Trent-Severn Waterway National Historic Site of Canada

Fact Sheet

Management of Lakes Simcoe and Couchiching Trent-Severn Waterway National Historic Site, Parks Canada

Trent-Severn Waterway is an interconnected series of lakes, improved river channels and artificial canal cuts stretching some 386 kilometres through the heart of Ontario. The water in the system comes from two major watersheds, the Trent and the Severn. Water levels and flows throughout the Trent and Severn drainage basins are managed by Parks Canada to allow for safe boating, to reduce flooding of agricultural, residential & commercial property, to protect fish & wildlife habitat, to support municipal services, to support hydroelectric generation, and to help maintain water quality.

Water level management on the lakes and rivers of the Trent-Severn Watersheds follows a complex protocol that incorporates many contributing factors. As a component of this protocol, Lakes Simcoe and Couchiching follow what has historically been known as the rule curve. First used nearly 100 years ago, this water management policy was reviewed by independent engineering consultants in 1988. Primary considerations inherent in this approach are flood abatement, protection of the fishery (especially the fall spawn), navigation and recreation - with flood abatement and public safety being of paramount concern. Many factors are taken into account before any water level adjustment is made to the lakes and rivers of the Trent-Severn Watersheds. Parks Canada takes great care in managing these waters to address a wide range of public values. Decisions affecting an individual body of water are scrutinized for impacts to other water bodies as well as the broader system.

Lakes Simcoe and Couchiching have a number of specific factors that need to be taken into account when managing water levels:

  • These lakes are large and the outlet to the lakes is very small. Parks Canada’s ability to lower the lakes quickly through the dams at Washago is limited. Hence, the need for a slow, prolonged draw down.
  • Natural processes play a major role in the water level changes on these lakes. Through evaporation, up to one centimetre of water can be lost to the atmosphere on a single hot sunny day. There are also significant exchanges occurring between lake and ground water. To illustrate, on September 16, 2011, Parks Canada was flowing 20 cubic metres per second through the dams at Washago. On that same day, our measurements show that the lake was dropping by 0.9 centimetres, which would in fact be at a rate of 79 cubic metres per second. Parks Canada plays a role in the water levels of these lakes; however, in this example natural hydrological processes played a greater role. There are many other examples such as this.
  • There is very little control of the water that flows into these two lakes. A significant rain event during the drawdown can have a significant impact. Indeed, one major rain fall can cause the lakes to rise quickly even when on the drawdown schedule.
  • Failure to reach drawdown levels on Lakes Simcoe and Couchiching increases the risk of flooding in low lying areas due to fall and winter storms, and the spring freshet.
  • With respect to the outflow, Parks Canada must account for additional water from the Black River (an uncontrolled river located downstream of Lake Couchiching) and manage flows out of Washago in a manner that reduces the threat of downstream flooding. Downstream obstructions and developments must also be considered. In other words, if the Black River is high and moving quickly, Parks Canada must reduce the flow out of Lakes Simcoe and Couchiching to reduce the potential for downstream flooding.
  • Throughout the year, minimum flows from the Washago dams are needed to protect the environment, water quality and additional values of the downstream environment. The option of closing the dams completely does not exist.
  • The levels of Lakes Simcoe and Couchiching need to be lowered by October 1 each year to address legally-mandated fisheries legislation.

All of these factors are built into the water management policy for Lakes Simcoe and Couchiching. These factors are as relevant today as they were when the protocol was initially developed. Additional factors could include the impact of climate change with more intense precipitation events, and the growth of urbanization, with increased development along the edges of these lakes. It is important to note that Parks Canada’s water management practices strongly mirror the natural hydrological cycle for these lakes.

In 2008, It’s All About the Water: Report of the Panel on the Future of the Trent-Severn Waterway was completed. In 2009, the Federal Government acknowledged the important work of this independent panel and set in place an action plan. While not all the recommendations of the Panel Report were accepted, a number of important initiatives were launched. With respect to water management, these included the creation of the Water Management Advisory Council and investment in water management infrastructure.

The Water Management Advisory Council is an independent body appointed by Parks Canada. The Council is chaired and populated by stakeholders representing a range of interest and expertise including scientists, engineers, resource managers, hydro managers, lake associations and citizens. The Council meets quarterly with a mandate to provide guidance to the TSW for water management. Members come from all parts of the watershed to offer insight and advice to Parks Canada on the management of water.

Over the last several meetings, the Council has been discussing water management of Lakes Simcoe and Couchiching. The Council received presentations from stakeholders including Lake Simcoe Region Conservation Authority, Parks Canada and boating and recreational stakeholders. At the seventh meeting of the Water Management Advisory Council, on October 27, 2011, members of the Council unanimously supported ongoing use of the current operating policy “rule curve” to govern water management decisions for lakes Simcoe and Couchiching. The Council also encouraged Parks Canada to engage with the community to build a broader base of understanding about the complexities of water management on lakes Simcoe and Couchiching.

Parks Canada Reaches Water Management Decision for Lakes Simcoe and Couchiching