In the summers of 2011 and 2012 this project evaluated an innovative cooling trench feature installed as part of the stormwater management pond operation design in the West Cathedral Subdivision in Markham. The technology, known as the Groundwater Emulation Management System (GEMS), was designed to maintain cool stream discharge from the SWM pond catchment at a level similar to that experienced prior to development. This is accomplished by slowly draining water from the permanent pool to a cooling/infiltration trench. The cooling trench lowers the temperature of pond water through below ground heat transfer and discharges to the receiving watercourse at a rate and volume mimicking the natural discharge of groundwater. Estimated reductions in groundwater recharge caused by the conversion of land from agriculture and open space to residential use provided the basis for setting continuous flow rates released into the system.

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