Drawdown is guided by research, engineering and decades of experience.
Drawdown is when water levels are lowered in the Trent-Severn Watershed.
It's a complex process that takes into consideration storage capacity of the lakes on the system, timing of fishery spawning, requirements for flood mitigation, typical fall and winter precipitation levels, downstream typography including constrictions like narrow river beds or dams, and overall volumes and flow rates.
For lakes Simcoe and Couchiching a unique guideline, called a "rule curve," is used to guide the lowering of water levels to allow room for future winter snow melt and precipitation. Since these lakes are so large and the outflows so small relative to the volume of water, the drawdown must be carefully managed to mitigate flooding and protect public safety.
In the Haliburton reservoir lakes area, drawdown occurs throughout the summer season to address downstream needs along the Trent-Severn Waterway. Water levels are based on equal percentage drawdown as developed through collaboration with local community participants.