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Trent-Severn Waterway National Historic Site of Canada

The Water Management Program

Appendix Two

Trent River Watershed – Kawartha Lakes

Includes Katchewanooka, Clear, Stony, Lovesick, Deer Bay, Chemong, Buckhorn, Pigeon, Sturgeon, Scugog, Cameron and Balsam Lakes.

Size: The easterly watershed of the Trent-Severn Waterway, covering 12,200 square kilometres.
Physiography: Lies off the southern limit of the Canadian Shield in rolling countryside. One third of the basin lies in the Canadian Shield, and two thirds in the rolling farmlands of southern Ontario.
Water Sources: Rain, snow, and ground water, as well as the reservoir lakes in the Haliburton Highlands.
Runoff Evaporation: Rainfall run-off is slow. Evaporation losses in the summer are high due to the shallowness of the lakes.
Dams: Because of the greater size of the Kawartha Lakes and the greater volumes of water feeding into these lakes, the Kawartha Lake dams are larger. The dam at Buckhorn, for example, has four 15-metre radial sluice gates, while the Youngs Point dam has six vertical gates.

Water levels decline over the winter to accommodate spring runoff. Levels are maintained at navigation levels during the summer and fall by supplementing local water supply with water from the reservoir lakes. The following graph shows the 30-year average percentage of storage capacity throughout the year.

Kawartha Storage Summary

Winter: The larger Kawartha Lakes are drawn down from January 1 to March 15. Normally, this ensures that all the lakes are at their natural low levels prior to the spring freshet. Some dams have all their logs out and the final level attained varies with the natural inflow during the winter. Winters with high inflows mean that some lakes drop less than required, thus reducing flood storage. Dry cold winters with low inflow can cause some lakes to drop below average levels. This situation can create problems on the dams because there is not enough water to run over the spillways to keep stoplogs from freezing in.
Spring: During spring, flows are managed to mitigate flooding and to bring the lakes to navigation levels. In some locations, flows are also managed to accommodate spring spawning fish.
Summer: Since evaporation takes more from the Kawarthas than can be replenished by natural precipitation and ground water inflows, additional water must be supplied to these lakes from the reservoir lakes.
Fall: In the Kawarthas, the smaller navigation route lakes (Canal, Mitchell, Cameron, Lower Buckhorn, and Lovesick) are lowered to winter levels between October 15 and December 1, to avoid access problems and reduce water control costs. The larger Kawartha Lakes are allowed to drop to the middle or bottom of their navigation ranges.

The flows from the Crowe River Watershed are managed by the Crowe Valley Conservation Authority (CVCA). The TSW maintains good communications with the CVCA. However, the CVCA manages flows and water levels to meet its objectives. Therefore, there can be a significant uncontrolled contribution of water from the Crowe Watershed into the TSW. Water from the Kawarthas needs to be controlled in relation to the Crowe flows to prevent downstream flooding.

Navigation: Water levels are maintained at levels that provide sufficient depth for safe boat navigation. Water is required for lock operations.
Flooding: During extreme flood conditions (400-450 m3/s at Peterborough), a decision may be made to raise the Kawartha Lakes above normal in order to prevent much more serious flooding downstream of Peterborough. After the flow peak has passed, logs are placed back in the Kawartha lake dams as the water levels decline, until they are slightly under filled. Then, when flows start to drop off, care is taken to catch enough water to top up the lakes.
Water Quality: Flows are required to dilute and flush pollutants through the system, thereby maintaining water quality and reducing undesirable weed and algae growth. Adjustments are then made to bring the lakes to their optimal level for water management.
Fish & Wildlife: Spring flooding can adversely affect nesting loons. Post freshet spring flows need to be sufficient to protect spring spawning fish (e.g., walleye). Slow fall drawdown of Mitchell Lake is needed to avoid stranding fish.

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