin Area and Lake Huron Water Supply Systems

In 2021, the Climate Change Vulnerability Assessment Tool (CCVAT) was applied to the Elgin Area Water Supply System (EAWSS) to evaluate the current and predicted condition of their water system and intake to identify which components are most susceptible to climate change. The tool uses widely established vulnerability assessment methods to yield quantitative measures of climate change exposure, sensitivity, adaptive capacity, and vulnerability of a drinking water system’s source water quality, based on information at a watershed, sub-watershed, and drinking water system scale. The results aid in capital planning to assess return on investment strategies for climate-related actions as well as assist in future management policies by prioritizing recommendations. CCVAT serves as science-based guidance to assist in adaptation and risk mitigation strategy planning. Based on the CCVAT’s successful application within the EAWSS, the assessment tool was used to evaluate the Lake Huron Water Supply System (LHWSS). It was concluded that both EAWSS and LHWSS intake and area are susceptible to climate change impacts but have a high adaptive capacity, which can be attributed to the existing policies and management. Draft recommendations for consideration for the EAWSS and LHWSS have been developed and include reviewing Source Protection Plan policies surrounding agricultural land use and a review of rainfall intensity-duration-frequency curves to address potential threats to water quality from changes in extreme precipitation. Collaboration with local conservation authorities to develop policies related to existing flood plains and potential flooding impacts due to climate change was also recommended.

Understanding and Assessing Impacts

In 2018, Conservation Ontario developed the CCVAT in response to proposed changes to the Clean Water Act to include the consideration of climate change in source water quality risk assessments. Together, the EAWSS and LHWSS service approximately 505,000 residents across many municipalities. In 2021, EAWSS in partnership with the Kettle Creek and Ausable Bayfield source protection areas and the Lake Erie Source Protection Region, implemented the CCVAT to determine if the Elgin Area Water Treatment Plant and intake were susceptible to climate change and determine if there were any actions that could be taken to reduce the impact. The EAWSS assessment was completed in July of 2021 while the LHWSS was completed in March 2022. CCVAT assessed climate change exposure, evaluated sensitivity, reviewed impacts and determined the adaptive capacity and vulnerability of the water supply system. It also incorporated climate change impacts on a range of factors including rainfall, surface runoff, and storm sewer capacity to assess water quality risk. Based on increasing historical and predicted climate trends retrieved from Environment and Climate Change Canada, the Climate Atlas of Canada,, and the Ontario Climate Data Portal, both EAWSS and LHWSS intake experience high exposure to multiple climate parameters through all seasons. Parameters contributing to the exposure are minimum/maximum temperatures, precipitation frequency and intensity, very hot days, frost-free days, and freeze-thaw cycle. The climate change impact assessment rating for the study area and the intake for both LHWSS and EAWSS was high suggesting that water quality of the drinking water source will be impacted by climate change. EAWSS and LHWSS both scored a high adaptive capacity of 82% and 70% respectively, attributed to the ability to rely on each other in the event of an emergency as well as existing policies and management procedures. EAWSS has a low vulnerability rating of 31% attributed to the existing high adaptive capacity of the system. The LHWSS scored a medium vulnerability rating of 34% based on its high area sensitivity score, mostly relating to the rural nature of the area, and the high adaptive capacity of the system.

Identifying Actions

The Tool can also support other activities including the development of capital budgets and plans, process optimization, and risk mitigation strategies.

Use of the CCVAT led to the following recommendations for both the EASWW and LHWSS including:

  • Conduct review of Source Protection Plan policies related to agricultural land use activities to assess and address the future impacts agricultural land use has on the area level sensitivity and overall climate change impact.
  • Collaborate with local conservation authorities to develop policies related to existing flood plains and potential flooding impacts due to climate change. This could address climate change impacts on area level sensitivities.
  • Perform a Climate Change Assessment Study and a review of rainfall intensity-duration-frequency curves to address potential threats to water quality from changes in extreme precipitation.

Specific recommendations for EASWW include:

  • Collaborate with local municipalities to increase stormwater system capacity to address area level sensitivity and increase adaptive capacity.
  • Perform an on-site storage capacity study to address potential increases in water demands in the future.
  • Perform an Intake Study to potentially address intake sensitivity and climate change impact ratings.

Specific recommendations for LHWSS:

  • Collaborate with local municipalities to address stormwater and wastewater capacity issues.


The results from the EAWSS and LHWSS assessment will be reviewed holistically to develop an implementation plan for the recommended actions identified. A primary objective is to maintain customer levels of service by being proactive when it comes to planning for climate change related impacts.

Outcomes and Monitoring Progress

Under the Safe Drinking Water Act, the Ontario Ministry of the Environment, Conservation and Parks (MECP) the EAWSS, LHWSS and the associated Source Protection Committees, will continue to provide science-based reports that identify vulnerable areas mapped around municipal wells and intakes in lakes and rivers, vulnerable groundwater areas, and groundwater recharge areas. These reports will also identify threats to drinking water sources within these areas, including threats from climate change.

Next Steps

The results of the tool will serve to further encourage climate change risk management of drinking water system infrastructure and support local climate change strategies and/or Climate Action Plans. The Lake Huron and Elgin Area Water Supply Systems will update the assessment tool on a 5-year basis to ensure current reports and climate conditions are captured and align with the Kettle Creek and Ausable Bayfield Conservation Authorities area assessment report data.