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Track 1 Day 2: Van Seters


Protecting Aquatic Ecosystems from the Thermal Impacts of Stormwater: New Research on Mitigation Opportunities

Thursday March 26, 2020
9:00 to 9:30 a.m. (Hall A)


Water temperature is a critical component of stream health, as it regulates both biotic and abiotic processes in streams. It can be both the driving and constraining factor for the survival of aquatic organisms.

When runoff is drained through stormwater wet ponds, solar radiation heats the open pond water, resulting in thermally enriched outflows that exceed tolerance thresholds of aquatic organisms adapted to cooler water.

Several measures have been devised to help mitigate temperatures and thermal loads from stormwater ponds. These include:

    • Subsurface draw outlets
    • Cooling trenches
    • Night-time release outlets
    • Low impact development techniques

This presentation reviews performance results from over 45 thermal mitigation projects in Ontario and presents data on two new techniques recently installed and monitored in the City of Brampton.

One of these helps cool pond outflows through borehole geo-exchange, while the other utilizes a surface cover to prevent solar heating of pond water.

The relative advantages and disadvantages of the different approaches are discussed, and recommendations are provided on the design and application of the measures under different site conditions.

Learning Objectives

1. Learn about the problem of stormwater thermal enrichment in streams and the various mitigation measures that have been implemented in northern climates.

2. Understand how the mitigation measures implemented in Ontario have performed, and how these should be designed to optimize effectiveness.

3. Learn about the application and effectiveness of two new thermal mitigation measures piloted in the City of Brampton in 2018, and how these may be utilized to mitigate thermal impacts from stormwater ponds.



Tim Van Seters

Tim Van Seters

Tim Van Seters is Manager of the Sustainable Technologies Evaluation Program (STEP) at Toronto and Region Conservation Authority (TRCA).

Tim has more than 19 years of experience designing and implementing field monitoring studies of stormwater management technologies and developing best practice guidance documents on the design, implementation, operation, and maintenance of stormwater practices.

Throughout his career, Tim has presented widely on urban runoff management. and published several reports and papers on urban systems hydrology, watershed water quality, stormwater pond thermal mitigation, and low impact development stormwater management.

Tim holds a Master’s degree specializing in water resources from the University of Waterloo and a Bachelor of Science degree from the University of Toronto.